/src/FreeRDP/winpr/libwinpr/sspi/Kerberos/kerberos.c

Source (jump to first uncovered line)
/**
 * FreeRDP: A Remote Desktop Protocol Client
 * Kerberos Auth Protocol
 *
 * Copyright 2015 ANSSI, Author Thomas Calderon
 * Copyright 2017 Dorian Ducournau <dorian.ducournau@gmail.com>
 * Copyright 2022 David Fort <contact@hardening-consulting.com>
 * Copyright 2022 Isaac Klein <fifthdegree@protonmail.com>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
#include <winpr/config.h>

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
#include <ctype.h>

#include <winpr/assert.h>
#include <winpr/cast.h>
#include <winpr/asn1.h>
#include <winpr/crt.h>
#include <winpr/interlocked.h>
#include <winpr/sspi.h>
#include <winpr/print.h>
#include <winpr/tchar.h>
#include <winpr/sysinfo.h>
#include <winpr/registry.h>
#include <winpr/endian.h>
#include <winpr/crypto.h>
#include <winpr/path.h>
#include <winpr/wtypes.h>
#include <winpr/winsock.h>
#include <winpr/schannel.h>
#include <winpr/secapi.h>

#include "kerberos.h"

#ifdef WITH_KRB5_MIT
#include "krb5glue.h"
#include <profile.h>
#endif

#ifdef WITH_KRB5_HEIMDAL
#include "krb5glue.h"
#include <krb5-protos.h>
#endif

#include "../sspi.h"
#include "../../log.h"
#define TAG WINPR_TAG("sspi.Kerberos")

#define KRB_TGT_REQ 16
#define KRB_TGT_REP 17

const SecPkgInfoA KERBEROS_SecPkgInfoA = {
  0x000F3BBF,                 /* fCapabilities */
  1,                          /* wVersion */
  0x0010,                     /* wRPCID */
  0x0000BB80,                 /* cbMaxToken : 48k bytes maximum for Windows Server 2012 */
  "Kerberos",                 /* Name */
  "Kerberos Security Package" /* Comment */
};

static WCHAR KERBEROS_SecPkgInfoW_NameBuffer[32] = { 0 };
static WCHAR KERBEROS_SecPkgInfoW_CommentBuffer[32] = { 0 };

const SecPkgInfoW KERBEROS_SecPkgInfoW = {
  0x000F3BBF,                        /* fCapabilities */
  1,                                 /* wVersion */
  0x0010,                            /* wRPCID */
  0x0000BB80,                        /* cbMaxToken : 48k bytes maximum for Windows Server 2012 */
  KERBEROS_SecPkgInfoW_NameBuffer,   /* Name */
  KERBEROS_SecPkgInfoW_CommentBuffer /* Comment */
};

#ifdef WITH_KRB5

enum KERBEROS_STATE
{
  KERBEROS_STATE_INITIAL,
  KERBEROS_STATE_TGT_REQ,
  KERBEROS_STATE_TGT_REP,
  KERBEROS_STATE_AP_REQ,
  KERBEROS_STATE_AP_REP,
  KERBEROS_STATE_FINAL
};

typedef struct KRB_CREDENTIALS_st
{
  volatile LONG refCount;
  krb5_context ctx;
  char* kdc_url;
  krb5_ccache ccache;
  krb5_keytab keytab;
  krb5_keytab client_keytab;
  BOOL own_ccache; /**< Whether we created ccache, and must destroy it after use.  */
} KRB_CREDENTIALS;

struct s_KRB_CONTEXT
{
  enum KERBEROS_STATE state;
  KRB_CREDENTIALS* credentials;
  krb5_auth_context auth_ctx;
  BOOL acceptor;
  uint32_t flags;
  uint64_t local_seq;
  uint64_t remote_seq;
  struct krb5glue_keyset keyset;
  BOOL u2u;
  char* targetHost;
};

static const WinPrAsn1_OID kerberos_OID = { 9, (void*)"\x2a\x86\x48\x86\xf7\x12\x01\x02\x02" };
static const WinPrAsn1_OID kerberos_u2u_OID = { 10,
                                              (void*)"\x2a\x86\x48\x86\xf7\x12\x01\x02\x02\x03" };

#define krb_log_exec(fkt, ctx, ...) \
  kerberos_log_msg(ctx, fkt(ctx, ##__VA_ARGS__), #fkt, __FILE__, __func__, __LINE__)
#define krb_log_exec_ptr(fkt, ctx, ...) \
  kerberos_log_msg(*ctx, fkt(ctx, ##__VA_ARGS__), #fkt, __FILE__, __func__, __LINE__)
static krb5_error_code kerberos_log_msg(krb5_context ctx, krb5_error_code code, const char* what,
                                        const char* file, const char* fkt, size_t line)
{
  switch (code)
  {
    case 0:
    case KRB5_KT_END:
      break;
    default:
    {
      const DWORD level = WLOG_ERROR;

      wLog* log = WLog_Get(TAG);
      if (WLog_IsLevelActive(log, level))
      {
        const char* msg = krb5_get_error_message(ctx, code);
        WLog_PrintMessage(log, WLOG_MESSAGE_TEXT, level, line, file, fkt, "%s (%s [%d])",
                          what, msg, code);
        krb5_free_error_message(ctx, msg);
      }
    }
    break;
  }
  return code;
}

static void credentials_unref(KRB_CREDENTIALS* credentials);

static void kerberos_ContextFree(KRB_CONTEXT* ctx, BOOL allocated)
{
  if (!ctx)
    return;

  free(ctx->targetHost);
  ctx->targetHost = NULL;

  if (ctx->credentials)
  {
    krb5_context krbctx = ctx->credentials->ctx;
    if (krbctx)
    {
      if (ctx->auth_ctx)
        krb5_auth_con_free(krbctx, ctx->auth_ctx);

      krb5glue_keys_free(krbctx, &ctx->keyset);
    }

    credentials_unref(ctx->credentials);
  }

  if (allocated)
    free(ctx);
}

static KRB_CONTEXT* kerberos_ContextNew(KRB_CREDENTIALS* credentials)
{
  KRB_CONTEXT* context = NULL;

  context = (KRB_CONTEXT*)calloc(1, sizeof(KRB_CONTEXT));
  if (!context)
    return NULL;

  context->credentials = credentials;
  InterlockedIncrement(&credentials->refCount);
  return context;
}

static krb5_error_code krb5_prompter(krb5_context context, void* data,
                                     WINPR_ATTR_UNUSED const char* name,
                                     WINPR_ATTR_UNUSED const char* banner, int num_prompts,
                                     krb5_prompt prompts[])
{
  for (int i = 0; i < num_prompts; i++)
  {
    krb5_prompt_type type = krb5glue_get_prompt_type(context, prompts, i);
    if (type && (type == KRB5_PROMPT_TYPE_PREAUTH || type == KRB5_PROMPT_TYPE_PASSWORD) && data)
    {
      prompts[i].reply->data = _strdup((const char*)data);

      const size_t len = strlen((const char*)data);
      if (len > UINT32_MAX)
        return KRB5KRB_ERR_GENERIC;
      prompts[i].reply->length = (UINT32)len;
    }
  }
  return 0;
}

static INLINE krb5glue_key get_key(struct krb5glue_keyset* keyset)
{
  return keyset->acceptor_key    ? keyset->acceptor_key
         : keyset->initiator_key ? keyset->initiator_key
                                 : keyset->session_key;
}

static BOOL isValidIPv4(const char* ipAddress)
{
  struct sockaddr_in sa = { 0 };
  int result = inet_pton(AF_INET, ipAddress, &(sa.sin_addr));
  return result != 0;
}

static BOOL isValidIPv6(const char* ipAddress)
{
  struct sockaddr_in6 sa = { 0 };
  int result = inet_pton(AF_INET6, ipAddress, &(sa.sin6_addr));
  return result != 0;
}

static BOOL isValidIP(const char* ipAddress)
{
  return isValidIPv4(ipAddress) || isValidIPv6(ipAddress);
}

#if defined(WITH_KRB5_MIT)
WINPR_ATTR_MALLOC(free, 1)
static char* get_realm_name(krb5_data realm, size_t* plen)
{
  WINPR_ASSERT(plen);
  *plen = 0;
  if ((realm.length <= 0) || (!realm.data))
    return NULL;

  char* name = NULL;
  (void)winpr_asprintf(&name, plen, "krbtgt/%*s@%*s", realm.length, realm.data, realm.length,
                       realm.data);
  return name;
}
#elif defined(WITH_KRB5_HEIMDAL)
WINPR_ATTR_MALLOC(free, 1)
static char* get_realm_name(Realm realm, size_t* plen)
{
  WINPR_ASSERT(plen);
  *plen = 0;
  if (!realm)
    return NULL;

  char* name = NULL;
  (void)winpr_asprintf(&name, plen, "krbtgt/%s@%s", realm, realm);
  return name;
}
#endif

static int build_krbtgt(krb5_context ctx, krb5_principal principal, krb5_principal* ptarget)
{
  /* "krbtgt/" + realm + "@" + realm */
  size_t len = 0;
  krb5_error_code rv = KRB5_CC_NOMEM;

  char* name = get_realm_name(principal->realm, &len);
  if (!name || (len == 0))
    goto fail;

  krb5_principal target = { 0 };
  rv = krb5_parse_name(ctx, name, &target);
  *ptarget = target;
fail:
  free(name);
  return rv;
}

#endif /* WITH_KRB5 */

static SECURITY_STATUS SEC_ENTRY kerberos_AcquireCredentialsHandleA(
    SEC_CHAR* pszPrincipal, WINPR_ATTR_UNUSED SEC_CHAR* pszPackage, ULONG fCredentialUse,
    WINPR_ATTR_UNUSED void* pvLogonID, void* pAuthData, WINPR_ATTR_UNUSED SEC_GET_KEY_FN pGetKeyFn,
    WINPR_ATTR_UNUSED void* pvGetKeyArgument, PCredHandle phCredential,
    WINPR_ATTR_UNUSED PTimeStamp ptsExpiry)
{
#ifdef WITH_KRB5
  SEC_WINPR_KERBEROS_SETTINGS* krb_settings = NULL;
  KRB_CREDENTIALS* credentials = NULL;
  krb5_context ctx = NULL;
  krb5_ccache ccache = NULL;
  krb5_keytab keytab = NULL;
  krb5_principal principal = NULL;
  char* domain = NULL;
  char* username = NULL;
  char* password = NULL;
  BOOL own_ccache = FALSE;
  const char* const default_ccache_type = "MEMORY";

  if (pAuthData)
  {
    UINT32 identityFlags = sspi_GetAuthIdentityFlags(pAuthData);

    if (identityFlags & SEC_WINNT_AUTH_IDENTITY_EXTENDED)
      krb_settings = (((SEC_WINNT_AUTH_IDENTITY_WINPR*)pAuthData)->kerberosSettings);

    if (!sspi_CopyAuthIdentityFieldsA((const SEC_WINNT_AUTH_IDENTITY_INFO*)pAuthData, &username,
                                      &domain, &password))
    {
      WLog_ERR(TAG, "Failed to copy auth identity fields");
      goto cleanup;
    }

    if (!pszPrincipal)
      pszPrincipal = username;
  }

  if (krb_log_exec_ptr(krb5_init_context, &ctx))
    goto cleanup;

  if (domain)
  {
    char* udomain = _strdup(domain);
    if (!udomain)
      goto cleanup;

    CharUpperA(udomain);
    /* Will use domain if realm is not specified in username */
    krb5_error_code rv = krb_log_exec(krb5_set_default_realm, ctx, udomain);
    free(udomain);

    if (rv)
      goto cleanup;
  }

  if (pszPrincipal)
  {
    char* cpszPrincipal = _strdup(pszPrincipal);
    if (!cpszPrincipal)
      goto cleanup;

    /* Find realm component if included and convert to uppercase */
    char* p = strchr(cpszPrincipal, '@');
    if (p)
      CharUpperA(p);

    krb5_error_code rv = krb_log_exec(krb5_parse_name, ctx, cpszPrincipal, &principal);
    free(cpszPrincipal);

    if (rv)
      goto cleanup;
    WINPR_ASSERT(principal);
  }

  if (krb_settings && krb_settings->cache)
  {
    if ((krb_log_exec(krb5_cc_set_default_name, ctx, krb_settings->cache)))
      goto cleanup;
  }
  else
    own_ccache = TRUE;

  if (principal)
  {
    /* Use the default cache if it's initialized with the right principal */
    if (krb5_cc_cache_match(ctx, principal, &ccache) == KRB5_CC_NOTFOUND)
    {
      if (own_ccache)
      {
        if (krb_log_exec(krb5_cc_new_unique, ctx, default_ccache_type, 0, &ccache))
          goto cleanup;
      }
      else
      {
        if (krb_log_exec(krb5_cc_resolve, ctx, krb_settings->cache, &ccache))
          goto cleanup;
      }

      if (krb_log_exec(krb5_cc_initialize, ctx, ccache, principal))
        goto cleanup;
    }
    else
      own_ccache = FALSE;
  }
  else if (fCredentialUse & SECPKG_CRED_OUTBOUND)
  {
    /* Use the default cache with it's default principal */
    if (krb_log_exec(krb5_cc_default, ctx, &ccache))
      goto cleanup;
    if (krb_log_exec(krb5_cc_get_principal, ctx, ccache, &principal))
      goto cleanup;
    own_ccache = FALSE;
  }
  else
  {
    if (own_ccache)
    {
      if (krb_log_exec(krb5_cc_new_unique, ctx, default_ccache_type, 0, &ccache))
        goto cleanup;
    }
    else
    {
      if (krb_log_exec(krb5_cc_resolve, ctx, krb_settings->cache, &ccache))
        goto cleanup;
    }
  }

  if (krb_settings && krb_settings->keytab)
  {
    if (krb_log_exec(krb5_kt_resolve, ctx, krb_settings->keytab, &keytab))
      goto cleanup;
  }
  else
  {
    if (fCredentialUse & SECPKG_CRED_INBOUND)
      if (krb_log_exec(krb5_kt_default, ctx, &keytab))
        goto cleanup;
  }

  /* Get initial credentials if required */
  if (fCredentialUse & SECPKG_CRED_OUTBOUND)
  {
    krb5_creds creds = { 0 };
    krb5_creds matchCreds = { 0 };
    krb5_flags matchFlags = KRB5_TC_MATCH_TIMES;

    krb5_timeofday(ctx, &matchCreds.times.endtime);
    matchCreds.times.endtime += 60;
    matchCreds.client = principal;

    WINPR_ASSERT(principal);
    if (krb_log_exec(build_krbtgt, ctx, principal, &matchCreds.server))
      goto cleanup;

    int rv = krb5_cc_retrieve_cred(ctx, ccache, matchFlags, &matchCreds, &creds);
    krb5_free_principal(ctx, matchCreds.server);
    krb5_free_cred_contents(ctx, &creds);
    if (rv)
    {
      if (krb_log_exec(krb5glue_get_init_creds, ctx, principal, ccache, krb5_prompter,
                       password, krb_settings))
        goto cleanup;
    }
  }

  credentials = calloc(1, sizeof(KRB_CREDENTIALS));
  if (!credentials)
    goto cleanup;
  credentials->refCount = 1;
  credentials->ctx = ctx;
  credentials->ccache = ccache;
  credentials->keytab = keytab;
  credentials->own_ccache = own_ccache;

cleanup:

  free(domain);
  free(username);
  free(password);

  if (principal)
    krb5_free_principal(ctx, principal);
  if (ctx)
  {
    if (!credentials)
    {
      if (ccache)
      {
        if (own_ccache)
          krb5_cc_destroy(ctx, ccache);
        else
          krb5_cc_close(ctx, ccache);
      }
      if (keytab)
        krb5_kt_close(ctx, keytab);

      krb5_free_context(ctx);
    }
  }

  /* If we managed to get credentials set the output */
  if (credentials)
  {
    sspi_SecureHandleSetLowerPointer(phCredential, (void*)credentials);
    sspi_SecureHandleSetUpperPointer(phCredential, (void*)KERBEROS_SSP_NAME);
    return SEC_E_OK;
  }

  return SEC_E_NO_CREDENTIALS;
#else
  return SEC_E_UNSUPPORTED_FUNCTION;
#endif
}

static SECURITY_STATUS SEC_ENTRY kerberos_AcquireCredentialsHandleW(
    SEC_WCHAR* pszPrincipal, SEC_WCHAR* pszPackage, ULONG fCredentialUse, void* pvLogonID,
    void* pAuthData, SEC_GET_KEY_FN pGetKeyFn, void* pvGetKeyArgument, PCredHandle phCredential,
    PTimeStamp ptsExpiry)
{
  SECURITY_STATUS status = SEC_E_INSUFFICIENT_MEMORY;
  char* principal = NULL;
  char* package = NULL;

  if (pszPrincipal)
  {
    principal = ConvertWCharToUtf8Alloc(pszPrincipal, NULL);
    if (!principal)
      goto fail;
  }
  if (pszPackage)
  {
    package = ConvertWCharToUtf8Alloc(pszPackage, NULL);
    if (!package)
      goto fail;
  }

  status =
      kerberos_AcquireCredentialsHandleA(principal, package, fCredentialUse, pvLogonID, pAuthData,
                                         pGetKeyFn, pvGetKeyArgument, phCredential, ptsExpiry);

fail:
  free(principal);
  free(package);

  return status;
}

#ifdef WITH_KRB5
static void credentials_unref(KRB_CREDENTIALS* credentials)
{
  WINPR_ASSERT(credentials);

  if (InterlockedDecrement(&credentials->refCount))
    return;

  free(credentials->kdc_url);

  if (credentials->ccache)
  {
    if (credentials->own_ccache)
      krb5_cc_destroy(credentials->ctx, credentials->ccache);
    else
      krb5_cc_close(credentials->ctx, credentials->ccache);
  }
  if (credentials->keytab)
    krb5_kt_close(credentials->ctx, credentials->keytab);

  krb5_free_context(credentials->ctx);
  free(credentials);
}
#endif

static SECURITY_STATUS SEC_ENTRY kerberos_FreeCredentialsHandle(PCredHandle phCredential)
{
#ifdef WITH_KRB5
  KRB_CREDENTIALS* credentials = sspi_SecureHandleGetLowerPointer(phCredential);
  if (!credentials)
    return SEC_E_INVALID_HANDLE;

  credentials_unref(credentials);

  sspi_SecureHandleInvalidate(phCredential);
  return SEC_E_OK;
#else
  return SEC_E_UNSUPPORTED_FUNCTION;
#endif
}

static SECURITY_STATUS SEC_ENTRY kerberos_QueryCredentialsAttributesW(
    WINPR_ATTR_UNUSED PCredHandle phCredential, ULONG ulAttribute, WINPR_ATTR_UNUSED void* pBuffer)
{
#ifdef WITH_KRB5
  switch (ulAttribute)
  {
    case SECPKG_CRED_ATTR_NAMES:
      return SEC_E_OK;
    default:
      WLog_ERR(TAG, "TODO: QueryCredentialsAttributesW, implement ulAttribute=%08" PRIx32,
               ulAttribute);
      return SEC_E_UNSUPPORTED_FUNCTION;
  }

#else
  return SEC_E_UNSUPPORTED_FUNCTION;
#endif
}

static SECURITY_STATUS SEC_ENTRY kerberos_QueryCredentialsAttributesA(PCredHandle phCredential,
                                                                      ULONG ulAttribute,
                                                                      void* pBuffer)
{
  return kerberos_QueryCredentialsAttributesW(phCredential, ulAttribute, pBuffer);
}

#ifdef WITH_KRB5

static BOOL kerberos_mk_tgt_token(SecBuffer* buf, int msg_type, char* sname, char* host,
                                  const krb5_data* ticket)
{
  WinPrAsn1Encoder* enc = NULL;
  WinPrAsn1_MemoryChunk data;
  wStream s;
  size_t len = 0;
  sspi_gss_data token;
  BOOL ret = FALSE;

  WINPR_ASSERT(buf);

  if (msg_type != KRB_TGT_REQ && msg_type != KRB_TGT_REP)
    return FALSE;
  if (msg_type == KRB_TGT_REP && !ticket)
    return FALSE;

  enc = WinPrAsn1Encoder_New(WINPR_ASN1_DER);
  if (!enc)
    return FALSE;

  /* KERB-TGT-REQUEST (SEQUENCE) */
  if (!WinPrAsn1EncSeqContainer(enc))
    goto cleanup;

  /* pvno [0] INTEGER */
  if (!WinPrAsn1EncContextualInteger(enc, 0, 5))
    goto cleanup;

  /* msg-type [1] INTEGER */
  if (!WinPrAsn1EncContextualInteger(enc, 1, msg_type))
    goto cleanup;

  if (msg_type == KRB_TGT_REQ && sname)
  {
    /* server-name [2] PrincipalName (SEQUENCE) */
    if (!WinPrAsn1EncContextualSeqContainer(enc, 2))
      goto cleanup;

    /* name-type [0] INTEGER */
    if (!WinPrAsn1EncContextualInteger(enc, 0, KRB5_NT_SRV_HST))
      goto cleanup;

    /* name-string [1] SEQUENCE OF GeneralString */
    if (!WinPrAsn1EncContextualSeqContainer(enc, 1))
      goto cleanup;

    if (!WinPrAsn1EncGeneralString(enc, sname))
      goto cleanup;

    if (host && !WinPrAsn1EncGeneralString(enc, host))
      goto cleanup;

    if (!WinPrAsn1EncEndContainer(enc) || !WinPrAsn1EncEndContainer(enc))
      goto cleanup;
  }
  else if (msg_type == KRB_TGT_REP)
  {
    /* ticket [2] Ticket */
    data.data = (BYTE*)ticket->data;
    data.len = ticket->length;
    if (!WinPrAsn1EncContextualRawContent(enc, 2, &data))
      goto cleanup;
  }

  if (!WinPrAsn1EncEndContainer(enc))
    goto cleanup;

  if (!WinPrAsn1EncStreamSize(enc, &len) || len > buf->cbBuffer)
    goto cleanup;

  Stream_StaticInit(&s, buf->pvBuffer, len);
  if (!WinPrAsn1EncToStream(enc, &s))
    goto cleanup;

  token.data = buf->pvBuffer;
  token.length = (UINT)len;
  if (sspi_gss_wrap_token(buf, &kerberos_u2u_OID,
                          msg_type == KRB_TGT_REQ ? TOK_ID_TGT_REQ : TOK_ID_TGT_REP, &token))
    ret = TRUE;

cleanup:
  WinPrAsn1Encoder_Free(&enc);
  return ret;
}

static BOOL append(char* dst, size_t dstSize, const char* src)
{
  const size_t dlen = strnlen(dst, dstSize);
  const size_t slen = strlen(src);
  if (dlen + slen >= dstSize)
    return FALSE;
  if (!strncat(dst, src, dstSize - dlen))
    return FALSE;
  return TRUE;
}

static BOOL kerberos_rd_tgt_req_tag2(WinPrAsn1Decoder* dec, char* buf, size_t len)
{
  BOOL rc = FALSE;
  WinPrAsn1Decoder seq = { 0 };

  /* server-name [2] PrincipalName (SEQUENCE) */
  if (!WinPrAsn1DecReadSequence(dec, &seq))
    goto end;

  /* name-type [0] INTEGER */
  BOOL error = FALSE;
  WinPrAsn1_INTEGER val = 0;
  if (!WinPrAsn1DecReadContextualInteger(&seq, 0, &error, &val))
    goto end;

  /* name-string [1] SEQUENCE OF GeneralString */
  if (!WinPrAsn1DecReadContextualSequence(&seq, 1, &error, dec))
    goto end;

  WinPrAsn1_tag tag = 0;
  BOOL first = TRUE;
  while (WinPrAsn1DecPeekTag(dec, &tag))
  {
    BOOL success = FALSE;
    char* lstr = NULL;
    if (!WinPrAsn1DecReadGeneralString(dec, &lstr))
      goto fail;

    if (!first)
    {
      if (!append(buf, len, "/"))
        goto fail;
    }
    first = FALSE;

    if (!append(buf, len, lstr))
      goto fail;

    success = TRUE;
  fail:
    free(lstr);
    if (!success)
      goto end;
  }

  rc = TRUE;
end:
  return rc;
}

static BOOL kerberos_rd_tgt_req_tag3(WinPrAsn1Decoder* dec, char* buf, size_t len)
{
  /* realm [3] Realm */
  BOOL rc = FALSE;
  WinPrAsn1_STRING str = NULL;
  if (!WinPrAsn1DecReadGeneralString(dec, &str))
    goto end;

  if (!append(buf, len, "@"))
    goto end;
  if (!append(buf, len, str))
    goto end;

  rc = TRUE;
end:
  free(str);
  return rc;
}

static BOOL kerberos_rd_tgt_req(WinPrAsn1Decoder* dec, char** target)
{
  BOOL rc = FALSE;

  if (!target)
    return FALSE;
  *target = NULL;

  wStream s = WinPrAsn1DecGetStream(dec);
  const size_t len = Stream_Length(&s);
  if (len == 0)
    return TRUE;

  WinPrAsn1Decoder dec2 = { 0 };
  WinPrAsn1_tagId tag = 0;
  if (WinPrAsn1DecReadContextualTag(dec, &tag, &dec2) == 0)
    return FALSE;

  char* buf = calloc(len + 1, sizeof(char));
  if (!buf)
    return FALSE;

  /* We expect ASN1 context tag values 2 or 3.
   *
   * In case we got value 2 an (optional) context tag value 3 might follow.
   */
  BOOL checkForTag3 = TRUE;
  if (tag == 2)
  {
    rc = kerberos_rd_tgt_req_tag2(&dec2, buf, len);
    if (rc)
    {
      const size_t res = WinPrAsn1DecReadContextualTag(dec, &tag, dec);
      if (res == 0)
        checkForTag3 = FALSE;
    }
  }

  if (checkForTag3)
  {
    if (tag == 3)
      rc = kerberos_rd_tgt_req_tag3(&dec2, buf, len);
    else
      rc = FALSE;
  }

  if (rc)
    *target = buf;
  else
    free(buf);
  return rc;
}

static BOOL kerberos_rd_tgt_rep(WinPrAsn1Decoder* dec, krb5_data* ticket)
{
  if (!ticket)
    return FALSE;

  /* ticket [2] Ticket */
  WinPrAsn1Decoder asnTicket = { 0 };
  WinPrAsn1_tagId tag = 0;
  if (WinPrAsn1DecReadContextualTag(dec, &tag, &asnTicket) == 0)
    return FALSE;

  if (tag != 2)
    return FALSE;

  wStream s = WinPrAsn1DecGetStream(&asnTicket);
  ticket->data = Stream_BufferAs(&s, char);

  const size_t len = Stream_Length(&s);
  if (len > UINT32_MAX)
    return FALSE;
  ticket->length = (UINT32)len;
  return TRUE;
}

static BOOL kerberos_rd_tgt_token(const sspi_gss_data* token, char** target, krb5_data* ticket)
{
  BOOL error = 0;
  WinPrAsn1_INTEGER val = 0;

  WINPR_ASSERT(token);

  if (target)
    *target = NULL;

  WinPrAsn1Decoder der = { 0 };
  WinPrAsn1Decoder_InitMem(&der, WINPR_ASN1_DER, (BYTE*)token->data, token->length);

  /* KERB-TGT-REQUEST (SEQUENCE) */
  WinPrAsn1Decoder seq = { 0 };
  if (!WinPrAsn1DecReadSequence(&der, &seq))
    return FALSE;

  /* pvno [0] INTEGER */
  if (!WinPrAsn1DecReadContextualInteger(&seq, 0, &error, &val) || val != 5)
    return FALSE;

  /* msg-type [1] INTEGER */
  if (!WinPrAsn1DecReadContextualInteger(&seq, 1, &error, &val))
    return FALSE;

  switch (val)
  {
    case KRB_TGT_REQ:
      return kerberos_rd_tgt_req(&seq, target);
    case KRB_TGT_REP:
      return kerberos_rd_tgt_rep(&seq, ticket);
    default:
      break;
  }
  return FALSE;
}

#endif /* WITH_KRB5 */

static BOOL kerberos_hash_channel_bindings(WINPR_DIGEST_CTX* md5, SEC_CHANNEL_BINDINGS* bindings)
{
  BYTE buf[4];

  winpr_Data_Write_UINT32(buf, bindings->dwInitiatorAddrType);
  if (!winpr_Digest_Update(md5, buf, 4))
    return FALSE;

  winpr_Data_Write_UINT32(buf, bindings->cbInitiatorLength);
  if (!winpr_Digest_Update(md5, buf, 4))
    return FALSE;

  if (bindings->cbInitiatorLength &&
      !winpr_Digest_Update(md5, (BYTE*)bindings + bindings->dwInitiatorOffset,
                           bindings->cbInitiatorLength))
    return FALSE;

  winpr_Data_Write_UINT32(buf, bindings->dwAcceptorAddrType);
  if (!winpr_Digest_Update(md5, buf, 4))
    return FALSE;

  winpr_Data_Write_UINT32(buf, bindings->cbAcceptorLength);
  if (!winpr_Digest_Update(md5, buf, 4))
    return FALSE;

  if (bindings->cbAcceptorLength &&
      !winpr_Digest_Update(md5, (BYTE*)bindings + bindings->dwAcceptorOffset,
                           bindings->cbAcceptorLength))
    return FALSE;

  winpr_Data_Write_UINT32(buf, bindings->cbApplicationDataLength);
  if (!winpr_Digest_Update(md5, buf, 4))
    return FALSE;

  if (bindings->cbApplicationDataLength &&
      !winpr_Digest_Update(md5, (BYTE*)bindings + bindings->dwApplicationDataOffset,
                           bindings->cbApplicationDataLength))
    return FALSE;

  return TRUE;
}

static SECURITY_STATUS SEC_ENTRY kerberos_InitializeSecurityContextA(
    PCredHandle phCredential, PCtxtHandle phContext, SEC_CHAR* pszTargetName, ULONG fContextReq,
    WINPR_ATTR_UNUSED ULONG Reserved1, WINPR_ATTR_UNUSED ULONG TargetDataRep, PSecBufferDesc pInput,
    WINPR_ATTR_UNUSED ULONG Reserved2, PCtxtHandle phNewContext, PSecBufferDesc pOutput,
    WINPR_ATTR_UNUSED ULONG* pfContextAttr, WINPR_ATTR_UNUSED PTimeStamp ptsExpiry)
{
#ifdef WITH_KRB5
  PSecBuffer input_buffer = NULL;
  PSecBuffer output_buffer = NULL;
  PSecBuffer bindings_buffer = NULL;
  WINPR_DIGEST_CTX* md5 = NULL;
  char* target = NULL;
  char* sname = NULL;
  char* host = NULL;
  krb5_data input_token = { 0 };
  krb5_data output_token = { 0 };
  SECURITY_STATUS status = SEC_E_INTERNAL_ERROR;
  WinPrAsn1_OID oid = { 0 };
  uint16_t tok_id = 0;
  krb5_ap_rep_enc_part* reply = NULL;
  krb5_flags ap_flags = AP_OPTS_USE_SUBKEY;
  char cksum_contents[24] = { 0 };
  krb5_data cksum = { 0 };
  krb5_creds in_creds = { 0 };
  krb5_creds* creds = NULL;
  BOOL isNewContext = FALSE;
  KRB_CONTEXT* context = NULL;
  KRB_CREDENTIALS* credentials = sspi_SecureHandleGetLowerPointer(phCredential);

  /* behave like windows SSPIs that don't want empty context */
  if (phContext && !phContext->dwLower && !phContext->dwUpper)
    return SEC_E_INVALID_HANDLE;

  context = sspi_SecureHandleGetLowerPointer(phContext);

  if (!credentials)
    return SEC_E_NO_CREDENTIALS;

  if (pInput)
  {
    input_buffer = sspi_FindSecBuffer(pInput, SECBUFFER_TOKEN);
    bindings_buffer = sspi_FindSecBuffer(pInput, SECBUFFER_CHANNEL_BINDINGS);
  }
  if (pOutput)
    output_buffer = sspi_FindSecBuffer(pOutput, SECBUFFER_TOKEN);

  if (fContextReq & ISC_REQ_MUTUAL_AUTH)
    ap_flags |= AP_OPTS_MUTUAL_REQUIRED;

  if (fContextReq & ISC_REQ_USE_SESSION_KEY)
    ap_flags |= AP_OPTS_USE_SESSION_KEY;

  /* Split target name into service/hostname components */
  if (pszTargetName)
  {
    target = _strdup(pszTargetName);
    if (!target)
    {
      status = SEC_E_INSUFFICIENT_MEMORY;
      goto cleanup;
    }
    host = strchr(target, '/');
    if (host)
    {
      *host++ = 0;
      sname = target;
    }
    else
      host = target;
    if (isValidIP(host))
    {
      status = SEC_E_NO_CREDENTIALS;
      goto cleanup;
    }
  }

  if (!context)
  {
    context = kerberos_ContextNew(credentials);
    if (!context)
    {
      status = SEC_E_INSUFFICIENT_MEMORY;
      goto cleanup;
    }

    isNewContext = TRUE;

    if (host)
      context->targetHost = _strdup(host);
    if (!context->targetHost)
    {
      status = SEC_E_INSUFFICIENT_MEMORY;
      goto cleanup;
    }

    if (fContextReq & ISC_REQ_USE_SESSION_KEY)
    {
      context->state = KERBEROS_STATE_TGT_REQ;
      context->u2u = TRUE;
    }
    else
      context->state = KERBEROS_STATE_AP_REQ;
  }
  else
  {
    if (!input_buffer || !sspi_gss_unwrap_token(input_buffer, &oid, &tok_id, &input_token))
      goto bad_token;
    if ((context->u2u && !sspi_gss_oid_compare(&oid, &kerberos_u2u_OID)) ||
        (!context->u2u && !sspi_gss_oid_compare(&oid, &kerberos_OID)))
      goto bad_token;
  }

  /* SSPI flags are compatible with GSS flags except INTEG_FLAG */
  context->flags |= (fContextReq & 0x1F);
  if ((fContextReq & ISC_REQ_INTEGRITY) && !(fContextReq & ISC_REQ_NO_INTEGRITY))
    context->flags |= SSPI_GSS_C_INTEG_FLAG;

  switch (context->state)
  {
    case KERBEROS_STATE_TGT_REQ:

      if (!kerberos_mk_tgt_token(output_buffer, KRB_TGT_REQ, sname, host, NULL))
        goto cleanup;

      context->state = KERBEROS_STATE_TGT_REP;
      status = SEC_I_CONTINUE_NEEDED;
      break;

    case KERBEROS_STATE_TGT_REP:

      if (tok_id != TOK_ID_TGT_REP)
        goto bad_token;

      if (!kerberos_rd_tgt_token(&input_token, NULL, &in_creds.second_ticket))
        goto bad_token;

      /* Continue to AP-REQ */
      /* fallthrough */
      WINPR_FALLTHROUGH

    case KERBEROS_STATE_AP_REQ:

      /* Set auth_context options */
      if (krb_log_exec(krb5_auth_con_init, credentials->ctx, &context->auth_ctx))
        goto cleanup;
      if (krb_log_exec(krb5_auth_con_setflags, credentials->ctx, context->auth_ctx,
                       KRB5_AUTH_CONTEXT_DO_SEQUENCE | KRB5_AUTH_CONTEXT_USE_SUBKEY))
        goto cleanup;
      if (krb_log_exec(krb5glue_auth_con_set_cksumtype, credentials->ctx, context->auth_ctx,
                       GSS_CHECKSUM_TYPE))
        goto cleanup;

      /* Get a service ticket */
      if (krb_log_exec(krb5_sname_to_principal, credentials->ctx, host, sname,
                       KRB5_NT_SRV_HST, &in_creds.server))
        goto cleanup;

      if (krb_log_exec(krb5_cc_get_principal, credentials->ctx, credentials->ccache,
                       &in_creds.client))
      {
        status = SEC_E_WRONG_PRINCIPAL;
        goto cleanup;
      }

      if (krb_log_exec(krb5_get_credentials, credentials->ctx,
                       context->u2u ? KRB5_GC_USER_USER : 0, credentials->ccache, &in_creds,
                       &creds))
      {
        status = SEC_E_NO_CREDENTIALS;
        goto cleanup;
      }

      /* Write the checksum (delegation not implemented) */
      cksum.data = cksum_contents;
      cksum.length = sizeof(cksum_contents);
      winpr_Data_Write_UINT32(cksum_contents, 16);
      winpr_Data_Write_UINT32((cksum_contents + 20), context->flags);

      if (bindings_buffer)
      {
        SEC_CHANNEL_BINDINGS* bindings = bindings_buffer->pvBuffer;

        /* Sanity checks */
        if (bindings_buffer->cbBuffer < sizeof(SEC_CHANNEL_BINDINGS) ||
            (bindings->cbInitiatorLength + bindings->dwInitiatorOffset) >
                bindings_buffer->cbBuffer ||
            (bindings->cbAcceptorLength + bindings->dwAcceptorOffset) >
                bindings_buffer->cbBuffer ||
            (bindings->cbApplicationDataLength + bindings->dwApplicationDataOffset) >
                bindings_buffer->cbBuffer)
        {
          status = SEC_E_BAD_BINDINGS;
          goto cleanup;
        }

        md5 = winpr_Digest_New();
        if (!md5)
          goto cleanup;

        if (!winpr_Digest_Init(md5, WINPR_MD_MD5))
          goto cleanup;

        if (!kerberos_hash_channel_bindings(md5, bindings))
          goto cleanup;

        if (!winpr_Digest_Final(md5, (BYTE*)cksum_contents + 4, 16))
          goto cleanup;
      }

      /* Make the AP_REQ message */
      if (krb_log_exec(krb5_mk_req_extended, credentials->ctx, &context->auth_ctx, ap_flags,
                       &cksum, creds, &output_token))
        goto cleanup;

      if (!sspi_gss_wrap_token(output_buffer,
                               context->u2u ? &kerberos_u2u_OID : &kerberos_OID,
                               TOK_ID_AP_REQ, &output_token))
        goto cleanup;

      if (context->flags & SSPI_GSS_C_SEQUENCE_FLAG)
      {
        if (krb_log_exec(krb5_auth_con_getlocalseqnumber, credentials->ctx,
                         context->auth_ctx, (INT32*)&context->local_seq))
          goto cleanup;
        context->remote_seq ^= context->local_seq;
      }

      if (krb_log_exec(krb5glue_update_keyset, credentials->ctx, context->auth_ctx, FALSE,
                       &context->keyset))
        goto cleanup;

      context->state = KERBEROS_STATE_AP_REP;

      if (context->flags & SSPI_GSS_C_MUTUAL_FLAG)
        status = SEC_I_CONTINUE_NEEDED;
      else
        status = SEC_E_OK;
      break;

    case KERBEROS_STATE_AP_REP:

      if (tok_id == TOK_ID_AP_REP)
      {
        if (krb_log_exec(krb5_rd_rep, credentials->ctx, context->auth_ctx, &input_token,
                         &reply))
          goto cleanup;
        krb5_free_ap_rep_enc_part(credentials->ctx, reply);
      }
      else if (tok_id == TOK_ID_ERROR)
      {
        krb5glue_log_error(credentials->ctx, &input_token, TAG);
        goto cleanup;
      }
      else
        goto bad_token;

      if (context->flags & SSPI_GSS_C_SEQUENCE_FLAG)
      {
        if (krb_log_exec(krb5_auth_con_getremoteseqnumber, credentials->ctx,
                         context->auth_ctx, (INT32*)&context->remote_seq))
          goto cleanup;
      }

      if (krb_log_exec(krb5glue_update_keyset, credentials->ctx, context->auth_ctx, FALSE,
                       &context->keyset))
        goto cleanup;

      context->state = KERBEROS_STATE_FINAL;

      if (output_buffer)
        output_buffer->cbBuffer = 0;
      status = SEC_E_OK;
      break;

    case KERBEROS_STATE_FINAL:
    default:
      WLog_ERR(TAG, "Kerberos in invalid state!");
      goto cleanup;
  }

cleanup:
{
  /* second_ticket is not allocated */
  krb5_data edata = { 0 };
  in_creds.second_ticket = edata;
  krb5_free_cred_contents(credentials->ctx, &in_creds);
}

  krb5_free_creds(credentials->ctx, creds);
  if (output_token.data)
    krb5glue_free_data_contents(credentials->ctx, &output_token);

  winpr_Digest_Free(md5);

  free(target);

  if (isNewContext)
  {
    switch (status)
    {
      case SEC_E_OK:
      case SEC_I_CONTINUE_NEEDED:
        sspi_SecureHandleSetLowerPointer(phNewContext, context);
        sspi_SecureHandleSetUpperPointer(phNewContext, KERBEROS_SSP_NAME);
        break;
      default:
        kerberos_ContextFree(context, TRUE);
        break;
    }
  }

  return status;

bad_token:
  status = SEC_E_INVALID_TOKEN;
  goto cleanup;
#else
  return SEC_E_UNSUPPORTED_FUNCTION;
#endif /* WITH_KRB5 */
}

static SECURITY_STATUS SEC_ENTRY kerberos_InitializeSecurityContextW(
    PCredHandle phCredential, PCtxtHandle phContext, SEC_WCHAR* pszTargetName, ULONG fContextReq,
    ULONG Reserved1, ULONG TargetDataRep, PSecBufferDesc pInput, ULONG Reserved2,
    PCtxtHandle phNewContext, PSecBufferDesc pOutput, ULONG* pfContextAttr, PTimeStamp ptsExpiry)
{
  SECURITY_STATUS status = 0;
  char* target_name = NULL;

  if (pszTargetName)
  {
    target_name = ConvertWCharToUtf8Alloc(pszTargetName, NULL);
    if (!target_name)
      return SEC_E_INSUFFICIENT_MEMORY;
  }

  status = kerberos_InitializeSecurityContextA(phCredential, phContext, target_name, fContextReq,
                                               Reserved1, TargetDataRep, pInput, Reserved2,
                                               phNewContext, pOutput, pfContextAttr, ptsExpiry);

  if (target_name)
    free(target_name);

  return status;
}

static SECURITY_STATUS SEC_ENTRY kerberos_AcceptSecurityContext(
    PCredHandle phCredential, PCtxtHandle phContext, PSecBufferDesc pInput,
    WINPR_ATTR_UNUSED ULONG fContextReq, WINPR_ATTR_UNUSED ULONG TargetDataRep,
    PCtxtHandle phNewContext, PSecBufferDesc pOutput, ULONG* pfContextAttr,
    WINPR_ATTR_UNUSED PTimeStamp ptsExpity)
{
#ifdef WITH_KRB5
  BOOL isNewContext = FALSE;
  PSecBuffer input_buffer = NULL;
  PSecBuffer output_buffer = NULL;
  WinPrAsn1_OID oid = { 0 };
  uint16_t tok_id = 0;
  krb5_data input_token = { 0 };
  krb5_data output_token = { 0 };
  SECURITY_STATUS status = SEC_E_INTERNAL_ERROR;
  krb5_flags ap_flags = 0;
  krb5glue_authenticator authenticator = NULL;
  char* target = NULL;
  char* sname = NULL;
  char* realm = NULL;
  krb5_kt_cursor cur = { 0 };
  krb5_keytab_entry entry = { 0 };
  krb5_principal principal = NULL;
  krb5_creds creds = { 0 };

  /* behave like windows SSPIs that don't want empty context */
  if (phContext && !phContext->dwLower && !phContext->dwUpper)
    return SEC_E_INVALID_HANDLE;

  KRB_CONTEXT* context = sspi_SecureHandleGetLowerPointer(phContext);
  KRB_CREDENTIALS* credentials = sspi_SecureHandleGetLowerPointer(phCredential);

  if (pInput)
    input_buffer = sspi_FindSecBuffer(pInput, SECBUFFER_TOKEN);
  if (pOutput)
    output_buffer = sspi_FindSecBuffer(pOutput, SECBUFFER_TOKEN);

  if (!input_buffer)
    return SEC_E_INVALID_TOKEN;

  if (!sspi_gss_unwrap_token(input_buffer, &oid, &tok_id, &input_token))
    return SEC_E_INVALID_TOKEN;

  if (!context)
  {
    isNewContext = TRUE;
    context = kerberos_ContextNew(credentials);
    context->acceptor = TRUE;

    if (sspi_gss_oid_compare(&oid, &kerberos_u2u_OID))
    {
      context->u2u = TRUE;
      context->state = KERBEROS_STATE_TGT_REQ;
    }
    else if (sspi_gss_oid_compare(&oid, &kerberos_OID))
      context->state = KERBEROS_STATE_AP_REQ;
    else
      goto bad_token;
  }
  else
  {
    if ((context->u2u && !sspi_gss_oid_compare(&oid, &kerberos_u2u_OID)) ||
        (!context->u2u && !sspi_gss_oid_compare(&oid, &kerberos_OID)))
      goto bad_token;
  }

  if (context->state == KERBEROS_STATE_TGT_REQ && tok_id == TOK_ID_TGT_REQ)
  {
    if (!kerberos_rd_tgt_token(&input_token, &target, NULL))
      goto bad_token;

    /*
     *  we're requested with target="TERMSRV/<host>@<REALM>" but we're gonna look
     *  at <host>$@<REALM> in the keytab (notice the $), so we build a new "target"
     *  string containing
     *
     *  sname   realm
     *  |       |
     *  v       v
     *  <host>$@<REALM>
     *
     */
    if (target)
    {
      sname = strchr(target, '/');
      if (!sname)
        goto cleanup;
      sname++;

      /* target goes from TERMSRV/<host>[@<REALM>] to <host>[@<REALM>] */
      sname = memmove(target, sname, strlen(sname) + 1);

      realm = strchr(target, '@');
      if (realm)
      {
        *realm = '$';
        realm++;

        size_t len = strlen(realm);
        memmove(realm + 1, realm, len + 1);

        *realm = '@';
        realm++;
      }
      else
      {
        size_t len = strlen(sname);
        target[len] = '$';
        target[len + 1] = 0;
      }
    }

    if (krb_log_exec(krb5_parse_name_flags, credentials->ctx, sname ? sname : "",
                     KRB5_PRINCIPAL_PARSE_NO_REALM, &principal))
      goto cleanup;

    WINPR_ASSERT(principal);

    if (realm)
    {
      if (krb_log_exec(krb5glue_set_principal_realm, credentials->ctx, principal, realm))
        goto cleanup;
    }

    if (krb_log_exec(krb5_kt_start_seq_get, credentials->ctx, credentials->keytab, &cur))
      goto cleanup;

    do
    {
      krb5_error_code rv = krb_log_exec(krb5_kt_next_entry, credentials->ctx,
                                        credentials->keytab, &entry, &cur);
      if (rv == KRB5_KT_END)
        break;
      if (rv != 0)
        goto cleanup;

      if ((!sname ||
           krb5_principal_compare_any_realm(credentials->ctx, principal, entry.principal)) &&
          (!realm || krb5_realm_compare(credentials->ctx, principal, entry.principal)))
        break;
      const krb5_error_code res =
          krb_log_exec(krb5glue_free_keytab_entry_contents, credentials->ctx, &entry);
      memset(&entry, 0, sizeof(entry));
      if (res != 0)
        goto cleanup;
    } while (1);

    if (krb_log_exec(krb5_kt_end_seq_get, credentials->ctx, credentials->keytab, &cur))
      goto cleanup;

    if (!entry.principal)
      goto cleanup;

    /* Get the TGT */
    if (krb_log_exec(krb5_get_init_creds_keytab, credentials->ctx, &creds, entry.principal,
                     credentials->keytab, 0, NULL, NULL))
      goto cleanup;

    if (!kerberos_mk_tgt_token(output_buffer, KRB_TGT_REP, NULL, NULL, &creds.ticket))
      goto cleanup;

    if (krb_log_exec(krb5_auth_con_init, credentials->ctx, &context->auth_ctx))
      goto cleanup;

    if (krb_log_exec(krb5glue_auth_con_setuseruserkey, credentials->ctx, context->auth_ctx,
                     &krb5glue_creds_getkey(creds)))
      goto cleanup;

    context->state = KERBEROS_STATE_AP_REQ;
  }
  else if (context->state == KERBEROS_STATE_AP_REQ && tok_id == TOK_ID_AP_REQ)
  {
    if (krb_log_exec(krb5_rd_req, credentials->ctx, &context->auth_ctx, &input_token, NULL,
                     credentials->keytab, &ap_flags, NULL))
      goto cleanup;

    if (krb_log_exec(krb5_auth_con_setflags, credentials->ctx, context->auth_ctx,
                     KRB5_AUTH_CONTEXT_DO_SEQUENCE | KRB5_AUTH_CONTEXT_USE_SUBKEY))
      goto cleanup;

    /* Retrieve and validate the checksum */
    if (krb_log_exec(krb5_auth_con_getauthenticator, credentials->ctx, context->auth_ctx,
                     &authenticator))
      goto cleanup;
    if (!krb5glue_authenticator_validate_chksum(authenticator, GSS_CHECKSUM_TYPE,
                                                &context->flags))
      goto bad_token;

    if ((ap_flags & AP_OPTS_MUTUAL_REQUIRED) && (context->flags & SSPI_GSS_C_MUTUAL_FLAG))
    {
      if (!output_buffer)
        goto bad_token;
      if (krb_log_exec(krb5_mk_rep, credentials->ctx, context->auth_ctx, &output_token))
        goto cleanup;
      if (!sspi_gss_wrap_token(output_buffer,
                               context->u2u ? &kerberos_u2u_OID : &kerberos_OID,
                               TOK_ID_AP_REP, &output_token))
        goto cleanup;
    }
    else
    {
      if (output_buffer)
        output_buffer->cbBuffer = 0;
    }

    *pfContextAttr = (context->flags & 0x1F);
    if (context->flags & SSPI_GSS_C_INTEG_FLAG)
      *pfContextAttr |= ASC_RET_INTEGRITY;

    if (context->flags & SSPI_GSS_C_SEQUENCE_FLAG)
    {
      if (krb_log_exec(krb5_auth_con_getlocalseqnumber, credentials->ctx, context->auth_ctx,
                       (INT32*)&context->local_seq))
        goto cleanup;
      if (krb_log_exec(krb5_auth_con_getremoteseqnumber, credentials->ctx, context->auth_ctx,
                       (INT32*)&context->remote_seq))
        goto cleanup;
    }

    if (krb_log_exec(krb5glue_update_keyset, credentials->ctx, context->auth_ctx, TRUE,
                     &context->keyset))
      goto cleanup;

    context->state = KERBEROS_STATE_FINAL;
  }
  else
    goto bad_token;

  /* On first call allocate new context */
  if (context->state == KERBEROS_STATE_FINAL)
    status = SEC_E_OK;
  else
    status = SEC_I_CONTINUE_NEEDED;

cleanup:
  free(target);
  if (output_token.data)
    krb5glue_free_data_contents(credentials->ctx, &output_token);
  if (entry.principal)
    krb5glue_free_keytab_entry_contents(credentials->ctx, &entry);

  if (isNewContext)
  {
    switch (status)
    {
      case SEC_E_OK:
      case SEC_I_CONTINUE_NEEDED:
        sspi_SecureHandleSetLowerPointer(phNewContext, context);
        sspi_SecureHandleSetUpperPointer(phNewContext, KERBEROS_SSP_NAME);
        break;
      default:
        kerberos_ContextFree(context, TRUE);
        break;
    }
  }

  return status;

bad_token:
  status = SEC_E_INVALID_TOKEN;
  goto cleanup;
#else
  return SEC_E_UNSUPPORTED_FUNCTION;
#endif /* WITH_KRB5 */
}

#ifdef WITH_KRB5
static KRB_CONTEXT* get_context(PCtxtHandle phContext)
{
  if (!phContext)
    return NULL;

  TCHAR* name = sspi_SecureHandleGetUpperPointer(phContext);
  if (!name)
    return NULL;

  if (_tcsncmp(KERBEROS_SSP_NAME, name, ARRAYSIZE(KERBEROS_SSP_NAME)) != 0)
    return NULL;
  return sspi_SecureHandleGetLowerPointer(phContext);
}

static BOOL copy_krb5_data(krb5_data* data, PUCHAR* ptr, ULONG* psize)
{
  WINPR_ASSERT(data);
  WINPR_ASSERT(ptr);
  WINPR_ASSERT(psize);

  *ptr = (PUCHAR)malloc(data->length);
  if (!*ptr)
    return FALSE;

  *psize = data->length;
  memcpy(*ptr, data->data, data->length);
  return TRUE;
}
#endif

static SECURITY_STATUS SEC_ENTRY kerberos_DeleteSecurityContext(PCtxtHandle phContext)
{
#ifdef WITH_KRB5
  KRB_CONTEXT* context = get_context(phContext);
  if (!context)
    return SEC_E_INVALID_HANDLE;

  kerberos_ContextFree(context, TRUE);

  return SEC_E_OK;
#else
  return SEC_E_UNSUPPORTED_FUNCTION;
#endif
}

#ifdef WITH_KRB5

static SECURITY_STATUS krb5_error_to_SECURITY_STATUS(krb5_error_code code)
{
  switch (code)
  {
    case 0:
      return SEC_E_OK;
    default:
      return SEC_E_INTERNAL_ERROR;
  }
}

static SECURITY_STATUS kerberos_ATTR_SIZES(KRB_CONTEXT* context, KRB_CREDENTIALS* credentials,
                                           SecPkgContext_Sizes* ContextSizes)
{
  UINT header = 0;
  UINT pad = 0;
  UINT trailer = 0;
  krb5glue_key key = NULL;

  WINPR_ASSERT(context);
  WINPR_ASSERT(context->auth_ctx);

  /* The MaxTokenSize by default is 12,000 bytes. This has been the default value
   * since Windows 2000 SP2 and still remains in Windows 7 and Windows 2008 R2.
   *  For Windows Server 2012, the default value of the MaxTokenSize registry
   *  entry is 48,000 bytes.*/
  ContextSizes->cbMaxToken = KERBEROS_SecPkgInfoA.cbMaxToken;
  ContextSizes->cbMaxSignature = 0;
  ContextSizes->cbBlockSize = 1;
  ContextSizes->cbSecurityTrailer = 0;

  key = get_key(&context->keyset);

  if (context->flags & SSPI_GSS_C_CONF_FLAG)
  {
    krb5_error_code rv = krb_log_exec(krb5glue_crypto_length, credentials->ctx, key,
                                      KRB5_CRYPTO_TYPE_HEADER, &header);
    if (rv)
      return krb5_error_to_SECURITY_STATUS(rv);

    rv = krb_log_exec(krb5glue_crypto_length, credentials->ctx, key, KRB5_CRYPTO_TYPE_PADDING,
                      &pad);
    if (rv)
      return krb5_error_to_SECURITY_STATUS(rv);

    rv = krb_log_exec(krb5glue_crypto_length, credentials->ctx, key, KRB5_CRYPTO_TYPE_TRAILER,
                      &trailer);
    if (rv)
      return krb5_error_to_SECURITY_STATUS(rv);

    /* GSS header (= 16 bytes) + encrypted header = 32 bytes */
    ContextSizes->cbSecurityTrailer = header + pad + trailer + 32;
  }

  if (context->flags & SSPI_GSS_C_INTEG_FLAG)
  {
    krb5_error_code rv = krb_log_exec(krb5glue_crypto_length, credentials->ctx, key,
                                      KRB5_CRYPTO_TYPE_CHECKSUM, &ContextSizes->cbMaxSignature);
    if (rv)
      return krb5_error_to_SECURITY_STATUS(rv);

    ContextSizes->cbMaxSignature += 16;
  }

  return SEC_E_OK;
}

static SECURITY_STATUS kerberos_ATTR_TICKET_LOGON(KRB_CONTEXT* context,
                                                  KRB_CREDENTIALS* credentials,
                                                  KERB_TICKET_LOGON* ticketLogon)
{
  krb5_creds matchCred = { 0 };
  krb5_auth_context authContext = NULL;
  krb5_flags getCredsFlags = KRB5_GC_CACHED;
  BOOL firstRun = TRUE;
  krb5_creds* hostCred = NULL;
  SECURITY_STATUS ret = SEC_E_INSUFFICIENT_MEMORY;
  int rv = krb_log_exec(krb5_sname_to_principal, credentials->ctx, context->targetHost, "HOST",
                        KRB5_NT_SRV_HST, &matchCred.server);
  if (rv)
    goto out;

  rv = krb_log_exec(krb5_cc_get_principal, credentials->ctx, credentials->ccache,
                    &matchCred.client);
  if (rv)
    goto out;

  /* try from the cache first, and then do a new request */
again:
  rv = krb_log_exec(krb5_get_credentials, credentials->ctx, getCredsFlags, credentials->ccache,
                    &matchCred, &hostCred);
  switch (rv)
  {
    case 0:
      break;
    case KRB5_CC_NOTFOUND:
      getCredsFlags = 0;
      if (firstRun)
      {
        firstRun = FALSE;
        goto again;
      }
      WINPR_FALLTHROUGH
    default:
      WLog_ERR(TAG, "krb5_get_credentials(hostCreds), rv=%d", rv);
      goto out;
  }

  if (krb_log_exec(krb5_auth_con_init, credentials->ctx, &authContext))
    goto out;

  krb5_data derOut = { 0 };
  if (krb_log_exec(krb5_fwd_tgt_creds, credentials->ctx, authContext, context->targetHost,
                   matchCred.client, matchCred.server, credentials->ccache, 1, &derOut))
  {
    ret = SEC_E_LOGON_DENIED;
    goto out;
  }

  ticketLogon->MessageType = KerbTicketLogon;
  ticketLogon->Flags = KERB_LOGON_FLAG_REDIRECTED;

  if (!copy_krb5_data(&hostCred->ticket, &ticketLogon->ServiceTicket,
                      &ticketLogon->ServiceTicketLength))
  {
    krb5_free_data(credentials->ctx, &derOut);
    goto out;
  }

  ticketLogon->TicketGrantingTicketLength = derOut.length;
  ticketLogon->TicketGrantingTicket = (PUCHAR)derOut.data;

  ret = SEC_E_OK;
out:
  krb5_auth_con_free(credentials->ctx, authContext);
  krb5_free_creds(credentials->ctx, hostCred);
  krb5_free_cred_contents(credentials->ctx, &matchCred);
  return ret;
}

#endif /* WITH_KRB5 */

static SECURITY_STATUS SEC_ENTRY kerberos_QueryContextAttributesA(PCtxtHandle phContext,
                                                                  ULONG ulAttribute, void* pBuffer)
{
  if (!phContext)
    return SEC_E_INVALID_HANDLE;

  if (!pBuffer)
    return SEC_E_INVALID_PARAMETER;

#ifdef WITH_KRB5
  KRB_CONTEXT* context = get_context(phContext);
  if (!context)
    return SEC_E_INVALID_PARAMETER;

  KRB_CREDENTIALS* credentials = context->credentials;

  switch (ulAttribute)
  {
    case SECPKG_ATTR_SIZES:
      return kerberos_ATTR_SIZES(context, credentials, (SecPkgContext_Sizes*)pBuffer);

    case SECPKG_CRED_ATTR_TICKET_LOGON:
      return kerberos_ATTR_TICKET_LOGON(context, credentials, (KERB_TICKET_LOGON*)pBuffer);

    default:
      WLog_ERR(TAG, "TODO: QueryContextAttributes implement ulAttribute=0x%08" PRIx32,
               ulAttribute);
      return SEC_E_UNSUPPORTED_FUNCTION;
  }
#else
  return SEC_E_UNSUPPORTED_FUNCTION;
#endif
}

static SECURITY_STATUS SEC_ENTRY kerberos_QueryContextAttributesW(PCtxtHandle phContext,
                                                                  ULONG ulAttribute, void* pBuffer)
{
  return kerberos_QueryContextAttributesA(phContext, ulAttribute, pBuffer);
}

static SECURITY_STATUS SEC_ENTRY kerberos_SetContextAttributesW(
    WINPR_ATTR_UNUSED PCtxtHandle phContext, WINPR_ATTR_UNUSED ULONG ulAttribute,
    WINPR_ATTR_UNUSED void* pBuffer, WINPR_ATTR_UNUSED ULONG cbBuffer)
{
  return SEC_E_UNSUPPORTED_FUNCTION;
}

static SECURITY_STATUS SEC_ENTRY kerberos_SetContextAttributesA(
    WINPR_ATTR_UNUSED PCtxtHandle phContext, WINPR_ATTR_UNUSED ULONG ulAttribute,
    WINPR_ATTR_UNUSED void* pBuffer, WINPR_ATTR_UNUSED ULONG cbBuffer)
{
  return SEC_E_UNSUPPORTED_FUNCTION;
}

static SECURITY_STATUS SEC_ENTRY kerberos_SetCredentialsAttributesX(PCredHandle phCredential,
                                                                    ULONG ulAttribute,
                                                                    void* pBuffer, ULONG cbBuffer,
                                                                    WINPR_ATTR_UNUSED BOOL unicode)
{
#ifdef WITH_KRB5
  KRB_CREDENTIALS* credentials = NULL;

  if (!phCredential)
    return SEC_E_INVALID_HANDLE;

  credentials = sspi_SecureHandleGetLowerPointer(phCredential);

  if (!credentials)
    return SEC_E_INVALID_HANDLE;

  if (!pBuffer)
    return SEC_E_INSUFFICIENT_MEMORY;

  switch (ulAttribute)
  {
    case SECPKG_CRED_ATTR_KDC_PROXY_SETTINGS:
    {
      SecPkgCredentials_KdcProxySettingsW* kdc_settings = pBuffer;

      /* Sanity checks */
      if (cbBuffer < sizeof(SecPkgCredentials_KdcProxySettingsW) ||
          kdc_settings->Version != KDC_PROXY_SETTINGS_V1 ||
          kdc_settings->ProxyServerOffset < sizeof(SecPkgCredentials_KdcProxySettingsW) ||
          cbBuffer < sizeof(SecPkgCredentials_KdcProxySettingsW) +
                         kdc_settings->ProxyServerOffset + kdc_settings->ProxyServerLength)
        return SEC_E_INVALID_TOKEN;

      if (credentials->kdc_url)
      {
        free(credentials->kdc_url);
        credentials->kdc_url = NULL;
      }

      if (kdc_settings->ProxyServerLength > 0)
      {
        WCHAR* proxy = (WCHAR*)((BYTE*)pBuffer + kdc_settings->ProxyServerOffset);

        credentials->kdc_url = ConvertWCharNToUtf8Alloc(
            proxy, kdc_settings->ProxyServerLength / sizeof(WCHAR), NULL);
        if (!credentials->kdc_url)
          return SEC_E_INSUFFICIENT_MEMORY;
      }

      return SEC_E_OK;
    }
    case SECPKG_CRED_ATTR_NAMES:
    case SECPKG_ATTR_SUPPORTED_ALGS:
    default:
      WLog_ERR(TAG, "TODO: SetCredentialsAttributesX implement ulAttribute=0x%08" PRIx32,
               ulAttribute);
      return SEC_E_UNSUPPORTED_FUNCTION;
  }

#else
  return SEC_E_UNSUPPORTED_FUNCTION;
#endif
}

static SECURITY_STATUS SEC_ENTRY kerberos_SetCredentialsAttributesW(PCredHandle phCredential,
                                                                    ULONG ulAttribute,
                                                                    void* pBuffer, ULONG cbBuffer)
{
  return kerberos_SetCredentialsAttributesX(phCredential, ulAttribute, pBuffer, cbBuffer, TRUE);
}

static SECURITY_STATUS SEC_ENTRY kerberos_SetCredentialsAttributesA(PCredHandle phCredential,
                                                                    ULONG ulAttribute,
                                                                    void* pBuffer, ULONG cbBuffer)
{
  return kerberos_SetCredentialsAttributesX(phCredential, ulAttribute, pBuffer, cbBuffer, FALSE);
}

static SECURITY_STATUS SEC_ENTRY kerberos_EncryptMessage(PCtxtHandle phContext, ULONG fQOP,
                                                         PSecBufferDesc pMessage,
                                                         ULONG MessageSeqNo)
{
#ifdef WITH_KRB5
  KRB_CONTEXT* context = get_context(phContext);
  PSecBuffer sig_buffer = NULL;
  PSecBuffer data_buffer = NULL;
  char* header = NULL;
  BYTE flags = 0;
  krb5glue_key key = NULL;
  krb5_keyusage usage = 0;
  krb5_crypto_iov encrypt_iov[] = { { KRB5_CRYPTO_TYPE_HEADER, { 0 } },
                                  { KRB5_CRYPTO_TYPE_DATA, { 0 } },
                                  { KRB5_CRYPTO_TYPE_DATA, { 0 } },
                                  { KRB5_CRYPTO_TYPE_PADDING, { 0 } },
                                  { KRB5_CRYPTO_TYPE_TRAILER, { 0 } } };

  if (!context)
    return SEC_E_INVALID_HANDLE;

  if (!(context->flags & SSPI_GSS_C_CONF_FLAG))
    return SEC_E_UNSUPPORTED_FUNCTION;

  KRB_CREDENTIALS* creds = context->credentials;

  sig_buffer = sspi_FindSecBuffer(pMessage, SECBUFFER_TOKEN);
  data_buffer = sspi_FindSecBuffer(pMessage, SECBUFFER_DATA);

  if (!sig_buffer || !data_buffer)
    return SEC_E_INVALID_TOKEN;

  if (fQOP)
    return SEC_E_QOP_NOT_SUPPORTED;

  flags |= context->acceptor ? FLAG_SENDER_IS_ACCEPTOR : 0;
  flags |= FLAG_WRAP_CONFIDENTIAL;

  key = get_key(&context->keyset);
  if (!key)
    return SEC_E_INTERNAL_ERROR;

  flags |= context->keyset.acceptor_key == key ? FLAG_ACCEPTOR_SUBKEY : 0;

  usage = context->acceptor ? KG_USAGE_ACCEPTOR_SEAL : KG_USAGE_INITIATOR_SEAL;

  /* Set the lengths of the data (plaintext + header) */
  encrypt_iov[1].data.length = data_buffer->cbBuffer;
  encrypt_iov[2].data.length = 16;

  /* Get the lengths of the header, trailer, and padding and ensure sig_buffer is large enough */
  if (krb_log_exec(krb5glue_crypto_length_iov, creds->ctx, key, encrypt_iov,
                   ARRAYSIZE(encrypt_iov)))
    return SEC_E_INTERNAL_ERROR;
  if (sig_buffer->cbBuffer <
      encrypt_iov[0].data.length + encrypt_iov[3].data.length + encrypt_iov[4].data.length + 32)
    return SEC_E_INSUFFICIENT_MEMORY;

  /* Set up the iov array in sig_buffer */
  header = sig_buffer->pvBuffer;
  encrypt_iov[2].data.data = header + 16;
  encrypt_iov[3].data.data = encrypt_iov[2].data.data + encrypt_iov[2].data.length;
  encrypt_iov[4].data.data = encrypt_iov[3].data.data + encrypt_iov[3].data.length;
  encrypt_iov[0].data.data = encrypt_iov[4].data.data + encrypt_iov[4].data.length;
  encrypt_iov[1].data.data = data_buffer->pvBuffer;

  /* Write the GSS header with 0 in RRC */
  winpr_Data_Write_UINT16_BE(header, TOK_ID_WRAP);
  header[2] = WINPR_ASSERTING_INT_CAST(char, flags);
  header[3] = (char)0xFF;
  winpr_Data_Write_UINT32(header + 4, 0);
  winpr_Data_Write_UINT64_BE(header + 8, (context->local_seq + MessageSeqNo));

  /* Copy header to be encrypted */
  CopyMemory(encrypt_iov[2].data.data, header, 16);

  /* Set the correct RRC */
  const size_t len = 16 + encrypt_iov[3].data.length + encrypt_iov[4].data.length;
  winpr_Data_Write_UINT16_BE(header + 6, WINPR_ASSERTING_INT_CAST(UINT16, len));

  if (krb_log_exec(krb5glue_encrypt_iov, creds->ctx, key, usage, encrypt_iov,
                   ARRAYSIZE(encrypt_iov)))
    return SEC_E_INTERNAL_ERROR;

  return SEC_E_OK;
#else
  return SEC_E_UNSUPPORTED_FUNCTION;
#endif
}

static SECURITY_STATUS SEC_ENTRY kerberos_DecryptMessage(PCtxtHandle phContext,
                                                         PSecBufferDesc pMessage,
                                                         ULONG MessageSeqNo, ULONG* pfQOP)
{
#ifdef WITH_KRB5
  KRB_CONTEXT* context = get_context(phContext);
  PSecBuffer sig_buffer = NULL;
  PSecBuffer data_buffer = NULL;
  krb5glue_key key = NULL;
  krb5_keyusage usage = 0;
  uint16_t tok_id = 0;
  BYTE flags = 0;
  uint16_t ec = 0;
  uint16_t rrc = 0;
  uint64_t seq_no = 0;
  krb5_crypto_iov iov[] = { { KRB5_CRYPTO_TYPE_HEADER, { 0 } },
                          { KRB5_CRYPTO_TYPE_DATA, { 0 } },
                          { KRB5_CRYPTO_TYPE_DATA, { 0 } },
                          { KRB5_CRYPTO_TYPE_PADDING, { 0 } },
                          { KRB5_CRYPTO_TYPE_TRAILER, { 0 } } };

  if (!context)
    return SEC_E_INVALID_HANDLE;

  if (!(context->flags & SSPI_GSS_C_CONF_FLAG))
    return SEC_E_UNSUPPORTED_FUNCTION;

  KRB_CREDENTIALS* creds = context->credentials;

  sig_buffer = sspi_FindSecBuffer(pMessage, SECBUFFER_TOKEN);
  data_buffer = sspi_FindSecBuffer(pMessage, SECBUFFER_DATA);

  if (!sig_buffer || !data_buffer || sig_buffer->cbBuffer < 16)
    return SEC_E_INVALID_TOKEN;

  /* Read in header information */
  BYTE* header = sig_buffer->pvBuffer;
  tok_id = winpr_Data_Get_UINT16_BE(header);
  flags = header[2];
  ec = winpr_Data_Get_UINT16_BE(&header[4]);
  rrc = winpr_Data_Get_UINT16_BE(&header[6]);
  seq_no = winpr_Data_Get_UINT64_BE(&header[8]);

  /* Check that the header is valid */
  if ((tok_id != TOK_ID_WRAP) || (header[3] != 0xFF))
    return SEC_E_INVALID_TOKEN;

  if ((flags & FLAG_SENDER_IS_ACCEPTOR) == context->acceptor)
    return SEC_E_INVALID_TOKEN;

  if ((context->flags & ISC_REQ_SEQUENCE_DETECT) &&
      (seq_no != context->remote_seq + MessageSeqNo))
    return SEC_E_OUT_OF_SEQUENCE;

  if (!(flags & FLAG_WRAP_CONFIDENTIAL))
    return SEC_E_INVALID_TOKEN;

  /* We don't expect a trailer buffer; the encrypted header must be rotated */
  if (rrc < 16)
    return SEC_E_INVALID_TOKEN;

  /* Find the proper key and key usage */
  key = get_key(&context->keyset);
  if (!key || ((flags & FLAG_ACCEPTOR_SUBKEY) && (context->keyset.acceptor_key != key)))
    return SEC_E_INTERNAL_ERROR;
  usage = context->acceptor ? KG_USAGE_INITIATOR_SEAL : KG_USAGE_ACCEPTOR_SEAL;

  /* Fill in the lengths of the iov array */
  iov[1].data.length = data_buffer->cbBuffer;
  iov[2].data.length = 16;
  if (krb_log_exec(krb5glue_crypto_length_iov, creds->ctx, key, iov, ARRAYSIZE(iov)))
    return SEC_E_INTERNAL_ERROR;

  /* We don't expect a trailer buffer; everything must be in sig_buffer */
  if (rrc != 16 + iov[3].data.length + iov[4].data.length)
    return SEC_E_INVALID_TOKEN;
  if (sig_buffer->cbBuffer != 16 + rrc + iov[0].data.length)
    return SEC_E_INVALID_TOKEN;

  /* Locate the parts of the message */
  iov[0].data.data = (char*)&header[16 + rrc + ec];
  iov[1].data.data = data_buffer->pvBuffer;
  iov[2].data.data = (char*)&header[16 + ec];
  char* data2 = iov[2].data.data;
  iov[3].data.data = &data2[iov[2].data.length];

  char* data3 = iov[3].data.data;
  iov[4].data.data = &data3[iov[3].data.length];

  if (krb_log_exec(krb5glue_decrypt_iov, creds->ctx, key, usage, iov, ARRAYSIZE(iov)))
    return SEC_E_INTERNAL_ERROR;

  /* Validate the encrypted header */
  winpr_Data_Write_UINT16_BE(iov[2].data.data + 4, ec);
  winpr_Data_Write_UINT16_BE(iov[2].data.data + 6, rrc);
  if (memcmp(iov[2].data.data, header, 16) != 0)
    return SEC_E_MESSAGE_ALTERED;

  *pfQOP = 0;

  return SEC_E_OK;
#else
  return SEC_E_UNSUPPORTED_FUNCTION;
#endif
}

static SECURITY_STATUS SEC_ENTRY kerberos_MakeSignature(PCtxtHandle phContext,
                                                        WINPR_ATTR_UNUSED ULONG fQOP,
                                                        PSecBufferDesc pMessage, ULONG MessageSeqNo)
{
#ifdef WITH_KRB5
  KRB_CONTEXT* context = get_context(phContext);
  PSecBuffer sig_buffer = NULL;
  PSecBuffer data_buffer = NULL;
  krb5glue_key key = NULL;
  krb5_keyusage usage = 0;
  BYTE flags = 0;
  krb5_crypto_iov iov[] = { { KRB5_CRYPTO_TYPE_DATA, { 0 } },
                          { KRB5_CRYPTO_TYPE_DATA, { 0 } },
                          { KRB5_CRYPTO_TYPE_CHECKSUM, { 0 } } };

  if (!context)
    return SEC_E_INVALID_HANDLE;

  if (!(context->flags & SSPI_GSS_C_INTEG_FLAG))
    return SEC_E_UNSUPPORTED_FUNCTION;

  KRB_CREDENTIALS* creds = context->credentials;

  sig_buffer = sspi_FindSecBuffer(pMessage, SECBUFFER_TOKEN);
  data_buffer = sspi_FindSecBuffer(pMessage, SECBUFFER_DATA);

  if (!sig_buffer || !data_buffer)
    return SEC_E_INVALID_TOKEN;

  flags |= context->acceptor ? FLAG_SENDER_IS_ACCEPTOR : 0;

  key = get_key(&context->keyset);
  if (!key)
    return SEC_E_INTERNAL_ERROR;
  usage = context->acceptor ? KG_USAGE_ACCEPTOR_SIGN : KG_USAGE_INITIATOR_SIGN;

  flags |= context->keyset.acceptor_key == key ? FLAG_ACCEPTOR_SUBKEY : 0;

  /* Fill in the lengths of the iov array */
  iov[0].data.length = data_buffer->cbBuffer;
  iov[1].data.length = 16;
  if (krb_log_exec(krb5glue_crypto_length_iov, creds->ctx, key, iov, ARRAYSIZE(iov)))
    return SEC_E_INTERNAL_ERROR;

  /* Ensure the buffer is big enough */
  if (sig_buffer->cbBuffer < iov[2].data.length + 16)
    return SEC_E_INSUFFICIENT_MEMORY;

  /* Write the header */
  char* header = sig_buffer->pvBuffer;
  winpr_Data_Write_UINT16_BE(header, TOK_ID_MIC);
  header[2] = WINPR_ASSERTING_INT_CAST(char, flags);
  memset(header + 3, 0xFF, 5);
  winpr_Data_Write_UINT64_BE(header + 8, (context->local_seq + MessageSeqNo));

  /* Set up the iov array */
  iov[0].data.data = data_buffer->pvBuffer;
  iov[1].data.data = header;
  iov[2].data.data = header + 16;

  if (krb_log_exec(krb5glue_make_checksum_iov, creds->ctx, key, usage, iov, ARRAYSIZE(iov)))
    return SEC_E_INTERNAL_ERROR;

  sig_buffer->cbBuffer = iov[2].data.length + 16;

  return SEC_E_OK;
#else
  return SEC_E_UNSUPPORTED_FUNCTION;
#endif
}

static SECURITY_STATUS SEC_ENTRY kerberos_VerifySignature(PCtxtHandle phContext,
                                                          PSecBufferDesc pMessage,
                                                          ULONG MessageSeqNo,
                                                          WINPR_ATTR_UNUSED ULONG* pfQOP)
{
#ifdef WITH_KRB5
  PSecBuffer sig_buffer = NULL;
  PSecBuffer data_buffer = NULL;
  krb5glue_key key = NULL;
  krb5_keyusage usage = 0;
  BYTE flags = 0;
  uint16_t tok_id = 0;
  uint64_t seq_no = 0;
  krb5_boolean is_valid = 0;
  krb5_crypto_iov iov[] = { { KRB5_CRYPTO_TYPE_DATA, { 0 } },
                          { KRB5_CRYPTO_TYPE_DATA, { 0 } },
                          { KRB5_CRYPTO_TYPE_CHECKSUM, { 0 } } };
  BYTE cmp_filler[] = { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF };

  KRB_CONTEXT* context = get_context(phContext);
  if (!context)
    return SEC_E_INVALID_HANDLE;

  if (!(context->flags & SSPI_GSS_C_INTEG_FLAG))
    return SEC_E_UNSUPPORTED_FUNCTION;

  sig_buffer = sspi_FindSecBuffer(pMessage, SECBUFFER_TOKEN);
  data_buffer = sspi_FindSecBuffer(pMessage, SECBUFFER_DATA);

  if (!sig_buffer || !data_buffer || sig_buffer->cbBuffer < 16)
    return SEC_E_INVALID_TOKEN;

  /* Read in header info */
  BYTE* header = sig_buffer->pvBuffer;
  tok_id = winpr_Data_Get_UINT16_BE(header);
  flags = header[2];
  seq_no = winpr_Data_Get_UINT64_BE((header + 8));

  /* Validate header */
  if (tok_id != TOK_ID_MIC)
    return SEC_E_INVALID_TOKEN;

  if ((flags & FLAG_SENDER_IS_ACCEPTOR) == context->acceptor || flags & FLAG_WRAP_CONFIDENTIAL)
    return SEC_E_INVALID_TOKEN;

  if (memcmp(header + 3, cmp_filler, sizeof(cmp_filler)) != 0)
    return SEC_E_INVALID_TOKEN;

  if (context->flags & ISC_REQ_SEQUENCE_DETECT && seq_no != context->remote_seq + MessageSeqNo)
    return SEC_E_OUT_OF_SEQUENCE;

  /* Find the proper key and usage */
  key = get_key(&context->keyset);
  if (!key || (flags & FLAG_ACCEPTOR_SUBKEY && context->keyset.acceptor_key != key))
    return SEC_E_INTERNAL_ERROR;
  usage = context->acceptor ? KG_USAGE_INITIATOR_SIGN : KG_USAGE_ACCEPTOR_SIGN;

  /* Fill in the iov array lengths */
  KRB_CREDENTIALS* creds = context->credentials;
  iov[0].data.length = data_buffer->cbBuffer;
  iov[1].data.length = 16;
  if (krb_log_exec(krb5glue_crypto_length_iov, creds->ctx, key, iov, ARRAYSIZE(iov)))
    return SEC_E_INTERNAL_ERROR;

  if (sig_buffer->cbBuffer != iov[2].data.length + 16)
    return SEC_E_INTERNAL_ERROR;

  /* Set up the iov array */
  iov[0].data.data = data_buffer->pvBuffer;
  iov[1].data.data = (char*)header;
  iov[2].data.data = (char*)&header[16];

  if (krb_log_exec(krb5glue_verify_checksum_iov, creds->ctx, key, usage, iov, ARRAYSIZE(iov),
                   &is_valid))
    return SEC_E_INTERNAL_ERROR;

  if (!is_valid)
    return SEC_E_MESSAGE_ALTERED;

  return SEC_E_OK;
#else
  return SEC_E_UNSUPPORTED_FUNCTION;
#endif
}

const SecurityFunctionTableA KERBEROS_SecurityFunctionTableA = {
  3,                                    /* dwVersion */
  NULL,                                 /* EnumerateSecurityPackages */
  kerberos_QueryCredentialsAttributesA, /* QueryCredentialsAttributes */
  kerberos_AcquireCredentialsHandleA,   /* AcquireCredentialsHandle */
  kerberos_FreeCredentialsHandle,       /* FreeCredentialsHandle */
  NULL,                                 /* Reserved2 */
  kerberos_InitializeSecurityContextA,  /* InitializeSecurityContext */
  kerberos_AcceptSecurityContext,       /* AcceptSecurityContext */
  NULL,                                 /* CompleteAuthToken */
  kerberos_DeleteSecurityContext,       /* DeleteSecurityContext */
  NULL,                                 /* ApplyControlToken */
  kerberos_QueryContextAttributesA,     /* QueryContextAttributes */
  NULL,                                 /* ImpersonateSecurityContext */
  NULL,                                 /* RevertSecurityContext */
  kerberos_MakeSignature,               /* MakeSignature */
  kerberos_VerifySignature,             /* VerifySignature */
  NULL,                                 /* FreeContextBuffer */
  NULL,                                 /* QuerySecurityPackageInfo */
  NULL,                                 /* Reserved3 */
  NULL,                                 /* Reserved4 */
  NULL,                                 /* ExportSecurityContext */
  NULL,                                 /* ImportSecurityContext */
  NULL,                                 /* AddCredentials */
  NULL,                                 /* Reserved8 */
  NULL,                                 /* QuerySecurityContextToken */
  kerberos_EncryptMessage,              /* EncryptMessage */
  kerberos_DecryptMessage,              /* DecryptMessage */
  kerberos_SetContextAttributesA,       /* SetContextAttributes */
  kerberos_SetCredentialsAttributesA,   /* SetCredentialsAttributes */
};

const SecurityFunctionTableW KERBEROS_SecurityFunctionTableW = {
  3,                                    /* dwVersion */
  NULL,                                 /* EnumerateSecurityPackages */
  kerberos_QueryCredentialsAttributesW, /* QueryCredentialsAttributes */
  kerberos_AcquireCredentialsHandleW,   /* AcquireCredentialsHandle */
  kerberos_FreeCredentialsHandle,       /* FreeCredentialsHandle */
  NULL,                                 /* Reserved2 */
  kerberos_InitializeSecurityContextW,  /* InitializeSecurityContext */
  kerberos_AcceptSecurityContext,       /* AcceptSecurityContext */
  NULL,                                 /* CompleteAuthToken */
  kerberos_DeleteSecurityContext,       /* DeleteSecurityContext */
  NULL,                                 /* ApplyControlToken */
  kerberos_QueryContextAttributesW,     /* QueryContextAttributes */
  NULL,                                 /* ImpersonateSecurityContext */
  NULL,                                 /* RevertSecurityContext */
  kerberos_MakeSignature,               /* MakeSignature */
  kerberos_VerifySignature,             /* VerifySignature */
  NULL,                                 /* FreeContextBuffer */
  NULL,                                 /* QuerySecurityPackageInfo */
  NULL,                                 /* Reserved3 */
  NULL,                                 /* Reserved4 */
  NULL,                                 /* ExportSecurityContext */
  NULL,                                 /* ImportSecurityContext */
  NULL,                                 /* AddCredentials */
  NULL,                                 /* Reserved8 */
  NULL,                                 /* QuerySecurityContextToken */
  kerberos_EncryptMessage,              /* EncryptMessage */
  kerberos_DecryptMessage,              /* DecryptMessage */
  kerberos_SetContextAttributesW,       /* SetContextAttributes */
  kerberos_SetCredentialsAttributesW,   /* SetCredentialsAttributes */
};

BOOL KERBEROS_init(void)
{
  InitializeConstWCharFromUtf8(KERBEROS_SecPkgInfoA.Name, KERBEROS_SecPkgInfoW_NameBuffer,
                               ARRAYSIZE(KERBEROS_SecPkgInfoW_NameBuffer));
  InitializeConstWCharFromUtf8(KERBEROS_SecPkgInfoA.Comment, KERBEROS_SecPkgInfoW_CommentBuffer,
                               ARRAYSIZE(KERBEROS_SecPkgInfoW_CommentBuffer));
  return TRUE;
}

Coverage Report

Created: 2025-07-01 06:46