/*

 *   This program is free software; you can redistribute it and/or modify

 *   it under the terms of the GNU General Public License as published by

 *   the Free Software Foundation; either version 2 of the License, or

 *   (at your option) any later version.

 *

 *   This program is distributed in the hope that it will be useful,

 *   but WITHOUT ANY WARRANTY; without even the implied warranty of

 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 *   GNU General Public License for more details.

 *

 *   You should have received a copy of the GNU General Public License

 *   along with this program; if not, write to the Free Software

 *   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA

 */

/**

 * $Id: f028b9c59d8bff5438bc19d23ad3d4067952a811 $

 *

 * @file tls/verify.c

 * @brief Expose certificate OIDs as attributes, and call validation virtual

 *  server to check cert is valid.

 *

 * @copyright 2001 hereUare Communications, Inc. (raghud@hereuare.com)

 * @copyright 2003 Alan DeKok (aland@freeradius.org)

 * @copyright 2006-2016 The FreeRADIUS server project

 */

#ifdef WITH_TLS

#define LOG_PREFIX "tls"

#include <freeradius-devel/server/exec.h>

#include <freeradius-devel/server/pair.h>

#include <freeradius-devel/tls/log.h>

#include <freeradius-devel/unlang/function.h>

#include <freeradius-devel/unlang/subrequest.h>

#include <freeradius-devel/util/debug.h>

#include <freeradius-devel/util/strerror.h>

#include <freeradius-devel/util/syserror.h>

#include "attrs.h"

#include "base.h"

/** Check to see if a verification operation should apply to a certificate

 *

 * @param[in] depth starting at 0.

 *      Certificate 0 is the leaf cert (i.e. the client or server cert);

 * @param[in] untrusted The number of untrusted certificates.

 * @param[in] mode  to check

 * @return

 *  - true if a given validation check should apply.

 **     - false if a validation check should not apply.

 */

static inline CC_HINT(always_inline)

bool verify_applies(fr_tls_verify_mode_t mode, int depth, int untrusted)

{

  if (mode == FR_TLS_VERIFY_MODE_ALL) return true;

  if (mode == FR_TLS_VERIFY_MODE_DISABLED) return false;

  if ((mode & FR_TLS_VERIFY_MODE_LEAF) && (depth == 0)) return true;

  if ((mode & FR_TLS_VERIFY_MODE_ISSUER) && (depth == 1)) return true;

  if ((mode & FR_TLS_VERIFY_MODE_UNTRUSTED) && (depth < untrusted)) return true;

  return false;

}

DIAG_OFF(DIAG_UNKNOWN_PRAGMAS)

DIAG_OFF(used-but-marked-unused)  /* fix spurious warnings for sk macros */

/** Print verbose humanly readable messages about why certificate validation failed

 *

 */

static void tls_verify_error_detail(request_t *request, SSL_CTX *ctx, int err)

{

  X509_STORE  *store = SSL_CTX_get_ex_data(ctx, FR_TLS_EX_CTX_INDEX_VERIFY_STORE);

  switch (err) {

  /*

   *  We linked the provided cert to at least one

   *  other in a chain, but the chain doesn't terminate

   *  in a root CA.

   */

  case X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT:

    FALL_THROUGH;

  /*

   *  We failed to link the provided cert to any

   *  other local certificates in the chain.

   */

  case X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT_LOCALLY:

    RDEBUG2("Static certificates in verification store are");

    if (RDEBUG_ENABLED2) {

      RINDENT();

      fr_tls_x509_objects_log(request, L_DBG, X509_STORE_get0_objects(store));

      REXDENT();

    }

    break;

  default:

    break;

  }

}

/** Validates a certificate using custom logic

 *

 * Before trusting a certificate, we make sure that the certificate is

 * 'valid'. There are several checks we perform to verify its validity.

 *

 *   1. Verify the certificate's signature, and verifying that the certificate has

 *      been issued by a trusted Certificate Authority (this is done for us by OpenSSL).

 *

 *   2. Verify that the certificate is valid for the present date (i.e. it is being

 *      presented within its validity dates).

 *

 *   3. Verify that the certificate has not been revoked by its issuing Certificate

 *      Authority, by checking with respect to a Certificate Revocation List (CRL).

 *

 * @note This callback will be called multiple times based on the depth of the root

 *  certificate chain.

 *

 * @note As a byproduct of validation, various OIDs will be extracted from the

 *  certificates, and inserted into the session-state list as fr_pair_t.

 *

 * @param ok    preverify ok.  1 if true, 0 if false.

 * @param x509_ctx  containing certs to verify.

 * @return

 *  - 0 if not valid.

 *  - 1 if valid.

 */

int fr_tls_verify_cert_cb(int ok, X509_STORE_CTX *x509_ctx)

{

  X509      *cert;

  SSL_CTX     *ssl_ctx;

  SSL     *ssl;

  fr_tls_session_t  *tls_session;

  int     err, depth;

  fr_tls_conf_t   *conf;

  int     my_ok = ok;

  int     untrusted;

  request_t   *request;

  fr_pair_t   *container = NULL;

  fr_pair_t   *depth_pair;

  cert = X509_STORE_CTX_get_current_cert(x509_ctx);

  err = X509_STORE_CTX_get_error(x509_ctx);

  depth = X509_STORE_CTX_get_error_depth(x509_ctx);

  untrusted = X509_STORE_CTX_get_num_untrusted(x509_ctx);

  /*

   *  Retrieve the pointer to the SSL of the connection currently treated

   *  and the application specific data stored into the SSL object.

   */

  ssl = X509_STORE_CTX_get_ex_data(x509_ctx, SSL_get_ex_data_X509_STORE_CTX_idx());

  ssl_ctx = SSL_get_SSL_CTX(ssl);

  conf = fr_tls_session_conf(ssl);

  tls_session = talloc_get_type_abort(SSL_get_ex_data(ssl, FR_TLS_EX_INDEX_TLS_SESSION), fr_tls_session_t);

  request = fr_tls_session_request(tls_session->ssl);

  /*

   *  If this error appears it suggests

   *  that OpenSSL is trying to perform post-handshake

   *  certificate validation which we don't support.

   */

  if (!tls_session->can_pause) {

    fr_assert_msg("Unexpected call to %s. "

            "tls_session_async_handshake_cont must be in call stack", __FUNCTION__);

    return 0;

  }

  /*

   *  Bail out as quickly as possible, producing

   *  as few errors as possible.

   */

  if (unlang_request_is_cancelled(request)) {

    X509_STORE_CTX_set_error(x509_ctx, 0);

    return 1;

  }

  /*

   *  Find or add the chain depth attribute and record the greatest depth we see + 1,

   *  as depth is zero based.

   */

  if (unlikely(fr_pair_find_or_append_by_da(request->session_state_ctx, &depth_pair, &request->session_state_pairs,

           attr_tls_certificate_chain_depth) < 0)) {

    RERROR("Failed to add certificate chain depth pair");

    return 0;

  }

  if (depth_pair->vp_uint32 < ((uint32_t)depth) + 1) depth_pair->vp_uint32 = (uint32_t)depth + 1;

  if (RDEBUG_ENABLED3) {

    char    subject[2048];

    STACK_OF(X509)  *our_chain;

    int   i;

    our_chain = X509_STORE_CTX_get0_chain(x509_ctx);

    RDEBUG3("Certificate chain - %i cert(s) untrusted", untrusted);

    for (i = sk_X509_num(our_chain); i > 0 ; i--) {

      X509 *this_cert = sk_X509_value(our_chain, i - 1);

      X509_NAME_oneline(X509_get_subject_name(this_cert), subject, sizeof(subject));

      subject[sizeof(subject) - 1] = '\0';

      RDEBUG3("%s [%i] %s", this_cert == cert ? ">" : " ", i - 1, subject);

    }

  }

  /*

   *  See if the user has disabled verification for

   *      this certificate.  If they have, force verification

   *  to succeed.

   */

  if (!my_ok) {

    char const *p = X509_verify_cert_error_string(err);

    if (!verify_applies(conf->verify.mode, depth, untrusted)) {

      RDEBUG2("Ignoring verification error - %s (%i)", p, err);

      tls_verify_error_detail(request, ssl_ctx, err);

      my_ok = 1;

      X509_STORE_CTX_set_error(x509_ctx, 0);

    } else {

      RERROR("Verification error - %s (%i)", p, err);

      tls_verify_error_detail(request, ssl_ctx, err);

      goto done;

    }

  }

  if (verify_applies(conf->verify.attribute_mode, depth, untrusted) &&

      (!(container = fr_pair_find_by_da_idx(&request->session_state_pairs, attr_tls_certificate, depth)) ||

       fr_pair_list_empty(&container->vp_group))) {

        if (!container) {

              unsigned int i;

      /*

       *  Build a stack of container attributes.

       *

       *  OpenSSL passes us the deepest certificate

       *      first, so we need to build out sufficient

       *      TLS-Certificate container TLVs so the TLS-Certificate

       *  indexes match the attribute depth.

       */

      for (i = fr_pair_count_by_da(&request->session_state_pairs, attr_tls_certificate);

           i <= (unsigned int)depth;

           i++) {

        MEM(container = fr_pair_afrom_da(request->session_state_ctx, attr_tls_certificate));

        fr_pair_append(&request->session_state_pairs, container);

      }

        }

#ifdef STATIC_ANALYZER

    /*

     *  Container can never be NULL, because if container

     *  was previously NULL, i will be <= depth.

     */

    if (!fr_cond_assert(container)) {

      my_ok = 0;

      goto done;

    }

#endif

    /*

     *  If we fail to populate the cert attributes,

     *  trash all instances in the session-state list

     *  and cause validation to fail.

     */

    if (fr_tls_session_pairs_from_x509_cert(&container->vp_group, container,

              request, cert, conf->verify.der_decode) < 0) {

      fr_pair_delete_by_da(&request->session_state_pairs, attr_tls_certificate);

      if (conf->verify.der_decode) {

        fr_pair_delete_by_da(&request->session_state_pairs, attr_der_certificate);

      }

      my_ok = 0;

      goto done;

    }

    log_request_pair(L_DBG_LVL_2, request, NULL, container, "session-state.");

  }

done:

  /*

   *  If verification hasn't already failed

   *  and we're meant to verify this cert

   *  then call the virtual server.

   *

   *  We only call the virtual server for

   *      the certificate at depth 0 as all

   *      other certificate attributes should

   *  have been added by this point.

   */

  if (my_ok && (depth == 0)) {

    if (conf->verify_certificate && tls_session->verify_client_cert) {

      RDEBUG2("Requesting certificate validation");

      /*

       *  This sets the validation state of the tls_session

       *  so that when we call ASYNC_pause_job(), and execution

       *  jumps back to tls_session_async_handshake_cont

       *  (just under SSL_read())

       *  the code there knows what job it needs to push onto

       *  the unlang stack.

       */

      fr_tls_verify_cert_request(tls_session, SSL_session_reused(tls_session->ssl));

      /*

       *  Jumps back to SSL_read() in session.c

       *

       *  Be aware that if the request is cancelled

       *  whatever was meant to be done during the

       *  time we yielded may not have been completed.

       */

      ASYNC_pause_job();

      /*

       *  Just try and bail out as quickly as possible.

       */

      if (unlang_request_is_cancelled(request)) {

        X509_STORE_CTX_set_error(x509_ctx, 0);

        fr_tls_verify_cert_reset(tls_session);

        return 1;

      }

      /*

       *  If we couldn't validate the certificate

       *  then validation overall fails.

       */

      if (!fr_tls_verify_cert_result(tls_session)) {

        REDEBUG("Certificate validation failed");

        my_ok = 0;

        X509_STORE_CTX_set_error(x509_ctx, X509_V_ERR_APPLICATION_VERIFICATION);

      }

    }

  }

  tls_session->client_cert_ok = (my_ok > 0);

  RDEBUG2("[verify] = %s", my_ok ? "ok" : "invalid");

  return my_ok;

}

DIAG_ON(used-but-marked-unused)

DIAG_ON(DIAG_UNKNOWN_PRAGMAS)

/** Revalidates the client's certificate chain

 *

 * Wraps the fr_tls_verify_cert_cb callback, allowing us to use the same

 * validation logic whenever we need to.

 *

 * @note Only use so far is forcing the chain to be re-validated on session

 *  resumption.

 *

 * @return

 *  - 1 if the chain could be validated.

 *  - 0 if the chain failed validation.

 */

int fr_tls_verify_cert_chain(request_t *request, SSL *ssl)

{

  int   err;

  int   verify;

  int   ret = 1;

  SSL_CTX   *ssl_ctx;

  STACK_OF(X509)  *chain;

  X509    *cert;

  X509_STORE  *store;

  X509_STORE_CTX  *store_ctx;

  /*

   *  If there's no client certificate, we just return OK.

   */

  cert = SSL_get0_peer_certificate(ssl);      /* Does not increase ref count */

  if (!cert) return 1;

  ssl_ctx = SSL_get_SSL_CTX(ssl);

  store_ctx = X509_STORE_CTX_new();

  chain = SSL_get_peer_cert_chain(ssl);     /* Does not increase ref count */

  store = SSL_CTX_get_ex_data(ssl_ctx, FR_TLS_EX_CTX_INDEX_VERIFY_STORE);  /* Gets the verification store */

  /*

   *  This sets up a store_ctx for doing peer certificate verification.

   *

   *  store_ctx - Is the ctx to initialise

   *  store   - Is an X509_STORE of implicitly

   *        trusted certificates.  Here we're using

   *        the verify store that was created when we

   *        allocated the SSL_CTX.

   *  cert    - Is the certificate to validate.

   *  chain   - Is any other certificates the peer provided

   *        us in order to build a chain from a trusted

   *            root or intermediary to its leaf (cert).

   *

   *  Note: SSL_CTX_get_cert_store() returns the ctx->cert_store, which

   *      is not the same as the verification cert store.

   */

  X509_STORE_CTX_init(store_ctx, store, cert, chain);

  X509_STORE_CTX_set_ex_data(store_ctx, SSL_get_ex_data_X509_STORE_CTX_idx(), ssl);

  X509_STORE_CTX_set_verify_cb(store_ctx, fr_tls_verify_cert_cb);

  verify = X509_verify_cert(store_ctx);

  if (verify != 1) {

    err = X509_STORE_CTX_get_error(store_ctx);

    if (err != X509_V_OK) {

      REDEBUG("Failed re-validating resumed session: %s", X509_verify_cert_error_string(err));

      ret = 0;

    }

  }

  X509_STORE_CTX_free(store_ctx);

  return ret;

}

/** Process the result of `verify certificate { ... }`

 *

 */

static unlang_action_t tls_verify_client_cert_result(request_t *request, void *uctx)

{

  fr_tls_session_t  *tls_session = talloc_get_type_abort(uctx, fr_tls_session_t);

  fr_pair_t   *vp, *next;

  fr_assert(tls_session->validate.state == FR_TLS_VALIDATION_REQUESTED);

  vp = fr_pair_find_by_da(&request->reply_pairs, NULL, attr_tls_packet_type);

  if (!vp || (vp->vp_uint32 != enum_tls_packet_type_success->vb_uint32)) {

    REDEBUG("Failed (re-)validating certificates");

    /*

     *  Hoist any instances of Module-Failure-Message from the subrequest

     *  so they can be used for logging failures.

     */

    vp = fr_pair_find_by_da(&request->request_pairs, NULL, attr_module_failure_message);

    while (vp && request->parent) {

      next = fr_pair_find_by_da(&request->request_pairs, vp, attr_module_failure_message);

      fr_pair_remove(&request->request_pairs, vp);

      fr_pair_steal_append(request->parent->request_ctx, &request->parent->request_pairs, vp);

      vp = next;

    }

    tls_session->validate.state = FR_TLS_VALIDATION_FAILED;

    return UNLANG_ACTION_CALCULATE_RESULT;

  }

  tls_session->validate.state = FR_TLS_VALIDATION_SUCCESS;

  RDEBUG2("Certificates (re-)validated");

  return UNLANG_ACTION_CALCULATE_RESULT;

}

/** Push a `verify certificate { ... }` call into the current request, using a subrequest

 *

 * @param[in] request   The current request.

 * @param[in] tls_session The current TLS session.

 * @return

 *      - UNLANG_ACTION_CALCULATE_RESULT on noop.

 *  - UNLANG_ACTION_PUSHED_CHILD on success.

 *      - UNLANG_ACTION_FAIL on failure.

 */

static unlang_action_t tls_verify_client_cert_push(request_t *request, fr_tls_session_t *tls_session)

{

  fr_tls_conf_t   *conf = fr_tls_session_conf(tls_session->ssl);

  request_t   *child;

  fr_pair_t   *vp;

  unlang_action_t   ua;

  MEM(child = unlang_subrequest_alloc(request, dict_tls));

  request = child;

  /*

   *  Add extra pairs to the subrequest

   */

  fr_tls_session_extra_pairs_copy_to_child(child, tls_session);

  /*

   *  Setup the child request for loading

   *  session resumption data.

   */

  MEM(pair_prepend_request(&vp, attr_tls_packet_type) >= 0);

  vp->vp_uint32 = enum_tls_packet_type_verify_certificate->vb_uint32;

  /*

   *  Copy certificate pairs to the child session state

   */

  vp = NULL;

  while ((vp = fr_pair_find_by_da(&request->parent->session_state_pairs, vp, attr_tls_certificate))) {

    fr_pair_append(&request->session_state_pairs, fr_pair_copy(request->session_state_ctx, vp));

  }

  if (conf->verify.der_decode) {

    while ((vp = fr_pair_find_by_da(&request->parent->session_state_pairs, vp, attr_der_certificate))) {

      fr_pair_append(&request->session_state_pairs, fr_pair_copy(request->session_state_ctx, vp));

    }

  }

  MEM(pair_append_request(&vp, attr_tls_session_resumed) >= 0);

  vp->vp_bool = tls_session->validate.resumed;

  /*

   *  Allocate a child, and set it up to call

   *      the TLS virtual server.

   */

  ua = fr_tls_call_push(child, tls_verify_client_cert_result, conf, tls_session, false);

  if (ua < 0) {

          PERROR("Failed calling TLS virtual server");

    talloc_free(child);

    return UNLANG_ACTION_FAIL;

  }

  return ua;

}

/** Clear any previous validation result

 *

 * Should be called by the validation requestor to get the result and reset

 * the validation state.

 *

 * @return

 *  - true if the certificate chain was validated.

 *  - false if the certificate chain failed validation.

 */

bool fr_tls_verify_cert_result(fr_tls_session_t *tls_session)

{

  bool result;

  fr_assert(tls_session->validate.state != FR_TLS_VALIDATION_INIT);

  result = tls_session->validate.state == FR_TLS_VALIDATION_SUCCESS;

  tls_session->validate.state = FR_TLS_VALIDATION_INIT;

  tls_session->validate.resumed = false;

  return result;

}

/** Reset the verification state

 *

 */

void fr_tls_verify_cert_reset(fr_tls_session_t *tls_session)

{

  tls_session->validate.state = FR_TLS_VALIDATION_INIT;

  tls_session->validate.resumed  = false;

}

/** Setup a verification request

 *

 */

void fr_tls_verify_cert_request(fr_tls_session_t *tls_session, bool session_resumed)

{

  fr_assert(tls_session->validate.state == FR_TLS_VALIDATION_INIT);

  tls_session->validate.state = FR_TLS_VALIDATION_REQUESTED;

  tls_session->validate.resumed = session_resumed;

}

/** Push a `verify certificate { ... }` section

 *

 * @param[in] request   The current request.

 * @param[in] tls_session The current TLS session.

 * @return

 *  - UNLANG_ACTION_CALCULATE_RESULT  - No pending actions

 *  - UNLANG_ACTION_PUSHED_CHILD    - Pending operations to evaluate.

 */

unlang_action_t fr_tls_verify_cert_pending_push(request_t *request, fr_tls_session_t *tls_session)

{

  if (tls_session->validate.state == FR_TLS_VALIDATION_REQUESTED) {

    return tls_verify_client_cert_push(request, tls_session);

  }

  return UNLANG_ACTION_CALCULATE_RESULT;

}

#endif /* WITH_TLS */