/src/openssh/sshsig.c

Source (jump to first uncovered line)
/* $OpenBSD: sshsig.c,v 1.32 2023/04/06 03:56:02 djm Exp $ */
/*
 * Copyright (c) 2019 Google LLC
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include "includes.h"

#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>

#include "authfd.h"
#include "authfile.h"
#include "log.h"
#include "misc.h"
#include "sshbuf.h"
#include "sshsig.h"
#include "ssherr.h"
#include "sshkey.h"
#include "match.h"
#include "digest.h"

#define SIG_VERSION   0x01
#define MAGIC_PREAMBLE    "SSHSIG"
#define MAGIC_PREAMBLE_LEN  (sizeof(MAGIC_PREAMBLE) - 1)
#define BEGIN_SIGNATURE   "-----BEGIN SSH SIGNATURE-----\n"
#define END_SIGNATURE   "-----END SSH SIGNATURE-----"
#define RSA_SIGN_ALG    "rsa-sha2-512" /* XXX maybe make configurable */
#define RSA_SIGN_ALLOWED  "rsa-sha2-512,rsa-sha2-256"
#define HASHALG_DEFAULT   "sha512" /* XXX maybe make configurable */
#define HASHALG_ALLOWED   "sha256,sha512"

int
sshsig_armor(const struct sshbuf *blob, struct sshbuf **out)
{
  struct sshbuf *buf = NULL;
  int r = SSH_ERR_INTERNAL_ERROR;

  *out = NULL;

  if ((buf = sshbuf_new()) == NULL) {
    error_f("sshbuf_new failed");
    r = SSH_ERR_ALLOC_FAIL;
    goto out;
  }

  if ((r = sshbuf_put(buf, BEGIN_SIGNATURE,
      sizeof(BEGIN_SIGNATURE)-1)) != 0) {
    error_fr(r, "sshbuf_putf");
    goto out;
  }

  if ((r = sshbuf_dtob64(blob, buf, 1)) != 0) {
    error_fr(r, "base64 encode signature");
    goto out;
  }

  if ((r = sshbuf_put(buf, END_SIGNATURE,
      sizeof(END_SIGNATURE)-1)) != 0 ||
      (r = sshbuf_put_u8(buf, '\n')) != 0) {
    error_fr(r, "sshbuf_put");
    goto out;
  }
  /* success */
  *out = buf;
  buf = NULL; /* transferred */
  r = 0;
 out:
  sshbuf_free(buf);
  return r;
}

int
sshsig_dearmor(struct sshbuf *sig, struct sshbuf **out)
{
  int r;
  size_t eoffset = 0;
  struct sshbuf *buf = NULL;
  struct sshbuf *sbuf = NULL;
  char *b64 = NULL;

  if ((sbuf = sshbuf_fromb(sig)) == NULL) {
    error_f("sshbuf_fromb failed");
    return SSH_ERR_ALLOC_FAIL;
  }

  if ((r = sshbuf_cmp(sbuf, 0,
      BEGIN_SIGNATURE, sizeof(BEGIN_SIGNATURE)-1)) != 0) {
    error("Couldn't parse signature: missing header");
    goto done;
  }

  if ((r = sshbuf_consume(sbuf, sizeof(BEGIN_SIGNATURE)-1)) != 0) {
    error_fr(r, "consume");
    goto done;
  }

  if ((r = sshbuf_find(sbuf, 0, "\n" END_SIGNATURE,
      sizeof("\n" END_SIGNATURE)-1, &eoffset)) != 0) {
    error("Couldn't parse signature: missing footer");
    goto done;
  }

  if ((r = sshbuf_consume_end(sbuf, sshbuf_len(sbuf)-eoffset)) != 0) {
    error_fr(r, "consume");
    goto done;
  }

  if ((b64 = sshbuf_dup_string(sbuf)) == NULL) {
    error_f("sshbuf_dup_string failed");
    r = SSH_ERR_ALLOC_FAIL;
    goto done;
  }

  if ((buf = sshbuf_new()) == NULL) {
    error_f("sshbuf_new() failed");
    r = SSH_ERR_ALLOC_FAIL;
    goto done;
  }

  if ((r = sshbuf_b64tod(buf, b64)) != 0) {
    error_fr(r, "decode base64");
    goto done;
  }

  /* success */
  *out = buf;
  r = 0;
  buf = NULL; /* transferred */
done:
  sshbuf_free(buf);
  sshbuf_free(sbuf);
  free(b64);
  return r;
}

static int
sshsig_wrap_sign(struct sshkey *key, const char *hashalg,
    const char *sk_provider, const char *sk_pin, const struct sshbuf *h_message,
    const char *sig_namespace, struct sshbuf **out,
    sshsig_signer *signer, void *signer_ctx)
{
  int r;
  size_t slen = 0;
  u_char *sig = NULL;
  struct sshbuf *blob = NULL;
  struct sshbuf *tosign = NULL;
  const char *sign_alg = NULL;

  if ((tosign = sshbuf_new()) == NULL ||
      (blob = sshbuf_new()) == NULL) {
    error_f("sshbuf_new failed");
    r = SSH_ERR_ALLOC_FAIL;
    goto done;
  }

  if ((r = sshbuf_put(tosign, MAGIC_PREAMBLE, MAGIC_PREAMBLE_LEN)) != 0 ||
      (r = sshbuf_put_cstring(tosign, sig_namespace)) != 0 ||
      (r = sshbuf_put_string(tosign, NULL, 0)) != 0 || /* reserved */
      (r = sshbuf_put_cstring(tosign, hashalg)) != 0 ||
      (r = sshbuf_put_stringb(tosign, h_message)) != 0) {
    error_fr(r, "assemble message to sign");
    goto done;
  }

  /* If using RSA keys then default to a good signature algorithm */
  if (sshkey_type_plain(key->type) == KEY_RSA)
    sign_alg = RSA_SIGN_ALG;

  if (signer != NULL) {
    if ((r = signer(key, &sig, &slen,
        sshbuf_ptr(tosign), sshbuf_len(tosign),
        sign_alg, sk_provider, sk_pin, 0, signer_ctx)) != 0) {
      error_r(r, "Couldn't sign message (signer)");
      goto done;
    }
  } else {
    if ((r = sshkey_sign(key, &sig, &slen,
        sshbuf_ptr(tosign), sshbuf_len(tosign),
        sign_alg, sk_provider, sk_pin, 0)) != 0) {
      error_r(r, "Couldn't sign message");
      goto done;
    }
  }

  if ((r = sshbuf_put(blob, MAGIC_PREAMBLE, MAGIC_PREAMBLE_LEN)) != 0 ||
      (r = sshbuf_put_u32(blob, SIG_VERSION)) != 0 ||
      (r = sshkey_puts(key, blob)) != 0 ||
      (r = sshbuf_put_cstring(blob, sig_namespace)) != 0 ||
      (r = sshbuf_put_string(blob, NULL, 0)) != 0 || /* reserved */
      (r = sshbuf_put_cstring(blob, hashalg)) != 0 ||
      (r = sshbuf_put_string(blob, sig, slen)) != 0) {
    error_fr(r, "assemble signature object");
    goto done;
  }

  if (out != NULL) {
    *out = blob;
    blob = NULL;
  }
  r = 0;
done:
  free(sig);
  sshbuf_free(blob);
  sshbuf_free(tosign);
  return r;
}

/* Check preamble and version. */
static int
sshsig_parse_preamble(struct sshbuf *buf)
{
  int r = SSH_ERR_INTERNAL_ERROR;
  uint32_t sversion;

  if ((r = sshbuf_cmp(buf, 0, MAGIC_PREAMBLE, MAGIC_PREAMBLE_LEN)) != 0 ||
      (r = sshbuf_consume(buf, (sizeof(MAGIC_PREAMBLE)-1))) != 0 ||
      (r = sshbuf_get_u32(buf, &sversion)) != 0) {
    error("Couldn't verify signature: invalid format");
    return r;
  }

  if (sversion > SIG_VERSION) {
    error("Signature version %lu is larger than supported "
        "version %u", (unsigned long)sversion, SIG_VERSION);
    return SSH_ERR_INVALID_FORMAT;
  }
  return 0;
}

static int
sshsig_check_hashalg(const char *hashalg)
{
  if (hashalg == NULL ||
      match_pattern_list(hashalg, HASHALG_ALLOWED, 0) == 1)
    return 0;
  error_f("unsupported hash algorithm \"%.100s\"", hashalg);
  return SSH_ERR_SIGN_ALG_UNSUPPORTED;
}

static int
sshsig_peek_hashalg(struct sshbuf *signature, char **hashalgp)
{
  struct sshbuf *buf = NULL;
  char *hashalg = NULL;
  int r = SSH_ERR_INTERNAL_ERROR;

  if (hashalgp != NULL)
    *hashalgp = NULL;
  if ((buf = sshbuf_fromb(signature)) == NULL)
    return SSH_ERR_ALLOC_FAIL;
  if ((r = sshsig_parse_preamble(buf)) != 0)
    goto done;
  if ((r = sshbuf_get_string_direct(buf, NULL, NULL)) != 0 ||
      (r = sshbuf_get_string_direct(buf, NULL, NULL)) != 0 ||
      (r = sshbuf_get_string(buf, NULL, NULL)) != 0 ||
      (r = sshbuf_get_cstring(buf, &hashalg, NULL)) != 0 ||
      (r = sshbuf_get_string_direct(buf, NULL, NULL)) != 0) {
    error_fr(r, "parse signature object");
    goto done;
  }

  /* success */
  r = 0;
  *hashalgp = hashalg;
  hashalg = NULL;
 done:
  free(hashalg);
  sshbuf_free(buf);
  return r;
}

static int
sshsig_wrap_verify(struct sshbuf *signature, const char *hashalg,
    const struct sshbuf *h_message, const char *expect_namespace,
    struct sshkey **sign_keyp, struct sshkey_sig_details **sig_details)
{
  int r = SSH_ERR_INTERNAL_ERROR;
  struct sshbuf *buf = NULL, *toverify = NULL;
  struct sshkey *key = NULL;
  const u_char *sig;
  char *got_namespace = NULL, *sigtype = NULL, *sig_hashalg = NULL;
  size_t siglen;

  debug_f("verify message length %zu", sshbuf_len(h_message));
  if (sig_details != NULL)
    *sig_details = NULL;
  if (sign_keyp != NULL)
    *sign_keyp = NULL;

  if ((toverify = sshbuf_new()) == NULL) {
    error_f("sshbuf_new failed");
    r = SSH_ERR_ALLOC_FAIL;
    goto done;
  }
  if ((r = sshbuf_put(toverify, MAGIC_PREAMBLE,
      MAGIC_PREAMBLE_LEN)) != 0 ||
      (r = sshbuf_put_cstring(toverify, expect_namespace)) != 0 ||
      (r = sshbuf_put_string(toverify, NULL, 0)) != 0 || /* reserved */
      (r = sshbuf_put_cstring(toverify, hashalg)) != 0 ||
      (r = sshbuf_put_stringb(toverify, h_message)) != 0) {
    error_fr(r, "assemble message to verify");
    goto done;
  }

  if ((r = sshsig_parse_preamble(signature)) != 0)
    goto done;

  if ((r = sshkey_froms(signature, &key)) != 0 ||
      (r = sshbuf_get_cstring(signature, &got_namespace, NULL)) != 0 ||
      (r = sshbuf_get_string(signature, NULL, NULL)) != 0 ||
      (r = sshbuf_get_cstring(signature, &sig_hashalg, NULL)) != 0 ||
      (r = sshbuf_get_string_direct(signature, &sig, &siglen)) != 0) {
    error_fr(r, "parse signature object");
    goto done;
  }

  if (sshbuf_len(signature) != 0) {
    error("Signature contains trailing data");
    r = SSH_ERR_INVALID_FORMAT;
    goto done;
  }

  if (strcmp(expect_namespace, got_namespace) != 0) {
    error("Couldn't verify signature: namespace does not match");
    debug_f("expected namespace \"%s\" received \"%s\"",
        expect_namespace, got_namespace);
    r = SSH_ERR_SIGNATURE_INVALID;
    goto done;
  }
  if (strcmp(hashalg, sig_hashalg) != 0) {
    error("Couldn't verify signature: hash algorithm mismatch");
    debug_f("expected algorithm \"%s\" received \"%s\"",
        hashalg, sig_hashalg);
    r = SSH_ERR_SIGNATURE_INVALID;
    goto done;
  }
  /* Ensure that RSA keys use an acceptable signature algorithm */
  if (sshkey_type_plain(key->type) == KEY_RSA) {
    if ((r = sshkey_get_sigtype(sig, siglen, &sigtype)) != 0) {
      error_r(r, "Couldn't verify signature: unable to get "
          "signature type");
      goto done;
    }
    if (match_pattern_list(sigtype, RSA_SIGN_ALLOWED, 0) != 1) {
      error("Couldn't verify signature: unsupported RSA "
          "signature algorithm %s", sigtype);
      r = SSH_ERR_SIGN_ALG_UNSUPPORTED;
      goto done;
    }
  }
  if ((r = sshkey_verify(key, sig, siglen, sshbuf_ptr(toverify),
      sshbuf_len(toverify), NULL, 0, sig_details)) != 0) {
    error_r(r, "Signature verification failed");
    goto done;
  }

  /* success */
  r = 0;
  if (sign_keyp != NULL) {
    *sign_keyp = key;
    key = NULL; /* transferred */
  }
done:
  free(got_namespace);
  free(sigtype);
  free(sig_hashalg);
  sshbuf_free(buf);
  sshbuf_free(toverify);
  sshkey_free(key);
  return r;
}

static int
hash_buffer(const struct sshbuf *m, const char *hashalg, struct sshbuf **bp)
{
  char *hex, hash[SSH_DIGEST_MAX_LENGTH];
  int alg, r = SSH_ERR_INTERNAL_ERROR;
  struct sshbuf *b = NULL;

  *bp = NULL;
  memset(hash, 0, sizeof(hash));

  if ((r = sshsig_check_hashalg(hashalg)) != 0)
    return r;
  if ((alg = ssh_digest_alg_by_name(hashalg)) == -1) {
    error_f("can't look up hash algorithm %s", hashalg);
    return SSH_ERR_INTERNAL_ERROR;
  }
  if ((r = ssh_digest_buffer(alg, m, hash, sizeof(hash))) != 0) {
    error_fr(r, "ssh_digest_buffer");
    return r;
  }
  if ((hex = tohex(hash, ssh_digest_bytes(alg))) != NULL) {
    debug3_f("final hash: %s", hex);
    freezero(hex, strlen(hex));
  }
  if ((b = sshbuf_new()) == NULL) {
    r = SSH_ERR_ALLOC_FAIL;
    goto out;
  }
  if ((r = sshbuf_put(b, hash, ssh_digest_bytes(alg))) != 0) {
    error_fr(r, "sshbuf_put");
    goto out;
  }
  *bp = b;
  b = NULL; /* transferred */
  /* success */
  r = 0;
 out:
  sshbuf_free(b);
  explicit_bzero(hash, sizeof(hash));
  return r;
}

int
sshsig_signb(struct sshkey *key, const char *hashalg,
    const char *sk_provider, const char *sk_pin,
    const struct sshbuf *message, const char *sig_namespace,
    struct sshbuf **out, sshsig_signer *signer, void *signer_ctx)
{
  struct sshbuf *b = NULL;
  int r = SSH_ERR_INTERNAL_ERROR;

  if (hashalg == NULL)
    hashalg = HASHALG_DEFAULT;
  if (out != NULL)
    *out = NULL;
  if ((r = hash_buffer(message, hashalg, &b)) != 0) {
    error_fr(r, "hash buffer");
    goto out;
  }
  if ((r = sshsig_wrap_sign(key, hashalg, sk_provider, sk_pin, b,
      sig_namespace, out, signer, signer_ctx)) != 0)
    goto out;
  /* success */
  r = 0;
 out:
  sshbuf_free(b);
  return r;
}

int
sshsig_verifyb(struct sshbuf *signature, const struct sshbuf *message,
    const char *expect_namespace, struct sshkey **sign_keyp,
    struct sshkey_sig_details **sig_details)
{
  struct sshbuf *b = NULL;
  int r = SSH_ERR_INTERNAL_ERROR;
  char *hashalg = NULL;

  if (sig_details != NULL)
    *sig_details = NULL;
  if (sign_keyp != NULL)
    *sign_keyp = NULL;
  if ((r = sshsig_peek_hashalg(signature, &hashalg)) != 0)
    return r;
  debug_f("signature made with hash \"%s\"", hashalg);
  if ((r = hash_buffer(message, hashalg, &b)) != 0) {
    error_fr(r, "hash buffer");
    goto out;
  }
  if ((r = sshsig_wrap_verify(signature, hashalg, b, expect_namespace,
      sign_keyp, sig_details)) != 0)
    goto out;
  /* success */
  r = 0;
 out:
  sshbuf_free(b);
  free(hashalg);
  return r;
}

static int
hash_file(int fd, const char *hashalg, struct sshbuf **bp)
{
  char *hex, rbuf[8192], hash[SSH_DIGEST_MAX_LENGTH];
  ssize_t n, total = 0;
  struct ssh_digest_ctx *ctx = NULL;
  int alg, oerrno, r = SSH_ERR_INTERNAL_ERROR;
  struct sshbuf *b = NULL;

  *bp = NULL;
  memset(hash, 0, sizeof(hash));

  if ((r = sshsig_check_hashalg(hashalg)) != 0)
    return r;
  if ((alg = ssh_digest_alg_by_name(hashalg)) == -1) {
    error_f("can't look up hash algorithm %s", hashalg);
    return SSH_ERR_INTERNAL_ERROR;
  }
  if ((ctx = ssh_digest_start(alg)) == NULL) {
    error_f("ssh_digest_start failed");
    return SSH_ERR_INTERNAL_ERROR;
  }
  for (;;) {
    if ((n = read(fd, rbuf, sizeof(rbuf))) == -1) {
      if (errno == EINTR || errno == EAGAIN)
        continue;
      oerrno = errno;
      error_f("read: %s", strerror(errno));
      errno = oerrno;
      r = SSH_ERR_SYSTEM_ERROR;
      goto out;
    } else if (n == 0) {
      debug2_f("hashed %zu bytes", total);
      break; /* EOF */
    }
    total += (size_t)n;
    if ((r = ssh_digest_update(ctx, rbuf, (size_t)n)) != 0) {
      error_fr(r, "ssh_digest_update");
      goto out;
    }
  }
  if ((r = ssh_digest_final(ctx, hash, sizeof(hash))) != 0) {
    error_fr(r, "ssh_digest_final");
    goto out;
  }
  if ((hex = tohex(hash, ssh_digest_bytes(alg))) != NULL) {
    debug3_f("final hash: %s", hex);
    freezero(hex, strlen(hex));
  }
  if ((b = sshbuf_new()) == NULL) {
    r = SSH_ERR_ALLOC_FAIL;
    goto out;
  }
  if ((r = sshbuf_put(b, hash, ssh_digest_bytes(alg))) != 0) {
    error_fr(r, "sshbuf_put");
    goto out;
  }
  *bp = b;
  b = NULL; /* transferred */
  /* success */
  r = 0;
 out:
  oerrno = errno;
  sshbuf_free(b);
  ssh_digest_free(ctx);
  explicit_bzero(hash, sizeof(hash));
  errno = oerrno;
  return r;
}

int
sshsig_sign_fd(struct sshkey *key, const char *hashalg,
    const char *sk_provider, const char *sk_pin,
    int fd, const char *sig_namespace, struct sshbuf **out,
    sshsig_signer *signer, void *signer_ctx)
{
  struct sshbuf *b = NULL;
  int r = SSH_ERR_INTERNAL_ERROR;

  if (hashalg == NULL)
    hashalg = HASHALG_DEFAULT;
  if (out != NULL)
    *out = NULL;
  if ((r = hash_file(fd, hashalg, &b)) != 0) {
    error_fr(r, "hash_file");
    return r;
  }
  if ((r = sshsig_wrap_sign(key, hashalg, sk_provider, sk_pin, b,
      sig_namespace, out, signer, signer_ctx)) != 0)
    goto out;
  /* success */
  r = 0;
 out:
  sshbuf_free(b);
  return r;
}

int
sshsig_verify_fd(struct sshbuf *signature, int fd,
    const char *expect_namespace, struct sshkey **sign_keyp,
    struct sshkey_sig_details **sig_details)
{
  struct sshbuf *b = NULL;
  int r = SSH_ERR_INTERNAL_ERROR;
  char *hashalg = NULL;

  if (sig_details != NULL)
    *sig_details = NULL;
  if (sign_keyp != NULL)
    *sign_keyp = NULL;
  if ((r = sshsig_peek_hashalg(signature, &hashalg)) != 0)
    return r;
  debug_f("signature made with hash \"%s\"", hashalg);
  if ((r = hash_file(fd, hashalg, &b)) != 0) {
    error_fr(r, "hash_file");
    goto out;
  }
  if ((r = sshsig_wrap_verify(signature, hashalg, b, expect_namespace,
      sign_keyp, sig_details)) != 0)
    goto out;
  /* success */
  r = 0;
 out:
  sshbuf_free(b);
  free(hashalg);
  return r;
}

struct sshsigopt {
  int ca;
  char *namespaces;
  uint64_t valid_after, valid_before;
};

struct sshsigopt *
sshsigopt_parse(const char *opts, const char *path, u_long linenum,
    const char **errstrp)
{
  struct sshsigopt *ret;
  int r;
  char *opt;
  const char *errstr = NULL;

  if ((ret = calloc(1, sizeof(*ret))) == NULL)
    return NULL;
  if (opts == NULL || *opts == '\0')
    return ret; /* Empty options yields empty options :) */

  while (*opts && *opts != ' ' && *opts != '\t') {
    /* flag options */
    if ((r = opt_flag("cert-authority", 0, &opts)) != -1) {
      ret->ca = 1;
    } else if (opt_match(&opts, "namespaces")) {
      if (ret->namespaces != NULL) {
        errstr = "multiple \"namespaces\" clauses";
        goto fail;
      }
      ret->namespaces = opt_dequote(&opts, &errstr);
      if (ret->namespaces == NULL)
        goto fail;
    } else if (opt_match(&opts, "valid-after")) {
      if (ret->valid_after != 0) {
        errstr = "multiple \"valid-after\" clauses";
        goto fail;
      }
      if ((opt = opt_dequote(&opts, &errstr)) == NULL)
        goto fail;
      if (parse_absolute_time(opt, &ret->valid_after) != 0 ||
          ret->valid_after == 0) {
        free(opt);
        errstr = "invalid \"valid-after\" time";
        goto fail;
      }
      free(opt);
    } else if (opt_match(&opts, "valid-before")) {
      if (ret->valid_before != 0) {
        errstr = "multiple \"valid-before\" clauses";
        goto fail;
      }
      if ((opt = opt_dequote(&opts, &errstr)) == NULL)
        goto fail;
      if (parse_absolute_time(opt, &ret->valid_before) != 0 ||
          ret->valid_before == 0) {
        free(opt);
        errstr = "invalid \"valid-before\" time";
        goto fail;
      }
      free(opt);
    }
    /*
     * Skip the comma, and move to the next option
     * (or break out if there are no more).
     */
    if (*opts == '\0' || *opts == ' ' || *opts == '\t')
      break;    /* End of options. */
    /* Anything other than a comma is an unknown option */
    if (*opts != ',') {
      errstr = "unknown key option";
      goto fail;
    }
    opts++;
    if (*opts == '\0') {
      errstr = "unexpected end-of-options";
      goto fail;
    }
  }
  /* final consistency check */
  if (ret->valid_after != 0 && ret->valid_before != 0 &&
      ret->valid_before <= ret->valid_after) {
    errstr = "\"valid-before\" time is before \"valid-after\"";
    goto fail;
  }
  /* success */
  return ret;
 fail:
  if (errstrp != NULL)
    *errstrp = errstr;
  sshsigopt_free(ret);
  return NULL;
}

void
sshsigopt_free(struct sshsigopt *opts)
{
  if (opts == NULL)
    return;
  free(opts->namespaces);
  free(opts);
}

static int
parse_principals_key_and_options(const char *path, u_long linenum, char *line,
    const char *required_principal, char **principalsp, struct sshkey **keyp,
    struct sshsigopt **sigoptsp)
{
  char *opts = NULL, *tmp, *cp, *principals = NULL;
  const char *reason = NULL;
  struct sshsigopt *sigopts = NULL;
  struct sshkey *key = NULL;
  int r = SSH_ERR_INTERNAL_ERROR;

  if (principalsp != NULL)
    *principalsp = NULL;
  if (sigoptsp != NULL)
    *sigoptsp = NULL;
  if (keyp != NULL)
    *keyp = NULL;

  cp = line;
  cp = cp + strspn(cp, " \t"); /* skip leading whitespace */
  if (*cp == '#' || *cp == '\0')
    return SSH_ERR_KEY_NOT_FOUND; /* blank or all-comment line */

  /* format: identity[,identity...] [option[,option...]] key */
  if ((tmp = strdelimw(&cp)) == NULL || cp == NULL) {
    error("%s:%lu: invalid line", path, linenum);
    r = SSH_ERR_INVALID_FORMAT;
    goto out;
  }
  if ((principals = strdup(tmp)) == NULL) {
    error_f("strdup failed");
    r = SSH_ERR_ALLOC_FAIL;
    goto out;
  }
  /*
   * Bail out early if we're looking for a particular principal and this
   * line does not list it.
   */
  if (required_principal != NULL) {
    if (match_pattern_list(required_principal,
        principals, 0) != 1) {
      /* principal didn't match */
      r = SSH_ERR_KEY_NOT_FOUND;
      goto out;
    }
    debug_f("%s:%lu: matched principal \"%s\"",
        path, linenum, required_principal);
  }

  if ((key = sshkey_new(KEY_UNSPEC)) == NULL) {
    error_f("sshkey_new failed");
    r = SSH_ERR_ALLOC_FAIL;
    goto out;
  }
  if (sshkey_read(key, &cp) != 0) {
    /* no key? Check for options */
    opts = cp;
    if (sshkey_advance_past_options(&cp) != 0) {
      error("%s:%lu: invalid options", path, linenum);
      r = SSH_ERR_INVALID_FORMAT;
      goto out;
    }
    if (cp == NULL || *cp == '\0') {
      error("%s:%lu: missing key", path, linenum);
      r = SSH_ERR_INVALID_FORMAT;
      goto out;
    }
    *cp++ = '\0';
    skip_space(&cp);
    if (sshkey_read(key, &cp) != 0) {
      error("%s:%lu: invalid key", path, linenum);
      r = SSH_ERR_INVALID_FORMAT;
      goto out;
    }
  }
  debug3("%s:%lu: options %s", path, linenum, opts == NULL ? "" : opts);
  if ((sigopts = sshsigopt_parse(opts, path, linenum, &reason)) == NULL) {
    error("%s:%lu: bad options: %s", path, linenum, reason);
    r = SSH_ERR_INVALID_FORMAT;
    goto out;
  }
  /* success */
  if (principalsp != NULL) {
    *principalsp = principals;
    principals = NULL; /* transferred */
  }
  if (sigoptsp != NULL) {
    *sigoptsp = sigopts;
    sigopts = NULL; /* transferred */
  }
  if (keyp != NULL) {
    *keyp = key;
    key = NULL; /* transferred */
  }
  r = 0;
 out:
  free(principals);
  sshsigopt_free(sigopts);
  sshkey_free(key);
  return r;
}

static int
cert_filter_principals(const char *path, u_long linenum,
    char **principalsp, const struct sshkey *cert, uint64_t verify_time)
{
  char *cp, *oprincipals, *principals;
  const char *reason;
  struct sshbuf *nprincipals;
  int r = SSH_ERR_INTERNAL_ERROR, success = 0;
  u_int i;

  oprincipals = principals = *principalsp;
  *principalsp = NULL;

  if ((nprincipals = sshbuf_new()) == NULL) {
    r = SSH_ERR_ALLOC_FAIL;
    goto out;
  }

  while ((cp = strsep(&principals, ",")) != NULL && *cp != '\0') {
    /* Check certificate validity */
    if ((r = sshkey_cert_check_authority(cert, 0, 1, 0,
        verify_time, NULL, &reason)) != 0) {
      debug("%s:%lu: principal \"%s\" not authorized: %s",
          path, linenum, cp, reason);
      continue;
    }
    /* Return all matching principal names from the cert */
    for (i = 0; i < cert->cert->nprincipals; i++) {
      if (match_pattern(cert->cert->principals[i], cp)) {
        if ((r = sshbuf_putf(nprincipals, "%s%s",
          sshbuf_len(nprincipals) != 0 ? "," : "",
            cert->cert->principals[i])) != 0) {
          error_f("buffer error");
          goto out;
        }
      }
    }
  }
  if (sshbuf_len(nprincipals) == 0) {
    error("%s:%lu: no valid principals found", path, linenum);
    r = SSH_ERR_KEY_CERT_INVALID;
    goto out;
  }
  if ((principals = sshbuf_dup_string(nprincipals)) == NULL) {
    error_f("buffer error");
    goto out;
  }
  /* success */
  success = 1;
  *principalsp = principals;
 out:
  sshbuf_free(nprincipals);
  free(oprincipals);
  return success ? 0 : r;
}

static int
check_allowed_keys_line(const char *path, u_long linenum, char *line,
    const struct sshkey *sign_key, const char *principal,
    const char *sig_namespace, uint64_t verify_time, char **principalsp)
{
  struct sshkey *found_key = NULL;
  char *principals = NULL;
  int r, success = 0;
  const char *reason = NULL;
  struct sshsigopt *sigopts = NULL;
  char tvalid[64], tverify[64];

  if (principalsp != NULL)
    *principalsp = NULL;

  /* Parse the line */
  if ((r = parse_principals_key_and_options(path, linenum, line,
      principal, &principals, &found_key, &sigopts)) != 0) {
    /* error already logged */
    goto done;
  }

  if (!sigopts->ca && sshkey_equal(found_key, sign_key)) {
    /* Exact match of key */
    debug("%s:%lu: matched key", path, linenum);
  } else if (sigopts->ca && sshkey_is_cert(sign_key) &&
      sshkey_equal_public(sign_key->cert->signature_key, found_key)) {
    if (principal) {
      /* Match certificate CA key with specified principal */
      if ((r = sshkey_cert_check_authority(sign_key, 0, 1, 0,
          verify_time, principal, &reason)) != 0) {
        error("%s:%lu: certificate not authorized: %s",
            path, linenum, reason);
        goto done;
      }
      debug("%s:%lu: matched certificate CA key",
          path, linenum);
    } else {
      /* No principal specified - find all matching ones */
      if ((r = cert_filter_principals(path, linenum,
          &principals, sign_key, verify_time)) != 0) {
        /* error already displayed */
        debug_r(r, "%s:%lu: cert_filter_principals",
            path, linenum);
        goto done;
      }
      debug("%s:%lu: matched certificate CA key",
          path, linenum);
    }
  } else {
    /* Didn't match key */
    goto done;
  }

  /* Check whether options preclude the use of this key */
  if (sigopts->namespaces != NULL && sig_namespace != NULL &&
      match_pattern_list(sig_namespace, sigopts->namespaces, 0) != 1) {
    error("%s:%lu: key is not permitted for use in signature "
        "namespace \"%s\"", path, linenum, sig_namespace);
    goto done;
  }

  /* check key time validity */
  format_absolute_time((uint64_t)verify_time, tverify, sizeof(tverify));
  if (sigopts->valid_after != 0 &&
      (uint64_t)verify_time < sigopts->valid_after) {
    format_absolute_time(sigopts->valid_after,
        tvalid, sizeof(tvalid));
    error("%s:%lu: key is not yet valid: "
        "verify time %s < valid-after %s", path, linenum,
        tverify, tvalid);
    goto done;
  }
  if (sigopts->valid_before != 0 &&
      (uint64_t)verify_time > sigopts->valid_before) {
    format_absolute_time(sigopts->valid_before,
        tvalid, sizeof(tvalid));
    error("%s:%lu: key has expired: "
        "verify time %s > valid-before %s", path, linenum,
        tverify, tvalid);
    goto done;
  }
  success = 1;

 done:
  if (success && principalsp != NULL) {
    *principalsp = principals;
    principals = NULL; /* transferred */
  }
  free(principals);
  sshkey_free(found_key);
  sshsigopt_free(sigopts);
  return success ? 0 : SSH_ERR_KEY_NOT_FOUND;
}

int
sshsig_check_allowed_keys(const char *path, const struct sshkey *sign_key,
    const char *principal, const char *sig_namespace, uint64_t verify_time)
{
  FILE *f = NULL;
  char *line = NULL;
  size_t linesize = 0;
  u_long linenum = 0;
  int r = SSH_ERR_KEY_NOT_FOUND, oerrno;

  /* Check key and principal against file */
  if ((f = fopen(path, "r")) == NULL) {
    oerrno = errno;
    error("Unable to open allowed keys file \"%s\": %s",
        path, strerror(errno));
    errno = oerrno;
    return SSH_ERR_SYSTEM_ERROR;
  }

  while (getline(&line, &linesize, f) != -1) {
    linenum++;
    r = check_allowed_keys_line(path, linenum, line, sign_key,
        principal, sig_namespace, verify_time, NULL);
    free(line);
    line = NULL;
    linesize = 0;
    if (r == SSH_ERR_KEY_NOT_FOUND)
      continue;
    else if (r == 0) {
      /* success */
      fclose(f);
      return 0;
    } else
      break;
  }
  /* Either we hit an error parsing or we simply didn't find the key */
  fclose(f);
  free(line);
  return r;
}

int
sshsig_find_principals(const char *path, const struct sshkey *sign_key,
    uint64_t verify_time, char **principals)
{
  FILE *f = NULL;
  char *line = NULL;
  size_t linesize = 0;
  u_long linenum = 0;
  int r = SSH_ERR_KEY_NOT_FOUND, oerrno;

  if ((f = fopen(path, "r")) == NULL) {
    oerrno = errno;
    error("Unable to open allowed keys file \"%s\": %s",
        path, strerror(errno));
    errno = oerrno;
    return SSH_ERR_SYSTEM_ERROR;
  }

  while (getline(&line, &linesize, f) != -1) {
    linenum++;
    r = check_allowed_keys_line(path, linenum, line,
        sign_key, NULL, NULL, verify_time, principals);
    free(line);
    line = NULL;
    linesize = 0;
    if (r == SSH_ERR_KEY_NOT_FOUND)
      continue;
    else if (r == 0) {
      /* success */
      fclose(f);
      return 0;
    } else
      break;
  }
  free(line);
  /* Either we hit an error parsing or we simply didn't find the key */
  if (ferror(f) != 0) {
    oerrno = errno;
    fclose(f);
    error("Unable to read allowed keys file \"%s\": %s",
        path, strerror(errno));
    errno = oerrno;
    return SSH_ERR_SYSTEM_ERROR;
  }
  fclose(f);
  return r;
}

int
sshsig_match_principals(const char *path, const char *principal,
    char ***principalsp, size_t *nprincipalsp)
{
  FILE *f = NULL;
  char *found, *line = NULL, **principals = NULL, **tmp;
  size_t i, nprincipals = 0, linesize = 0;
  u_long linenum = 0;
  int oerrno = 0, r, ret = 0;

  if (principalsp != NULL)
    *principalsp = NULL;
  if (nprincipalsp != NULL)
    *nprincipalsp = 0;

  /* Check key and principal against file */
  if ((f = fopen(path, "r")) == NULL) {
    oerrno = errno;
    error("Unable to open allowed keys file \"%s\": %s",
        path, strerror(errno));
    errno = oerrno;
    return SSH_ERR_SYSTEM_ERROR;
  }

  while (getline(&line, &linesize, f) != -1) {
    linenum++;
    /* Parse the line */
    if ((r = parse_principals_key_and_options(path, linenum, line,
        principal, &found, NULL, NULL)) != 0) {
      if (r == SSH_ERR_KEY_NOT_FOUND)
        continue;
      ret = r;
      oerrno = errno;
      break; /* unexpected error */
    }
    if ((tmp = recallocarray(principals, nprincipals,
        nprincipals + 1, sizeof(*principals))) == NULL) {
      ret = SSH_ERR_ALLOC_FAIL;
      free(found);
      break;
    }
    principals = tmp;
    principals[nprincipals++] = found; /* transferred */
    free(line);
    line = NULL;
    linesize = 0;
  }
  fclose(f);

  if (ret == 0) {
    if (nprincipals == 0)
      ret = SSH_ERR_KEY_NOT_FOUND;
    if (principalsp != NULL) {
      *principalsp = principals;
      principals = NULL; /* transferred */
    }
    if (nprincipalsp != 0) {
      *nprincipalsp = nprincipals;
      nprincipals = 0;
    }
  }

  for (i = 0; i < nprincipals; i++)
    free(principals[i]);
  free(principals);

  errno = oerrno;
  return ret;
}

int
sshsig_get_pubkey(struct sshbuf *signature, struct sshkey **pubkey)
{
  struct sshkey *pk = NULL;
  int r = SSH_ERR_SIGNATURE_INVALID;

  if (pubkey == NULL)
    return SSH_ERR_INTERNAL_ERROR;
  if ((r = sshsig_parse_preamble(signature)) != 0)
    return r;
  if ((r = sshkey_froms(signature, &pk)) != 0)
    return r;

  *pubkey = pk;
  pk = NULL;
  return 0;
}

Coverage Report

Created: 2023-06-07 07:08