/src/openssh/hostfile.c

Source
/* $OpenBSD: hostfile.c,v 1.100 2025/11/25 00:57:04 djm Exp $ */
/*
 * Author: Tatu Ylonen <ylo@cs.hut.fi>
 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
 *                    All rights reserved
 * Functions for manipulating the known hosts files.
 *
 * As far as I am concerned, the code I have written for this software
 * can be used freely for any purpose.  Any derived versions of this
 * software must be clearly marked as such, and if the derived work is
 * incompatible with the protocol description in the RFC file, it must be
 * called by a name other than "ssh" or "Secure Shell".
 *
 *
 * Copyright (c) 1999, 2000 Markus Friedl.  All rights reserved.
 * Copyright (c) 1999 Niels Provos.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "includes.h"

#include <sys/types.h>
#include <sys/stat.h>

#include <netinet/in.h>

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

#include "xmalloc.h"
#include "match.h"
#include "sshkey.h"
#include "hostfile.h"
#include "log.h"
#include "misc.h"
#include "pathnames.h"
#include "ssherr.h"
#include "digest.h"
#include "hmac.h"
#include "sshbuf.h"

/* XXX hmac is too easy to dictionary attack; use bcrypt? */

static int
extract_salt(const char *s, u_int l, u_char *salt, size_t salt_len)
{
  char *p, *b64salt;
  u_int b64len;
  int ret;

  if (l < sizeof(HASH_MAGIC) - 1) {
    debug2("extract_salt: string too short");
    return (-1);
  }
  if (strncmp(s, HASH_MAGIC, sizeof(HASH_MAGIC) - 1) != 0) {
    debug2("extract_salt: invalid magic identifier");
    return (-1);
  }
  s += sizeof(HASH_MAGIC) - 1;
  l -= sizeof(HASH_MAGIC) - 1;
  if ((p = memchr(s, HASH_DELIM, l)) == NULL) {
    debug2("extract_salt: missing salt termination character");
    return (-1);
  }

  b64len = p - s;
  /* Sanity check */
  if (b64len == 0 || b64len > 1024) {
    debug2("extract_salt: bad encoded salt length %u", b64len);
    return (-1);
  }
  b64salt = xmalloc(1 + b64len);
  memcpy(b64salt, s, b64len);
  b64salt[b64len] = '\0';

  ret = __b64_pton(b64salt, salt, salt_len);
  free(b64salt);
  if (ret == -1) {
    debug2("extract_salt: salt decode error");
    return (-1);
  }
  if (ret != (int)ssh_hmac_bytes(SSH_DIGEST_SHA1)) {
    debug2("extract_salt: expected salt len %zd, got %d",
        ssh_hmac_bytes(SSH_DIGEST_SHA1), ret);
    return (-1);
  }

  return (0);
}

char *
host_hash(const char *host, const char *name_from_hostfile, u_int src_len)
{
  struct ssh_hmac_ctx *ctx;
  u_char salt[256], result[256];
  char uu_salt[512], uu_result[512];
  char *encoded = NULL;
  u_int len;

  len = ssh_digest_bytes(SSH_DIGEST_SHA1);

  if (name_from_hostfile == NULL) {
    /* Create new salt */
    arc4random_buf(salt, len);
  } else {
    /* Extract salt from known host entry */
    if (extract_salt(name_from_hostfile, src_len, salt,
        sizeof(salt)) == -1)
      return (NULL);
  }

  if ((ctx = ssh_hmac_start(SSH_DIGEST_SHA1)) == NULL ||
      ssh_hmac_init(ctx, salt, len) < 0 ||
      ssh_hmac_update(ctx, host, strlen(host)) < 0 ||
      ssh_hmac_final(ctx, result, sizeof(result)))
    fatal_f("ssh_hmac failed");
  ssh_hmac_free(ctx);

  if (__b64_ntop(salt, len, uu_salt, sizeof(uu_salt)) == -1 ||
      __b64_ntop(result, len, uu_result, sizeof(uu_result)) == -1)
    fatal_f("__b64_ntop failed");
  xasprintf(&encoded, "%s%s%c%s", HASH_MAGIC, uu_salt, HASH_DELIM,
      uu_result);

  return (encoded);
}

/*
 * Parses an RSA key from a string. Moves the pointer over the key.
 * Skips any whitespace at the beginning and at end.
 */

int
hostfile_read_key(char **cpp, u_int *bitsp, struct sshkey *ret)
{
  char *cp;

  /* Skip leading whitespace. */
  for (cp = *cpp; *cp == ' ' || *cp == '\t'; cp++)
    ;

  if (sshkey_read(ret, &cp) != 0)
    return 0;

  /* Skip trailing whitespace. */
  for (; *cp == ' ' || *cp == '\t'; cp++)
    ;

  /* Return results. */
  *cpp = cp;
  if (bitsp != NULL)
    *bitsp = sshkey_size(ret);
  return 1;
}

static HostkeyMarker
check_markers(char **cpp)
{
  char marker[32], *sp, *cp = *cpp;
  int ret = MRK_NONE;

  while (*cp == '@') {
    /* Only one marker is allowed */
    if (ret != MRK_NONE)
      return MRK_ERROR;
    /* Markers are terminated by whitespace */
    if ((sp = strchr(cp, ' ')) == NULL &&
        (sp = strchr(cp, '\t')) == NULL)
      return MRK_ERROR;
    /* Extract marker for comparison */
    if (sp <= cp + 1 || sp >= cp + sizeof(marker))
      return MRK_ERROR;
    memcpy(marker, cp, sp - cp);
    marker[sp - cp] = '\0';
    if (strcmp(marker, CA_MARKER) == 0)
      ret = MRK_CA;
    else if (strcmp(marker, REVOKE_MARKER) == 0)
      ret = MRK_REVOKE;
    else
      return MRK_ERROR;

    /* Skip past marker and any whitespace that follows it */
    cp = sp;
    for (; *cp == ' ' || *cp == '\t'; cp++)
      ;
  }
  *cpp = cp;
  return ret;
}

struct hostkeys *
init_hostkeys(void)
{
  struct hostkeys *ret = xcalloc(1, sizeof(*ret));

  ret->entries = NULL;
  return ret;
}

struct load_callback_ctx {
  const char *host;
  u_long num_loaded;
  struct hostkeys *hostkeys;
};

static int
record_hostkey(struct hostkey_foreach_line *l, void *_ctx)
{
  struct load_callback_ctx *ctx = (struct load_callback_ctx *)_ctx;
  struct hostkeys *hostkeys = ctx->hostkeys;
  struct hostkey_entry *tmp;

  if (l->status == HKF_STATUS_INVALID) {
    /* XXX make this verbose() in the future */
    debug("%s:%ld: parse error in hostkeys file",
        l->path, l->linenum);
    return 0;
  }

  debug3_f("found %skey type %s in file %s:%lu",
      l->marker == MRK_NONE ? "" :
      (l->marker == MRK_CA ? "ca " : "revoked "),
      sshkey_type(l->key), l->path, l->linenum);
  if ((tmp = recallocarray(hostkeys->entries, hostkeys->num_entries,
      hostkeys->num_entries + 1, sizeof(*hostkeys->entries))) == NULL)
    return SSH_ERR_ALLOC_FAIL;
  hostkeys->entries = tmp;
  hostkeys->entries[hostkeys->num_entries].host = xstrdup(ctx->host);
  hostkeys->entries[hostkeys->num_entries].file = xstrdup(l->path);
  hostkeys->entries[hostkeys->num_entries].line = l->linenum;
  hostkeys->entries[hostkeys->num_entries].key = l->key;
  l->key = NULL; /* steal it */
  hostkeys->entries[hostkeys->num_entries].marker = l->marker;
  hostkeys->entries[hostkeys->num_entries].note = l->note;
  hostkeys->num_entries++;
  ctx->num_loaded++;

  return 0;
}

void
load_hostkeys_file(struct hostkeys *hostkeys, const char *host,
    const char *path, FILE *f, u_int note)
{
  int r;
  struct load_callback_ctx ctx;

  ctx.host = host;
  ctx.num_loaded = 0;
  ctx.hostkeys = hostkeys;

  if ((r = hostkeys_foreach_file(path, f, record_hostkey, &ctx, host,
      NULL, HKF_WANT_MATCH|HKF_WANT_PARSE_KEY, note)) != 0) {
    if (r != SSH_ERR_SYSTEM_ERROR && errno != ENOENT)
      debug_fr(r, "hostkeys_foreach failed for %s", path);
  }
  if (ctx.num_loaded != 0)
    debug3_f("loaded %lu keys from %s", ctx.num_loaded, host);
}

void
load_hostkeys(struct hostkeys *hostkeys, const char *host, const char *path,
    u_int note)
{
  FILE *f;

  if ((f = fopen(path, "r")) == NULL) {
    debug_f("fopen %s: %s", path, strerror(errno));
    return;
  }

  load_hostkeys_file(hostkeys, host, path, f, note);
  fclose(f);
}

void
free_hostkeys(struct hostkeys *hostkeys)
{
  u_int i;

  for (i = 0; i < hostkeys->num_entries; i++) {
    free(hostkeys->entries[i].host);
    free(hostkeys->entries[i].file);
    sshkey_free(hostkeys->entries[i].key);
    explicit_bzero(hostkeys->entries + i, sizeof(*hostkeys->entries));
  }
  free(hostkeys->entries);
  freezero(hostkeys, sizeof(*hostkeys));
}

static int
check_key_not_revoked(struct hostkeys *hostkeys, struct sshkey *k)
{
  int is_cert = sshkey_is_cert(k);
  u_int i;

  for (i = 0; i < hostkeys->num_entries; i++) {
    if (hostkeys->entries[i].marker != MRK_REVOKE)
      continue;
    if (sshkey_equal_public(k, hostkeys->entries[i].key))
      return -1;
    if (is_cert && k != NULL &&
        sshkey_equal_public(k->cert->signature_key,
        hostkeys->entries[i].key))
      return -1;
  }
  return 0;
}

/*
 * Match keys against a specified key, or look one up by key type.
 *
 * If looking for a keytype (key == NULL) and one is found then return
 * HOST_FOUND, otherwise HOST_NEW.
 *
 * If looking for a key (key != NULL):
 *  1. If the key is a cert and a matching CA is found, return HOST_OK
 *  2. If the key is not a cert and a matching key is found, return HOST_OK
 *  3. If no key matches but a key with a different type is found, then
 *     return HOST_CHANGED
 *  4. If no matching keys are found, then return HOST_NEW.
 *
 * Finally, check any found key is not revoked.
 */
static HostStatus
check_hostkeys_by_key_or_type(struct hostkeys *hostkeys,
    struct sshkey *k, int keytype, int nid, const struct hostkey_entry **found)
{
  u_int i;
  HostStatus end_return = HOST_NEW;
  int want_cert = sshkey_is_cert(k);
  HostkeyMarker want_marker = want_cert ? MRK_CA : MRK_NONE;

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

  for (i = 0; i < hostkeys->num_entries; i++) {
    if (hostkeys->entries[i].marker != want_marker)
      continue;
    if (k == NULL) {
      if (hostkeys->entries[i].key->type != keytype)
        continue;
      if (nid != -1 &&
          sshkey_type_plain(keytype) == KEY_ECDSA &&
          hostkeys->entries[i].key->ecdsa_nid != nid)
        continue;
      end_return = HOST_FOUND;
      if (found != NULL)
        *found = hostkeys->entries + i;
      k = hostkeys->entries[i].key;
      break;
    }
    if (want_cert) {
      if (sshkey_equal_public(k->cert->signature_key,
          hostkeys->entries[i].key)) {
        /* A matching CA exists */
        end_return = HOST_OK;
        if (found != NULL)
          *found = hostkeys->entries + i;
        break;
      }
    } else {
      if (sshkey_equal(k, hostkeys->entries[i].key)) {
        end_return = HOST_OK;
        if (found != NULL)
          *found = hostkeys->entries + i;
        break;
      }
      /* A non-matching key exists */
      end_return = HOST_CHANGED;
      if (found != NULL)
        *found = hostkeys->entries + i;
    }
  }
  if (check_key_not_revoked(hostkeys, k) != 0) {
    end_return = HOST_REVOKED;
    if (found != NULL)
      *found = NULL;
  }
  return end_return;
}

HostStatus
check_key_in_hostkeys(struct hostkeys *hostkeys, struct sshkey *key,
    const struct hostkey_entry **found)
{
  if (key == NULL)
    fatal("no key to look up");
  return check_hostkeys_by_key_or_type(hostkeys, key, 0, -1, found);
}

int
lookup_key_in_hostkeys_by_type(struct hostkeys *hostkeys, int keytype, int nid,
    const struct hostkey_entry **found)
{
  return (check_hostkeys_by_key_or_type(hostkeys, NULL, keytype, nid,
      found) == HOST_FOUND);
}

int
lookup_marker_in_hostkeys(struct hostkeys *hostkeys, int want_marker)
{
  u_int i;

  for (i = 0; i < hostkeys->num_entries; i++) {
    if (hostkeys->entries[i].marker == (HostkeyMarker)want_marker)
      return 1;
  }
  return 0;
}

static int
format_host_entry(struct sshbuf *entry, const char *host, const char *ip,
    const struct sshkey *key, int store_hash)
{
  int r, success = 0;
  char *hashed_host = NULL, *lhost;

  lhost = xstrdup(host);
  lowercase(lhost);

  if (store_hash) {
    if ((hashed_host = host_hash(lhost, NULL, 0)) == NULL) {
      error_f("host_hash failed");
      free(lhost);
      return 0;
    }
    if ((r = sshbuf_putf(entry, "%s ", hashed_host)) != 0)
      fatal_fr(r, "sshbuf_putf");
  } else if (ip != NULL) {
    if ((r = sshbuf_putf(entry, "%s,%s ", lhost, ip)) != 0)
      fatal_fr(r, "sshbuf_putf");
  } else {
    if ((r = sshbuf_putf(entry, "%s ", lhost)) != 0)
      fatal_fr(r, "sshbuf_putf");
  }
  free(hashed_host);
  free(lhost);
  if ((r = sshkey_format_text(key, entry)) == 0)
    success = 1;
  else
    error_fr(r, "sshkey_write");
  if ((r = sshbuf_putf(entry, "\n")) != 0)
    fatal_fr(r, "sshbuf_putf");

  /* If hashing is enabled, the IP address needs to go on its own line */
  if (success && store_hash && ip != NULL)
    success = format_host_entry(entry, ip, NULL, key, 1);
  return success;
}

static int
write_host_entry(FILE *f, const char *host, const char *ip,
    const struct sshkey *key, int store_hash)
{
  int r, success = 0;
  struct sshbuf *entry = NULL;

  if ((entry = sshbuf_new()) == NULL)
    fatal_f("allocation failed");
  if ((r = format_host_entry(entry, host, ip, key, store_hash)) != 1) {
    debug_f("failed to format host entry");
    goto out;
  }
  if ((r = fwrite(sshbuf_ptr(entry), sshbuf_len(entry), 1, f)) != 1) {
    error_f("fwrite: %s", strerror(errno));
    goto out;
  }
  success = 1;
 out:
  sshbuf_free(entry);
  return success;
}

/*
 * Create user ~/.ssh directory if it doesn't exist and we want to write to it.
 * If notify is set, a message will be emitted if the directory is created.
 */
void
hostfile_create_user_ssh_dir(const char *filename, int notify)
{
  char *dotsshdir = NULL, *p;
  size_t len;
  struct stat st;

  if ((p = strrchr(filename, '/')) == NULL)
    return;
  len = p - filename;
  dotsshdir = tilde_expand_filename("~/" _PATH_SSH_USER_DIR, getuid());
  if (strlen(dotsshdir) > len || strncmp(filename, dotsshdir, len) != 0)
    goto out; /* not ~/.ssh prefixed */
  if (stat(dotsshdir, &st) == 0)
    goto out; /* dir already exists */
  else if (errno != ENOENT)
    error("Could not stat %s: %s", dotsshdir, strerror(errno));
  else {
#ifdef WITH_SELINUX
    ssh_selinux_setfscreatecon(dotsshdir);
#endif
    if (mkdir(dotsshdir, 0700) == -1)
      error("Could not create directory '%.200s' (%s).",
          dotsshdir, strerror(errno));
    else if (notify)
      logit("Created directory '%s'.", dotsshdir);
#ifdef WITH_SELINUX
    ssh_selinux_setfscreatecon(NULL);
#endif
  }
 out:
  free(dotsshdir);
}

/*
 * Appends an entry to the host file.  Returns false if the entry could not
 * be appended.
 */
int
add_host_to_hostfile(const char *filename, const char *host,
    const struct sshkey *key, int store_hash)
{
  FILE *f;
  int success, addnl = 0;

  if (key == NULL)
    return 1; /* XXX ? */
  hostfile_create_user_ssh_dir(filename, 0);
  if ((f = fopen(filename, "a+")) == NULL)
    return 0;
  setvbuf(f, NULL, _IONBF, 0);
  /* Make sure we have a terminating newline. */
  if (fseek(f, -1L, SEEK_END) == 0 && fgetc(f) != '\n')
    addnl = 1;
  if (fseek(f, 0L, SEEK_END) != 0 || (addnl && fputc('\n', f) != '\n')) {
    error("Failed to add terminating newline to %s: %s",
       filename, strerror(errno));
    fclose(f);
    return 0;
  }
  success = write_host_entry(f, host, NULL, key, store_hash);
  fclose(f);
  return success;
}

struct host_delete_ctx {
  FILE *out;
  int quiet;
  const char *host, *ip;
  u_int *match_keys;  /* mask of HKF_MATCH_* for this key */
  struct sshkey * const *keys;
  size_t nkeys;
  int modified;
};

static int
host_delete(struct hostkey_foreach_line *l, void *_ctx)
{
  struct host_delete_ctx *ctx = (struct host_delete_ctx *)_ctx;
  int loglevel = ctx->quiet ? SYSLOG_LEVEL_DEBUG1 : SYSLOG_LEVEL_VERBOSE;
  size_t i;

  /* Don't remove CA and revocation lines */
  if (l->status == HKF_STATUS_MATCHED && l->marker == MRK_NONE) {
    /*
     * If this line contains one of the keys that we will be
     * adding later, then don't change it and mark the key for
     * skipping.
     */
    for (i = 0; i < ctx->nkeys; i++) {
      if (!sshkey_equal(ctx->keys[i], l->key))
        continue;
      ctx->match_keys[i] |= l->match;
      fprintf(ctx->out, "%s\n", l->line);
      debug3_f("%s key already at %s:%ld",
          sshkey_type(l->key), l->path, l->linenum);
      return 0;
    }

    /*
     * Hostname matches and has no CA/revoke marker, delete it
     * by *not* writing the line to ctx->out.
     */
    do_log2(loglevel, "%s%s%s:%ld: Removed %s key for host %s",
        ctx->quiet ? __func__ : "", ctx->quiet ? ": " : "",
        l->path, l->linenum, sshkey_type(l->key), ctx->host);
    ctx->modified = 1;
    return 0;
  }
  /* Retain non-matching hosts and invalid lines when deleting */
  if (l->status == HKF_STATUS_INVALID) {
    do_log2(loglevel, "%s%s%s:%ld: invalid known_hosts entry",
        ctx->quiet ? __func__ : "", ctx->quiet ? ": " : "",
        l->path, l->linenum);
  }
  fprintf(ctx->out, "%s\n", l->line);
  return 0;
}

int
hostfile_replace_entries(const char *filename, const char *host, const char *ip,
    struct sshkey **keys, size_t nkeys, int store_hash, int quiet, int hash_alg)
{
  int r, fd, oerrno = 0;
  int loglevel = quiet ? SYSLOG_LEVEL_DEBUG1 : SYSLOG_LEVEL_VERBOSE;
  struct host_delete_ctx ctx;
  char *fp = NULL, *temp = NULL, *back = NULL;
  const char *what;
  mode_t omask;
  size_t i;
  u_int want;

  omask = umask(077);

  memset(&ctx, 0, sizeof(ctx));
  ctx.host = host;
  ctx.ip = ip;
  ctx.quiet = quiet;

  if ((ctx.match_keys = calloc(nkeys, sizeof(*ctx.match_keys))) == NULL)
    return SSH_ERR_ALLOC_FAIL;
  ctx.keys = keys;
  ctx.nkeys = nkeys;
  ctx.modified = 0;

  /*
   * Prepare temporary file for in-place deletion.
   */
  if ((r = asprintf(&temp, "%s.XXXXXXXXXXX", filename)) == -1 ||
      (r = asprintf(&back, "%s.old", filename)) == -1) {
    r = SSH_ERR_ALLOC_FAIL;
    goto fail;
  }

  if ((fd = mkstemp(temp)) == -1) {
    oerrno = errno;
    error_f("mkstemp: %s", strerror(oerrno));
    r = SSH_ERR_SYSTEM_ERROR;
    goto fail;
  }
  if ((ctx.out = fdopen(fd, "w")) == NULL) {
    oerrno = errno;
    close(fd);
    error_f("fdopen: %s", strerror(oerrno));
    r = SSH_ERR_SYSTEM_ERROR;
    goto fail;
  }

  /* Remove stale/mismatching entries for the specified host */
  if ((r = hostkeys_foreach(filename, host_delete, &ctx, host, ip,
      HKF_WANT_PARSE_KEY, 0)) != 0) {
    oerrno = errno;
    error_fr(r, "hostkeys_foreach");
    goto fail;
  }

  /* Re-add the requested keys */
  want = HKF_MATCH_HOST | (ip == NULL ? 0 : HKF_MATCH_IP);
  for (i = 0; i < nkeys; i++) {
    if (keys[i] == NULL || (want & ctx.match_keys[i]) == want)
      continue;
    if ((fp = sshkey_fingerprint(keys[i], hash_alg,
        SSH_FP_DEFAULT)) == NULL) {
      r = SSH_ERR_ALLOC_FAIL;
      goto fail;
    }
    /* write host/ip */
    what = "";
    if (ctx.match_keys[i] == 0) {
      what = "Adding new key";
      if (!write_host_entry(ctx.out, host, ip,
          keys[i], store_hash)) {
        r = SSH_ERR_INTERNAL_ERROR;
        goto fail;
      }
    } else if ((want & ~ctx.match_keys[i]) == HKF_MATCH_HOST) {
      what = "Fixing match (hostname)";
      if (!write_host_entry(ctx.out, host, NULL,
          keys[i], store_hash)) {
        r = SSH_ERR_INTERNAL_ERROR;
        goto fail;
      }
    } else if ((want & ~ctx.match_keys[i]) == HKF_MATCH_IP) {
      what = "Fixing match (address)";
      if (!write_host_entry(ctx.out, ip, NULL,
          keys[i], store_hash)) {
        r = SSH_ERR_INTERNAL_ERROR;
        goto fail;
      }
    }
    do_log2(loglevel, "%s%s%s for %s%s%s to %s: %s %s",
        quiet ? __func__ : "", quiet ? ": " : "", what,
        host, ip == NULL ? "" : ",", ip == NULL ? "" : ip, filename,
        sshkey_ssh_name(keys[i]), fp);
    free(fp);
    fp = NULL;
    ctx.modified = 1;
  }
  fclose(ctx.out);
  ctx.out = NULL;

  if (ctx.modified) {
    /* Backup the original file and replace it with the temporary */
    if (unlink(back) == -1 && errno != ENOENT) {
      oerrno = errno;
      error_f("unlink %.100s: %s", back, strerror(errno));
      r = SSH_ERR_SYSTEM_ERROR;
      goto fail;
    }
    if (link(filename, back) == -1) {
      oerrno = errno;
      error_f("link %.100s to %.100s: %s", filename,
          back, strerror(errno));
      r = SSH_ERR_SYSTEM_ERROR;
      goto fail;
    }
    if (rename(temp, filename) == -1) {
      oerrno = errno;
      error_f("rename \"%s\" to \"%s\": %s", temp,
          filename, strerror(errno));
      r = SSH_ERR_SYSTEM_ERROR;
      goto fail;
    }
  } else {
    /* No changes made; just delete the temporary file */
    if (unlink(temp) != 0)
      error_f("unlink \"%s\": %s", temp, strerror(errno));
  }

  /* success */
  r = 0;
 fail:
  if (temp != NULL && r != 0)
    unlink(temp);
  free(temp);
  free(back);
  free(fp);
  if (ctx.out != NULL)
    fclose(ctx.out);
  free(ctx.match_keys);
  umask(omask);
  if (r == SSH_ERR_SYSTEM_ERROR)
    errno = oerrno;
  return r;
}

static int
match_maybe_hashed(const char *host, const char *names, int *was_hashed)
{
  int hashed = *names == HASH_DELIM, ret;
  char *hashed_host = NULL;
  size_t nlen = strlen(names);

  if (was_hashed != NULL)
    *was_hashed = hashed;
  if (hashed) {
    if ((hashed_host = host_hash(host, names, nlen)) == NULL)
      return -1;
    ret = (nlen == strlen(hashed_host) &&
        strncmp(hashed_host, names, nlen) == 0);
    free(hashed_host);
    return ret;
  }
  return match_hostname(host, names) == 1;
}

int
hostkeys_foreach_file(const char *path, FILE *f, hostkeys_foreach_fn *callback,
    void *ctx, const char *host, const char *ip, u_int options, u_int note)
{
  char *line = NULL, ktype[128];
  u_long linenum = 0;
  char *cp, *cp2;
  u_int kbits;
  int hashed;
  int s, r = 0;
  struct hostkey_foreach_line lineinfo;
  size_t linesize = 0, l;

  memset(&lineinfo, 0, sizeof(lineinfo));
  if (host == NULL && (options & HKF_WANT_MATCH) != 0)
    return SSH_ERR_INVALID_ARGUMENT;

  while (getline(&line, &linesize, f) != -1) {
    linenum++;
    line[strcspn(line, "\n")] = '\0';

    free(lineinfo.line);
    sshkey_free(lineinfo.key);
    memset(&lineinfo, 0, sizeof(lineinfo));
    lineinfo.path = path;
    lineinfo.linenum = linenum;
    lineinfo.line = xstrdup(line);
    lineinfo.marker = MRK_NONE;
    lineinfo.status = HKF_STATUS_OK;
    lineinfo.keytype = KEY_UNSPEC;
    lineinfo.note = note;

    /* Skip any leading whitespace, comments and empty lines. */
    for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
      ;
    if (!*cp || *cp == '#' || *cp == '\n') {
      if ((options & HKF_WANT_MATCH) == 0) {
        lineinfo.status = HKF_STATUS_COMMENT;
        if ((r = callback(&lineinfo, ctx)) != 0)
          break;
      }
      continue;
    }

    if ((lineinfo.marker = check_markers(&cp)) == MRK_ERROR) {
      verbose_f("invalid marker at %s:%lu", path, linenum);
      if ((options & HKF_WANT_MATCH) == 0)
        goto bad;
      continue;
    }

    /* Find the end of the host name portion. */
    for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++)
      ;
    if (*cp2 == '\0') {
      verbose_f("truncated line at %s:%lu", path, linenum);
      if ((options & HKF_WANT_MATCH) == 0)
        goto bad;
      continue;
    }
    lineinfo.hosts = cp;
    *cp2++ = '\0';

    /* Check if the host name matches. */
    if (host != NULL) {
      if ((s = match_maybe_hashed(host, lineinfo.hosts,
          &hashed)) == -1) {
        debug2_f("%s:%ld: bad host hash \"%.32s\"",
            path, linenum, lineinfo.hosts);
        goto bad;
      }
      if (s == 1) {
        lineinfo.status = HKF_STATUS_MATCHED;
        lineinfo.match |= HKF_MATCH_HOST |
            (hashed ? HKF_MATCH_HOST_HASHED : 0);
      }
      /* Try matching IP address if supplied */
      if (ip != NULL) {
        if ((s = match_maybe_hashed(ip, lineinfo.hosts,
            &hashed)) == -1) {
          debug2_f("%s:%ld: bad ip hash "
              "\"%.32s\"", path, linenum,
              lineinfo.hosts);
          goto bad;
        }
        if (s == 1) {
          lineinfo.status = HKF_STATUS_MATCHED;
          lineinfo.match |= HKF_MATCH_IP |
              (hashed ? HKF_MATCH_IP_HASHED : 0);
        }
      }
      /*
       * Skip this line if host matching requested and
       * neither host nor address matched.
       */
      if ((options & HKF_WANT_MATCH) != 0 &&
          lineinfo.status != HKF_STATUS_MATCHED)
        continue;
    }

    /* Got a match.  Skip host name and any following whitespace */
    for (; *cp2 == ' ' || *cp2 == '\t'; cp2++)
      ;
    if (*cp2 == '\0' || *cp2 == '#') {
      debug2("%s:%ld: truncated before key type",
          path, linenum);
      goto bad;
    }
    lineinfo.rawkey = cp = cp2;

    if ((options & HKF_WANT_PARSE_KEY) != 0) {
      /*
       * Extract the key from the line.  This will skip
       * any leading whitespace.  Ignore badly formatted
       * lines.
       */
      if ((lineinfo.key = sshkey_new(KEY_UNSPEC)) == NULL) {
        error_f("sshkey_new failed");
        r = SSH_ERR_ALLOC_FAIL;
        break;
      }
      if (!hostfile_read_key(&cp, &kbits, lineinfo.key)) {
        goto bad;
      }
      lineinfo.keytype = lineinfo.key->type;
      lineinfo.comment = cp;
    } else {
      /* Extract and parse key type */
      l = strcspn(lineinfo.rawkey, " \t");
      if (l <= 1 || l >= sizeof(ktype) ||
          lineinfo.rawkey[l] == '\0')
        goto bad;
      memcpy(ktype, lineinfo.rawkey, l);
      ktype[l] = '\0';
      lineinfo.keytype = sshkey_type_from_name(ktype);

      /*
       * Assume legacy RSA1 if the first component is a short
       * decimal number.
       */
      if (lineinfo.keytype == KEY_UNSPEC && l < 8 &&
          strspn(ktype, "0123456789") == l)
        goto bad;

      /*
       * Check that something other than whitespace follows
       * the key type. This won't catch all corruption, but
       * it does catch trivial truncation.
       */
      cp2 += l; /* Skip past key type */
      for (; *cp2 == ' ' || *cp2 == '\t'; cp2++)
        ;
      if (*cp2 == '\0' || *cp2 == '#') {
        debug2("%s:%ld: truncated after key type",
            path, linenum);
        lineinfo.keytype = KEY_UNSPEC;
      }
      if (lineinfo.keytype == KEY_UNSPEC) {
 bad:
        sshkey_free(lineinfo.key);
        lineinfo.key = NULL;
        lineinfo.status = HKF_STATUS_INVALID;
        if ((r = callback(&lineinfo, ctx)) != 0)
          break;
        continue;
      }
    }
    if ((r = callback(&lineinfo, ctx)) != 0)
      break;
  }
  sshkey_free(lineinfo.key);
  free(lineinfo.line);
  free(line);
  return r;
}

int
hostkeys_foreach(const char *path, hostkeys_foreach_fn *callback, void *ctx,
    const char *host, const char *ip, u_int options, u_int note)
{
  FILE *f;
  int r, oerrno;

  if ((f = fopen(path, "r")) == NULL)
    return SSH_ERR_SYSTEM_ERROR;

  debug3_f("reading file \"%s\"", path);
  r = hostkeys_foreach_file(path, f, callback, ctx, host, ip,
      options, note);
  oerrno = errno;
  fclose(f);
  errno = oerrno;
  return r;
}

Coverage Report

Created: 2026-10-17 06:39