/* $OpenBSD: authfile.c,v 1.144 2023/03/14 07:26:25 dtucker Exp $ */

/*

 * Copyright (c) 2000, 2013 Markus Friedl.  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 <sys/uio.h>

#include <errno.h>

#include <fcntl.h>

#include <stdio.h>

#include <stdarg.h>

#include <stdlib.h>

#include <string.h>

#include <unistd.h>

#include <limits.h>

#include "cipher.h"

#include "ssh.h"

#include "log.h"

#include "authfile.h"

#include "misc.h"

#include "atomicio.h"

#include "sshkey.h"

#include "sshbuf.h"

#include "ssherr.h"

#include "krl.h"

#define MAX_KEY_FILE_SIZE (1024 * 1024)

/* Save a key blob to a file */

static int

sshkey_save_private_blob(struct sshbuf *keybuf, const char *filename)

{

  int r;

  mode_t omask;

  omask = umask(077);

  r = sshbuf_write_file(filename, keybuf);

  umask(omask);

  return r;

}

int

sshkey_save_private(struct sshkey *key, const char *filename,

    const char *passphrase, const char *comment,

    int format, const char *openssh_format_cipher, int openssh_format_rounds)

{

  struct sshbuf *keyblob = NULL;

  int r;

  if ((keyblob = sshbuf_new()) == NULL)

    return SSH_ERR_ALLOC_FAIL;

  if ((r = sshkey_private_to_fileblob(key, keyblob, passphrase, comment,

      format, openssh_format_cipher, openssh_format_rounds)) != 0)

    goto out;

  if ((r = sshkey_save_private_blob(keyblob, filename)) != 0)

    goto out;

  r = 0;

 out:

  sshbuf_free(keyblob);

  return r;

}

/* XXX remove error() calls from here? */

int

sshkey_perm_ok(int fd, const char *filename)

{

  struct stat st;

  if (fstat(fd, &st) == -1)

    return SSH_ERR_SYSTEM_ERROR;

  /*

   * if a key owned by the user is accessed, then we check the

   * permissions of the file. if the key owned by a different user,

   * then we don't care.

   */

#ifdef HAVE_CYGWIN

  if (check_ntsec(filename))

#endif

  if ((st.st_uid == getuid()) && (st.st_mode & 077) != 0) {

    error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");

    error("@         WARNING: UNPROTECTED PRIVATE KEY FILE!          @");

    error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");

    error("Permissions 0%3.3o for '%s' are too open.",

        (u_int)st.st_mode & 0777, filename);

    error("It is required that your private key files are NOT accessible by others.");

    error("This private key will be ignored.");

    return SSH_ERR_KEY_BAD_PERMISSIONS;

  }

  return 0;

}

int

sshkey_load_private_type(int type, const char *filename, const char *passphrase,

    struct sshkey **keyp, char **commentp)

{

  int fd, r;

  if (keyp != NULL)

    *keyp = NULL;

  if (commentp != NULL)

    *commentp = NULL;

  if ((fd = open(filename, O_RDONLY)) == -1)

    return SSH_ERR_SYSTEM_ERROR;

  r = sshkey_perm_ok(fd, filename);

  if (r != 0)

    goto out;

  r = sshkey_load_private_type_fd(fd, type, passphrase, keyp, commentp);

  if (r == 0 && keyp && *keyp)

    r = sshkey_set_filename(*keyp, filename);

 out:

  close(fd);

  return r;

}

int

sshkey_load_private(const char *filename, const char *passphrase,

    struct sshkey **keyp, char **commentp)

{

  return sshkey_load_private_type(KEY_UNSPEC, filename, passphrase,

      keyp, commentp);

}

int

sshkey_load_private_type_fd(int fd, int type, const char *passphrase,

    struct sshkey **keyp, char **commentp)

{

  struct sshbuf *buffer = NULL;

  int r;

  if (keyp != NULL)

    *keyp = NULL;

  if ((r = sshbuf_load_fd(fd, &buffer)) != 0 ||

      (r = sshkey_parse_private_fileblob_type(buffer, type,

      passphrase, keyp, commentp)) != 0)

    goto out;

  /* success */

  r = 0;

 out:

  sshbuf_free(buffer);

  return r;

}

/* Load a pubkey from the unencrypted envelope of a new-format private key */

static int

sshkey_load_pubkey_from_private(const char *filename, struct sshkey **pubkeyp)

{

  struct sshbuf *buffer = NULL;

  struct sshkey *pubkey = NULL;

  int r, fd;

  if (pubkeyp != NULL)

    *pubkeyp = NULL;

  if ((fd = open(filename, O_RDONLY)) == -1)

    return SSH_ERR_SYSTEM_ERROR;

  if ((r = sshbuf_load_fd(fd, &buffer)) != 0 ||

      (r = sshkey_parse_pubkey_from_private_fileblob_type(buffer,

      KEY_UNSPEC, &pubkey)) != 0)

    goto out;

  if ((r = sshkey_set_filename(pubkey, filename)) != 0)

    goto out;

  /* success */

  if (pubkeyp != NULL) {

    *pubkeyp = pubkey;

    pubkey = NULL;

  }

  r = 0;

 out:

  close(fd);

  sshbuf_free(buffer);

  sshkey_free(pubkey);

  return r;

}

static int

sshkey_try_load_public(struct sshkey **kp, const char *filename,

    char **commentp)

{

  FILE *f;

  char *line = NULL, *cp;

  size_t linesize = 0;

  int r;

  struct sshkey *k = NULL;

  if (kp == NULL)

    return SSH_ERR_INVALID_ARGUMENT;

  *kp = NULL;

  if (commentp != NULL)

    *commentp = NULL;

  if ((f = fopen(filename, "r")) == NULL)

    return SSH_ERR_SYSTEM_ERROR;

  if ((k = sshkey_new(KEY_UNSPEC)) == NULL) {

    fclose(f);

    return SSH_ERR_ALLOC_FAIL;

  }

  while (getline(&line, &linesize, f) != -1) {

    cp = line;

    switch (*cp) {

    case '#':

    case '\n':

    case '\0':

      continue;

    }

    /* Abort loading if this looks like a private key */

    if (strncmp(cp, "-----BEGIN", 10) == 0 ||

        strcmp(cp, "SSH PRIVATE KEY FILE") == 0)

      break;

    /* Skip leading whitespace. */

    for (; *cp && (*cp == ' ' || *cp == '\t'); cp++)

      ;

    if (*cp) {

      if ((r = sshkey_read(k, &cp)) == 0) {

        cp[strcspn(cp, "\r\n")] = '\0';

        if (commentp) {

          *commentp = strdup(*cp ?

              cp : filename);

          if (*commentp == NULL)

            r = SSH_ERR_ALLOC_FAIL;

        }

        /* success */

        *kp = k;

        free(line);

        fclose(f);

        return r;

      }

    }

  }

  free(k);

  free(line);

  fclose(f);

  return SSH_ERR_INVALID_FORMAT;

}

/* load public key from any pubkey file */

int

sshkey_load_public(const char *filename, struct sshkey **keyp, char **commentp)

{

  char *pubfile = NULL;

  int r, oerrno;

  if (keyp != NULL)

    *keyp = NULL;

  if (commentp != NULL)

    *commentp = NULL;

  if ((r = sshkey_try_load_public(keyp, filename, commentp)) == 0)

    goto out;

  /* try .pub suffix */

  if (asprintf(&pubfile, "%s.pub", filename) == -1)

    return SSH_ERR_ALLOC_FAIL;

  if ((r = sshkey_try_load_public(keyp, pubfile, commentp)) == 0)

    goto out;

  /* finally, try to extract public key from private key file */

  if ((r = sshkey_load_pubkey_from_private(filename, keyp)) == 0)

    goto out;

  /* Pretend we couldn't find the key */

  r = SSH_ERR_SYSTEM_ERROR;

  errno = ENOENT;

 out:

  oerrno = errno;

  free(pubfile);

  errno = oerrno;

  return r;

}

/* Load the certificate associated with the named private key */

int

sshkey_load_cert(const char *filename, struct sshkey **keyp)

{

  struct sshkey *pub = NULL;

  char *file = NULL;

  int r = SSH_ERR_INTERNAL_ERROR;

  if (keyp != NULL)

    *keyp = NULL;

  if (asprintf(&file, "%s-cert.pub", filename) == -1)

    return SSH_ERR_ALLOC_FAIL;

  r = sshkey_try_load_public(keyp, file, NULL);

  free(file);

  sshkey_free(pub);

  return r;

}

/* Load private key and certificate */

int

sshkey_load_private_cert(int type, const char *filename, const char *passphrase,

    struct sshkey **keyp)

{

  struct sshkey *key = NULL, *cert = NULL;

  int r;

  if (keyp != NULL)

    *keyp = NULL;

  switch (type) {

#ifdef WITH_OPENSSL

  case KEY_RSA:

  case KEY_DSA:

  case KEY_ECDSA:

#endif /* WITH_OPENSSL */

  case KEY_ED25519:

  case KEY_XMSS:

  case KEY_UNSPEC:

    break;

  default:

    return SSH_ERR_KEY_TYPE_UNKNOWN;

  }

  if ((r = sshkey_load_private_type(type, filename,

      passphrase, &key, NULL)) != 0 ||

      (r = sshkey_load_cert(filename, &cert)) != 0)

    goto out;

  /* Make sure the private key matches the certificate */

  if (sshkey_equal_public(key, cert) == 0) {

    r = SSH_ERR_KEY_CERT_MISMATCH;

    goto out;

  }

  if ((r = sshkey_to_certified(key)) != 0 ||

      (r = sshkey_cert_copy(cert, key)) != 0)

    goto out;

  r = 0;

  if (keyp != NULL) {

    *keyp = key;

    key = NULL;

  }

 out:

  sshkey_free(key);

  sshkey_free(cert);

  return r;

}

/*

 * Returns success if the specified "key" is listed in the file "filename",

 * SSH_ERR_KEY_NOT_FOUND: if the key is not listed or another error.

 * If "strict_type" is set then the key type must match exactly,

 * otherwise a comparison that ignores certificate data is performed.

 * If "check_ca" is set and "key" is a certificate, then its CA key is

 * also checked and sshkey_in_file() will return success if either is found.

 */

int

sshkey_in_file(struct sshkey *key, const char *filename, int strict_type,

    int check_ca)

{

  FILE *f;

  char *line = NULL, *cp;

  size_t linesize = 0;

  int r = 0;

  struct sshkey *pub = NULL;

  int (*sshkey_compare)(const struct sshkey *, const struct sshkey *) =

      strict_type ?  sshkey_equal : sshkey_equal_public;

  if ((f = fopen(filename, "r")) == NULL)

    return SSH_ERR_SYSTEM_ERROR;

  while (getline(&line, &linesize, f) != -1) {

    sshkey_free(pub);

    pub = NULL;

    cp = line;

    /* Skip leading whitespace. */

    for (; *cp && (*cp == ' ' || *cp == '\t'); cp++)

      ;

    /* Skip comments and empty lines */

    switch (*cp) {

    case '#':

    case '\n':

    case '\0':

      continue;

    }

    if ((pub = sshkey_new(KEY_UNSPEC)) == NULL) {

      r = SSH_ERR_ALLOC_FAIL;

      goto out;

    }

    switch (r = sshkey_read(pub, &cp)) {

    case 0:

      break;

    case SSH_ERR_KEY_LENGTH:

      continue;

    default:

      goto out;

    }

    if (sshkey_compare(key, pub) ||

        (check_ca && sshkey_is_cert(key) &&

        sshkey_compare(key->cert->signature_key, pub))) {

      r = 0;

      goto out;

    }

  }

  r = SSH_ERR_KEY_NOT_FOUND;

 out:

  free(line);

  sshkey_free(pub);

  fclose(f);

  return r;

}

/*

 * Checks whether the specified key is revoked, returning 0 if not,

 * SSH_ERR_KEY_REVOKED if it is or another error code if something

 * unexpected happened.

 * This will check both the key and, if it is a certificate, its CA key too.

 * "revoked_keys_file" may be a KRL or a one-per-line list of public keys.

 */

int

sshkey_check_revoked(struct sshkey *key, const char *revoked_keys_file)

{

  int r;

  r = ssh_krl_file_contains_key(revoked_keys_file, key);

  /* If this was not a KRL to begin with then continue below */

  if (r != SSH_ERR_KRL_BAD_MAGIC)

    return r;

  /*

   * If the file is not a KRL or we can't handle KRLs then attempt to

   * parse the file as a flat list of keys.

   */

  switch ((r = sshkey_in_file(key, revoked_keys_file, 0, 1))) {

  case 0:

    /* Key found => revoked */

    return SSH_ERR_KEY_REVOKED;

  case SSH_ERR_KEY_NOT_FOUND:

    /* Key not found => not revoked */

    return 0;

  default:

    /* Some other error occurred */

    return r;

  }

}

/*

 * Advanced *cpp past the end of key options, defined as the first unquoted

 * whitespace character. Returns 0 on success or -1 on failure (e.g.

 * unterminated quotes).

 */

int

sshkey_advance_past_options(char **cpp)

{

  char *cp = *cpp;

  int quoted = 0;

  for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) {

    if (*cp == '\\' && cp[1] == '"')

      cp++; /* Skip both */

    else if (*cp == '"')

      quoted = !quoted;

  }

  *cpp = cp;

  /* return failure for unterminated quotes */

  return (*cp == '\0' && quoted) ? -1 : 0;

}

/* Save a public key */

int

sshkey_save_public(const struct sshkey *key, const char *path,

    const char *comment)

{

  int fd, oerrno;

  FILE *f = NULL;

  int r = SSH_ERR_INTERNAL_ERROR;

  if ((fd = open(path, O_WRONLY|O_CREAT|O_TRUNC, 0644)) == -1)

    return SSH_ERR_SYSTEM_ERROR;

  if ((f = fdopen(fd, "w")) == NULL) {

    r = SSH_ERR_SYSTEM_ERROR;

    close(fd);

    goto fail;

  }

  if ((r = sshkey_write(key, f)) != 0)

    goto fail;

  fprintf(f, " %s\n", comment);

  if (ferror(f)) {

    r = SSH_ERR_SYSTEM_ERROR;

    goto fail;

  }

  if (fclose(f) != 0) {

    r = SSH_ERR_SYSTEM_ERROR;

    f = NULL;

 fail:

    if (f != NULL) {

      oerrno = errno;

      fclose(f);

      errno = oerrno;

    }

    return r;

  }

  return 0;

}