487 lines
13 KiB
C
487 lines
13 KiB
C
/* $OpenBSD: hostfile.c,v 1.51 2013/05/17 00:13:13 djm Exp $ */
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/*
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* Author: Tatu Ylonen <ylo@cs.hut.fi>
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* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
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* All rights reserved
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* Functions for manipulating the known hosts files.
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*
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* As far as I am concerned, the code I have written for this software
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* can be used freely for any purpose. Any derived versions of this
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* software must be clearly marked as such, and if the derived work is
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* incompatible with the protocol description in the RFC file, it must be
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* called by a name other than "ssh" or "Secure Shell".
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*
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*
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* Copyright (c) 1999, 2000 Markus Friedl. All rights reserved.
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* Copyright (c) 1999 Niels Provos. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "includes.h"
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#include <sys/types.h>
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#include <netinet/in.h>
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#include <openssl/hmac.h>
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#include <openssl/sha.h>
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#include <resolv.h>
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#include <stdarg.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include "xmalloc.h"
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#include "match.h"
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#include "key.h"
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#include "hostfile.h"
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#include "log.h"
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#include "misc.h"
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struct hostkeys {
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struct hostkey_entry *entries;
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u_int num_entries;
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};
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static int
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extract_salt(const char *s, u_int l, char *salt, size_t salt_len)
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{
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char *p, *b64salt;
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u_int b64len;
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int ret;
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if (l < sizeof(HASH_MAGIC) - 1) {
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debug2("extract_salt: string too short");
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return (-1);
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}
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if (strncmp(s, HASH_MAGIC, sizeof(HASH_MAGIC) - 1) != 0) {
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debug2("extract_salt: invalid magic identifier");
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return (-1);
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}
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s += sizeof(HASH_MAGIC) - 1;
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l -= sizeof(HASH_MAGIC) - 1;
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if ((p = memchr(s, HASH_DELIM, l)) == NULL) {
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debug2("extract_salt: missing salt termination character");
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return (-1);
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}
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b64len = p - s;
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/* Sanity check */
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if (b64len == 0 || b64len > 1024) {
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debug2("extract_salt: bad encoded salt length %u", b64len);
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return (-1);
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}
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b64salt = xmalloc(1 + b64len);
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memcpy(b64salt, s, b64len);
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b64salt[b64len] = '\0';
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ret = __b64_pton(b64salt, salt, salt_len);
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free(b64salt);
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if (ret == -1) {
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debug2("extract_salt: salt decode error");
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return (-1);
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}
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if (ret != SHA_DIGEST_LENGTH) {
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debug2("extract_salt: expected salt len %d, got %d",
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SHA_DIGEST_LENGTH, ret);
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return (-1);
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}
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return (0);
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}
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char *
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host_hash(const char *host, const char *name_from_hostfile, u_int src_len)
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{
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const EVP_MD *md = EVP_sha1();
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HMAC_CTX mac_ctx;
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char salt[256], result[256], uu_salt[512], uu_result[512];
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static char encoded[1024];
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u_int i, len;
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len = EVP_MD_size(md);
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if (name_from_hostfile == NULL) {
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/* Create new salt */
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for (i = 0; i < len; i++)
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salt[i] = arc4random();
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} else {
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/* Extract salt from known host entry */
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if (extract_salt(name_from_hostfile, src_len, salt,
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sizeof(salt)) == -1)
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return (NULL);
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}
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HMAC_Init(&mac_ctx, salt, len, md);
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HMAC_Update(&mac_ctx, host, strlen(host));
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HMAC_Final(&mac_ctx, result, NULL);
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HMAC_cleanup(&mac_ctx);
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if (__b64_ntop(salt, len, uu_salt, sizeof(uu_salt)) == -1 ||
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__b64_ntop(result, len, uu_result, sizeof(uu_result)) == -1)
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fatal("host_hash: __b64_ntop failed");
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snprintf(encoded, sizeof(encoded), "%s%s%c%s", HASH_MAGIC, uu_salt,
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HASH_DELIM, uu_result);
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return (encoded);
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}
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/*
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* Parses an RSA (number of bits, e, n) or DSA key from a string. Moves the
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* pointer over the key. Skips any whitespace at the beginning and at end.
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*/
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int
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hostfile_read_key(char **cpp, u_int *bitsp, Key *ret)
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{
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char *cp;
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/* Skip leading whitespace. */
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for (cp = *cpp; *cp == ' ' || *cp == '\t'; cp++)
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;
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if (key_read(ret, &cp) != 1)
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return 0;
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/* Skip trailing whitespace. */
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for (; *cp == ' ' || *cp == '\t'; cp++)
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;
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/* Return results. */
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*cpp = cp;
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if (bitsp != NULL)
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*bitsp = key_size(ret);
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return 1;
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}
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static int
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hostfile_check_key(int bits, const Key *key, const char *host,
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const char *filename, u_long linenum)
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{
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if (key == NULL || key->type != KEY_RSA1 || key->rsa == NULL)
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return 1;
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if (bits != BN_num_bits(key->rsa->n)) {
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logit("Warning: %s, line %lu: keysize mismatch for host %s: "
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"actual %d vs. announced %d.",
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filename, linenum, host, BN_num_bits(key->rsa->n), bits);
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logit("Warning: replace %d with %d in %s, line %lu.",
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bits, BN_num_bits(key->rsa->n), filename, linenum);
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}
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return 1;
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}
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static HostkeyMarker
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check_markers(char **cpp)
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{
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char marker[32], *sp, *cp = *cpp;
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int ret = MRK_NONE;
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while (*cp == '@') {
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/* Only one marker is allowed */
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if (ret != MRK_NONE)
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return MRK_ERROR;
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/* Markers are terminated by whitespace */
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if ((sp = strchr(cp, ' ')) == NULL &&
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(sp = strchr(cp, '\t')) == NULL)
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return MRK_ERROR;
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/* Extract marker for comparison */
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if (sp <= cp + 1 || sp >= cp + sizeof(marker))
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return MRK_ERROR;
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memcpy(marker, cp, sp - cp);
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marker[sp - cp] = '\0';
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if (strcmp(marker, CA_MARKER) == 0)
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ret = MRK_CA;
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else if (strcmp(marker, REVOKE_MARKER) == 0)
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ret = MRK_REVOKE;
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else
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return MRK_ERROR;
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/* Skip past marker and any whitespace that follows it */
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cp = sp;
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for (; *cp == ' ' || *cp == '\t'; cp++)
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;
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}
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*cpp = cp;
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return ret;
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}
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struct hostkeys *
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init_hostkeys(void)
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{
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struct hostkeys *ret = xcalloc(1, sizeof(*ret));
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ret->entries = NULL;
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return ret;
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}
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void
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load_hostkeys(struct hostkeys *hostkeys, const char *host, const char *path)
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{
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FILE *f;
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char line[8192];
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u_long linenum = 0, num_loaded = 0;
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char *cp, *cp2, *hashed_host;
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HostkeyMarker marker;
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Key *key;
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int kbits;
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if ((f = fopen(path, "r")) == NULL)
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return;
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debug3("%s: loading entries for host \"%.100s\" from file \"%s\"",
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__func__, host, path);
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while (read_keyfile_line(f, path, line, sizeof(line), &linenum) == 0) {
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cp = line;
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/* Skip any leading whitespace, comments and empty lines. */
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for (; *cp == ' ' || *cp == '\t'; cp++)
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;
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if (!*cp || *cp == '#' || *cp == '\n')
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continue;
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if ((marker = check_markers(&cp)) == MRK_ERROR) {
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verbose("%s: invalid marker at %s:%lu",
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__func__, path, linenum);
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continue;
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}
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/* Find the end of the host name portion. */
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for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++)
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;
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/* Check if the host name matches. */
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if (match_hostname(host, cp, (u_int) (cp2 - cp)) != 1) {
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if (*cp != HASH_DELIM)
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continue;
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hashed_host = host_hash(host, cp, (u_int) (cp2 - cp));
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if (hashed_host == NULL) {
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debug("Invalid hashed host line %lu of %s",
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linenum, path);
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continue;
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}
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if (strncmp(hashed_host, cp, (u_int) (cp2 - cp)) != 0)
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continue;
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}
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/* Got a match. Skip host name. */
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cp = cp2;
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/*
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* Extract the key from the line. This will skip any leading
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* whitespace. Ignore badly formatted lines.
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*/
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key = key_new(KEY_UNSPEC);
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if (!hostfile_read_key(&cp, &kbits, key)) {
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key_free(key);
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key = key_new(KEY_RSA1);
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if (!hostfile_read_key(&cp, &kbits, key)) {
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key_free(key);
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continue;
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}
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}
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if (!hostfile_check_key(kbits, key, host, path, linenum))
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continue;
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debug3("%s: found %skey type %s in file %s:%lu", __func__,
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marker == MRK_NONE ? "" :
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(marker == MRK_CA ? "ca " : "revoked "),
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key_type(key), path, linenum);
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hostkeys->entries = xrealloc(hostkeys->entries,
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hostkeys->num_entries + 1, sizeof(*hostkeys->entries));
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hostkeys->entries[hostkeys->num_entries].host = xstrdup(host);
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hostkeys->entries[hostkeys->num_entries].file = xstrdup(path);
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hostkeys->entries[hostkeys->num_entries].line = linenum;
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hostkeys->entries[hostkeys->num_entries].key = key;
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hostkeys->entries[hostkeys->num_entries].marker = marker;
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hostkeys->num_entries++;
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num_loaded++;
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}
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debug3("%s: loaded %lu keys", __func__, num_loaded);
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fclose(f);
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return;
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}
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void
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free_hostkeys(struct hostkeys *hostkeys)
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{
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u_int i;
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for (i = 0; i < hostkeys->num_entries; i++) {
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free(hostkeys->entries[i].host);
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free(hostkeys->entries[i].file);
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key_free(hostkeys->entries[i].key);
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bzero(hostkeys->entries + i, sizeof(*hostkeys->entries));
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}
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free(hostkeys->entries);
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bzero(hostkeys, sizeof(*hostkeys));
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free(hostkeys);
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}
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static int
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check_key_not_revoked(struct hostkeys *hostkeys, Key *k)
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{
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int is_cert = key_is_cert(k);
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u_int i;
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for (i = 0; i < hostkeys->num_entries; i++) {
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if (hostkeys->entries[i].marker != MRK_REVOKE)
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continue;
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if (key_equal_public(k, hostkeys->entries[i].key))
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return -1;
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if (is_cert &&
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key_equal_public(k->cert->signature_key,
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hostkeys->entries[i].key))
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return -1;
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}
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return 0;
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}
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/*
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* Match keys against a specified key, or look one up by key type.
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*
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* If looking for a keytype (key == NULL) and one is found then return
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* HOST_FOUND, otherwise HOST_NEW.
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*
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* If looking for a key (key != NULL):
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* 1. If the key is a cert and a matching CA is found, return HOST_OK
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* 2. If the key is not a cert and a matching key is found, return HOST_OK
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* 3. If no key matches but a key with a different type is found, then
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* return HOST_CHANGED
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* 4. If no matching keys are found, then return HOST_NEW.
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*
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* Finally, check any found key is not revoked.
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*/
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static HostStatus
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check_hostkeys_by_key_or_type(struct hostkeys *hostkeys,
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Key *k, int keytype, const struct hostkey_entry **found)
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{
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u_int i;
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HostStatus end_return = HOST_NEW;
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int want_cert = key_is_cert(k);
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HostkeyMarker want_marker = want_cert ? MRK_CA : MRK_NONE;
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int proto = (k ? k->type : keytype) == KEY_RSA1 ? 1 : 2;
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if (found != NULL)
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*found = NULL;
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for (i = 0; i < hostkeys->num_entries; i++) {
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if (proto == 1 && hostkeys->entries[i].key->type != KEY_RSA1)
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continue;
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if (proto == 2 && hostkeys->entries[i].key->type == KEY_RSA1)
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continue;
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if (hostkeys->entries[i].marker != want_marker)
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continue;
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if (k == NULL) {
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if (hostkeys->entries[i].key->type != keytype)
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continue;
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end_return = HOST_FOUND;
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if (found != NULL)
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*found = hostkeys->entries + i;
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k = hostkeys->entries[i].key;
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break;
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}
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if (want_cert) {
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if (key_equal_public(k->cert->signature_key,
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hostkeys->entries[i].key)) {
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/* A matching CA exists */
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end_return = HOST_OK;
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if (found != NULL)
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*found = hostkeys->entries + i;
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break;
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}
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} else {
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if (key_equal(k, hostkeys->entries[i].key)) {
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end_return = HOST_OK;
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if (found != NULL)
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*found = hostkeys->entries + i;
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break;
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}
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/* A non-maching key exists */
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end_return = HOST_CHANGED;
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if (found != NULL)
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*found = hostkeys->entries + i;
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}
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}
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if (check_key_not_revoked(hostkeys, k) != 0) {
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end_return = HOST_REVOKED;
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if (found != NULL)
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*found = NULL;
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}
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return end_return;
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}
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HostStatus
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check_key_in_hostkeys(struct hostkeys *hostkeys, Key *key,
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const struct hostkey_entry **found)
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{
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if (key == NULL)
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fatal("no key to look up");
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return check_hostkeys_by_key_or_type(hostkeys, key, 0, found);
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}
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int
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lookup_key_in_hostkeys_by_type(struct hostkeys *hostkeys, int keytype,
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const struct hostkey_entry **found)
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{
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return (check_hostkeys_by_key_or_type(hostkeys, NULL, keytype,
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found) == HOST_FOUND);
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}
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/*
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* Appends an entry to the host file. Returns false if the entry could not
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* be appended.
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*/
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int
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add_host_to_hostfile(const char *filename, const char *host, const Key *key,
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int store_hash)
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{
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FILE *f;
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int success = 0;
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char *hashed_host = NULL;
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if (key == NULL)
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return 1; /* XXX ? */
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f = fopen(filename, "a");
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if (!f)
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return 0;
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if (store_hash) {
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if ((hashed_host = host_hash(host, NULL, 0)) == NULL) {
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error("add_host_to_hostfile: host_hash failed");
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fclose(f);
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return 0;
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}
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}
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fprintf(f, "%s ", store_hash ? hashed_host : host);
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if (key_write(key, f)) {
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success = 1;
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} else {
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error("add_host_to_hostfile: saving key in %s failed", filename);
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}
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fprintf(f, "\n");
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fclose(f);
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return success;
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}
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