mirror of git://anongit.mindrot.org/openssh.git
344 lines
9.2 KiB
C
344 lines
9.2 KiB
C
/*
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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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RCSID("$OpenBSD: hostfile.c,v 1.33 2005/03/01 10:40:26 djm Exp $");
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#include <resolv.h>
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#include <openssl/hmac.h>
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#include <openssl/sha.h>
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#include "packet.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 "xmalloc.h"
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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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xfree(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 %u, got %u",
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salt_len, 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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*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, const char *filename, int 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 %d: 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 %d.",
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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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/*
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* Checks whether the given host (which must be in all lowercase) is already
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* in the list of our known hosts. Returns HOST_OK if the host is known and
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* has the specified key, HOST_NEW if the host is not known, and HOST_CHANGED
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* if the host is known but used to have a different host key.
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*
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* If no 'key' has been specified and a key of type 'keytype' is known
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* for the specified host, then HOST_FOUND is returned.
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*/
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static HostStatus
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check_host_in_hostfile_by_key_or_type(const char *filename,
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const char *host, const Key *key, int keytype, Key *found, int *numret)
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{
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FILE *f;
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char line[8192];
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int linenum = 0;
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u_int kbits;
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char *cp, *cp2, *hashed_host;
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HostStatus end_return;
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debug3("check_host_in_hostfile: filename %s", filename);
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/* Open the file containing the list of known hosts. */
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f = fopen(filename, "r");
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if (!f)
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return HOST_NEW;
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/*
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* Return value when the loop terminates. This is set to
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* HOST_CHANGED if we have seen a different key for the host and have
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* not found the proper one.
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*/
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end_return = HOST_NEW;
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/* Go through the file. */
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while (fgets(line, sizeof(line), f)) {
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cp = line;
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linenum++;
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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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/* 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 %d of %s",
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linenum, filename);
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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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if (!hostfile_read_key(&cp, &kbits, found))
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continue;
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if (numret != NULL)
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*numret = linenum;
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if (key == NULL) {
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/* we found a key of the requested type */
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if (found->type == keytype)
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return HOST_FOUND;
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continue;
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}
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if (!hostfile_check_key(kbits, found, host, filename, linenum))
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continue;
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/* Check if the current key is the same as the given key. */
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if (key_equal(key, found)) {
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/* Ok, they match. */
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debug3("check_host_in_hostfile: match line %d", linenum);
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fclose(f);
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return HOST_OK;
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}
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/*
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* They do not match. We will continue to go through the
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* file; however, we note that we will not return that it is
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* new.
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*/
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end_return = HOST_CHANGED;
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}
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/* Clear variables and close the file. */
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fclose(f);
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/*
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* Return either HOST_NEW or HOST_CHANGED, depending on whether we
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* saw a different key for the host.
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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_host_in_hostfile(const char *filename, const char *host, const Key *key,
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Key *found, int *numret)
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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_host_in_hostfile_by_key_or_type(filename, host, key, 0,
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found, numret));
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}
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int
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lookup_key_in_hostfile_by_type(const char *filename, const char *host,
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int keytype, Key *found, int *numret)
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{
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return (check_host_in_hostfile_by_key_or_type(filename, host, NULL,
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keytype, found, numret) == 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;
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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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