/* $OpenBSD: hostfile.c,v 1.50 2010/12/04 13:31:37 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 <netinet/in.h>
#include <openssl/hmac.h>
#include <openssl/sha.h>
#include <resolv.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "xmalloc.h"
#include "match.h"
#include "key.h"
#include "hostfile.h"
#include "log.h"
#include "misc.h"
struct hostkeys {
struct hostkey_entry *entries;
u_int num_entries;
};
static int
extract_salt(const char *s, u_int l, 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);
xfree(b64salt);
if (ret == -1) {
debug2("extract_salt: salt decode error");
return (-1);
}
if (ret != SHA_DIGEST_LENGTH) {
debug2("extract_salt: expected salt len %d, got %d",
SHA_DIGEST_LENGTH, ret);
return (-1);
}
return (0);
}
char *
host_hash(const char *host, const char *name_from_hostfile, u_int src_len)
{
const EVP_MD *md = EVP_sha1();
HMAC_CTX mac_ctx;
char salt[256], result[256], uu_salt[512], uu_result[512];
static char encoded[1024];
u_int i, len;
len = EVP_MD_size(md);
if (name_from_hostfile == NULL) {
/* Create new salt */
for (i = 0; i < len; i++)
salt[i] = arc4random();
} else {
/* Extract salt from known host entry */
if (extract_salt(name_from_hostfile, src_len, salt,
sizeof(salt)) == -1)
return (NULL);
}
HMAC_Init(&mac_ctx, salt, len, md);
HMAC_Update(&mac_ctx, host, strlen(host));
HMAC_Final(&mac_ctx, result, NULL);
HMAC_cleanup(&mac_ctx);
if (__b64_ntop(salt, len, uu_salt, sizeof(uu_salt)) == -1 ||
__b64_ntop(result, len, uu_result, sizeof(uu_result)) == -1)
fatal("host_hash: __b64_ntop failed");
snprintf(encoded, sizeof(encoded), "%s%s%c%s", HASH_MAGIC, uu_salt,
HASH_DELIM, uu_result);
return (encoded);
}
/*
* Parses an RSA (number of bits, e, n) or DSA 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, Key *ret)
{
char *cp;
/* Skip leading whitespace. */
for (cp = *cpp; *cp == ' ' || *cp == '\t'; cp++)
;
if (key_read(ret, &cp) != 1)
return 0;
/* Skip trailing whitespace. */
for (; *cp == ' ' || *cp == '\t'; cp++)
;
/* Return results. */
*cpp = cp;
if (bitsp != NULL)
*bitsp = key_size(ret);
return 1;
}
static int
hostfile_check_key(int bits, const Key *key, const char *host,
const char *filename, u_long linenum)
{
if (key == NULL || key->type != KEY_RSA1 || key->rsa == NULL)
return 1;
if (bits != BN_num_bits(key->rsa->n)) {
logit("Warning: %s, line %lu: keysize mismatch for host %s: "
"actual %d vs. announced %d.",
filename, linenum, host, BN_num_bits(key->rsa->n), bits);
logit("Warning: replace %d with %d in %s, line %lu.",
bits, BN_num_bits(key->rsa->n), filename, linenum);
}
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;
}
void
load_hostkeys(struct hostkeys *hostkeys, const char *host, const char *path)
{
FILE *f;
char line[8192];
u_long linenum = 0, num_loaded = 0;
char *cp, *cp2, *hashed_host;
HostkeyMarker marker;
Key *key;
int kbits;
if ((f = fopen(path, "r")) == NULL)
return;
debug3("%s: loading entries for host \"%.100s\" from file \"%s\"",
__func__, host, path);
while (read_keyfile_line(f, path, line, sizeof(line), &linenum) == 0) {
cp = line;
/* Skip any leading whitespace, comments and empty lines. */
for (; *cp == ' ' || *cp == '\t'; cp++)
;
if (!*cp || *cp == '#' || *cp == '\n')
continue;
if ((marker = check_markers(&cp)) == MRK_ERROR) {
verbose("%s: invalid marker at %s:%lu",
__func__, path, linenum);
continue;
}
/* Find the end of the host name portion. */
for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++)
;
/* Check if the host name matches. */
if (match_hostname(host, cp, (u_int) (cp2 - cp)) != 1) {
if (*cp != HASH_DELIM)
continue;
hashed_host = host_hash(host, cp, (u_int) (cp2 - cp));
if (hashed_host == NULL) {
debug("Invalid hashed host line %lu of %s",
linenum, path);
continue;
}
if (strncmp(hashed_host, cp, (u_int) (cp2 - cp)) != 0)
continue;
}
/* Got a match. Skip host name. */
cp = cp2;
/*
* Extract the key from the line. This will skip any leading
* whitespace. Ignore badly formatted lines.
*/
key = key_new(KEY_UNSPEC);
if (!hostfile_read_key(&cp, &kbits, key)) {
key_free(key);
key = key_new(KEY_RSA1);
if (!hostfile_read_key(&cp, &kbits, key)) {
key_free(key);
continue;
}
}
if (!hostfile_check_key(kbits, key, host, path, linenum))
continue;
debug3("%s: found %skey type %s in file %s:%lu", __func__,
marker == MRK_NONE ? "" :
(marker == MRK_CA ? "ca " : "revoked "),
key_type(key), path, linenum);
hostkeys->entries = xrealloc(hostkeys->entries,
hostkeys->num_entries + 1, sizeof(*hostkeys->entries));
hostkeys->entries[hostkeys->num_entries].host = xstrdup(host);
hostkeys->entries[hostkeys->num_entries].file = xstrdup(path);
hostkeys->entries[hostkeys->num_entries].line = linenum;
hostkeys->entries[hostkeys->num_entries].key = key;
hostkeys->entries[hostkeys->num_entries].marker = marker;
hostkeys->num_entries++;
num_loaded++;
}
debug3("%s: loaded %lu keys", __func__, num_loaded);
fclose(f);
return;
}
void
free_hostkeys(struct hostkeys *hostkeys)
{
u_int i;
for (i = 0; i < hostkeys->num_entries; i++) {
xfree(hostkeys->entries[i].host);
xfree(hostkeys->entries[i].file);
key_free(hostkeys->entries[i].key);
bzero(hostkeys->entries + i, sizeof(*hostkeys->entries));
}
if (hostkeys->entries != NULL)
xfree(hostkeys->entries);
hostkeys->entries = NULL;
hostkeys->num_entries = 0;
xfree(hostkeys);
}
static int
check_key_not_revoked(struct hostkeys *hostkeys, Key *k)
{
int is_cert = key_is_cert(k);
u_int i;
for (i = 0; i < hostkeys->num_entries; i++) {
if (hostkeys->entries[i].marker != MRK_REVOKE)
continue;
if (key_equal_public(k, hostkeys->entries[i].key))
return -1;
if (is_cert &&
key_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,
Key *k, int keytype, const struct hostkey_entry **found)
{
u_int i;
HostStatus end_return = HOST_NEW;
int want_cert = key_is_cert(k);
HostkeyMarker want_marker = want_cert ? MRK_CA : MRK_NONE;
int proto = (k ? k->type : keytype) == KEY_RSA1 ? 1 : 2;
if (found != NULL)
*found = NULL;
for (i = 0; i < hostkeys->num_entries; i++) {
if (proto == 1 && hostkeys->entries[i].key->type != KEY_RSA1)
continue;
if (proto == 2 && hostkeys->entries[i].key->type == KEY_RSA1)
continue;
if (hostkeys->entries[i].marker != want_marker)
continue;
if (k == NULL) {
if (hostkeys->entries[i].key->type != keytype)
continue;
end_return = HOST_FOUND;
if (found != NULL)
*found = hostkeys->entries + i;
k = hostkeys->entries[i].key;
break;
}
if (want_cert) {
if (key_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 (key_equal(k, hostkeys->entries[i].key)) {
end_return = HOST_OK;
if (found != NULL)
*found = hostkeys->entries + i;
break;
}
/* A non-maching 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, Key *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, found);
}
int
lookup_key_in_hostkeys_by_type(struct hostkeys *hostkeys, int keytype,
const struct hostkey_entry **found)
{
return (check_hostkeys_by_key_or_type(hostkeys, NULL, keytype,
found) == HOST_FOUND);
}
/*
* 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 Key *key,
int store_hash)
{
FILE *f;
int success = 0;
char *hashed_host = NULL;
if (key == NULL)
return 1; /* XXX ? */
f = fopen(filename, "a");
if (!f)
return 0;
if (store_hash) {
if ((hashed_host = host_hash(host, NULL, 0)) == NULL) {
error("add_host_to_hostfile: host_hash failed");
fclose(f);
return 0;
}
}
fprintf(f, "%s ", store_hash ? hashed_host : host);
if (key_write(key, f)) {
success = 1;
} else {
error("add_host_to_hostfile: saving key in %s failed", filename);
}
fprintf(f, "\n");
fclose(f);
return success;
}