/* $OpenBSD: hostfile.c,v 1.95 2023/02/21 06:48:18 dtucker 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