hostfile.c - security/openssh-library - Rivoreo Source Code Repositories

 /*
  * 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"
 RCSID("$OpenBSD: hostfile.c,v 1.33 2005/03/01 10:40:26 djm Exp $");

 #include <resolv.h>
 #include <openssl/hmac.h>
 #include <openssl/sha.h>

 #include "packet.h"
 #include "match.h"
 #include "key.h"
 #include "hostfile.h"
 #include "log.h"
 #include "xmalloc.h"

 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 %u, got %u",
 		    salt_len, 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;
 	*bitsp = key_size(ret);
 	return 1;
 }

 static int
 hostfile_check_key(int bits, const Key *key, const char *host, const char *filename, int 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 %d: 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 %d.",
 		    bits, BN_num_bits(key->rsa->n), filename, linenum);
 	}
 	return 1;
 }

 /*
  * Checks whether the given host (which must be in all lowercase) is already
  * in the list of our known hosts. Returns HOST_OK if the host is known and
  * has the specified key, HOST_NEW if the host is not known, and HOST_CHANGED
  * if the host is known but used to have a different host key.
  *
  * If no 'key' has been specified and a key of type 'keytype' is known
  * for the specified host, then HOST_FOUND is returned.
  */

 static HostStatus
 check_host_in_hostfile_by_key_or_type(const char *filename,
     const char *host, const Key *key, int keytype, Key *found, int *numret)
 {
 	FILE *f;
 	char line[8192];
 	int linenum = 0;
 	u_int kbits;
 	char *cp, *cp2, *hashed_host;
 	HostStatus end_return;

 	debug3("check_host_in_hostfile: filename %s", filename);

 	/* Open the file containing the list of known hosts. */
 	f = fopen(filename, "r");
 	if (!f)
 		return HOST_NEW;

 	/*
 	 * Return value when the loop terminates.  This is set to
 	 * HOST_CHANGED if we have seen a different key for the host and have
 	 * not found the proper one.
 	 */
 	end_return = HOST_NEW;

 	/* Go through the file. */
 	while (fgets(line, sizeof(line), f)) {
 		cp = line;
 		linenum++;

 		/* Skip any leading whitespace, comments and empty lines. */
 		for (; *cp == ' ' || *cp == '\t'; cp++)
 			;
 		if (!*cp || *cp == '#' || *cp == '\n')
 			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 %d of %s",
 				    linenum, filename);
 				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.
 		 */
 		if (!hostfile_read_key(&cp, &kbits, found))
 			continue;

 		if (numret != NULL)
 			*numret = linenum;

 		if (key == NULL) {
 			/* we found a key of the requested type */
 			if (found->type == keytype)
 				return HOST_FOUND;
 			continue;
 		}

 		if (!hostfile_check_key(kbits, found, host, filename, linenum))
 			continue;

 		/* Check if the current key is the same as the given key. */
 		if (key_equal(key, found)) {
 			/* Ok, they match. */
 			debug3("check_host_in_hostfile: match line %d", linenum);
 			fclose(f);
 			return HOST_OK;
 		}
 		/*
 		 * They do not match.  We will continue to go through the
 		 * file; however, we note that we will not return that it is
 		 * new.
 		 */
 		end_return = HOST_CHANGED;
 	}
 	/* Clear variables and close the file. */
 	fclose(f);

 	/*
 	 * Return either HOST_NEW or HOST_CHANGED, depending on whether we
 	 * saw a different key for the host.
 	 */
 	return end_return;
 }

 HostStatus
 check_host_in_hostfile(const char *filename, const char *host, const Key *key,
     Key *found, int *numret)
 {
 	if (key == NULL)
 		fatal("no key to look up");
 	return (check_host_in_hostfile_by_key_or_type(filename, host, key, 0,
 	    found, numret));
 }

 int
 lookup_key_in_hostfile_by_type(const char *filename, const char *host,
     int keytype, Key *found, int *numret)
 {
 	return (check_host_in_hostfile_by_key_or_type(filename, host, NULL,
 	    keytype, found, numret) == 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;

 	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;
 }
	/*
	* 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"
	RCSID("$OpenBSD: hostfile.c,v 1.33 2005/03/01 10:40:26 djm Exp $");

	#include <resolv.h>
	#include <openssl/hmac.h>
	#include <openssl/sha.h>

	#include "packet.h"
	#include "match.h"
	#include "key.h"
	#include "hostfile.h"
	#include "log.h"
	#include "xmalloc.h"

	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 %u, got %u",
	salt_len, 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;
	*bitsp = key_size(ret);
	return 1;
	}

	static int
	hostfile_check_key(int bits, const Key key, const char host, const char *filename, int 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 %d: 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 %d.",
	bits, BN_num_bits(key->rsa->n), filename, linenum);
	}
	return 1;
	}

	/*
	* Checks whether the given host (which must be in all lowercase) is already
	* in the list of our known hosts. Returns HOST_OK if the host is known and
	* has the specified key, HOST_NEW if the host is not known, and HOST_CHANGED
	* if the host is known but used to have a different host key.
	*
	* If no 'key' has been specified and a key of type 'keytype' is known
	* for the specified host, then HOST_FOUND is returned.
	*/

	static HostStatus
	check_host_in_hostfile_by_key_or_type(const char *filename,
	const char host, const Key key, int keytype, Key found, int numret)
	{
	FILE *f;
	char line[8192];
	int linenum = 0;
	u_int kbits;
	char cp, cp2, *hashed_host;
	HostStatus end_return;

	debug3("check_host_in_hostfile: filename %s", filename);

	/* Open the file containing the list of known hosts. */
	f = fopen(filename, "r");
	if (!f)
	return HOST_NEW;

	/*
	* Return value when the loop terminates. This is set to
	* HOST_CHANGED if we have seen a different key for the host and have
	* not found the proper one.
	*/
	end_return = HOST_NEW;

	/* Go through the file. */
	while (fgets(line, sizeof(line), f)) {
	cp = line;
	linenum++;

	/* Skip any leading whitespace, comments and empty lines. */
	for (; cp == ' ' \|\| cp == '\t'; cp++)
	;
	if (!cp \|\| cp == '#' \|\| *cp == '\n')
	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 %d of %s",
	linenum, filename);
	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.
	*/
	if (!hostfile_read_key(&cp, &kbits, found))
	continue;

	if (numret != NULL)
	*numret = linenum;

	if (key == NULL) {
	/* we found a key of the requested type */
	if (found->type == keytype)
	return HOST_FOUND;
	continue;
	}

	if (!hostfile_check_key(kbits, found, host, filename, linenum))
	continue;

	/* Check if the current key is the same as the given key. */
	if (key_equal(key, found)) {
	/* Ok, they match. */
	debug3("check_host_in_hostfile: match line %d", linenum);
	fclose(f);
	return HOST_OK;
	}
	/*
	* They do not match. We will continue to go through the
	* file; however, we note that we will not return that it is
	* new.
	*/
	end_return = HOST_CHANGED;
	}
	/* Clear variables and close the file. */
	fclose(f);

	/*
	* Return either HOST_NEW or HOST_CHANGED, depending on whether we
	* saw a different key for the host.
	*/
	return end_return;
	}

	HostStatus
	check_host_in_hostfile(const char filename, const char host, const Key *key,
	Key found, int numret)
	{
	if (key == NULL)
	fatal("no key to look up");
	return (check_host_in_hostfile_by_key_or_type(filename, host, key, 0,
	found, numret));
	}

	int
	lookup_key_in_hostfile_by_type(const char filename, const char host,
	int keytype, Key found, int numret)
	{
	return (check_host_in_hostfile_by_key_or_type(filename, host, NULL,
	keytype, found, numret) == 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;

	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;
	}