auth-rh-rsa.c revision 58583 
1/*
2 *
3 * auth-rh-rsa.c
4 *
5 * Author: Tatu Ylonen <ylo@cs.hut.fi>
6 *
7 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
8 *                    All rights reserved
9 *
10 * Created: Sun May  7 03:08:06 1995 ylo
11 *
12 * Rhosts or /etc/hosts.equiv authentication combined with RSA host
13 * authentication.
14 *
15 */
16
17#include "includes.h"
18RCSID("$Id: auth-rh-rsa.c,v 1.11 2000/03/23 22:15:33 markus Exp $");
19
20#include "packet.h"
21#include "ssh.h"
22#include "xmalloc.h"
23#include "uidswap.h"
24#include "servconf.h"
25
26#include <ssl/rsa.h>
27#include <ssl/dsa.h>
28#include "key.h"
29#include "hostfile.h"
30
31/*
32 * Tries to authenticate the user using the .rhosts file and the host using
33 * its host key.  Returns true if authentication succeeds.
34 */
35
36int
37auth_rhosts_rsa(struct passwd *pw, const char *client_user, RSA *client_host_key)
38{
39	extern ServerOptions options;
40	const char *canonical_hostname;
41	HostStatus host_status;
42	Key *client_key, *found;
43
44	debug("Trying rhosts with RSA host authentication for %.100s", client_user);
45
46	if (client_host_key == NULL)
47		return 0;
48
49	/* Check if we would accept it using rhosts authentication. */
50	if (!auth_rhosts(pw, client_user))
51		return 0;
52
53	canonical_hostname = get_canonical_hostname();
54
55	debug("Rhosts RSA authentication: canonical host %.900s", canonical_hostname);
56
57	/* wrap the RSA key into a 'generic' key */
58	client_key = key_new(KEY_RSA);
59	BN_copy(client_key->rsa->e, client_host_key->e);
60	BN_copy(client_key->rsa->n, client_host_key->n);
61	found = key_new(KEY_RSA);
62
63	/* Check if we know the host and its host key. */
64	host_status = check_host_in_hostfile(SSH_SYSTEM_HOSTFILE, canonical_hostname,
65	    client_key, found);
66
67	/* Check user host file unless ignored. */
68	if (host_status != HOST_OK && !options.ignore_user_known_hosts) {
69		struct stat st;
70		char *user_hostfile = tilde_expand_filename(SSH_USER_HOSTFILE, pw->pw_uid);
71		/*
72		 * Check file permissions of SSH_USER_HOSTFILE, auth_rsa()
73		 * did already check pw->pw_dir, but there is a race XXX
74		 */
75		if (options.strict_modes &&
76		    (stat(user_hostfile, &st) == 0) &&
77		    ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
78		     (st.st_mode & 022) != 0)) {
79			log("Rhosts RSA authentication refused for %.100s: bad owner or modes for %.200s",
80			    pw->pw_name, user_hostfile);
81		} else {
82			/* XXX race between stat and the following open() */
83			temporarily_use_uid(pw->pw_uid);
84			host_status = check_host_in_hostfile(user_hostfile, canonical_hostname,
85			    client_key, found);
86			restore_uid();
87		}
88		xfree(user_hostfile);
89	}
90	key_free(client_key);
91	key_free(found);
92
93	if (host_status != HOST_OK) {
94		debug("Rhosts with RSA host authentication denied: unknown or invalid host key");
95		packet_send_debug("Your host key cannot be verified: unknown or invalid host key.");
96		return 0;
97	}
98	/* A matching host key was found and is known. */
99
100	/* Perform the challenge-response dialog with the client for the host key. */
101	if (!auth_rsa_challenge_dialog(client_host_key)) {
102		log("Client on %.800s failed to respond correctly to host authentication.",
103		    canonical_hostname);
104		return 0;
105	}
106	/*
107	 * We have authenticated the user using .rhosts or /etc/hosts.equiv,
108	 * and the host using RSA. We accept the authentication.
109	 */
110
111	verbose("Rhosts with RSA host authentication accepted for %.100s, %.100s on %.700s.",
112	   pw->pw_name, client_user, canonical_hostname);
113	packet_send_debug("Rhosts with RSA host authentication accepted.");
114	return 1;
115}
116