auth-rh-rsa.c revision 65674 
1/*
2 * Author: Tatu Ylonen <ylo@cs.hut.fi>
3 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
4 *                    All rights reserved
5 * Rhosts or /etc/hosts.equiv authentication combined with RSA host
6 * authentication.
7 *
8 * As far as I am concerned, the code I have written for this software
9 * can be used freely for any purpose.  Any derived versions of this
10 * software must be clearly marked as such, and if the derived work is
11 * incompatible with the protocol description in the RFC file, it must be
12 * called by a name other than "ssh" or "Secure Shell".
13 */
14
15#include "includes.h"
16RCSID("$OpenBSD: auth-rh-rsa.c,v 1.16 2000/09/07 21:13:36 markus Exp $");
17RCSID("$FreeBSD: head/crypto/openssh/auth-rh-rsa.c 65674 2000-09-10 09:35:38Z kris $");
18
19#include "packet.h"
20#include "ssh.h"
21#include "xmalloc.h"
22#include "uidswap.h"
23#include "servconf.h"
24
25#include <openssl/rsa.h>
26#include <openssl/dsa.h>
27#include "key.h"
28#include "hostfile.h"
29
30/*
31 * Tries to authenticate the user using the .rhosts file and the host using
32 * its host key.  Returns true if authentication succeeds.
33 */
34
35int
36auth_rhosts_rsa(struct passwd *pw, const char *client_user, RSA *client_host_key)
37{
38	extern ServerOptions options;
39	const char *canonical_hostname;
40	HostStatus host_status;
41	Key *client_key, *found;
42
43	debug("Trying rhosts with RSA host authentication for %.100s", client_user);
44
45	if (client_host_key == NULL)
46		return 0;
47
48	/* Check if we would accept it using rhosts authentication. */
49	if (!auth_rhosts(pw, client_user))
50		return 0;
51
52	canonical_hostname = get_canonical_hostname();
53
54	debug("Rhosts RSA authentication: canonical host %.900s", canonical_hostname);
55
56	/* wrap the RSA key into a 'generic' key */
57	client_key = key_new(KEY_RSA);
58	BN_copy(client_key->rsa->e, client_host_key->e);
59	BN_copy(client_key->rsa->n, client_host_key->n);
60	found = key_new(KEY_RSA);
61
62	/* Check if we know the host and its host key. */
63	host_status = check_host_in_hostfile(SSH_SYSTEM_HOSTFILE, canonical_hostname,
64	    client_key, found);
65
66	/* Check user host file unless ignored. */
67	if (host_status != HOST_OK && !options.ignore_user_known_hosts) {
68		struct stat st;
69		char *user_hostfile = tilde_expand_filename(SSH_USER_HOSTFILE, pw->pw_uid);
70		/*
71		 * Check file permissions of SSH_USER_HOSTFILE, auth_rsa()
72		 * did already check pw->pw_dir, but there is a race XXX
73		 */
74		if (options.strict_modes &&
75		    (stat(user_hostfile, &st) == 0) &&
76		    ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
77		     (st.st_mode & 022) != 0)) {
78			log("Rhosts RSA authentication refused for %.100s: bad owner or modes for %.200s",
79			    pw->pw_name, user_hostfile);
80		} else {
81			/* XXX race between stat and the following open() */
82			temporarily_use_uid(pw->pw_uid);
83			host_status = check_host_in_hostfile(user_hostfile, canonical_hostname,
84			    client_key, found);
85			restore_uid();
86		}
87		xfree(user_hostfile);
88	}
89	key_free(client_key);
90	key_free(found);
91
92	if (host_status != HOST_OK) {
93		debug("Rhosts with RSA host authentication denied: unknown or invalid host key");
94		packet_send_debug("Your host key cannot be verified: unknown or invalid host key.");
95		return 0;
96	}
97	/* A matching host key was found and is known. */
98
99	/* Perform the challenge-response dialog with the client for the host key. */
100	if (!auth_rsa_challenge_dialog(client_host_key)) {
101		log("Client on %.800s failed to respond correctly to host authentication.",
102		    canonical_hostname);
103		return 0;
104	}
105	/*
106	 * We have authenticated the user using .rhosts or /etc/hosts.equiv,
107	 * and the host using RSA. We accept the authentication.
108	 */
109
110	verbose("Rhosts with RSA host authentication accepted for %.100s, %.100s on %.700s.",
111	   pw->pw_name, client_user, canonical_hostname);
112	packet_send_debug("Rhosts with RSA host authentication accepted.");
113	return 1;
114}
115