auth-rh-rsa.c revision 57429 
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 1.10 1999/11/24 19:53:43 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/*
27 * Tries to authenticate the user using the .rhosts file and the host using
28 * its host key.  Returns true if authentication succeeds.
29 */
30
31int
32auth_rhosts_rsa(struct passwd *pw, const char *client_user,
33		BIGNUM *client_host_key_e, BIGNUM *client_host_key_n)
34{
35	extern ServerOptions options;
36	const char *canonical_hostname;
37	HostStatus host_status;
38	BIGNUM *ke, *kn;
39
40	debug("Trying rhosts with RSA host authentication for %.100s", client_user);
41
42	/* Check if we would accept it using rhosts authentication. */
43	if (!auth_rhosts(pw, client_user))
44		return 0;
45
46	canonical_hostname = get_canonical_hostname();
47
48	debug("Rhosts RSA authentication: canonical host %.900s",
49	      canonical_hostname);
50
51	/* Check if we know the host and its host key. */
52	ke = BN_new();
53	kn = BN_new();
54	host_status = check_host_in_hostfile(SSH_SYSTEM_HOSTFILE, canonical_hostname,
55			   		     client_host_key_e, client_host_key_n,
56					     ke, kn);
57
58	/* Check user host file unless ignored. */
59	if (host_status != HOST_OK && !options.ignore_user_known_hosts) {
60		struct stat st;
61		char *user_hostfile = tilde_expand_filename(SSH_USER_HOSTFILE, pw->pw_uid);
62		/*
63		 * Check file permissions of SSH_USER_HOSTFILE, auth_rsa()
64		 * did already check pw->pw_dir, but there is a race XXX
65		 */
66		if (options.strict_modes &&
67		    (stat(user_hostfile, &st) == 0) &&
68		    ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
69		     (st.st_mode & 022) != 0)) {
70			log("Rhosts RSA authentication refused for %.100s: bad owner or modes for %.200s",
71			    pw->pw_name, user_hostfile);
72		} else {
73			/* XXX race between stat and the following open() */
74			temporarily_use_uid(pw->pw_uid);
75			host_status = check_host_in_hostfile(user_hostfile, canonical_hostname,
76							     client_host_key_e, client_host_key_n,
77							     ke, kn);
78			restore_uid();
79		}
80		xfree(user_hostfile);
81	}
82	BN_free(ke);
83	BN_free(kn);
84
85	if (host_status != HOST_OK) {
86		debug("Rhosts with RSA host authentication denied: unknown or invalid host key");
87		packet_send_debug("Your host key cannot be verified: unknown or invalid host key.");
88		return 0;
89	}
90	/* A matching host key was found and is known. */
91
92	/* Perform the challenge-response dialog with the client for the host key. */
93	if (!auth_rsa_challenge_dialog(client_host_key_e, client_host_key_n)) {
94		log("Client on %.800s failed to respond correctly to host authentication.",
95		    canonical_hostname);
96		return 0;
97	}
98	/*
99	 * We have authenticated the user using .rhosts or /etc/hosts.equiv,
100	 * and the host using RSA. We accept the authentication.
101	 */
102
103	verbose("Rhosts with RSA host authentication accepted for %.100s, %.100s on %.700s.",
104		pw->pw_name, client_user, canonical_hostname);
105	packet_send_debug("Rhosts with RSA host authentication accepted.");
106	return 1;
107}
108