auth-options.c revision 65668 
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 * RSA-based authentication.  This code determines whether to admit a login
6 * based on RSA authentication.  This file also contains functions to check
7 * validity of the host key.
8 *
9 * As far as I am concerned, the code I have written for this software
10 * can be used freely for any purpose.  Any derived versions of this
11 * software must be clearly marked as such, and if the derived work is
12 * incompatible with the protocol description in the RFC file, it must be
13 * called by a name other than "ssh" or "Secure Shell".
14 */
15
16#include "includes.h"
17RCSID("$OpenBSD: auth-options.c,v 1.4 2000/09/07 21:13:36 markus Exp $");
18
19#include "ssh.h"
20#include "packet.h"
21#include "xmalloc.h"
22#include "match.h"
23
24/* Flags set authorized_keys flags */
25int no_port_forwarding_flag = 0;
26int no_agent_forwarding_flag = 0;
27int no_x11_forwarding_flag = 0;
28int no_pty_flag = 0;
29
30/* "command=" option. */
31char *forced_command = NULL;
32
33/* "environment=" options. */
34struct envstring *custom_environment = NULL;
35
36/* return 1 if access is granted, 0 if not. side effect: sets key option flags */
37int
38auth_parse_options(struct passwd *pw, char *options, unsigned long linenum)
39{
40	const char *cp;
41	if (!options)
42		return 1;
43	while (*options && *options != ' ' && *options != '\t') {
44		cp = "no-port-forwarding";
45		if (strncmp(options, cp, strlen(cp)) == 0) {
46			packet_send_debug("Port forwarding disabled.");
47			no_port_forwarding_flag = 1;
48			options += strlen(cp);
49			goto next_option;
50		}
51		cp = "no-agent-forwarding";
52		if (strncmp(options, cp, strlen(cp)) == 0) {
53			packet_send_debug("Agent forwarding disabled.");
54			no_agent_forwarding_flag = 1;
55			options += strlen(cp);
56			goto next_option;
57		}
58		cp = "no-X11-forwarding";
59		if (strncmp(options, cp, strlen(cp)) == 0) {
60			packet_send_debug("X11 forwarding disabled.");
61			no_x11_forwarding_flag = 1;
62			options += strlen(cp);
63			goto next_option;
64		}
65		cp = "no-pty";
66		if (strncmp(options, cp, strlen(cp)) == 0) {
67			packet_send_debug("Pty allocation disabled.");
68			no_pty_flag = 1;
69			options += strlen(cp);
70			goto next_option;
71		}
72		cp = "command=\"";
73		if (strncmp(options, cp, strlen(cp)) == 0) {
74			int i;
75			options += strlen(cp);
76			forced_command = xmalloc(strlen(options) + 1);
77			i = 0;
78			while (*options) {
79				if (*options == '"')
80					break;
81				if (*options == '\\' && options[1] == '"') {
82					options += 2;
83					forced_command[i++] = '"';
84					continue;
85				}
86				forced_command[i++] = *options++;
87			}
88			if (!*options) {
89				debug("%.100s, line %lu: missing end quote",
90				      SSH_USER_PERMITTED_KEYS, linenum);
91				packet_send_debug("%.100s, line %lu: missing end quote",
92						  SSH_USER_PERMITTED_KEYS, linenum);
93				continue;
94			}
95			forced_command[i] = 0;
96			packet_send_debug("Forced command: %.900s", forced_command);
97			options++;
98			goto next_option;
99		}
100		cp = "environment=\"";
101		if (strncmp(options, cp, strlen(cp)) == 0) {
102			int i;
103			char *s;
104			struct envstring *new_envstring;
105			options += strlen(cp);
106			s = xmalloc(strlen(options) + 1);
107			i = 0;
108			while (*options) {
109				if (*options == '"')
110					break;
111				if (*options == '\\' && options[1] == '"') {
112					options += 2;
113					s[i++] = '"';
114					continue;
115				}
116				s[i++] = *options++;
117			}
118			if (!*options) {
119				debug("%.100s, line %lu: missing end quote",
120				      SSH_USER_PERMITTED_KEYS, linenum);
121				packet_send_debug("%.100s, line %lu: missing end quote",
122						  SSH_USER_PERMITTED_KEYS, linenum);
123				continue;
124			}
125			s[i] = 0;
126			packet_send_debug("Adding to environment: %.900s", s);
127			debug("Adding to environment: %.900s", s);
128			options++;
129			new_envstring = xmalloc(sizeof(struct envstring));
130			new_envstring->s = s;
131			new_envstring->next = custom_environment;
132			custom_environment = new_envstring;
133			goto next_option;
134		}
135		cp = "from=\"";
136		if (strncmp(options, cp, strlen(cp)) == 0) {
137			int mname, mip;
138			char *patterns = xmalloc(strlen(options) + 1);
139			int i;
140			options += strlen(cp);
141			i = 0;
142			while (*options) {
143				if (*options == '"')
144					break;
145				if (*options == '\\' && options[1] == '"') {
146					options += 2;
147					patterns[i++] = '"';
148					continue;
149				}
150				patterns[i++] = *options++;
151			}
152			if (!*options) {
153				debug("%.100s, line %lu: missing end quote",
154				    SSH_USER_PERMITTED_KEYS, linenum);
155				packet_send_debug("%.100s, line %lu: missing end quote",
156				    SSH_USER_PERMITTED_KEYS, linenum);
157				continue;
158			}
159			patterns[i] = 0;
160			options++;
161			/*
162			 * Deny access if we get a negative
163			 * match for the hostname or the ip
164			 * or if we get not match at all
165			 */
166			mname = match_hostname(get_canonical_hostname(),
167			    patterns, strlen(patterns));
168			mip = match_hostname(get_remote_ipaddr(),
169			    patterns, strlen(patterns));
170			xfree(patterns);
171			if (mname == -1 || mip == -1 ||
172			    (mname != 1 && mip != 1)) {
173				log("Authentication tried for %.100s with correct key but not from a permitted host (host=%.200s, ip=%.200s).",
174				    pw->pw_name, get_canonical_hostname(),
175				    get_remote_ipaddr());
176				packet_send_debug("Your host '%.200s' is not permitted to use this key for login.",
177				get_canonical_hostname());
178				/* key invalid for this host, reset flags */
179				no_agent_forwarding_flag = 0;
180				no_port_forwarding_flag = 0;
181				no_pty_flag = 0;
182				no_x11_forwarding_flag = 0;
183				while (custom_environment) {
184					struct envstring *ce = custom_environment;
185					custom_environment = ce->next;
186					xfree(ce->s);
187					xfree(ce);
188				}
189				if (forced_command) {
190					xfree(forced_command);
191					forced_command = NULL;
192				}
193				/* deny access */
194				return 0;
195			}
196			/* Host name matches. */
197			goto next_option;
198		}
199next_option:
200		/*
201		 * Skip the comma, and move to the next option
202		 * (or break out if there are no more).
203		 */
204		if (!*options)
205			fatal("Bugs in auth-options.c option processing.");
206		if (*options == ' ' || *options == '\t')
207			break;		/* End of options. */
208		if (*options != ',')
209			goto bad_option;
210		options++;
211		/* Process the next option. */
212	}
213	/* grant access */
214	return 1;
215
216bad_option:
217	log("Bad options in %.100s file, line %lu: %.50s",
218	    SSH_USER_PERMITTED_KEYS, linenum, options);
219	packet_send_debug("Bad options in %.100s file, line %lu: %.50s",
220	    SSH_USER_PERMITTED_KEYS, linenum, options);
221	/* deny access */
222	return 0;
223}
224