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comparison svr-agentfwd.c @ 4:fe6bca95afa7

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Makefile.in contains updated files required
author Matt Johnston <matt@ucc.asn.au>
date Tue, 01 Jun 2004 02:46:09 +0000
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children bc6477a6c393
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-1:000000000000 4:fe6bca95afa7
1 /*
2 * Dropbear - a SSH2 server
3 *
4 * Copyright (c) 2002,2003 Matt Johnston
5 * All rights reserved.
6 *
7 * Permission is hereby granted, free of charge, to any person obtaining a copy
8 * of this software and associated documentation files (the "Software"), to deal
9 * in the Software without restriction, including without limitation the rights
10 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
11 * copies of the Software, and to permit persons to whom the Software is
12 * furnished to do so, subject to the following conditions:
13 *
14 * The above copyright notice and this permission notice shall be included in
15 * all copies or substantial portions of the Software.
16 *
17 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
18 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
19 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
20 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
21 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
22 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
23 * SOFTWARE. */
24
25 /* This file (agentfwd.c) handles authentication agent forwarding, for OpenSSH
26 * style agents. */
27
28 #include "includes.h"
29
30 #ifndef DISABLE_AGENTFWD
31
32 #include "agentfwd.h"
33 #include "session.h"
34 #include "ssh.h"
35 #include "dbutil.h"
36 #include "chansession.h"
37 #include "channel.h"
38 #include "packet.h"
39 #include "buffer.h"
40 #include "random.h"
41
42 #define AGENTDIRPREFIX "/tmp/dropbear-"
43
44 static int send_msg_channel_open_agent(int fd);
45 static int bindagent(struct ChanSess * chansess);
46
47 /* Handles client requests to start agent forwarding, sets up listening socket.
48 * Returns DROPBEAR_SUCCESS or DROPBEAR_FAILURE */
49 int agentreq(struct ChanSess * chansess) {
50
51 if (chansess->agentfd != -1) {
52 return DROPBEAR_FAILURE;
53 }
54
55 /* create listening socket */
56 chansess->agentfd = socket(PF_UNIX, SOCK_STREAM, 0);
57 if (chansess->agentfd < 0) {
58 goto fail;
59 }
60
61 /* create the unix socket dir and file */
62 if (bindagent(chansess) == DROPBEAR_FAILURE) {
63 return DROPBEAR_FAILURE;
64 }
65
66 /* listen */
67 if (listen(chansess->agentfd, 20) < 0) {
68 goto fail;
69 }
70
71 /* set non-blocking */
72 if (fcntl(chansess->agentfd, F_SETFL, O_NONBLOCK) < 0) {
73 goto fail;
74 }
75
76 /* channel.c's channel fd code will handle the socket now */
77
78 /* set the maxfd so that select() loop will notice it */
79 ses.maxfd = MAX(ses.maxfd, chansess->agentfd);
80
81 return DROPBEAR_SUCCESS;
82
83 fail:
84 /* cleanup */
85 agentcleanup(chansess);
86
87 return DROPBEAR_FAILURE;
88 }
89
90 /* accepts a connection on the forwarded socket and opens a new channel for it
91 * back to the client */
92 /* returns DROPBEAR_SUCCESS or DROPBEAR_FAILURE */
93 int agentaccept(struct ChanSess * chansess) {
94
95 int fd;
96
97 fd = accept(chansess->agentfd, NULL, NULL);
98 if (fd < 0) {
99 return DROPBEAR_FAILURE;
100 }
101
102 return send_msg_channel_open_agent(fd);
103
104 }
105
106 /* set up the environment variable pointing to the socket. This is called
107 * just before command/shell execution, after dropping priveleges */
108 void agentset(struct ChanSess * chansess) {
109
110 char *path = NULL;
111 int len;
112
113 if (chansess->agentfd == -1) {
114 return;
115 }
116
117 /* 2 for "/" and "\0" */
118 len = strlen(chansess->agentdir) + strlen(chansess->agentfile) + 2;
119
120 path = m_malloc(len);
121 snprintf(path, len, "%s/%s", chansess->agentdir, chansess->agentfile);
122 addnewvar("SSH_AUTH_SOCK", path);
123 m_free(path);
124 }
125
126 /* close the socket, remove the socket-file */
127 void agentcleanup(struct ChanSess * chansess) {
128
129 char *path = NULL;
130 uid_t uid;
131 gid_t gid;
132 int len;
133
134 if (chansess->agentfd == -1) {
135 return;
136 }
137
138 close(chansess->agentfd);
139
140 /* Remove the dir as the user. That way they can't cause problems except
141 * for themselves */
142 uid = getuid();
143 gid = getgid();
144 if ((setegid(ses.authstate.pw->pw_gid)) < 0 ||
145 (seteuid(ses.authstate.pw->pw_uid)) < 0) {
146 dropbear_exit("failed to set euid");
147 }
148
149 /* 2 for "/" and "\0" */
150 len = strlen(chansess->agentdir) + strlen(chansess->agentfile) + 2;
151
152 path = m_malloc(len);
153 snprintf(path, len, "%s/%s", chansess->agentdir, chansess->agentfile);
154 unlink(path);
155 m_free(path);
156
157 rmdir(chansess->agentdir);
158
159 if ((seteuid(uid)) < 0 ||
160 (setegid(gid)) < 0) {
161 dropbear_exit("failed to revert euid");
162 }
163
164 m_free(chansess->agentfile);
165 m_free(chansess->agentdir);
166
167 }
168
169 /* helper for accepting an agent request */
170 static int send_msg_channel_open_agent(int fd) {
171
172 if (send_msg_channel_open_init(fd, CHANNEL_ID_AGENT,
173 "[email protected]") == DROPBEAR_SUCCESS) {
174 encrypt_packet();
175 return DROPBEAR_SUCCESS;
176 } else {
177 return DROPBEAR_FAILURE;
178 }
179 }
180
181 /* helper for creating the agent socket-file
182 returns DROPBEAR_SUCCESS or DROPBEAR_FAILURE */
183 static int bindagent(struct ChanSess * chansess) {
184
185 struct sockaddr_un addr;
186 unsigned int prefix;
187 char path[sizeof(addr.sun_path)], sockfile[sizeof(addr.sun_path)];
188 mode_t mode;
189 int i;
190 uid_t uid;
191 gid_t gid;
192 int ret = DROPBEAR_FAILURE;
193
194 /* drop to user privs to make the dir/file */
195 uid = getuid();
196 gid = getgid();
197 if ((setegid(ses.authstate.pw->pw_gid)) < 0 ||
198 (seteuid(ses.authstate.pw->pw_uid)) < 0) {
199 dropbear_exit("failed to set euid");
200 }
201
202 memset((void*)&addr, 0x0, sizeof(addr));
203 addr.sun_family = AF_UNIX;
204
205 mode = S_IRWXU;
206
207 for (i = 0; i < 20; i++) {
208 genrandom((unsigned char*)&prefix, sizeof(prefix));
209 /* we want 32 bits (8 hex digits) - "/tmp/dropbear-f19c62c0" */
210 snprintf(path, sizeof(path), AGENTDIRPREFIX "%.8x", prefix);
211
212 if (mkdir(path, mode) == 0) {
213 goto bindsocket;
214 }
215 if (errno != EEXIST) {
216 break;
217 }
218 }
219 /* couldn't make a dir */
220 goto out;
221
222 bindsocket:
223 /* Format is "/tmp/dropbear-0246dead/auth-d00f7654-23".
224 * The "23" is the file desc, the random data is to avoid collisions
225 * between subsequent user processes reusing socket fds (odds are now
226 * 1/(2^64) */
227 genrandom((unsigned char*)&prefix, sizeof(prefix));
228 snprintf(sockfile, sizeof(sockfile), "auth-%.8x-%d", prefix,
229 chansess->agentfd);
230 snprintf(addr.sun_path, sizeof(addr.sun_path), "%s/%s", path, sockfile);
231
232 if (bind(chansess->agentfd, (struct sockaddr*)&addr, sizeof(addr)) == 0) {
233 chansess->agentdir = strdup(path);
234 chansess->agentfile = strdup(sockfile);
235 ret = DROPBEAR_SUCCESS;
236 }
237
238
239 out:
240 if ((seteuid(uid)) < 0 ||
241 (setegid(gid)) < 0) {
242 dropbear_exit("failed to revert euid");
243 }
244 return ret;
245 }
246
247 #endif