Mercurial > dropbear

comparison cli-kex.c @ 285:1b9e69c058d2

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
propagate from branch 'au.asn.ucc.matt.ltc.dropbear' (head 20dccfc09627970a312d77fb41dc2970b62689c3) to branch 'au.asn.ucc.matt.dropbear' (head fdf4a7a3b97ae5046139915de7e40399cceb2c01)
author Matt Johnston <matt@ucc.asn.au>
date Wed, 08 Mar 2006 13:23:58 +0000
parents a62cb364f615
children 740e782679be 9916350d7d8b
comparison
equal deleted inserted replaced
281:997e6f7dc01e 285:1b9e69c058d2
1 /*
2 * Dropbear - a SSH2 server
3 *
4 * Copyright (c) 2002-2004 Matt Johnston
5 * Copyright (c) 2004 by Mihnea Stoenescu
6 * All rights reserved.
7 *
8 * Permission is hereby granted, free of charge, to any person obtaining a copy
9 * of this software and associated documentation files (the "Software"), to deal
10 * in the Software without restriction, including without limitation the rights
11 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
12 * copies of the Software, and to permit persons to whom the Software is
13 * furnished to do so, subject to the following conditions:
14 *
15 * The above copyright notice and this permission notice shall be included in
16 * all copies or substantial portions of the Software.
17 *
18 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
19 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
20 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
21 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
22 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
23 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
24 * SOFTWARE. */
25
26 #include "includes.h"
27 #include "session.h"
28 #include "dbutil.h"
29 #include "algo.h"
30 #include "buffer.h"
31 #include "session.h"
32 #include "kex.h"
33 #include "ssh.h"
34 #include "packet.h"
35 #include "bignum.h"
36 #include "random.h"
37 #include "runopts.h"
38 #include "signkey.h"
39
40
41 static void checkhostkey(unsigned char* keyblob, unsigned int keybloblen);
42 #define MAX_KNOWNHOSTS_LINE 4500
43
44 void send_msg_kexdh_init() {
45
46 cli_ses.dh_e = (mp_int*)m_malloc(sizeof(mp_int));
47 cli_ses.dh_x = (mp_int*)m_malloc(sizeof(mp_int));
48 m_mp_init_multi(cli_ses.dh_e, cli_ses.dh_x, NULL);
49
50 gen_kexdh_vals(cli_ses.dh_e, cli_ses.dh_x);
51
52 CHECKCLEARTOWRITE();
53 buf_putbyte(ses.writepayload, SSH_MSG_KEXDH_INIT);
54 buf_putmpint(ses.writepayload, cli_ses.dh_e);
55 encrypt_packet();
56 ses.requirenext = SSH_MSG_KEXDH_REPLY;
57 }
58
59 /* Handle a diffie-hellman key exchange reply. */
60 void recv_msg_kexdh_reply() {
61
62 DEF_MP_INT(dh_f);
63 sign_key *hostkey = NULL;
64 unsigned int type, keybloblen;
65 unsigned char* keyblob = NULL;
66
67
68 TRACE(("enter recv_msg_kexdh_reply"))
69
70 if (cli_ses.kex_state != KEXDH_INIT_SENT) {
71 dropbear_exit("Received out-of-order kexdhreply");
72 }
73 m_mp_init(&dh_f);
74 type = ses.newkeys->algo_hostkey;
75 TRACE(("type is %d", type))
76
77 hostkey = new_sign_key();
78 keybloblen = buf_getint(ses.payload);
79
80 keyblob = buf_getptr(ses.payload, keybloblen);
81 if (!ses.kexstate.donefirstkex) {
82 /* Only makes sense the first time */
83 checkhostkey(keyblob, keybloblen);
84 }
85
86 if (buf_get_pub_key(ses.payload, hostkey, &type) != DROPBEAR_SUCCESS) {
87 TRACE(("failed getting pubkey"))
88 dropbear_exit("Bad KEX packet");
89 }
90
91 if (buf_getmpint(ses.payload, &dh_f) != DROPBEAR_SUCCESS) {
92 TRACE(("failed getting mpint"))
93 dropbear_exit("Bad KEX packet");
94 }
95
96 kexdh_comb_key(cli_ses.dh_e, cli_ses.dh_x, &dh_f, hostkey);
97 mp_clear(&dh_f);
98 mp_clear_multi(cli_ses.dh_e, cli_ses.dh_x, NULL);
99 m_free(cli_ses.dh_e);
100 m_free(cli_ses.dh_x);
101
102 if (buf_verify(ses.payload, hostkey, ses.hash, SHA1_HASH_SIZE)
103 != DROPBEAR_SUCCESS) {
104 dropbear_exit("Bad hostkey signature");
105 }
106
107 sign_key_free(hostkey);
108 hostkey = NULL;
109
110 send_msg_newkeys();
111 ses.requirenext = SSH_MSG_NEWKEYS;
112 TRACE(("leave recv_msg_kexdh_init"))
113 }
114
115 static void ask_to_confirm(unsigned char* keyblob, unsigned int keybloblen) {
116
117 char* fp = NULL;
118 FILE *tty = NULL;
119 char response = 'z';
120
121 fp = sign_key_fingerprint(keyblob, keybloblen);
122 fprintf(stderr, "\nHost '%s' is not in the trusted hosts file.\n(fingerprint %s)\nDo you want to continue connecting? (y/n)\n",
123 cli_opts.remotehost,
124 fp);
125
126 tty = fopen(_PATH_TTY, "r");
127 if (tty) {
128 response = getc(tty);
129 fclose(tty);
130 } else {
131 response = getc(stdin);
132 }
133
134 if (response == 'y') {
135 m_free(fp);
136 return;
137 }
138
139 dropbear_exit("Didn't validate host key");
140 }
141
142 static void checkhostkey(unsigned char* keyblob, unsigned int keybloblen) {
143
144 char * filename = NULL;
145 FILE *hostsfile = NULL;
146 int readonly = 0;
147 struct passwd *pw = NULL;
148 unsigned int hostlen, algolen;
149 unsigned long len;
150 const char *algoname = NULL;
151 buffer * line = NULL;
152 int ret;
153
154 pw = getpwuid(getuid());
155
156 if (pw == NULL) {
157 dropbear_exit("Failed to get homedir");
158 }
159
160 len = strlen(pw->pw_dir);
161 filename = m_malloc(len + 18); /* "/.ssh/known_hosts" and null-terminator*/
162
163 snprintf(filename, len+18, "%s/.ssh", pw->pw_dir);
164 /* Check that ~/.ssh exists - easiest way is just to mkdir */
165 if (mkdir(filename, S_IRWXU) != 0) {
166 if (errno != EEXIST) {
167 dropbear_log(LOG_INFO, "Warning: failed creating ~/.ssh: %s",
168 strerror(errno));
169 TRACE(("mkdir didn't work: %s", strerror(errno)))
170 ask_to_confirm(keyblob, keybloblen);
171 goto out; /* only get here on success */
172 }
173 }
174
175 snprintf(filename, len+18, "%s/.ssh/known_hosts", pw->pw_dir);
176 hostsfile = fopen(filename, "a+");
177
178 if (hostsfile != NULL) {
179 fseek(hostsfile, 0, SEEK_SET);
180 } else {
181 /* We mightn't have been able to open it if it was read-only */
182 if (errno == EACCES || errno == EROFS) {
183 TRACE(("trying readonly: %s", strerror(errno)))
184 readonly = 1;
185 hostsfile = fopen(filename, "r");
186 }
187 }
188
189 if (hostsfile == NULL) {
190 TRACE(("hostsfile didn't open: %s", strerror(errno)))
191 ask_to_confirm(keyblob, keybloblen);
192 goto out; /* We only get here on success */
193 }
194
195 line = buf_new(MAX_KNOWNHOSTS_LINE);
196 hostlen = strlen(cli_opts.remotehost);
197 algoname = signkey_name_from_type(ses.newkeys->algo_hostkey, &algolen);
198
199 do {
200 if (buf_getline(line, hostsfile) == DROPBEAR_FAILURE) {
201 TRACE(("failed reading line: prob EOF"))
202 break;
203 }
204
205 /* The line is too short to be sensible */
206 /* "30" is 'enough to hold ssh-dss plus the spaces, ie so we don't
207 * buf_getfoo() past the end and die horribly - the base64 parsing
208 * code is what tiptoes up to the end nicely */
209 if (line->len < (hostlen+30) ) {
210 TRACE(("line is too short to be sensible"))
211 continue;
212 }
213
214 /* Compare hostnames */
215 if (strncmp(cli_opts.remotehost, buf_getptr(line, hostlen),
216 hostlen) != 0) {
217 TRACE(("hosts don't match"))
218 continue;
219 }
220
221 buf_incrpos(line, hostlen);
222 if (buf_getbyte(line) != ' ') {
223 /* there wasn't a space after the hostname, something dodgy */
224 TRACE(("missing space afte matching hostname"))
225 continue;
226 }
227
228 if ( strncmp(buf_getptr(line, algolen), algoname, algolen) != 0) {
229 TRACE(("algo doesn't match"))
230 continue;
231 }
232
233 buf_incrpos(line, algolen);
234 if (buf_getbyte(line) != ' ') {
235 TRACE(("missing space after algo"))
236 continue;
237 }
238
239 /* Now we're at the interesting hostkey */
240 ret = cmp_base64_key(keyblob, keybloblen, algoname, algolen, line);
241
242 if (ret == DROPBEAR_SUCCESS) {
243 /* Good matching key */
244 TRACE(("good matching key"))
245 goto out;
246 }
247
248 /* The keys didn't match. eep. */
249 } while (1); /* keep going 'til something happens */
250
251 /* Key doesn't exist yet */
252 ask_to_confirm(keyblob, keybloblen);
253
254 /* If we get here, they said yes */
255
256 if (readonly) {
257 TRACE(("readonly"))
258 goto out;
259 }
260
261 /* put the new entry in the file */
262 fseek(hostsfile, 0, SEEK_END); /* In case it wasn't opened append */
263 buf_setpos(line, 0);
264 buf_setlen(line, 0);
265 buf_putbytes(line, ses.remotehost, hostlen);
266 buf_putbyte(line, ' ');
267 buf_putbytes(line, algoname, algolen);
268 buf_putbyte(line, ' ');
269 len = line->size - line->pos;
270 TRACE(("keybloblen %d, len %d", keybloblen, len))
271 /* The only failure with base64 is buffer_overflow, but buf_getwriteptr
272 * will die horribly in the case anyway */
273 base64_encode(keyblob, keybloblen, buf_getwriteptr(line, len), &len);
274 buf_incrwritepos(line, len);
275 buf_putbyte(line, '\n');
276 buf_setpos(line, 0);
277 fwrite(buf_getptr(line, line->len), line->len, 1, hostsfile);
278 /* We ignore errors, since there's not much we can do about them */
279
280 out:
281 if (hostsfile != NULL) {
282 fclose(hostsfile);
283 }
284 m_free(filename);
285 if (line != NULL) {
286 buf_free(line);
287 }
288 }