1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
|
/*
ssh-agent.c
Author: Tatu Ylonen <ylo@cs.hut.fi>
Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
All rights reserved
Created: Wed Mar 29 03:46:59 1995 ylo
The authentication agent program.
*/
#include "includes.h"
RCSID("$Id: ssh-agent.c,v 1.6 1999/09/30 08:34:25 deraadt Exp $");
#include "ssh.h"
#include "rsa.h"
#include "authfd.h"
#include "buffer.h"
#include "bufaux.h"
#include "xmalloc.h"
#include "packet.h"
#include "ssh_md5.h"
#include "getput.h"
#include "mpaux.h"
typedef struct
{
int fd;
enum { AUTH_UNUSED, AUTH_FD, AUTH_SOCKET, AUTH_SOCKET_FD,
AUTH_CONNECTION } type;
Buffer input;
Buffer output;
} SocketEntry;
unsigned int sockets_alloc = 0;
SocketEntry *sockets = NULL;
typedef struct
{
RSA *key;
char *comment;
} Identity;
unsigned int num_identities = 0;
Identity *identities = NULL;
int max_fd = 0;
void
process_request_identity(SocketEntry *e)
{
Buffer msg;
int i;
buffer_init(&msg);
buffer_put_char(&msg, SSH_AGENT_RSA_IDENTITIES_ANSWER);
buffer_put_int(&msg, num_identities);
for (i = 0; i < num_identities; i++)
{
buffer_put_int(&msg, BN_num_bits(identities[i].key->n));
buffer_put_bignum(&msg, identities[i].key->e);
buffer_put_bignum(&msg, identities[i].key->n);
buffer_put_string(&msg, identities[i].comment,
strlen(identities[i].comment));
}
buffer_put_int(&e->output, buffer_len(&msg));
buffer_append(&e->output, buffer_ptr(&msg), buffer_len(&msg));
buffer_free(&msg);
}
void
process_authentication_challenge(SocketEntry *e)
{
int i, pub_bits, len;
BIGNUM *pub_e, *pub_n, *challenge;
Buffer msg;
struct MD5Context md;
unsigned char buf[32], mdbuf[16], session_id[16];
unsigned int response_type;
buffer_init(&msg);
pub_e = BN_new();
pub_n = BN_new();
challenge = BN_new();
pub_bits = buffer_get_int(&e->input);
buffer_get_bignum(&e->input, pub_e);
buffer_get_bignum(&e->input, pub_n);
buffer_get_bignum(&e->input, challenge);
if (buffer_len(&e->input) == 0)
{
/* Compatibility code for old servers. */
memset(session_id, 0, 16);
response_type = 0;
}
else
{
/* New code. */
buffer_get(&e->input, (char *)session_id, 16);
response_type = buffer_get_int(&e->input);
}
for (i = 0; i < num_identities; i++)
if (pub_bits == BN_num_bits(identities[i].key->n) &&
BN_cmp(pub_e, identities[i].key->e) == 0 &&
BN_cmp(pub_n, identities[i].key->n) == 0)
{
/* Decrypt the challenge using the private key. */
rsa_private_decrypt(challenge, challenge, identities[i].key);
/* Compute the desired response. */
switch (response_type)
{
case 0: /* As of protocol 1.0 */
/* This response type is no longer supported. */
log("Compatibility with ssh protocol 1.0 no longer supported.");
buffer_put_char(&msg, SSH_AGENT_FAILURE);
goto send;
case 1: /* As of protocol 1.1 */
/* The response is MD5 of decrypted challenge plus session id. */
len = BN_num_bytes(challenge);
assert(len <= 32 && len);
memset(buf, 0, 32);
BN_bn2bin(challenge, buf + 32 - len);
MD5Init(&md);
MD5Update(&md, buf, 32);
MD5Update(&md, session_id, 16);
MD5Final(mdbuf, &md);
break;
default:
fatal("process_authentication_challenge: bad response_type %d",
response_type);
break;
}
/* Send the response. */
buffer_put_char(&msg, SSH_AGENT_RSA_RESPONSE);
for (i = 0; i < 16; i++)
buffer_put_char(&msg, mdbuf[i]);
goto send;
}
/* Unknown identity. Send failure. */
buffer_put_char(&msg, SSH_AGENT_FAILURE);
send:
buffer_put_int(&e->output, buffer_len(&msg));
buffer_append(&e->output, buffer_ptr(&msg),
buffer_len(&msg));
buffer_free(&msg);
BN_clear_free(pub_e);
BN_clear_free(pub_n);
BN_clear_free(challenge);
}
void
process_remove_identity(SocketEntry *e)
{
unsigned int bits;
unsigned int i;
BIGNUM *dummy, *n;
dummy = BN_new();
n = BN_new();
/* Get the key from the packet. */
bits = buffer_get_int(&e->input);
buffer_get_bignum(&e->input, dummy);
buffer_get_bignum(&e->input, n);
/* Check if we have the key. */
for (i = 0; i < num_identities; i++)
if (BN_cmp(identities[i].key->n, n) == 0)
{
/* We have this key. Free the old key. Since we don\'t want to leave
empty slots in the middle of the array, we actually free the
key there and copy data from the last entry. */
RSA_free(identities[i].key);
xfree(identities[i].comment);
if (i < num_identities - 1)
identities[i] = identities[num_identities - 1];
num_identities--;
BN_clear_free(dummy);
BN_clear_free(n);
/* Send success. */
buffer_put_int(&e->output, 1);
buffer_put_char(&e->output, SSH_AGENT_SUCCESS);
return;
}
/* We did not have the key. */
BN_clear(dummy);
BN_clear(n);
/* Send failure. */
buffer_put_int(&e->output, 1);
buffer_put_char(&e->output, SSH_AGENT_FAILURE);
}
/* Removes all identities from the agent. */
void
process_remove_all_identities(SocketEntry *e)
{
unsigned int i;
/* Loop over all identities and clear the keys. */
for (i = 0; i < num_identities; i++)
{
RSA_free(identities[i].key);
xfree(identities[i].comment);
}
/* Mark that there are no identities. */
num_identities = 0;
/* Send success. */
buffer_put_int(&e->output, 1);
buffer_put_char(&e->output, SSH_AGENT_SUCCESS);
return;
}
/* Adds an identity to the agent. */
void
process_add_identity(SocketEntry *e)
{
RSA *k;
int i;
BIGNUM *aux;
BN_CTX *ctx;
if (num_identities == 0)
identities = xmalloc(sizeof(Identity));
else
identities = xrealloc(identities, (num_identities + 1) * sizeof(Identity));
identities[num_identities].key = RSA_new();
k = identities[num_identities].key;
buffer_get_int(&e->input); /* bits */
k->n = BN_new();
buffer_get_bignum(&e->input, k->n);
k->e = BN_new();
buffer_get_bignum(&e->input, k->e);
k->d = BN_new();
buffer_get_bignum(&e->input, k->d);
k->iqmp = BN_new();
buffer_get_bignum(&e->input, k->iqmp);
/* SSH and SSL have p and q swapped */
k->q = BN_new();
buffer_get_bignum(&e->input, k->q); /* p */
k->p = BN_new();
buffer_get_bignum(&e->input, k->p); /* q */
/* Generate additional parameters */
aux = BN_new();
ctx = BN_CTX_new();
BN_sub(aux, k->q, BN_value_one());
k->dmq1 = BN_new();
BN_mod(k->dmq1, k->d, aux, ctx);
BN_sub(aux, k->p, BN_value_one());
k->dmp1 = BN_new();
BN_mod(k->dmp1, k->d, aux, ctx);
BN_clear_free(aux);
BN_CTX_free(ctx);
identities[num_identities].comment = buffer_get_string(&e->input, NULL);
/* Check if we already have the key. */
for (i = 0; i < num_identities; i++)
if (BN_cmp(identities[i].key->n, k->n) == 0)
{
/* We already have this key. Clear and free the new data and
return success. */
RSA_free(k);
xfree(identities[num_identities].comment);
/* Send success. */
buffer_put_int(&e->output, 1);
buffer_put_char(&e->output, SSH_AGENT_SUCCESS);
return;
}
/* Increment the number of identities. */
num_identities++;
/* Send a success message. */
buffer_put_int(&e->output, 1);
buffer_put_char(&e->output, SSH_AGENT_SUCCESS);
}
void
process_message(SocketEntry *e)
{
unsigned int msg_len;
unsigned int type;
unsigned char *cp;
if (buffer_len(&e->input) < 5)
return; /* Incomplete message. */
cp = (unsigned char *)buffer_ptr(&e->input);
msg_len = GET_32BIT(cp);
if (msg_len > 256 * 1024)
{
shutdown(e->fd, 2);
close(e->fd);
e->type = AUTH_UNUSED;
return;
}
if (buffer_len(&e->input) < msg_len + 4)
return;
buffer_consume(&e->input, 4);
type = buffer_get_char(&e->input);
switch (type)
{
case SSH_AGENTC_REQUEST_RSA_IDENTITIES:
process_request_identity(e);
break;
case SSH_AGENTC_RSA_CHALLENGE:
process_authentication_challenge(e);
break;
case SSH_AGENTC_ADD_RSA_IDENTITY:
process_add_identity(e);
break;
case SSH_AGENTC_REMOVE_RSA_IDENTITY:
process_remove_identity(e);
break;
case SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES:
process_remove_all_identities(e);
break;
default:
/* Unknown message. Respond with failure. */
error("Unknown message %d", type);
buffer_clear(&e->input);
buffer_put_int(&e->output, 1);
buffer_put_char(&e->output, SSH_AGENT_FAILURE);
break;
}
}
void
new_socket(int type, int fd)
{
unsigned int i, old_alloc;
if (fcntl(fd, F_SETFL, O_NONBLOCK) < 0)
error("fcntl O_NONBLOCK: %s", strerror(errno));
if (fd > max_fd)
max_fd = fd;
for (i = 0; i < sockets_alloc; i++)
if (sockets[i].type == AUTH_UNUSED)
{
sockets[i].fd = fd;
sockets[i].type = type;
buffer_init(&sockets[i].input);
buffer_init(&sockets[i].output);
return;
}
old_alloc = sockets_alloc;
sockets_alloc += 10;
if (sockets)
sockets = xrealloc(sockets, sockets_alloc * sizeof(sockets[0]));
else
sockets = xmalloc(sockets_alloc * sizeof(sockets[0]));
for (i = old_alloc; i < sockets_alloc; i++)
sockets[i].type = AUTH_UNUSED;
sockets[old_alloc].type = type;
sockets[old_alloc].fd = fd;
buffer_init(&sockets[old_alloc].input);
buffer_init(&sockets[old_alloc].output);
}
void
prepare_select(fd_set *readset, fd_set *writeset)
{
unsigned int i;
for (i = 0; i < sockets_alloc; i++)
switch (sockets[i].type)
{
case AUTH_FD:
case AUTH_CONNECTION:
case AUTH_SOCKET:
case AUTH_SOCKET_FD:
FD_SET(sockets[i].fd, readset);
if (buffer_len(&sockets[i].output) > 0)
FD_SET(sockets[i].fd, writeset);
break;
case AUTH_UNUSED:
break;
default:
fatal("Unknown socket type %d", sockets[i].type);
break;
}
}
void after_select(fd_set *readset, fd_set *writeset)
{
unsigned int i;
int len, sock, port;
char buf[1024];
struct sockaddr_in sin;
struct sockaddr_un sunaddr;
for (i = 0; i < sockets_alloc; i++)
switch (sockets[i].type)
{
case AUTH_UNUSED:
break;
case AUTH_FD:
if (FD_ISSET(sockets[i].fd, readset))
{
len = recv(sockets[i].fd, buf, sizeof(buf), 0);
if (len <= 0)
{ /* All instances of the other side have been closed. */
log("Authentication agent exiting.");
exit(0);
}
process_auth_fd_input:
if (len != 3 || (unsigned char)buf[0] != SSH_AUTHFD_CONNECT)
break; /* Incorrect message; ignore it. */
/* It is a connection request message. */
port = (unsigned char)buf[1] * 256 + (unsigned char)buf[2];
memset(&sin, 0, sizeof(sin));
sin.sin_family = AF_INET;
sin.sin_addr.s_addr = htonl(0x7f000001); /* localhost */
sin.sin_port = htons(port);
sock = socket(AF_INET, SOCK_STREAM, 0);
if (sock < 0)
{
perror("socket");
break;
}
if (connect(sock, (struct sockaddr *)&sin, sizeof(sin)) < 0)
{
perror("connecting to port requested in authfd message");
close(sock);
break;
}
new_socket(AUTH_CONNECTION, sock);
}
break;
case AUTH_SOCKET:
if (FD_ISSET(sockets[i].fd, readset))
{
len = sizeof(sunaddr);
sock = accept(sockets[i].fd, (struct sockaddr *)&sunaddr, &len);
if (sock < 0)
{
perror("accept from AUTH_SOCKET");
break;
}
new_socket(AUTH_SOCKET_FD, sock);
}
break;
case AUTH_SOCKET_FD:
if (FD_ISSET(sockets[i].fd, readset))
{
len = recv(sockets[i].fd, buf, sizeof(buf), 0);
if (len <= 0)
{ /* The other side has closed the socket. */
shutdown(sockets[i].fd, 2);
close(sockets[i].fd);
sockets[i].type = AUTH_UNUSED;
break;
}
goto process_auth_fd_input;
}
break;
case AUTH_CONNECTION:
if (buffer_len(&sockets[i].output) > 0 &&
FD_ISSET(sockets[i].fd, writeset))
{
len = write(sockets[i].fd, buffer_ptr(&sockets[i].output),
buffer_len(&sockets[i].output));
if (len <= 0)
{
shutdown(sockets[i].fd, 2);
close(sockets[i].fd);
sockets[i].type = AUTH_UNUSED;
break;
}
buffer_consume(&sockets[i].output, len);
}
if (FD_ISSET(sockets[i].fd, readset))
{
len = read(sockets[i].fd, buf, sizeof(buf));
if (len <= 0)
{
shutdown(sockets[i].fd, 2);
close(sockets[i].fd);
sockets[i].type = AUTH_UNUSED;
break;
}
buffer_append(&sockets[i].input, buf, len);
process_message(&sockets[i]);
}
break;
default:
fatal("Unknown type %d", sockets[i].type);
}
}
int parent_pid = -1;
char socket_name[1024];
void
check_parent_exists(int sig)
{
if (kill(parent_pid, 0) < 0)
{
remove(socket_name);
/* printf("Parent has died - Authentication agent exiting.\n"); */
exit(1);
}
signal(SIGALRM, check_parent_exists);
alarm(10);
}
int
main(int ac, char **av)
{
fd_set readset, writeset;
char buf[1024];
int pfd;
int sock;
struct sockaddr_un sunaddr;
int sockets[2], i;
int *dups;
/* check if RSA support exists */
if (rsa_alive() == 0) {
extern char *__progname;
fprintf(stderr,
"%s: no RSA support in libssl and libcrypto. See ssl(8).\n",
__progname);
exit(1);
}
if (ac < 2)
{
fprintf(stderr, "ssh-agent version %s\n", SSH_VERSION);
fprintf(stderr, "Usage: %s command\n", av[0]);
exit(1);
}
pfd = get_permanent_fd(NULL);
if (pfd < 0)
{
/* The agent uses SSH_AUTHENTICATION_SOCKET. */
parent_pid = getpid();
snprintf(socket_name, sizeof socket_name, SSH_AGENT_SOCKET, parent_pid);
/* Fork, and have the parent execute the command. The child continues as
the authentication agent. */
if (fork() != 0)
{ /* Parent - execute the given command. */
snprintf(buf, sizeof buf, "SSH_AUTHENTICATION_SOCKET=%s", socket_name);
putenv(buf);
execvp(av[1], av + 1);
perror(av[1]);
exit(1);
}
sock = socket(AF_UNIX, SOCK_STREAM, 0);
if (sock < 0)
{
perror("socket");
exit(1);
}
memset(&sunaddr, 0, sizeof(sunaddr));
sunaddr.sun_family = AF_UNIX;
strlcpy(sunaddr.sun_path, socket_name, sizeof(sunaddr.sun_path));
if (bind(sock, (struct sockaddr *)&sunaddr, sizeof(sunaddr)) < 0)
{
perror("bind");
exit(1);
}
if (chmod(socket_name, 0700) < 0)
{
perror("chmod");
exit(1);
}
if (listen(sock, 5) < 0)
{
perror("listen");
exit(1);
}
new_socket(AUTH_SOCKET, sock);
signal(SIGALRM, check_parent_exists);
alarm(10);
}
else
{
/* The agent uses SSH_AUTHENTICATION_FD. */
int cnt, newfd;
dups = xmalloc(sizeof (int) * (1 + pfd));
if (socketpair(AF_UNIX, SOCK_STREAM, 0, sockets) < 0)
{
perror("socketpair");
exit(1);
}
/* Dup some descriptors to get the authentication fd to pfd,
because some shells arbitrarily close descriptors below that.
Don't use dup2 because maybe some systems don't have it?? */
for (cnt = 0;; cnt++) {
if ((dups[cnt] = dup(0)) < 0)
fatal("auth_input_request_forwarding: dup failed");
if (dups[cnt] == pfd)
break;
}
close(dups[cnt]);
/* Move the file descriptor we pass to children up high where
the shell won't close it. */
newfd = dup(sockets[1]);
if (newfd != pfd)
fatal("auth_input_request_forwarding: dup didn't return %d.", pfd);
close(sockets[1]);
sockets[1] = newfd;
/* Close duped descriptors. */
for (i = 0; i < cnt; i++)
close(dups[i]);
free(dups);
if (fork() != 0)
{ /* Parent - execute the given command. */
close(sockets[0]);
snprintf(buf, sizeof buf, "SSH_AUTHENTICATION_FD=%d", sockets[1]);
putenv(buf);
execvp(av[1], av + 1);
perror(av[1]);
exit(1);
}
close(sockets[1]);
new_socket(AUTH_FD, sockets[0]);
}
signal(SIGINT, SIG_IGN);
while (1)
{
FD_ZERO(&readset);
FD_ZERO(&writeset);
prepare_select(&readset, &writeset);
if (select(max_fd + 1, &readset, &writeset, NULL, NULL) < 0)
{
if (errno == EINTR)
continue;
perror("select");
exit(1);
}
after_select(&readset, &writeset);
}
/*NOTREACHED*/
}
|