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
|
/*
* Copyright (c) 2000 Damien Miller. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by Markus Friedl.
* 4. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "includes.h"
#include "ssh.h"
#include "xmalloc.h"
#include <openssl/rand.h>
#include <openssl/sha.h>
RCSID("$Id: entropy.c,v 1.6 2000/04/29 23:30:46 damien Exp $");
#ifdef EGD_SOCKET
#ifndef offsetof
# define offsetof(type, member) ((size_t) &((type *)0)->member)
#endif
/* Collect entropy from EGD */
void get_random_bytes(unsigned char *buf, int len)
{
static int egd_socket = -1;
int c;
char egd_message[2] = { 0x02, 0x00 };
struct sockaddr_un addr;
int addr_len;
memset(&addr, '\0', sizeof(addr));
addr.sun_family = AF_UNIX;
/* FIXME: compile time check? */
if (sizeof(EGD_SOCKET) > sizeof(addr.sun_path))
fatal("Random pool path is too long");
strcpy(addr.sun_path, EGD_SOCKET);
addr_len = offsetof(struct sockaddr_un, sun_path) + sizeof(EGD_SOCKET);
if (egd_socket == -1) {
egd_socket = socket(AF_UNIX, SOCK_STREAM, 0);
if (egd_socket == -1)
fatal("Couldn't create AF_UNIX socket: %s", strerror(errno));
if (connect(egd_socket, (struct sockaddr*)&addr, addr_len) == -1)
fatal("Couldn't connect to EGD socket \"%s\": %s", addr.sun_path, strerror(errno));
}
if (len > 255)
fatal("Too many bytes to read from EGD");
/* Send blocking read request to EGD */
egd_message[1] = len;
c = atomicio(write, egd_socket, egd_message, sizeof(egd_message));
if (c == -1)
fatal("Couldn't write to EGD socket \"%s\": %s", EGD_SOCKET, strerror(errno));
c = atomicio(read, egd_socket, buf, len);
if (c <= 0)
fatal("Couldn't read from EGD socket \"%s\": %s", EGD_SOCKET, strerror(errno));
close(EGD_SOCKET);
}
#else /* !EGD_SOCKET */
#ifdef RANDOM_POOL
/* Collect entropy from /dev/urandom or pipe */
void get_random_bytes(unsigned char *buf, int len)
{
static int random_pool = -1;
int c;
if (random_pool == -1) {
random_pool = open(RANDOM_POOL, O_RDONLY);
if (random_pool == -1)
fatal("Couldn't open random pool \"%s\": %s", RANDOM_POOL, strerror(errno));
}
c = atomicio(read, random_pool, buf, len);
if (c <= 0)
fatal("Couldn't read from random pool \"%s\": %s", RANDOM_POOL, strerror(errno));
}
#endif /* RANDOM_POOL */
#endif /* EGD_SOCKET */
#if !defined(EGD_SOCKET) && !defined(RANDOM_POOL)
/*
* FIXME: proper entropy estimations. All current values are guesses
* FIXME: (ATL) do estimates at compile time?
* FIXME: More entropy sources
* FIXME: (ATL) bring in entropy sources from file
* FIXME: (ATL) add heuristic to increase the timeout if needed
*/
/* slow command timeouts (all in milliseconds) */
/* static int entropy_timeout_default = ENTROPY_TIMEOUT_MSEC; */
static int entropy_timeout_current = ENTROPY_TIMEOUT_MSEC;
static int prng_seed_loaded = 0;
static int prng_seed_saved = 0;
typedef struct
{
/* Proportion of data that is entropy */
double rate;
/* Counter goes positive if this command times out */
unsigned int badness;
/* Increases by factor of two each timeout */
unsigned int sticky_badness;
/* Path to executable */
const char *path;
/* argv to pass to executable */
const char *args[5];
} entropy_source_t;
double stir_from_system(void);
double stir_from_programs(void);
double stir_gettimeofday(double entropy_estimate);
double stir_clock(double entropy_estimate);
double stir_rusage(int who, double entropy_estimate);
double hash_output_from_command(entropy_source_t *src, char *hash);
entropy_source_t entropy_sources[] = {
#ifdef PROG_LS
{ 0.002, 0, 1, PROG_LS, { "ls", "-alni", "/var/log", NULL } },
{ 0.002, 0, 1, PROG_LS, { "ls", "-alni", "/var/adm", NULL } },
{ 0.002, 0, 1, PROG_LS, { "ls", "-alni", "/var/mail", NULL } },
{ 0.002, 0, 1, PROG_LS, { "ls", "-alni", "/var/spool/mail", NULL } },
{ 0.002, 0, 1, PROG_LS, { "ls", "-alni", "/proc", NULL } },
{ 0.002, 0, 1, PROG_LS, { "ls", "-alni", "/tmp", NULL } },
#endif
#ifdef PROG_NETSTAT
{ 0.005, 0, 1, PROG_NETSTAT, { "netstat","-an", NULL, NULL } },
{ 0.010, 0, 1, PROG_NETSTAT, { "netstat","-in", NULL, NULL } },
{ 0.002, 0, 1, PROG_NETSTAT, { "netstat","-rn", NULL, NULL } },
{ 0.002, 0, 1, PROG_NETSTAT, { "netstat","-s", NULL, NULL } },
#endif
#ifdef PROG_ARP
{ 0.002, 0, 1, PROG_ARP, { "arp","-a","-n", NULL } },
#endif
#ifdef PROG_IFCONFIG
{ 0.002, 0, 1, PROG_IFCONFIG, { "ifconfig", "-a", NULL, NULL } },
#endif
#ifdef PROG_PS
{ 0.003, 0, 1, PROG_PS, { "ps", "laxww", NULL, NULL } },
{ 0.003, 0, 1, PROG_PS, { "ps", "-al", NULL, NULL } },
{ 0.003, 0, 1, PROG_PS, { "ps", "-efl", NULL, NULL } },
#endif
#ifdef PROG_W
{ 0.005, 0, 1, PROG_W, { "w", NULL, NULL, NULL } },
#endif
#ifdef PROG_WHO
{ 0.001, 0, 1, PROG_WHO, { "who","-i", NULL, NULL } },
#endif
#ifdef PROG_LAST
{ 0.001, 0, 1, PROG_LAST, { "last", NULL, NULL, NULL } },
#endif
#ifdef PROG_LASTLOG
{ 0.001, 0, 1, PROG_LASTLOG, { "lastlog", NULL, NULL, NULL } },
#endif
#ifdef PROG_DF
{ 0.010, 0, 1, PROG_DF, { "df", NULL, NULL, NULL } },
{ 0.010, 0, 1, PROG_DF, { "df", "-i", NULL, NULL } },
#endif
#ifdef PROG_VMSTAT
{ 0.010, 0, 1, PROG_VMSTAT, { "vmstat", NULL, NULL, NULL } },
#endif
#ifdef PROG_UPTIME
{ 0.001, 0, 1, PROG_UPTIME, { "uptime", NULL, NULL, NULL } },
#endif
#ifdef PROG_IPCS
{ 0.001, 0, 1, PROG_IPCS, { "-a", NULL, NULL, NULL } },
#endif
#ifdef PROG_TAIL
{ 0.001, 0, 1, PROG_TAIL, { "tail", "-200", "/var/log/messages", NULL, NULL } },
{ 0.001, 0, 1, PROG_TAIL, { "tail", "-200", "/var/log/syslog", NULL, NULL } },
{ 0.001, 0, 1, PROG_TAIL, { "tail", "-200", "/var/adm/messages", NULL, NULL } },
{ 0.001, 0, 1, PROG_TAIL, { "tail", "-200", "/var/adm/syslog", NULL, NULL } },
{ 0.001, 0, 1, PROG_TAIL, { "tail", "-200", "/var/log/maillog", NULL, NULL } },
{ 0.001, 0, 1, PROG_TAIL, { "tail", "-200", "/var/adm/maillog", NULL, NULL } },
#endif
{ 0.000, 0, 0, NULL, { NULL, NULL, NULL, NULL, NULL } },
};
double
stir_from_system(void)
{
double total_entropy_estimate;
long int i;
total_entropy_estimate = 0;
i = getpid();
RAND_add(&i, sizeof(i), 0.1);
total_entropy_estimate += 0.1;
i = getppid();
RAND_add(&i, sizeof(i), 0.1);
total_entropy_estimate += 0.1;
i = getuid();
RAND_add(&i, sizeof(i), 0.0);
i = getgid();
RAND_add(&i, sizeof(i), 0.0);
total_entropy_estimate += stir_gettimeofday(1.0);
total_entropy_estimate += stir_clock(0.2);
total_entropy_estimate += stir_rusage(RUSAGE_SELF, 2.0);
return(total_entropy_estimate);
}
double
stir_from_programs(void)
{
int i;
int c;
double entropy_estimate;
double total_entropy_estimate;
char hash[SHA_DIGEST_LENGTH];
/*
* Run through list of programs twice to catch differences
*/
total_entropy_estimate = 0;
for(i = 0; i < 2; i++) {
c = 0;
while (entropy_sources[c].path != NULL) {
if (!entropy_sources[c].badness) {
/* Hash output from command */
entropy_estimate = hash_output_from_command(&entropy_sources[c], hash);
/* Scale back entropy estimate according to command's rate */
entropy_estimate *= entropy_sources[c].rate;
/* Upper bound of entropy estimate is SHA_DIGEST_LENGTH */
if (entropy_estimate > SHA_DIGEST_LENGTH)
entropy_estimate = SHA_DIGEST_LENGTH;
/* * Scale back estimates for subsequent passes through list */
entropy_estimate /= 10.0 * (i + 1.0);
/* Stir it in */
RAND_add(hash, sizeof(hash), entropy_estimate);
/* FIXME: turn this off later */
#if 1
debug("Got %0.2f bytes of entropy from %s", entropy_estimate,
entropy_sources[c].path);
#endif
total_entropy_estimate += entropy_estimate;
/* Execution times should be a little unpredictable */
total_entropy_estimate += stir_gettimeofday(0.05);
total_entropy_estimate += stir_clock(0.05);
total_entropy_estimate += stir_rusage(RUSAGE_SELF, 0.1);
total_entropy_estimate += stir_rusage(RUSAGE_CHILDREN, 0.1);
} else {
/* FIXME: turn this off later */
#if 1
debug("Command '%s %s %s' disabled (badness %d)",
entropy_sources[c].path, entropy_sources[c].args[1],
entropy_sources[c].args[2], entropy_sources[c].badness);
#endif
if (entropy_sources[c].badness > 0)
entropy_sources[c].badness--;
}
c++;
}
}
return(total_entropy_estimate);
}
double
stir_gettimeofday(double entropy_estimate)
{
struct timeval tv;
if (gettimeofday(&tv, NULL) == -1)
fatal("Couldn't gettimeofday: %s", strerror(errno));
RAND_add(&tv, sizeof(tv), entropy_estimate);
return(entropy_estimate);
}
double
stir_clock(double entropy_estimate)
{
#ifdef HAVE_CLOCK
clock_t c;
c = clock();
RAND_add(&c, sizeof(c), entropy_estimate);
return(entropy_estimate);
#else /* _HAVE_CLOCK */
return(0);
#endif /* _HAVE_CLOCK */
}
double
stir_rusage(int who, double entropy_estimate)
{
#ifdef HAVE_GETRUSAGE
struct rusage ru;
if (getrusage(who, &ru) == -1)
fatal("Couldn't getrusage: %s", strerror(errno));
RAND_add(&ru, sizeof(ru), 0.1);
return(entropy_estimate);
#else /* _HAVE_GETRUSAGE */
return(0);
#endif /* _HAVE_GETRUSAGE */
}
double
hash_output_from_command(entropy_source_t *src, char *hash)
{
static int devnull = -1;
int p[2];
fd_set rdset;
int cmd_eof = 0, error_abort = 0;
pid_t pid;
int status;
char buf[2048];
int bytes_read;
int total_bytes_read;
SHA_CTX sha;
if (devnull == -1) {
devnull = open("/dev/null", O_RDWR);
if (devnull == -1)
fatal("Couldn't open /dev/null: %s", strerror(errno));
}
if (pipe(p) == -1)
fatal("Couldn't open pipe: %s", strerror(errno));
switch (pid = fork()) {
case -1: /* Error */
close(p[0]);
close(p[1]);
fatal("Couldn't fork: %s", strerror(errno));
/* NOTREACHED */
case 0: /* Child */
dup2(devnull, STDIN_FILENO);
dup2(p[1], STDOUT_FILENO);
dup2(p[1], STDERR_FILENO);
close(p[0]);
close(p[1]);
close(devnull);
execv(src->path, (char**)(src->args));
debug("(child) Couldn't exec '%s %s %s': %s", src->path,
src->args[1], src->args[2], strerror(errno));
src->badness = src->sticky_badness = 128;
_exit(-1);
default: /* Parent */
break;
}
RAND_add(&pid, sizeof(&pid), 0.0);
close(p[1]);
/* Hash output from child */
SHA1_Init(&sha);
total_bytes_read = 0;
while (!error_abort && !cmd_eof) {
int ret;
struct timeval tv;
FD_ZERO(&rdset);
FD_SET(p[0], &rdset);
tv.tv_sec = entropy_timeout_current / 1000;
tv.tv_usec = (entropy_timeout_current % 1000) * 1000;
ret = select(p[0]+1, &rdset, NULL, NULL, &tv);
switch (ret) {
case 0:
/* timer expired */
error_abort = 1;
break;
case 1:
/* command input */
bytes_read = read(p[0], buf, sizeof(buf));
if (bytes_read == -1) {
error_abort = 1;
break;
}
SHA1_Update(&sha, buf, bytes_read);
total_bytes_read += bytes_read;
RAND_add(&bytes_read, sizeof(&bytes_read), 0.0);
cmd_eof = bytes_read ? 0 : 1;
break;
case -1:
default:
error("Command '%s %s': select() failed: %s", src->path, src->args[1],
strerror(errno));
error_abort = 1;
break;
} /* switch ret */
RAND_add(&tv, sizeof(&tv), 0.0);
} /* while !error_abort && !cmd_eof */
SHA1_Final(hash, &sha);
close(p[0]);
if (waitpid(pid, &status, 0) == -1) {
error("Couldn't wait for child '%s %s' completion: %s", src->path,
src->args[1], strerror(errno));
/* return(-1); */ /* FIXME: (ATL) this doesn't feel right */
return(0.0);
}
RAND_add(&status, sizeof(&status), 0.0);
if (error_abort) {
/* closing p[0] on timeout causes the entropy command to
* SIGPIPE. Take whatever output we got, and mark this command
* as slow */
debug("Command %s %s timed out", src->path, src->args[1]);
src->sticky_badness *= 2;
src->badness = src->sticky_badness;
return(total_bytes_read);
}
if (WIFEXITED(status)) {
if (WEXITSTATUS(status)==0) {
return(total_bytes_read);
} else {
debug("Exit status was %d", WEXITSTATUS(status));
src->badness = src->sticky_badness = 128;
return (0.0);
}
} else if (WIFSIGNALED(status)) {
debug("Returned on uncaught signal %d !", status);
src->badness = src->sticky_badness = 128;
return(0.0);
} else
return(0.0);
}
/*
* prng seedfile functions
*/
int
prng_check_seedfile(char *filename) {
struct stat st;
/* FIXME raceable: eg replace seed between this stat and subsequent open */
/* Not such a problem because we don't trust the seed file anyway */
if (lstat(filename, &st) == -1) {
/* Fail on hard errors */
if (errno != ENOENT)
fatal("Couldn't stat random seed file \"%s\": %s", filename,
strerror(errno));
return(0);
}
/* regular file? */
if (!S_ISREG(st.st_mode))
fatal("PRNG seedfile %.100s is not a regular file", filename);
/* mode 0600, owned by root or the current user? */
if (((st.st_mode & 0177) != 0) || !(st.st_uid == geteuid()))
fatal("PRNG seedfile %.100s must be mode 0600, owned by uid %d",
filename, getuid());
return(1);
}
void
prng_write_seedfile(void) {
int fd;
char seed[1024];
char filename[1024];
struct passwd *pw;
/* Don't bother if we have already saved a seed */
if (prng_seed_saved)
return;
pw = getpwuid(getuid());
if (pw == NULL)
fatal("Couldn't get password entry for current user (%i): %s",
getuid(), strerror(errno));
/* Try to ensure that the parent directory is there */
snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
SSH_USER_DIR);
mkdir(filename, 0700);
snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
SSH_PRNG_SEED_FILE);
debug("writing PRNG seed to file %.100s", filename);
RAND_bytes(seed, sizeof(seed));
/* Don't care if the seed doesn't exist */
prng_check_seedfile(filename);
if ((fd = open(filename, O_WRONLY|O_TRUNC|O_CREAT, 0600)) == -1)
fatal("couldn't access PRNG seedfile %.100s (%.100s)", filename,
strerror(errno));
if (atomicio(write, fd, &seed, sizeof(seed)) != sizeof(seed))
fatal("problem writing PRNG seedfile %.100s (%.100s)", filename,
strerror(errno));
close(fd);
}
void
prng_read_seedfile(void) {
int fd;
char seed[1024];
char filename[1024];
struct passwd *pw;
pw = getpwuid(getuid());
if (pw == NULL)
fatal("Couldn't get password entry for current user (%i): %s",
getuid(), strerror(errno));
snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir,
SSH_PRNG_SEED_FILE);
debug("loading PRNG seed from file %.100s", filename);
if (!prng_check_seedfile(filename)) {
verbose("Random seed file not found, creating new");
prng_write_seedfile();
/* Reseed immediatly */
(void)stir_from_system();
(void)stir_from_programs();
return;
}
/* open the file and read in the seed */
fd = open(filename, O_RDONLY);
if (fd == -1)
fatal("could not open PRNG seedfile %.100s (%.100s)", filename,
strerror(errno));
if (atomicio(read, fd, &seed, sizeof(seed)) != sizeof(seed)) {
verbose("invalid or short read from PRNG seedfile %.100s - ignoring",
filename);
memset(seed, '\0', sizeof(seed));
}
close(fd);
/* stir in the seed, with estimated entropy zero */
RAND_add(&seed, sizeof(seed), 0.0);
}
#endif /* defined(EGD_SOCKET) || defined(RANDOM_POOL) */
#if defined(EGD_SOCKET) || defined(RANDOM_POOL)
/*
* Seed OpenSSL's random number pool from Kernel random number generator
* or EGD
*/
void
seed_rng(void)
{
char buf[32];
debug("Seeding random number generator");
get_random_bytes(buf, sizeof(buf));
RAND_add(buf, sizeof(buf), sizeof(buf));
memset(buf, '\0', sizeof(buf));
}
#else /* defined(EGD_SOCKET) || defined(RANDOM_POOL) */
/*
* Write a keyfile at exit
*/
void
prng_seed_cleanup(void *junk)
{
prng_write_seedfile();
}
/*
* Conditionally Seed OpenSSL's random number pool from
* syscalls and program output
*/
void
seed_rng(void)
{
debug("Seeding random number generator.");
debug("OpenSSL random status is now %i\n", RAND_status());
debug("%i bytes from system calls", (int)stir_from_system());
debug("%i bytes from programs", (int)stir_from_programs());
debug("OpenSSL random status is now %i\n", RAND_status());
if (!prng_seed_loaded)
{
prng_seed_loaded = 1;
prng_seed_saved = 0;
prng_read_seedfile();
fatal_add_cleanup(prng_seed_cleanup, NULL);
atexit(prng_write_seedfile);
}
}
#endif /* defined(EGD_SOCKET) || defined(RANDOM_POOL) */
|