res/res_crypto.c

   1 /*
   2  * Asterisk -- An open source telephony toolkit.
   3  *
   4  * Copyright (C) 1999 - 2006, Digium, Inc.
   5  *
   6  * Mark Spencer <markster@digium.com>
   7  *
   8  * See http://www.asterisk.org for more information about
   9  * the Asterisk project. Please do not directly contact
  10  * any of the maintainers of this project for assistance;
  11  * the project provides a web site, mailing lists and IRC
  12  * channels for your use.
  13  *
  14  * This program is free software, distributed under the terms of
  15  * the GNU General Public License Version 2. See the LICENSE file
  16  * at the top of the source tree.
  17  */
  18
  19 /*! \file
  20  *
  21  * \brief Provide Cryptographic Signature capability
  22  *
  23  * \author Mark Spencer <markster@digium.com>
  24  */
  25
  26 /*** MODULEINFO
  27         <depend>ssl</depend>
  28  ***/
  29
  30 #include "asterisk.h"
  31
  32 ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
  33
  34 #include <sys/types.h>
  35 #include <openssl/ssl.h>
  36 #include <openssl/err.h>
  37 #include <stdio.h>
  38 #include <dirent.h>
  39 #include <string.h>
  40 #include <errno.h>
  41 #include <unistd.h>
  42 #include <fcntl.h>
  43
  44 #include "asterisk/file.h"
  45 #include "asterisk/channel.h"
  46 #include "asterisk/logger.h"
  47 #include "asterisk/say.h"
  48 #include "asterisk/module.h"
  49 #include "asterisk/options.h"
  50 #include "asterisk/crypto.h"
  51 #include "asterisk/md5.h"
  52 #include "asterisk/cli.h"
  53 #include "asterisk/io.h"
  54 #include "asterisk/lock.h"
  55 #include "asterisk/utils.h"
  56
  57 /*
  58  * Asterisk uses RSA keys with SHA-1 message digests for its
  59  * digital signatures.  The choice of RSA is due to its higher
  60  * throughput on verification, and the choice of SHA-1 based
  61  * on the recently discovered collisions in MD5's compression
  62  * algorithm and recommendations of avoiding MD5 in new schemes
  63  * from various industry experts.
  64  *
  65  * We use OpenSSL to provide our crypto routines, although we never
  66  * actually use full-up SSL
  67  *
  68  */
  69
  70 /*
  71  * XXX This module is not very thread-safe.  It is for everyday stuff
  72  *     like reading keys and stuff, but there are all kinds of weird
  73  *     races with people running reload and key init at the same time
  74  *     for example
  75  *
  76  * XXXX
  77  */
  78
  79 AST_MUTEX_DEFINE_STATIC(keylock);
  80
  81 #define KEY_NEEDS_PASSCODE (1 << 16)
  82
  83 struct ast_key {
  84         /* Name of entity */
  85         char name[80];
  86         /* File name */
  87         char fn[256];
  88         /* Key type (AST_KEY_PUB or AST_KEY_PRIV, along with flags from above) */
  89         int ktype;
  90         /* RSA structure (if successfully loaded) */
  91         RSA *rsa;
  92         /* Whether we should be deleted */
  93         int delme;
  94         /* FD for input (or -1 if no input allowed, or -2 if we needed input) */
  95         int infd;
  96         /* FD for output */
  97         int outfd;
  98         /* Last MD5 Digest */
  99         unsigned char digest[16];
 100         struct ast_key *next;
 101 };
 102
 103 static struct ast_key *keys = NULL;
 104
 105
 106 #if 0
 107 static int fdprint(int fd, char *s)
 108 {
 109         return write(fd, s, strlen(s) + 1);
 110 }
 111 #endif
 112 static int pw_cb(char *buf, int size, int rwflag, void *userdata)
 113 {
 114         struct ast_key *key = (struct ast_key *)userdata;
 115         char prompt[256];
 116         int res;
 117         int tmp;
 118         if (key->infd > -1) {
 119                 snprintf(prompt, sizeof(prompt), ">>>> passcode for %s key '%s': ",
 120                          key->ktype == AST_KEY_PRIVATE ? "PRIVATE" : "PUBLIC", key->name);
 121                 write(key->outfd, prompt, strlen(prompt));
 122                 memset(buf, 0, sizeof(buf));
 123                 tmp = ast_hide_password(key->infd);
 124                 memset(buf, 0, size);
 125                 res = read(key->infd, buf, size);
 126                 ast_restore_tty(key->infd, tmp);
 127                 if (buf[strlen(buf) -1] == '\n')
 128                         buf[strlen(buf) - 1] = '\0';
 129                 return strlen(buf);
 130         } else {
 131                 /* Note that we were at least called */
 132                 key->infd = -2;
 133         }
 134         return -1;
 135 }
 136
 137 static struct ast_key *__ast_key_get(const char *kname, int ktype)
 138 {
 139         struct ast_key *key;
 140         ast_mutex_lock(&keylock);
 141         key = keys;
 142         while(key) {
 143                 if (!strcmp(kname, key->name) &&
 144                     (ktype == key->ktype))
 145                         break;
 146                 key = key->next;
 147         }
 148         ast_mutex_unlock(&keylock);
 149         return key;
 150 }
 151
 152 static struct ast_key *try_load_key (char *dir, char *fname, int ifd, int ofd, int *not2)
 153 {
 154         int ktype = 0;
 155         char *c = NULL;
 156         char ffname[256];
 157         unsigned char digest[16];
 158         FILE *f;
 159         struct MD5Context md5;
 160         struct ast_key *key;
 161         static int notice = 0;
 162         int found = 0;
 163
 164         /* Make sure its name is a public or private key */
 165
 166         if ((c = strstr(fname, ".pub")) && !strcmp(c, ".pub")) {
 167                 ktype = AST_KEY_PUBLIC;
 168         } else if ((c = strstr(fname, ".key")) && !strcmp(c, ".key")) {
 169                 ktype = AST_KEY_PRIVATE;
 170         } else
 171                 return NULL;
 172
 173         /* Get actual filename */
 174         snprintf(ffname, sizeof(ffname), "%s/%s", dir, fname);
 175
 176         ast_mutex_lock(&keylock);
 177         key = keys;
 178         while(key) {
 179                 /* Look for an existing version already */
 180                 if (!strcasecmp(key->fn, ffname))
 181                         break;
 182                 key = key->next;
 183         }
 184         ast_mutex_unlock(&keylock);
 185
 186         /* Open file */
 187         f = fopen(ffname, "r");
 188         if (!f) {
 189                 ast_log(LOG_WARNING, "Unable to open key file %s: %s\n", ffname, strerror(errno));
 190                 return NULL;
 191         }
 192         MD5Init(&md5);
 193         while(!feof(f)) {
 194                 /* Calculate a "whatever" quality md5sum of the key */
 195                 char buf[256];
 196                 memset(buf, 0, 256);
 197                 fgets(buf, sizeof(buf), f);
 198                 if (!feof(f)) {
 199                         MD5Update(&md5, (unsigned char *) buf, strlen(buf));
 200                 }
 201         }
 202         MD5Final(digest, &md5);
 203         if (key) {
 204                 /* If the MD5 sum is the same, and it isn't awaiting a passcode
 205                    then this is far enough */
 206                 if (!memcmp(digest, key->digest, 16) &&
 207                     !(key->ktype & KEY_NEEDS_PASSCODE)) {
 208                         fclose(f);
 209                         key->delme = 0;
 210                         return NULL;
 211                 } else {
 212                         /* Preserve keytype */
 213                         ktype = key->ktype;
 214                         /* Recycle the same structure */
 215                         found++;
 216                 }
 217         }
 218
 219         /* Make fname just be the normal name now */
 220         *c = '\0';
 221         if (!key) {
 222                 if (!(key = ast_calloc(1, sizeof(*key)))) {
 223                         fclose(f);
 224                         return NULL;
 225                 }
 226         }
 227         /* At this point we have a key structure (old or new).  Time to
 228            fill it with what we know */
 229         /* Gotta lock if this one already exists */
 230         if (found)
 231                 ast_mutex_lock(&keylock);
 232         /* First the filename */
 233         ast_copy_string(key->fn, ffname, sizeof(key->fn));
 234         /* Then the name */
 235         ast_copy_string(key->name, fname, sizeof(key->name));
 236         key->ktype = ktype;
 237         /* Yes, assume we're going to be deleted */
 238         key->delme = 1;
 239         /* Keep the key type */
 240         memcpy(key->digest, digest, 16);
 241         /* Can I/O takes the FD we're given */
 242         key->infd = ifd;
 243         key->outfd = ofd;
 244         /* Reset the file back to the beginning */
 245         rewind(f);
 246         /* Now load the key with the right method */
 247         if (ktype == AST_KEY_PUBLIC)
 248                 key->rsa = PEM_read_RSA_PUBKEY(f, NULL, pw_cb, key);
 249         else
 250                 key->rsa = PEM_read_RSAPrivateKey(f, NULL, pw_cb, key);
 251         fclose(f);
 252         if (key->rsa) {
 253                 if (RSA_size(key->rsa) == 128) {
 254                         /* Key loaded okay */
 255                         key->ktype &= ~KEY_NEEDS_PASSCODE;
 256                         if (option_verbose > 2)
 257                                 ast_verbose(VERBOSE_PREFIX_3 "Loaded %s key '%s'\n", key->ktype == AST_KEY_PUBLIC ? "PUBLIC" : "PRIVATE", key->name);
 258                         if (option_debug)
 259                                 ast_log(LOG_DEBUG, "Key '%s' loaded OK\n", key->name);
 260                         key->delme = 0;
 261                 } else
 262                         ast_log(LOG_NOTICE, "Key '%s' is not expected size.\n", key->name);
 263         } else if (key->infd != -2) {
 264                 ast_log(LOG_WARNING, "Key load %s '%s' failed\n",key->ktype == AST_KEY_PUBLIC ? "PUBLIC" : "PRIVATE", key->name);
 265                 if (ofd > -1) {
 266                         ERR_print_errors_fp(stderr);
 267                 } else
 268                         ERR_print_errors_fp(stderr);
 269         } else {
 270                 ast_log(LOG_NOTICE, "Key '%s' needs passcode.\n", key->name);
 271                 key->ktype |= KEY_NEEDS_PASSCODE;
 272                 if (!notice) {
 273                         if (!ast_opt_init_keys)
 274                                 ast_log(LOG_NOTICE, "Add the '-i' flag to the asterisk command line if you want to automatically initialize passcodes at launch.\n");
 275                         notice++;
 276                 }
 277                 /* Keep it anyway */
 278                 key->delme = 0;
 279                 /* Print final notice about "init keys" when done */
 280                 *not2 = 1;
 281         }
 282         if (found)
 283                 ast_mutex_unlock(&keylock);
 284         if (!found) {
 285                 ast_mutex_lock(&keylock);
 286                 key->next = keys;
 287                 keys = key;
 288                 ast_mutex_unlock(&keylock);
 289         }
 290         return key;
 291 }
 292
 293 #if 0
 294
 295 static void dump(unsigned char *src, int len)
 296 {
 297         int x;
 298         for (x=0;x<len;x++)
 299                 printf("%02x", *(src++));
 300         printf("\n");
 301 }
 302
 303 static char *binary(int y, int len)
 304 {
 305         static char res[80];
 306         int x;
 307         memset(res, 0, sizeof(res));
 308         for (x=0;x<len;x++) {
 309                 if (y & (1 << x))
 310                         res[(len - x - 1)] = '1';
 311                 else
 312                         res[(len - x - 1)] = '0';
 313         }
 314         return res;
 315 }
 316
 317 #endif
 318
 319 static int __ast_sign_bin(struct ast_key *key, const char *msg, int msglen, unsigned char *dsig)
 320 {
 321         unsigned char digest[20];
 322         unsigned int siglen = 128;
 323         int res;
 324
 325         if (key->ktype != AST_KEY_PRIVATE) {
 326                 ast_log(LOG_WARNING, "Cannot sign with a public key\n");
 327                 return -1;
 328         }
 329
 330         /* Calculate digest of message */
 331         SHA1((unsigned char *)msg, msglen, digest);
 332
 333         /* Verify signature */
 334         res = RSA_sign(NID_sha1, digest, sizeof(digest), dsig, &siglen, key->rsa);
 335
 336         if (!res) {
 337                 ast_log(LOG_WARNING, "RSA Signature (key %s) failed\n", key->name);
 338                 return -1;
 339         }
 340
 341         if (siglen != 128) {
 342                 ast_log(LOG_WARNING, "Unexpected signature length %d, expecting %d\n", (int)siglen, (int)128);
 343                 return -1;
 344         }
 345
 346         return 0;
 347
 348 }
 349
 350 static int __ast_decrypt_bin(unsigned char *dst, const unsigned char *src, int srclen, struct ast_key *key)
 351 {
 352         int res;
 353         int pos = 0;
 354         if (key->ktype != AST_KEY_PRIVATE) {
 355                 ast_log(LOG_WARNING, "Cannot decrypt with a public key\n");
 356                 return -1;
 357         }
 358
 359         if (srclen % 128) {
 360                 ast_log(LOG_NOTICE, "Tried to decrypt something not a multiple of 128 bytes\n");
 361                 return -1;
 362         }
 363         while(srclen) {
 364                 /* Process chunks 128 bytes at a time */
 365                 res = RSA_private_decrypt(128, src, dst, key->rsa, RSA_PKCS1_OAEP_PADDING);
 366                 if (res < 0)
 367                         return -1;
 368                 pos += res;
 369                 src += 128;
 370                 srclen -= 128;
 371                 dst += res;
 372         }
 373         return pos;
 374 }
 375
 376 static int __ast_encrypt_bin(unsigned char *dst, const unsigned char *src, int srclen, struct ast_key *key)
 377 {
 378         int res;
 379         int bytes;
 380         int pos = 0;
 381         if (key->ktype != AST_KEY_PUBLIC) {
 382                 ast_log(LOG_WARNING, "Cannot encrypt with a private key\n");
 383                 return -1;
 384         }
 385
 386         while(srclen) {
 387                 bytes = srclen;
 388                 if (bytes > 128 - 41)
 389                         bytes = 128 - 41;
 390                 /* Process chunks 128-41 bytes at a time */
 391                 res = RSA_public_encrypt(bytes, src, dst, key->rsa, RSA_PKCS1_OAEP_PADDING);
 392                 if (res != 128) {
 393                         ast_log(LOG_NOTICE, "How odd, encrypted size is %d\n", res);
 394                         return -1;
 395                 }
 396                 src += bytes;
 397                 srclen -= bytes;
 398                 pos += res;
 399                 dst += res;
 400         }
 401         return pos;
 402 }
 403
 404 static int __ast_sign(struct ast_key *key, char *msg, char *sig)
 405 {
 406         unsigned char dsig[128];
 407         int siglen = sizeof(dsig);
 408         int res;
 409         res = ast_sign_bin(key, msg, strlen(msg), dsig);
 410         if (!res)
 411                 /* Success -- encode (256 bytes max as documented) */
 412                 ast_base64encode(sig, dsig, siglen, 256);
 413         return res;
 414
 415 }
 416
 417 static int __ast_check_signature_bin(struct ast_key *key, const char *msg, int msglen, const unsigned char *dsig)
 418 {
 419         unsigned char digest[20];
 420         int res;
 421
 422         if (key->ktype != AST_KEY_PUBLIC) {
 423                 /* Okay, so of course you really *can* but for our purposes
 424                    we're going to say you can't */
 425                 ast_log(LOG_WARNING, "Cannot check message signature with a private key\n");
 426                 return -1;
 427         }
 428
 429         /* Calculate digest of message */
 430         SHA1((unsigned char *)msg, msglen, digest);
 431
 432         /* Verify signature */
 433         res = RSA_verify(NID_sha1, digest, sizeof(digest), (unsigned char *)dsig, 128, key->rsa);
 434
 435         if (!res) {
 436                 ast_log(LOG_DEBUG, "Key failed verification: %s\n", key->name);
 437                 return -1;
 438         }
 439         /* Pass */
 440         return 0;
 441 }
 442
 443 static int __ast_check_signature(struct ast_key *key, const char *msg, const char *sig)
 444 {
 445         unsigned char dsig[128];
 446         int res;
 447
 448         /* Decode signature */
 449         res = ast_base64decode(dsig, sig, sizeof(dsig));
 450         if (res != sizeof(dsig)) {
 451                 ast_log(LOG_WARNING, "Signature improper length (expect %d, got %d)\n", (int)sizeof(dsig), (int)res);
 452                 return -1;
 453         }
 454         res = ast_check_signature_bin(key, msg, strlen(msg), dsig);
 455         return res;
 456 }
 457
 458 static void crypto_load(int ifd, int ofd)
 459 {
 460         struct ast_key *key, *nkey, *last;
 461         DIR *dir = NULL;
 462         struct dirent *ent;
 463         int note = 0;
 464         /* Mark all keys for deletion */
 465         ast_mutex_lock(&keylock);
 466         key = keys;
 467         while(key) {
 468                 key->delme = 1;
 469                 key = key->next;
 470         }
 471         ast_mutex_unlock(&keylock);
 472         /* Load new keys */
 473         dir = opendir((char *)ast_config_AST_KEY_DIR);
 474         if (dir) {
 475                 while((ent = readdir(dir))) {
 476                         try_load_key((char *)ast_config_AST_KEY_DIR, ent->d_name, ifd, ofd, &note);
 477                 }
 478                 closedir(dir);
 479         } else
 480                 ast_log(LOG_WARNING, "Unable to open key directory '%s'\n", (char *)ast_config_AST_KEY_DIR);
 481         if (note) {
 482                 ast_log(LOG_NOTICE, "Please run the command 'init keys' to enter the passcodes for the keys\n");
 483         }
 484         ast_mutex_lock(&keylock);
 485         key = keys;
 486         last = NULL;
 487         while(key) {
 488                 nkey = key->next;
 489                 if (key->delme) {
 490                         ast_log(LOG_DEBUG, "Deleting key %s type %d\n", key->name, key->ktype);
 491                         /* Do the delete */
 492                         if (last)
 493                                 last->next = nkey;
 494                         else
 495                                 keys = nkey;
 496                         if (key->rsa)
 497                                 RSA_free(key->rsa);
 498                         free(key);
 499                 } else
 500                         last = key;
 501                 key = nkey;
 502         }
 503         ast_mutex_unlock(&keylock);
 504 }
 505
 506 static void md52sum(char *sum, unsigned char *md5)
 507 {
 508         int x;
 509         for (x=0;x<16;x++)
 510                 sum += sprintf(sum, "%02x", *(md5++));
 511 }
 512
 513 static int show_keys(int fd, int argc, char *argv[])
 514 {
 515         struct ast_key *key;
 516         char sum[16 * 2 + 1];
 517         int count_keys = 0;
 518
 519         ast_mutex_lock(&keylock);
 520         key = keys;
 521         ast_cli(fd, "%-18s %-8s %-16s %-33s\n", "Key Name", "Type", "Status", "Sum");
 522         while(key) {
 523                 md52sum(sum, key->digest);
 524                 ast_cli(fd, "%-18s %-8s %-16s %-33s\n", key->name,
 525                         (key->ktype & 0xf) == AST_KEY_PUBLIC ? "PUBLIC" : "PRIVATE",
 526                         key->ktype & KEY_NEEDS_PASSCODE ? "[Needs Passcode]" : "[Loaded]", sum);
 527
 528                 key = key->next;
 529                 count_keys++;
 530         }
 531         ast_mutex_unlock(&keylock);
 532         ast_cli(fd, "%d known RSA keys.\n", count_keys);
 533         return RESULT_SUCCESS;
 534 }
 535
 536 static int init_keys(int fd, int argc, char *argv[])
 537 {
 538         struct ast_key *key;
 539         int ign;
 540         char *kn;
 541         char tmp[256] = "";
 542
 543         key = keys;
 544         while(key) {
 545                 /* Reload keys that need pass codes now */
 546                 if (key->ktype & KEY_NEEDS_PASSCODE) {
 547                         kn = key->fn + strlen(ast_config_AST_KEY_DIR) + 1;
 548                         ast_copy_string(tmp, kn, sizeof(tmp));
 549                         try_load_key((char *)ast_config_AST_KEY_DIR, tmp, fd, fd, &ign);
 550                 }
 551                 key = key->next;
 552         }
 553         return RESULT_SUCCESS;
 554 }
 555
 556 static char show_key_usage[] =
 557 "Usage: keys show\n"
 558 "       Displays information about RSA keys known by Asterisk\n";
 559
 560 static char init_keys_usage[] =
 561 "Usage: keys init\n"
 562 "       Initializes private keys (by reading in pass code from the user)\n";
 563
 564 static struct ast_cli_entry cli_show_keys_deprecated = {
 565         { "show", "keys", NULL },
 566         show_keys, NULL,
 567         NULL };
 568
 569 static struct ast_cli_entry cli_init_keys_deprecated = {
 570         { "init", "keys", NULL },
 571         init_keys, NULL,
 572         NULL };
 573
 574 static struct ast_cli_entry cli_crypto[] = {
 575         { { "keys", "show", NULL },
 576         show_keys, "Displays RSA key information",
 577         show_key_usage, NULL, &cli_show_keys_deprecated },
 578
 579         { { "keys", "init", NULL },
 580         init_keys, "Initialize RSA key passcodes",
 581         init_keys_usage, NULL, &cli_init_keys_deprecated },
 582 };
 583
 584 static int crypto_init(void)
 585 {
 586         SSL_library_init();
 587         ERR_load_crypto_strings();
 588         ast_cli_register_multiple(cli_crypto, sizeof(cli_crypto) / sizeof(struct ast_cli_entry));
 589
 590         /* Install ourselves into stubs */
 591         ast_key_get = __ast_key_get;
 592         ast_check_signature = __ast_check_signature;
 593         ast_check_signature_bin = __ast_check_signature_bin;
 594         ast_sign = __ast_sign;
 595         ast_sign_bin = __ast_sign_bin;
 596         ast_encrypt_bin = __ast_encrypt_bin;
 597         ast_decrypt_bin = __ast_decrypt_bin;
 598         return 0;
 599 }
 600
 601 static int reload(void)
 602 {
 603         crypto_load(-1, -1);
 604         return 0;
 605 }
 606
 607 static int load_module(void)
 608 {
 609         crypto_init();
 610         if (ast_opt_init_keys)
 611                 crypto_load(STDIN_FILENO, STDOUT_FILENO);
 612         else
 613                 crypto_load(-1, -1);
 614         return 0;
 615 }
 616
 617 static int unload_module(void)
 618 {
 619         /* Can't unload this once we're loaded */
 620         return -1;
 621 }
 622
 623 /* needs usecount semantics defined */
 624 AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_GLOBAL_SYMBOLS, "Cryptographic Digital Signatures",
 625                 .load = load_module,
 626                 .unload = unload_module,
 627                 .reload = reload
 628         );