| 1 | /* |
| 2 | * Code for PuTTY to import and export private key files in other |
| 3 | * SSH clients' formats. |
| 4 | */ |
| 5 | |
| 6 | #include <stdio.h> |
| 7 | #include <stdlib.h> |
| 8 | #include <assert.h> |
| 9 | #include <ctype.h> |
| 10 | |
| 11 | #include "ssh.h" |
| 12 | #include "misc.h" |
| 13 | |
| 14 | #define PUT_32BIT(cp, value) do { \ |
| 15 | (cp)[3] = (value); \ |
| 16 | (cp)[2] = (value) >> 8; \ |
| 17 | (cp)[1] = (value) >> 16; \ |
| 18 | (cp)[0] = (value) >> 24; } while (0) |
| 19 | |
| 20 | #define GET_32BIT(cp) \ |
| 21 | (((unsigned long)(unsigned char)(cp)[0] << 24) | \ |
| 22 | ((unsigned long)(unsigned char)(cp)[1] << 16) | \ |
| 23 | ((unsigned long)(unsigned char)(cp)[2] << 8) | \ |
| 24 | ((unsigned long)(unsigned char)(cp)[3])) |
| 25 | |
| 26 | int openssh_encrypted(char *filename); |
| 27 | struct ssh2_userkey *openssh_read(char *filename, char *passphrase); |
| 28 | |
| 29 | int sshcom_encrypted(char *filename, char **comment); |
| 30 | struct ssh2_userkey *sshcom_read(char *filename, char *passphrase); |
| 31 | |
| 32 | /* |
| 33 | * Given a key type, determine whether we know how to import it. |
| 34 | */ |
| 35 | int import_possible(int type) |
| 36 | { |
| 37 | if (type == SSH_KEYTYPE_OPENSSH) |
| 38 | return 1; |
| 39 | if (type == SSH_KEYTYPE_SSHCOM) |
| 40 | return 1; |
| 41 | return 0; |
| 42 | } |
| 43 | |
| 44 | /* |
| 45 | * Given a key type, determine what native key type |
| 46 | * (SSH_KEYTYPE_SSH1 or SSH_KEYTYPE_SSH2) it will come out as once |
| 47 | * we've imported it. |
| 48 | */ |
| 49 | int import_target_type(int type) |
| 50 | { |
| 51 | /* |
| 52 | * There are no known foreign SSH1 key formats. |
| 53 | */ |
| 54 | return SSH_KEYTYPE_SSH2; |
| 55 | } |
| 56 | |
| 57 | /* |
| 58 | * Determine whether a foreign key is encrypted. |
| 59 | */ |
| 60 | int import_encrypted(char *filename, int type, char **comment) |
| 61 | { |
| 62 | if (type == SSH_KEYTYPE_OPENSSH) { |
| 63 | *comment = filename; /* OpenSSH doesn't do key comments */ |
| 64 | return openssh_encrypted(filename); |
| 65 | } |
| 66 | if (type == SSH_KEYTYPE_SSHCOM) { |
| 67 | return sshcom_encrypted(filename, comment); |
| 68 | } |
| 69 | return 0; |
| 70 | } |
| 71 | |
| 72 | /* |
| 73 | * Import an SSH1 key. |
| 74 | */ |
| 75 | int import_ssh1(char *filename, int type, struct RSAKey *key, char *passphrase) |
| 76 | { |
| 77 | return 0; |
| 78 | } |
| 79 | |
| 80 | /* |
| 81 | * Import an SSH2 key. |
| 82 | */ |
| 83 | struct ssh2_userkey *import_ssh2(char *filename, int type, char *passphrase) |
| 84 | { |
| 85 | if (type == SSH_KEYTYPE_OPENSSH) |
| 86 | return openssh_read(filename, passphrase); |
| 87 | if (type == SSH_KEYTYPE_SSHCOM) |
| 88 | return sshcom_read(filename, passphrase); |
| 89 | return NULL; |
| 90 | } |
| 91 | |
| 92 | /* |
| 93 | * Export an SSH1 key. |
| 94 | */ |
| 95 | int export_ssh1(char *filename, int type, struct RSAKey *key, char *passphrase) |
| 96 | { |
| 97 | return 0; |
| 98 | } |
| 99 | |
| 100 | /* |
| 101 | * Export an SSH2 key. |
| 102 | */ |
| 103 | int export_ssh2(char *filename, int type, |
| 104 | struct ssh2_userkey *key, char *passphrase) |
| 105 | { |
| 106 | #if 0 |
| 107 | if (type == SSH_KEYTYPE_OPENSSH) |
| 108 | return openssh_write(filename, key, passphrase); |
| 109 | if (type == SSH_KEYTYPE_SSHCOM) |
| 110 | return sshcom_write(filename, key, passphrase); |
| 111 | #endif |
| 112 | return 0; |
| 113 | } |
| 114 | |
| 115 | /* ---------------------------------------------------------------------- |
| 116 | * Helper routines. (The base64 ones are defined in sshpubk.c.) |
| 117 | */ |
| 118 | |
| 119 | #define isbase64(c) ( ((c) >= 'A' && (c) <= 'Z') || \ |
| 120 | ((c) >= 'a' && (c) <= 'z') || \ |
| 121 | ((c) >= '0' && (c) <= '9') || \ |
| 122 | (c) == '+' || (c) == '/' || (c) == '=' \ |
| 123 | ) |
| 124 | |
| 125 | extern int base64_decode_atom(char *atom, unsigned char *out); |
| 126 | extern int base64_lines(int datalen); |
| 127 | extern void base64_encode_atom(unsigned char *data, int n, char *out); |
| 128 | extern void base64_encode(FILE * fp, unsigned char *data, int datalen); |
| 129 | |
| 130 | /* |
| 131 | * Read an ASN.1/BER identifier and length pair. |
| 132 | * |
| 133 | * Flags are a combination of the #defines listed below. |
| 134 | * |
| 135 | * Returns -1 if unsuccessful; otherwise returns the number of |
| 136 | * bytes used out of the source data. |
| 137 | */ |
| 138 | |
| 139 | /* ASN.1 tag classes. */ |
| 140 | #define ASN1_CLASS_UNIVERSAL (0 << 6) |
| 141 | #define ASN1_CLASS_APPLICATION (1 << 6) |
| 142 | #define ASN1_CLASS_CONTEXT_SPECIFIC (2 << 6) |
| 143 | #define ASN1_CLASS_PRIVATE (3 << 6) |
| 144 | #define ASN1_CLASS_MASK (3 << 6) |
| 145 | |
| 146 | /* Primitive versus constructed bit. */ |
| 147 | #define ASN1_CONSTRUCTED (1 << 5) |
| 148 | |
| 149 | int ber_read_id_len(void *source, int sourcelen, |
| 150 | int *id, int *length, int *flags) |
| 151 | { |
| 152 | unsigned char *p = (unsigned char *) source; |
| 153 | |
| 154 | if (sourcelen == 0) |
| 155 | return -1; |
| 156 | |
| 157 | *flags = (*p & 0xE0); |
| 158 | if ((*p & 0x1F) == 0x1F) { |
| 159 | *id = 0; |
| 160 | while (*p & 0x80) { |
| 161 | *id = (*id << 7) | (*p & 0x7F); |
| 162 | p++, sourcelen--; |
| 163 | if (sourcelen == 0) |
| 164 | return -1; |
| 165 | } |
| 166 | *id = (*id << 7) | (*p & 0x7F); |
| 167 | p++, sourcelen--; |
| 168 | } else { |
| 169 | *id = *p & 0x1F; |
| 170 | p++, sourcelen--; |
| 171 | } |
| 172 | |
| 173 | if (sourcelen == 0) |
| 174 | return -1; |
| 175 | |
| 176 | if (*p & 0x80) { |
| 177 | int n = *p & 0x7F; |
| 178 | p++, sourcelen--; |
| 179 | if (sourcelen < n) |
| 180 | return -1; |
| 181 | *length = 0; |
| 182 | while (n--) |
| 183 | *length = (*length << 8) | (*p++); |
| 184 | sourcelen -= n; |
| 185 | } else { |
| 186 | *length = *p; |
| 187 | p++, sourcelen--; |
| 188 | } |
| 189 | |
| 190 | return p - (unsigned char *) source; |
| 191 | } |
| 192 | |
| 193 | static int put_string(void *target, void *data, int len) |
| 194 | { |
| 195 | unsigned char *d = (unsigned char *)target; |
| 196 | |
| 197 | PUT_32BIT(d, len); |
| 198 | memcpy(d+4, data, len); |
| 199 | return len+4; |
| 200 | } |
| 201 | |
| 202 | static int put_mp(void *target, void *data, int len) |
| 203 | { |
| 204 | unsigned char *d = (unsigned char *)target; |
| 205 | unsigned char *i = (unsigned char *)data; |
| 206 | |
| 207 | if (*i & 0x80) { |
| 208 | PUT_32BIT(d, len+1); |
| 209 | d[4] = 0; |
| 210 | memcpy(d+5, data, len); |
| 211 | return len+5; |
| 212 | } else { |
| 213 | PUT_32BIT(d, len); |
| 214 | memcpy(d+4, data, len); |
| 215 | return len+4; |
| 216 | } |
| 217 | } |
| 218 | |
| 219 | /* ---------------------------------------------------------------------- |
| 220 | * Code to read OpenSSH private keys. |
| 221 | */ |
| 222 | |
| 223 | enum { OSSH_DSA, OSSH_RSA }; |
| 224 | struct openssh_key { |
| 225 | int type; |
| 226 | int encrypted; |
| 227 | char iv[32]; |
| 228 | unsigned char *keyblob; |
| 229 | int keyblob_len, keyblob_size; |
| 230 | }; |
| 231 | |
| 232 | struct openssh_key *load_openssh_key(char *filename) |
| 233 | { |
| 234 | struct openssh_key *ret; |
| 235 | FILE *fp; |
| 236 | char buffer[256]; |
| 237 | char *errmsg, *p; |
| 238 | int headers_done; |
| 239 | char base64_bit[4]; |
| 240 | int base64_chars = 0; |
| 241 | |
| 242 | ret = smalloc(sizeof(*ret)); |
| 243 | ret->keyblob = NULL; |
| 244 | ret->keyblob_len = ret->keyblob_size = 0; |
| 245 | ret->encrypted = 0; |
| 246 | memset(ret->iv, 0, sizeof(ret->iv)); |
| 247 | |
| 248 | fp = fopen(filename, "r"); |
| 249 | if (!fp) { |
| 250 | errmsg = "Unable to open key file"; |
| 251 | goto error; |
| 252 | } |
| 253 | if (!fgets(buffer, sizeof(buffer), fp) || |
| 254 | 0 != strncmp(buffer, "-----BEGIN ", 11) || |
| 255 | 0 != strcmp(buffer+strlen(buffer)-17, "PRIVATE KEY-----\n")) { |
| 256 | errmsg = "File does not begin with OpenSSH key header"; |
| 257 | goto error; |
| 258 | } |
| 259 | if (!strcmp(buffer, "-----BEGIN RSA PRIVATE KEY-----\n")) |
| 260 | ret->type = OSSH_RSA; |
| 261 | else if (!strcmp(buffer, "-----BEGIN DSA PRIVATE KEY-----\n")) |
| 262 | ret->type = OSSH_DSA; |
| 263 | else { |
| 264 | errmsg = "Unrecognised key type"; |
| 265 | goto error; |
| 266 | } |
| 267 | |
| 268 | headers_done = 0; |
| 269 | while (1) { |
| 270 | if (!fgets(buffer, sizeof(buffer), fp)) { |
| 271 | errmsg = "Unexpected end of file"; |
| 272 | goto error; |
| 273 | } |
| 274 | if (0 == strncmp(buffer, "-----END ", 9) && |
| 275 | 0 == strcmp(buffer+strlen(buffer)-17, "PRIVATE KEY-----\n")) |
| 276 | break; /* done */ |
| 277 | if ((p = strchr(buffer, ':')) != NULL) { |
| 278 | if (headers_done) { |
| 279 | errmsg = "Header found in body of key data"; |
| 280 | goto error; |
| 281 | } |
| 282 | *p++ = '\0'; |
| 283 | while (*p && isspace((unsigned char)*p)) p++; |
| 284 | if (!strcmp(buffer, "Proc-Type")) { |
| 285 | if (p[0] != '4' || p[1] != ',') { |
| 286 | errmsg = "Proc-Type is not 4 (only 4 is supported)"; |
| 287 | goto error; |
| 288 | } |
| 289 | p += 2; |
| 290 | if (!strcmp(p, "ENCRYPTED\n")) |
| 291 | ret->encrypted = 1; |
| 292 | } else if (!strcmp(buffer, "DEK-Info")) { |
| 293 | int i, j; |
| 294 | |
| 295 | if (strncmp(p, "DES-EDE3-CBC,", 13)) { |
| 296 | errmsg = "Ciphers other than DES-EDE3-CBC not supported"; |
| 297 | goto error; |
| 298 | } |
| 299 | p += 13; |
| 300 | for (i = 0; i < 8; i++) { |
| 301 | if (1 != sscanf(p, "%2x", &j)) |
| 302 | break; |
| 303 | ret->iv[i] = j; |
| 304 | p += 2; |
| 305 | } |
| 306 | if (i < 8) { |
| 307 | errmsg = "Expected 16-digit iv in DEK-Info"; |
| 308 | goto error; |
| 309 | } |
| 310 | } |
| 311 | } else { |
| 312 | headers_done = 1; |
| 313 | |
| 314 | p = buffer; |
| 315 | while (isbase64(*p)) { |
| 316 | base64_bit[base64_chars++] = *p; |
| 317 | if (base64_chars == 4) { |
| 318 | unsigned char out[3]; |
| 319 | int len; |
| 320 | |
| 321 | base64_chars = 0; |
| 322 | |
| 323 | len = base64_decode_atom(base64_bit, out); |
| 324 | |
| 325 | if (len <= 0) { |
| 326 | errmsg = "Invalid base64 encoding"; |
| 327 | goto error; |
| 328 | } |
| 329 | |
| 330 | if (ret->keyblob_len + len > ret->keyblob_size) { |
| 331 | ret->keyblob_size = ret->keyblob_len + len + 256; |
| 332 | ret->keyblob = srealloc(ret->keyblob, ret->keyblob_size); |
| 333 | } |
| 334 | |
| 335 | memcpy(ret->keyblob + ret->keyblob_len, out, len); |
| 336 | ret->keyblob_len += len; |
| 337 | |
| 338 | memset(out, 0, sizeof(out)); |
| 339 | } |
| 340 | |
| 341 | p++; |
| 342 | } |
| 343 | } |
| 344 | } |
| 345 | |
| 346 | if (ret->keyblob_len == 0 || !ret->keyblob) { |
| 347 | errmsg = "Key body not present"; |
| 348 | goto error; |
| 349 | } |
| 350 | |
| 351 | if (ret->encrypted && ret->keyblob_len % 8 != 0) { |
| 352 | errmsg = "Encrypted key blob is not a multiple of cipher block size"; |
| 353 | goto error; |
| 354 | } |
| 355 | |
| 356 | memset(buffer, 0, sizeof(buffer)); |
| 357 | memset(base64_bit, 0, sizeof(base64_bit)); |
| 358 | return ret; |
| 359 | |
| 360 | error: |
| 361 | memset(buffer, 0, sizeof(buffer)); |
| 362 | memset(base64_bit, 0, sizeof(base64_bit)); |
| 363 | if (ret) { |
| 364 | if (ret->keyblob) { |
| 365 | memset(ret->keyblob, 0, ret->keyblob_size); |
| 366 | sfree(ret->keyblob); |
| 367 | } |
| 368 | memset(&ret, 0, sizeof(ret)); |
| 369 | sfree(ret); |
| 370 | } |
| 371 | return NULL; |
| 372 | } |
| 373 | |
| 374 | int openssh_encrypted(char *filename) |
| 375 | { |
| 376 | struct openssh_key *key = load_openssh_key(filename); |
| 377 | int ret; |
| 378 | |
| 379 | if (!key) |
| 380 | return 0; |
| 381 | ret = key->encrypted; |
| 382 | memset(key->keyblob, 0, key->keyblob_size); |
| 383 | sfree(key->keyblob); |
| 384 | memset(&key, 0, sizeof(key)); |
| 385 | sfree(key); |
| 386 | return ret; |
| 387 | } |
| 388 | |
| 389 | struct ssh2_userkey *openssh_read(char *filename, char *passphrase) |
| 390 | { |
| 391 | struct openssh_key *key = load_openssh_key(filename); |
| 392 | struct ssh2_userkey *retkey; |
| 393 | unsigned char *p; |
| 394 | int ret, id, len, flags; |
| 395 | int i, num_integers; |
| 396 | struct ssh2_userkey *retval = NULL; |
| 397 | char *errmsg; |
| 398 | unsigned char *blob; |
| 399 | int blobsize, blobptr, privptr; |
| 400 | char *modptr; |
| 401 | int modlen; |
| 402 | |
| 403 | if (!key) |
| 404 | return NULL; |
| 405 | |
| 406 | if (key->encrypted) { |
| 407 | /* |
| 408 | * Derive encryption key from passphrase and iv/salt: |
| 409 | * |
| 410 | * - let block A equal MD5(passphrase || iv) |
| 411 | * - let block B equal MD5(A || passphrase || iv) |
| 412 | * - block C would be MD5(B || passphrase || iv) and so on |
| 413 | * - encryption key is the first N bytes of A || B |
| 414 | */ |
| 415 | struct MD5Context md5c; |
| 416 | unsigned char keybuf[32]; |
| 417 | |
| 418 | MD5Init(&md5c); |
| 419 | MD5Update(&md5c, passphrase, strlen(passphrase)); |
| 420 | MD5Update(&md5c, key->iv, 8); |
| 421 | MD5Final(keybuf, &md5c); |
| 422 | |
| 423 | MD5Init(&md5c); |
| 424 | MD5Update(&md5c, keybuf, 16); |
| 425 | MD5Update(&md5c, passphrase, strlen(passphrase)); |
| 426 | MD5Update(&md5c, key->iv, 8); |
| 427 | MD5Final(keybuf+16, &md5c); |
| 428 | |
| 429 | /* |
| 430 | * Now decrypt the key blob. |
| 431 | */ |
| 432 | des3_decrypt_pubkey_ossh(keybuf, key->iv, |
| 433 | key->keyblob, key->keyblob_len); |
| 434 | |
| 435 | memset(&md5c, 0, sizeof(md5c)); |
| 436 | memset(keybuf, 0, sizeof(keybuf)); |
| 437 | } |
| 438 | |
| 439 | /* |
| 440 | * Now we have a decrypted key blob, which contains an ASN.1 |
| 441 | * encoded private key. We must now untangle the ASN.1. |
| 442 | * |
| 443 | * We expect the whole key blob to be formatted as a SEQUENCE |
| 444 | * (0x30 followed by a length code indicating that the rest of |
| 445 | * the blob is part of the sequence). Within that SEQUENCE we |
| 446 | * expect to see a bunch of INTEGERs. What those integers mean |
| 447 | * depends on the key type: |
| 448 | * |
| 449 | * - For RSA, we expect the integers to be 0, n, e, d, p, q, |
| 450 | * dmp1, dmq1, iqmp in that order. (The last three are d mod |
| 451 | * (p-1), d mod (q-1), inverse of q mod p respectively.) |
| 452 | * |
| 453 | * - For DSA, we expect them to be 0, p, q, g, y, x in that |
| 454 | * order. |
| 455 | */ |
| 456 | |
| 457 | p = key->keyblob; |
| 458 | |
| 459 | /* Expect the SEQUENCE header. Take its absence as a failure to decrypt. */ |
| 460 | ret = ber_read_id_len(p, key->keyblob_len, &id, &len, &flags); |
| 461 | p += ret; |
| 462 | if (ret < 0 || id != 16) { |
| 463 | errmsg = "ASN.1 decoding failure"; |
| 464 | retval = SSH2_WRONG_PASSPHRASE; |
| 465 | goto error; |
| 466 | } |
| 467 | |
| 468 | /* Expect a load of INTEGERs. */ |
| 469 | if (key->type == OSSH_RSA) |
| 470 | num_integers = 9; |
| 471 | else if (key->type == OSSH_DSA) |
| 472 | num_integers = 6; |
| 473 | |
| 474 | /* |
| 475 | * Space to create key blob in. |
| 476 | */ |
| 477 | blobsize = 256+key->keyblob_len; |
| 478 | blob = smalloc(blobsize); |
| 479 | PUT_32BIT(blob, 7); |
| 480 | if (key->type == OSSH_DSA) |
| 481 | memcpy(blob+4, "ssh-dss", 7); |
| 482 | else if (key->type == OSSH_RSA) |
| 483 | memcpy(blob+4, "ssh-rsa", 7); |
| 484 | blobptr = 4+7; |
| 485 | privptr = -1; |
| 486 | |
| 487 | for (i = 0; i < num_integers; i++) { |
| 488 | ret = ber_read_id_len(p, key->keyblob+key->keyblob_len-p, |
| 489 | &id, &len, &flags); |
| 490 | p += ret; |
| 491 | if (ret < 0 || id != 2 || |
| 492 | key->keyblob+key->keyblob_len-p < len) { |
| 493 | errmsg = "ASN.1 decoding failure"; |
| 494 | goto error; |
| 495 | } |
| 496 | |
| 497 | if (i == 0) { |
| 498 | /* |
| 499 | * The first integer should be zero always (I think |
| 500 | * this is some sort of version indication). |
| 501 | */ |
| 502 | if (len != 1 || p[0] != 0) { |
| 503 | errmsg = "Version number mismatch"; |
| 504 | goto error; |
| 505 | } |
| 506 | } else if (key->type == OSSH_RSA) { |
| 507 | /* |
| 508 | * Integers 1 and 2 go into the public blob but in the |
| 509 | * opposite order; integers 3, 4, 5 and 8 go into the |
| 510 | * private blob. The other two (6 and 7) are ignored. |
| 511 | */ |
| 512 | if (i == 1) { |
| 513 | /* Save the details for after we deal with number 2. */ |
| 514 | modptr = p; |
| 515 | modlen = len; |
| 516 | } else if (i != 6 && i != 7) { |
| 517 | PUT_32BIT(blob+blobptr, len); |
| 518 | memcpy(blob+blobptr+4, p, len); |
| 519 | blobptr += 4+len; |
| 520 | if (i == 2) { |
| 521 | PUT_32BIT(blob+blobptr, modlen); |
| 522 | memcpy(blob+blobptr+4, modptr, modlen); |
| 523 | blobptr += 4+modlen; |
| 524 | privptr = blobptr; |
| 525 | } |
| 526 | } |
| 527 | } else if (key->type == OSSH_DSA) { |
| 528 | /* |
| 529 | * Integers 1-4 go into the public blob; integer 5 goes |
| 530 | * into the private blob. |
| 531 | */ |
| 532 | PUT_32BIT(blob+blobptr, len); |
| 533 | memcpy(blob+blobptr+4, p, len); |
| 534 | blobptr += 4+len; |
| 535 | if (i == 4) |
| 536 | privptr = blobptr; |
| 537 | } |
| 538 | |
| 539 | /* Skip past the number. */ |
| 540 | p += len; |
| 541 | } |
| 542 | |
| 543 | /* |
| 544 | * Now put together the actual key. Simplest way to do this is |
| 545 | * to assemble our own key blobs and feed them to the createkey |
| 546 | * functions; this is a bit faffy but it does mean we get all |
| 547 | * the sanity checks for free. |
| 548 | */ |
| 549 | assert(privptr > 0); /* should have bombed by now if not */ |
| 550 | retkey = smalloc(sizeof(struct ssh2_userkey)); |
| 551 | retkey->alg = (key->type == OSSH_RSA ? &ssh_rsa : &ssh_dss); |
| 552 | retkey->data = retkey->alg->createkey(blob, privptr, |
| 553 | blob+privptr, blobptr-privptr); |
| 554 | if (!retkey->data) { |
| 555 | sfree(retkey); |
| 556 | errmsg = "unable to create key data structure"; |
| 557 | goto error; |
| 558 | } |
| 559 | |
| 560 | retkey->comment = dupstr("imported-openssh-key"); |
| 561 | errmsg = NULL; /* no error */ |
| 562 | retval = retkey; |
| 563 | |
| 564 | error: |
| 565 | if (blob) { |
| 566 | memset(blob, 0, blobsize); |
| 567 | sfree(blob); |
| 568 | } |
| 569 | memset(key->keyblob, 0, key->keyblob_size); |
| 570 | sfree(key->keyblob); |
| 571 | memset(&key, 0, sizeof(key)); |
| 572 | sfree(key); |
| 573 | return retval; |
| 574 | } |
| 575 | |
| 576 | /* ---------------------------------------------------------------------- |
| 577 | * Code to read ssh.com private keys. |
| 578 | */ |
| 579 | |
| 580 | /* |
| 581 | * The format of the base64 blob is largely ssh2-packet-formatted, |
| 582 | * except that mpints are a bit different: they're more like the |
| 583 | * old ssh1 mpint. You have a 32-bit bit count N, followed by |
| 584 | * (N+7)/8 bytes of data. |
| 585 | * |
| 586 | * So. The blob contains: |
| 587 | * |
| 588 | * - uint32 0x3f6ff9eb (magic number) |
| 589 | * - uint32 size (total blob size) |
| 590 | * - string key-type (see below) |
| 591 | * - string cipher-type (tells you if key is encrypted) |
| 592 | * - string encrypted-blob |
| 593 | * |
| 594 | * (The first size field includes the size field itself and the |
| 595 | * magic number before it. All other size fields are ordinary ssh2 |
| 596 | * strings, so the size field indicates how much data is to |
| 597 | * _follow_.) |
| 598 | * |
| 599 | * The encrypted blob, once decrypted, contains a single string |
| 600 | * which in turn contains the payload. (This allows padding to be |
| 601 | * added after that string while still making it clear where the |
| 602 | * real payload ends. Also it probably makes for a reasonable |
| 603 | * decryption check.) |
| 604 | * |
| 605 | * The payload blob, for an RSA key, contains: |
| 606 | * - mpint e |
| 607 | * - mpint d |
| 608 | * - mpint n (yes, the public and private stuff is intermixed) |
| 609 | * - mpint u (presumably inverse of p mod q) |
| 610 | * - mpint p (p is the smaller prime) |
| 611 | * - mpint q (q is the larger) |
| 612 | * |
| 613 | * For a DSA key, the payload blob contains: |
| 614 | * - uint32 0 |
| 615 | * - mpint p |
| 616 | * - mpint g |
| 617 | * - mpint q |
| 618 | * - mpint y |
| 619 | * - mpint x |
| 620 | * |
| 621 | * Alternatively, if the parameters are `predefined', that |
| 622 | * (0,p,g,q) sequence can be replaced by a uint32 1 and a string |
| 623 | * containing some predefined parameter specification. *shudder*, |
| 624 | * but I doubt we'll encounter this in real life. |
| 625 | * |
| 626 | * The key type strings are ghastly. The RSA key I looked at had a |
| 627 | * type string of |
| 628 | * |
| 629 | * `if-modn{sign{rsa-pkcs1-sha1},encrypt{rsa-pkcs1v2-oaep}}' |
| 630 | * |
| 631 | * and the DSA key wasn't much better: |
| 632 | * |
| 633 | * `dl-modp{sign{dsa-nist-sha1},dh{plain}}' |
| 634 | * |
| 635 | * It isn't clear that these will always be the same. I think it |
| 636 | * might be wise just to look at the `if-modn{sign{rsa' and |
| 637 | * `dl-modp{sign{dsa' prefixes. |
| 638 | * |
| 639 | * Finally, the encryption. The cipher-type string appears to be |
| 640 | * either `none' or `3des-cbc'. Looks as if this is SSH2-style |
| 641 | * 3des-cbc (i.e. outer cbc rather than inner). The key is created |
| 642 | * from the passphrase by means of yet another hashing faff: |
| 643 | * |
| 644 | * - first 16 bytes are MD5(passphrase) |
| 645 | * - next 16 bytes are MD5(passphrase || first 16 bytes) |
| 646 | * - if there were more, they'd be MD5(passphrase || first 32), |
| 647 | * and so on. |
| 648 | */ |
| 649 | |
| 650 | struct sshcom_key { |
| 651 | char comment[256]; /* allowing any length is overkill */ |
| 652 | unsigned char *keyblob; |
| 653 | int keyblob_len, keyblob_size; |
| 654 | }; |
| 655 | |
| 656 | struct sshcom_key *load_sshcom_key(char *filename) |
| 657 | { |
| 658 | struct sshcom_key *ret; |
| 659 | FILE *fp; |
| 660 | char buffer[256]; |
| 661 | int len; |
| 662 | char *errmsg, *p; |
| 663 | int headers_done; |
| 664 | char base64_bit[4]; |
| 665 | int base64_chars = 0; |
| 666 | |
| 667 | ret = smalloc(sizeof(*ret)); |
| 668 | ret->comment[0] = '\0'; |
| 669 | ret->keyblob = NULL; |
| 670 | ret->keyblob_len = ret->keyblob_size = 0; |
| 671 | |
| 672 | fp = fopen(filename, "r"); |
| 673 | if (!fp) { |
| 674 | errmsg = "Unable to open key file"; |
| 675 | goto error; |
| 676 | } |
| 677 | if (!fgets(buffer, sizeof(buffer), fp) || |
| 678 | 0 != strcmp(buffer, "---- BEGIN SSH2 ENCRYPTED PRIVATE KEY ----\n")) { |
| 679 | errmsg = "File does not begin with ssh.com key header"; |
| 680 | goto error; |
| 681 | } |
| 682 | |
| 683 | headers_done = 0; |
| 684 | while (1) { |
| 685 | if (!fgets(buffer, sizeof(buffer), fp)) { |
| 686 | errmsg = "Unexpected end of file"; |
| 687 | goto error; |
| 688 | } |
| 689 | if (!strcmp(buffer, "---- END SSH2 ENCRYPTED PRIVATE KEY ----\n")) |
| 690 | break; /* done */ |
| 691 | if ((p = strchr(buffer, ':')) != NULL) { |
| 692 | if (headers_done) { |
| 693 | errmsg = "Header found in body of key data"; |
| 694 | goto error; |
| 695 | } |
| 696 | *p++ = '\0'; |
| 697 | while (*p && isspace((unsigned char)*p)) p++; |
| 698 | /* |
| 699 | * Header lines can end in a trailing backslash for |
| 700 | * continuation. |
| 701 | */ |
| 702 | while ((len = strlen(p)) > sizeof(buffer) - (p-buffer) -1 || |
| 703 | p[len-1] != '\n' || p[len-2] == '\\') { |
| 704 | if (len > (p-buffer) + sizeof(buffer)-2) { |
| 705 | errmsg = "Header line too long to deal with"; |
| 706 | goto error; |
| 707 | } |
| 708 | if (!fgets(p+len-2, sizeof(buffer)-(p-buffer)-(len-2), fp)) { |
| 709 | errmsg = "Unexpected end of file"; |
| 710 | goto error; |
| 711 | } |
| 712 | } |
| 713 | p[strcspn(p, "\n")] = '\0'; |
| 714 | if (!strcmp(buffer, "Comment")) { |
| 715 | /* Strip quotes in comment if present. */ |
| 716 | if (p[0] == '"' && p[strlen(p)-1] == '"') { |
| 717 | p++; |
| 718 | p[strlen(p)-1] = '\0'; |
| 719 | } |
| 720 | strncpy(ret->comment, p, sizeof(ret->comment)); |
| 721 | ret->comment[sizeof(ret->comment)-1] = '\0'; |
| 722 | } |
| 723 | } else { |
| 724 | headers_done = 1; |
| 725 | |
| 726 | p = buffer; |
| 727 | while (isbase64(*p)) { |
| 728 | base64_bit[base64_chars++] = *p; |
| 729 | if (base64_chars == 4) { |
| 730 | unsigned char out[3]; |
| 731 | |
| 732 | base64_chars = 0; |
| 733 | |
| 734 | len = base64_decode_atom(base64_bit, out); |
| 735 | |
| 736 | if (len <= 0) { |
| 737 | errmsg = "Invalid base64 encoding"; |
| 738 | goto error; |
| 739 | } |
| 740 | |
| 741 | if (ret->keyblob_len + len > ret->keyblob_size) { |
| 742 | ret->keyblob_size = ret->keyblob_len + len + 256; |
| 743 | ret->keyblob = srealloc(ret->keyblob, ret->keyblob_size); |
| 744 | } |
| 745 | |
| 746 | memcpy(ret->keyblob + ret->keyblob_len, out, len); |
| 747 | ret->keyblob_len += len; |
| 748 | } |
| 749 | |
| 750 | p++; |
| 751 | } |
| 752 | } |
| 753 | } |
| 754 | |
| 755 | if (ret->keyblob_len == 0 || !ret->keyblob) { |
| 756 | errmsg = "Key body not present"; |
| 757 | goto error; |
| 758 | } |
| 759 | |
| 760 | return ret; |
| 761 | |
| 762 | error: |
| 763 | if (ret) { |
| 764 | if (ret->keyblob) { |
| 765 | memset(ret->keyblob, 0, ret->keyblob_size); |
| 766 | sfree(ret->keyblob); |
| 767 | } |
| 768 | memset(&ret, 0, sizeof(ret)); |
| 769 | sfree(ret); |
| 770 | } |
| 771 | return NULL; |
| 772 | } |
| 773 | |
| 774 | int sshcom_encrypted(char *filename, char **comment) |
| 775 | { |
| 776 | struct sshcom_key *key = load_sshcom_key(filename); |
| 777 | int pos, len, answer; |
| 778 | |
| 779 | *comment = NULL; |
| 780 | if (!key) |
| 781 | return 0; |
| 782 | |
| 783 | /* |
| 784 | * Check magic number. |
| 785 | */ |
| 786 | if (GET_32BIT(key->keyblob) != 0x3f6ff9eb) |
| 787 | return 0; /* key is invalid */ |
| 788 | |
| 789 | /* |
| 790 | * Find the cipher-type string. |
| 791 | */ |
| 792 | answer = 0; |
| 793 | pos = 8; |
| 794 | if (key->keyblob_len < pos+4) |
| 795 | goto done; /* key is far too short */ |
| 796 | pos += 4 + GET_32BIT(key->keyblob + pos); /* skip key type */ |
| 797 | if (key->keyblob_len < pos+4) |
| 798 | goto done; /* key is far too short */ |
| 799 | len = GET_32BIT(key->keyblob + pos); /* find cipher-type length */ |
| 800 | if (key->keyblob_len < pos+4+len) |
| 801 | goto done; /* cipher type string is incomplete */ |
| 802 | if (len != 4 || 0 != memcmp(key->keyblob + pos + 4, "none", 4)) |
| 803 | answer = 1; |
| 804 | |
| 805 | done: |
| 806 | *comment = dupstr(key->comment); |
| 807 | memset(key->keyblob, 0, key->keyblob_size); |
| 808 | sfree(key->keyblob); |
| 809 | memset(&key, 0, sizeof(key)); |
| 810 | sfree(key); |
| 811 | return answer; |
| 812 | } |
| 813 | |
| 814 | struct mpint_pos { void *start; int bytes; }; |
| 815 | |
| 816 | int sshcom_read_mpint(void *data, int len, struct mpint_pos *ret) |
| 817 | { |
| 818 | int bits; |
| 819 | int bytes; |
| 820 | unsigned char *d = (unsigned char *) data; |
| 821 | |
| 822 | if (len < 4) |
| 823 | goto error; |
| 824 | bits = GET_32BIT(d); |
| 825 | |
| 826 | bytes = (bits + 7) / 8; |
| 827 | if (len < 4+bytes) |
| 828 | goto error; |
| 829 | |
| 830 | ret->start = d + 4; |
| 831 | ret->bytes = bytes; |
| 832 | return bytes+4; |
| 833 | |
| 834 | error: |
| 835 | ret->start = NULL; |
| 836 | ret->bytes = -1; |
| 837 | return len; /* ensure further calls fail as well */ |
| 838 | } |
| 839 | |
| 840 | struct ssh2_userkey *sshcom_read(char *filename, char *passphrase) |
| 841 | { |
| 842 | struct sshcom_key *key = load_sshcom_key(filename); |
| 843 | char *errmsg; |
| 844 | int pos, len; |
| 845 | const char prefix_rsa[] = "if-modn{sign{rsa"; |
| 846 | const char prefix_dsa[] = "dl-modp{sign{dsa"; |
| 847 | enum { RSA, DSA } type; |
| 848 | int encrypted; |
| 849 | char *ciphertext; |
| 850 | int cipherlen; |
| 851 | struct ssh2_userkey *ret = NULL, *retkey; |
| 852 | const struct ssh_signkey *alg; |
| 853 | unsigned char *blob = NULL; |
| 854 | int blobsize, publen, privlen; |
| 855 | |
| 856 | if (!key) |
| 857 | return NULL; |
| 858 | |
| 859 | /* |
| 860 | * Check magic number. |
| 861 | */ |
| 862 | if (GET_32BIT(key->keyblob) != 0x3f6ff9eb) { |
| 863 | errmsg = "Key does not begin with magic number"; |
| 864 | goto error; |
| 865 | } |
| 866 | |
| 867 | /* |
| 868 | * Determine the key type. |
| 869 | */ |
| 870 | pos = 8; |
| 871 | if (key->keyblob_len < pos+4 || |
| 872 | (len = GET_32BIT(key->keyblob + pos)) > key->keyblob_len - pos - 4) { |
| 873 | errmsg = "Key blob does not contain a key type string"; |
| 874 | goto error; |
| 875 | } |
| 876 | if (len > sizeof(prefix_rsa) - 1 && |
| 877 | !memcmp(key->keyblob+pos+4, prefix_rsa, sizeof(prefix_rsa) - 1)) { |
| 878 | type = RSA; |
| 879 | } else if (len > sizeof(prefix_dsa) - 1 && |
| 880 | !memcmp(key->keyblob+pos+4, prefix_dsa, sizeof(prefix_dsa) - 1)) { |
| 881 | type = DSA; |
| 882 | } else { |
| 883 | errmsg = "Key is of unknown type"; |
| 884 | goto error; |
| 885 | } |
| 886 | pos += 4+len; |
| 887 | |
| 888 | /* |
| 889 | * Determine the cipher type. |
| 890 | */ |
| 891 | if (key->keyblob_len < pos+4 || |
| 892 | (len = GET_32BIT(key->keyblob + pos)) > key->keyblob_len - pos - 4) { |
| 893 | errmsg = "Key blob does not contain a cipher type string"; |
| 894 | goto error; |
| 895 | } |
| 896 | if (len == 4 && !memcmp(key->keyblob+pos+4, "none", 4)) |
| 897 | encrypted = 0; |
| 898 | else if (len == 8 && !memcmp(key->keyblob+pos+4, "3des-cbc", 8)) |
| 899 | encrypted = 1; |
| 900 | else { |
| 901 | errmsg = "Key encryption is of unknown type"; |
| 902 | goto error; |
| 903 | } |
| 904 | pos += 4+len; |
| 905 | |
| 906 | /* |
| 907 | * Get hold of the encrypted part of the key. |
| 908 | */ |
| 909 | if (key->keyblob_len < pos+4 || |
| 910 | (len = GET_32BIT(key->keyblob + pos)) > key->keyblob_len - pos - 4) { |
| 911 | errmsg = "Key blob does not contain actual key data"; |
| 912 | goto error; |
| 913 | } |
| 914 | ciphertext = key->keyblob + pos + 4; |
| 915 | cipherlen = len; |
| 916 | if (cipherlen == 0) { |
| 917 | errmsg = "Length of key data is zero"; |
| 918 | goto error; |
| 919 | } |
| 920 | |
| 921 | /* |
| 922 | * Decrypt it if necessary. |
| 923 | */ |
| 924 | if (encrypted) { |
| 925 | /* |
| 926 | * Derive encryption key from passphrase and iv/salt: |
| 927 | * |
| 928 | * - let block A equal MD5(passphrase) |
| 929 | * - let block B equal MD5(passphrase || A) |
| 930 | * - block C would be MD5(passphrase || A || B) and so on |
| 931 | * - encryption key is the first N bytes of A || B |
| 932 | */ |
| 933 | struct MD5Context md5c; |
| 934 | unsigned char keybuf[32], iv[8]; |
| 935 | |
| 936 | if (cipherlen % 8 != 0) { |
| 937 | errmsg = "Encrypted part of key is not a multiple of cipher block" |
| 938 | " size"; |
| 939 | goto error; |
| 940 | } |
| 941 | |
| 942 | MD5Init(&md5c); |
| 943 | MD5Update(&md5c, passphrase, strlen(passphrase)); |
| 944 | MD5Final(keybuf, &md5c); |
| 945 | |
| 946 | MD5Init(&md5c); |
| 947 | MD5Update(&md5c, passphrase, strlen(passphrase)); |
| 948 | MD5Update(&md5c, keybuf, 16); |
| 949 | MD5Final(keybuf+16, &md5c); |
| 950 | |
| 951 | /* |
| 952 | * Now decrypt the key blob. |
| 953 | */ |
| 954 | memset(iv, 0, sizeof(iv)); |
| 955 | des3_decrypt_pubkey_ossh(keybuf, iv, ciphertext, cipherlen); |
| 956 | |
| 957 | memset(&md5c, 0, sizeof(md5c)); |
| 958 | memset(keybuf, 0, sizeof(keybuf)); |
| 959 | |
| 960 | /* |
| 961 | * Hereafter we return WRONG_PASSPHRASE for any parsing |
| 962 | * error. (But only if we've just tried to decrypt it! |
| 963 | * Returning WRONG_PASSPHRASE for an unencrypted key is |
| 964 | * automatic doom.) |
| 965 | */ |
| 966 | if (encrypted) |
| 967 | ret = SSH2_WRONG_PASSPHRASE; |
| 968 | } |
| 969 | |
| 970 | /* |
| 971 | * Strip away the containing string to get to the real meat. |
| 972 | */ |
| 973 | len = GET_32BIT(ciphertext); |
| 974 | if (len > cipherlen-4) { |
| 975 | errmsg = "containing string was ill-formed"; |
| 976 | goto error; |
| 977 | } |
| 978 | ciphertext += 4; |
| 979 | cipherlen = len; |
| 980 | |
| 981 | /* |
| 982 | * Now we break down into RSA versus DSA. In either case we'll |
| 983 | * construct public and private blobs in our own format, and |
| 984 | * end up feeding them to alg->createkey(). |
| 985 | */ |
| 986 | blobsize = cipherlen + 256; |
| 987 | blob = smalloc(blobsize); |
| 988 | privlen = 0; |
| 989 | if (type == RSA) { |
| 990 | struct mpint_pos n, e, d, u, p, q; |
| 991 | int pos = 0; |
| 992 | pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &e); |
| 993 | pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &d); |
| 994 | pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &n); |
| 995 | pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &u); |
| 996 | pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &p); |
| 997 | pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &q); |
| 998 | if (!q.start) { |
| 999 | errmsg = "key data did not contain six integers"; |
| 1000 | goto error; |
| 1001 | } |
| 1002 | |
| 1003 | alg = &ssh_rsa; |
| 1004 | pos = 0; |
| 1005 | pos += put_string(blob+pos, "ssh-rsa", 7); |
| 1006 | pos += put_mp(blob+pos, e.start, e.bytes); |
| 1007 | pos += put_mp(blob+pos, n.start, n.bytes); |
| 1008 | publen = pos; |
| 1009 | pos += put_string(blob+pos, d.start, d.bytes); |
| 1010 | pos += put_mp(blob+pos, q.start, q.bytes); |
| 1011 | pos += put_mp(blob+pos, p.start, p.bytes); |
| 1012 | pos += put_mp(blob+pos, u.start, u.bytes); |
| 1013 | privlen = pos - publen; |
| 1014 | } else if (type == DSA) { |
| 1015 | struct mpint_pos p, q, g, x, y; |
| 1016 | int pos = 4; |
| 1017 | if (GET_32BIT(ciphertext) != 0) { |
| 1018 | errmsg = "predefined DSA parameters not supported"; |
| 1019 | goto error; |
| 1020 | } |
| 1021 | pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &p); |
| 1022 | pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &g); |
| 1023 | pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &q); |
| 1024 | pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &y); |
| 1025 | pos += sshcom_read_mpint(ciphertext+pos, cipherlen-pos, &x); |
| 1026 | if (!x.start) { |
| 1027 | errmsg = "key data did not contain five integers"; |
| 1028 | goto error; |
| 1029 | } |
| 1030 | |
| 1031 | alg = &ssh_dss; |
| 1032 | pos = 0; |
| 1033 | pos += put_string(blob+pos, "ssh-dss", 7); |
| 1034 | pos += put_mp(blob+pos, p.start, p.bytes); |
| 1035 | pos += put_mp(blob+pos, q.start, q.bytes); |
| 1036 | pos += put_mp(blob+pos, g.start, g.bytes); |
| 1037 | pos += put_mp(blob+pos, y.start, y.bytes); |
| 1038 | publen = pos; |
| 1039 | pos += put_mp(blob+pos, x.start, x.bytes); |
| 1040 | privlen = pos - publen; |
| 1041 | } |
| 1042 | |
| 1043 | assert(privlen > 0); /* should have bombed by now if not */ |
| 1044 | |
| 1045 | retkey = smalloc(sizeof(struct ssh2_userkey)); |
| 1046 | retkey->alg = alg; |
| 1047 | retkey->data = alg->createkey(blob, publen, blob+publen, privlen); |
| 1048 | if (!retkey->data) { |
| 1049 | sfree(retkey); |
| 1050 | errmsg = "unable to create key data structure"; |
| 1051 | goto error; |
| 1052 | } |
| 1053 | retkey->comment = dupstr(key->comment); |
| 1054 | |
| 1055 | errmsg = NULL; /* no error */ |
| 1056 | ret = retkey; |
| 1057 | |
| 1058 | error: |
| 1059 | if (blob) { |
| 1060 | memset(blob, 0, blobsize); |
| 1061 | sfree(blob); |
| 1062 | } |
| 1063 | memset(key->keyblob, 0, key->keyblob_size); |
| 1064 | sfree(key->keyblob); |
| 1065 | memset(&key, 0, sizeof(key)); |
| 1066 | sfree(key); |
| 1067 | return ret; |
| 1068 | } |