1 /*- 2 * Copyright (c) 2016 Konrad Witaszczyk <def@FreeBSD.org> 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND 15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE 18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24 * SUCH DAMAGE. 25 */ 26 27 #include <sys/cdefs.h> 28 __FBSDID("$FreeBSD$"); 29 30 #include <sys/types.h> 31 #include <sys/capsicum.h> 32 #include <sys/endian.h> 33 #include <sys/kerneldump.h> 34 #include <sys/sysctl.h> 35 #include <sys/wait.h> 36 37 #include <ctype.h> 38 #include <capsicum_helpers.h> 39 #include <fcntl.h> 40 #include <stdbool.h> 41 #include <stdlib.h> 42 #include <string.h> 43 #include <unistd.h> 44 45 #include <openssl/evp.h> 46 #include <openssl/pem.h> 47 #include <openssl/rsa.h> 48 #include <openssl/engine.h> 49 50 #include "pjdlog.h" 51 52 #define DECRYPTCORE_CRASHDIR "/var/crash" 53 54 static void 55 usage(void) 56 { 57 58 pjdlog_exitx(1, 59 "usage: decryptcore [-fLv] -p privatekeyfile -k keyfile -e encryptedcore -c core\n" 60 " decryptcore [-fLv] [-d crashdir] -p privatekeyfile -n dumpnr"); 61 } 62 63 static int 64 wait_for_process(pid_t pid) 65 { 66 int status; 67 68 if (waitpid(pid, &status, WUNTRACED | WEXITED) == -1) { 69 pjdlog_errno(LOG_ERR, "Unable to wait for a child process"); 70 return (1); 71 } 72 73 if (WIFEXITED(status)) 74 return (WEXITSTATUS(status)); 75 76 return (1); 77 } 78 79 static struct kerneldumpkey * 80 read_key(int kfd) 81 { 82 struct kerneldumpkey *kdk; 83 ssize_t size; 84 size_t kdksize; 85 86 PJDLOG_ASSERT(kfd >= 0); 87 88 kdksize = sizeof(*kdk); 89 kdk = calloc(1, kdksize); 90 if (kdk == NULL) { 91 pjdlog_errno(LOG_ERR, "Unable to allocate kernel dump key"); 92 goto failed; 93 } 94 95 size = read(kfd, kdk, kdksize); 96 if (size == (ssize_t)kdksize) { 97 kdk->kdk_encryptedkeysize = dtoh32(kdk->kdk_encryptedkeysize); 98 kdksize += (size_t)kdk->kdk_encryptedkeysize; 99 kdk = realloc(kdk, kdksize); 100 if (kdk == NULL) { 101 pjdlog_errno(LOG_ERR, "Unable to reallocate kernel dump key"); 102 goto failed; 103 } 104 size += read(kfd, &kdk->kdk_encryptedkey, 105 kdk->kdk_encryptedkeysize); 106 } 107 if (size != (ssize_t)kdksize) { 108 pjdlog_errno(LOG_ERR, "Unable to read key"); 109 goto failed; 110 } 111 112 return (kdk); 113 failed: 114 free(kdk); 115 return (NULL); 116 } 117 118 static bool 119 decrypt(int ofd, const char *privkeyfile, const char *keyfile, 120 const char *input) 121 { 122 uint8_t buf[KERNELDUMP_BUFFER_SIZE], key[KERNELDUMP_KEY_MAX_SIZE], 123 chachaiv[4 * 4]; 124 EVP_CIPHER_CTX *ctx; 125 const EVP_CIPHER *cipher; 126 FILE *fp; 127 struct kerneldumpkey *kdk; 128 RSA *privkey; 129 int ifd, kfd, olen, privkeysize; 130 ssize_t bytes; 131 pid_t pid; 132 133 PJDLOG_ASSERT(ofd >= 0); 134 PJDLOG_ASSERT(privkeyfile != NULL); 135 PJDLOG_ASSERT(keyfile != NULL); 136 PJDLOG_ASSERT(input != NULL); 137 138 ctx = NULL; 139 privkey = NULL; 140 141 /* 142 * Decrypt a core dump in a child process so we can unlink a partially 143 * decrypted core if the child process fails. 144 */ 145 pid = fork(); 146 if (pid == -1) { 147 pjdlog_errno(LOG_ERR, "Unable to create child process"); 148 close(ofd); 149 return (false); 150 } 151 152 if (pid > 0) { 153 close(ofd); 154 return (wait_for_process(pid) == 0); 155 } 156 157 kfd = open(keyfile, O_RDONLY); 158 if (kfd == -1) { 159 pjdlog_errno(LOG_ERR, "Unable to open %s", keyfile); 160 goto failed; 161 } 162 ifd = open(input, O_RDONLY); 163 if (ifd == -1) { 164 pjdlog_errno(LOG_ERR, "Unable to open %s", input); 165 goto failed; 166 } 167 fp = fopen(privkeyfile, "r"); 168 if (fp == NULL) { 169 pjdlog_errno(LOG_ERR, "Unable to open %s", privkeyfile); 170 goto failed; 171 } 172 173 if (caph_enter() < 0) { 174 pjdlog_errno(LOG_ERR, "Unable to enter capability mode"); 175 goto failed; 176 } 177 178 privkey = RSA_new(); 179 if (privkey == NULL) { 180 pjdlog_error("Unable to allocate an RSA structure: %s", 181 ERR_error_string(ERR_get_error(), NULL)); 182 goto failed; 183 } 184 ctx = EVP_CIPHER_CTX_new(); 185 if (ctx == NULL) 186 goto failed; 187 188 kdk = read_key(kfd); 189 close(kfd); 190 if (kdk == NULL) 191 goto failed; 192 193 privkey = PEM_read_RSAPrivateKey(fp, &privkey, NULL, NULL); 194 fclose(fp); 195 if (privkey == NULL) { 196 pjdlog_error("Unable to read data from %s.", privkeyfile); 197 goto failed; 198 } 199 200 privkeysize = RSA_size(privkey); 201 if (privkeysize != (int)kdk->kdk_encryptedkeysize) { 202 pjdlog_error("RSA modulus size mismatch: equals %db and should be %ub.", 203 8 * privkeysize, 8 * kdk->kdk_encryptedkeysize); 204 goto failed; 205 } 206 207 switch (kdk->kdk_encryption) { 208 case KERNELDUMP_ENC_AES_256_CBC: 209 cipher = EVP_aes_256_cbc(); 210 break; 211 case KERNELDUMP_ENC_CHACHA20: 212 cipher = EVP_chacha20(); 213 break; 214 default: 215 pjdlog_error("Invalid encryption algorithm."); 216 goto failed; 217 } 218 219 if (RSA_private_decrypt(kdk->kdk_encryptedkeysize, 220 kdk->kdk_encryptedkey, key, privkey, 221 RSA_PKCS1_PADDING) != sizeof(key)) { 222 pjdlog_error("Unable to decrypt key: %s", 223 ERR_error_string(ERR_get_error(), NULL)); 224 goto failed; 225 } 226 RSA_free(privkey); 227 privkey = NULL; 228 229 if (kdk->kdk_encryption == KERNELDUMP_ENC_CHACHA20) { 230 /* 231 * OpenSSL treats the IV as 4 little-endian 32 bit integers. 232 * 233 * The first two represent a 64-bit counter, where the low half 234 * is the first 32-bit word. 235 * 236 * Start at counter block zero... 237 */ 238 memset(chachaiv, 0, 4 * 2); 239 /* 240 * And use the IV specified by the dump. 241 */ 242 memcpy(&chachaiv[4 * 2], kdk->kdk_iv, 4 * 2); 243 EVP_DecryptInit_ex(ctx, cipher, NULL, key, chachaiv); 244 } else 245 EVP_DecryptInit_ex(ctx, cipher, NULL, key, kdk->kdk_iv); 246 EVP_CIPHER_CTX_set_padding(ctx, 0); 247 248 explicit_bzero(key, sizeof(key)); 249 250 do { 251 bytes = read(ifd, buf, sizeof(buf)); 252 if (bytes < 0) { 253 pjdlog_errno(LOG_ERR, "Unable to read data from %s", 254 input); 255 goto failed; 256 } 257 258 if (bytes > 0) { 259 if (EVP_DecryptUpdate(ctx, buf, &olen, buf, 260 bytes) == 0) { 261 pjdlog_error("Unable to decrypt core."); 262 goto failed; 263 } 264 } else { 265 if (EVP_DecryptFinal_ex(ctx, buf, &olen) == 0) { 266 pjdlog_error("Unable to decrypt core."); 267 goto failed; 268 } 269 } 270 271 if (olen > 0 && write(ofd, buf, olen) != olen) { 272 pjdlog_errno(LOG_ERR, "Unable to write core"); 273 goto failed; 274 } 275 } while (bytes > 0); 276 277 explicit_bzero(buf, sizeof(buf)); 278 EVP_CIPHER_CTX_free(ctx); 279 exit(0); 280 failed: 281 explicit_bzero(key, sizeof(key)); 282 explicit_bzero(buf, sizeof(buf)); 283 RSA_free(privkey); 284 if (ctx != NULL) 285 EVP_CIPHER_CTX_free(ctx); 286 exit(1); 287 } 288 289 int 290 main(int argc, char **argv) 291 { 292 char core[PATH_MAX], encryptedcore[PATH_MAX], keyfile[PATH_MAX]; 293 const char *crashdir, *dumpnr, *privatekey; 294 int ch, debug, error, ofd; 295 size_t ii; 296 bool force, usesyslog; 297 298 error = 1; 299 300 pjdlog_init(PJDLOG_MODE_STD); 301 pjdlog_prefix_set("(decryptcore) "); 302 303 debug = 0; 304 *core = '\0'; 305 crashdir = NULL; 306 dumpnr = NULL; 307 *encryptedcore = '\0'; 308 force = false; 309 *keyfile = '\0'; 310 privatekey = NULL; 311 usesyslog = false; 312 while ((ch = getopt(argc, argv, "Lc:d:e:fk:n:p:v")) != -1) { 313 switch (ch) { 314 case 'L': 315 usesyslog = true; 316 break; 317 case 'c': 318 if (strlcpy(core, optarg, sizeof(core)) >= sizeof(core)) 319 pjdlog_exitx(1, "Core file path is too long."); 320 break; 321 case 'd': 322 crashdir = optarg; 323 break; 324 case 'e': 325 if (strlcpy(encryptedcore, optarg, 326 sizeof(encryptedcore)) >= sizeof(encryptedcore)) { 327 pjdlog_exitx(1, "Encrypted core file path is too long."); 328 } 329 break; 330 case 'f': 331 force = true; 332 break; 333 case 'k': 334 if (strlcpy(keyfile, optarg, sizeof(keyfile)) >= 335 sizeof(keyfile)) { 336 pjdlog_exitx(1, "Key file path is too long."); 337 } 338 break; 339 case 'n': 340 dumpnr = optarg; 341 break; 342 case 'p': 343 privatekey = optarg; 344 break; 345 case 'v': 346 debug++; 347 break; 348 default: 349 usage(); 350 } 351 } 352 argc -= optind; 353 argv += optind; 354 355 if (argc != 0) 356 usage(); 357 358 /* Verify mutually exclusive options. */ 359 if ((crashdir != NULL || dumpnr != NULL) && 360 (*keyfile != '\0' || *encryptedcore != '\0' || *core != '\0')) { 361 usage(); 362 } 363 364 /* 365 * Set key, encryptedcore and core file names using crashdir and dumpnr. 366 */ 367 if (dumpnr != NULL) { 368 for (ii = 0; ii < strnlen(dumpnr, PATH_MAX); ii++) { 369 if (isdigit((int)dumpnr[ii]) == 0) 370 usage(); 371 } 372 373 if (crashdir == NULL) 374 crashdir = DECRYPTCORE_CRASHDIR; 375 PJDLOG_VERIFY(snprintf(keyfile, sizeof(keyfile), 376 "%s/key.%s", crashdir, dumpnr) > 0); 377 PJDLOG_VERIFY(snprintf(core, sizeof(core), 378 "%s/vmcore.%s", crashdir, dumpnr) > 0); 379 PJDLOG_VERIFY(snprintf(encryptedcore, sizeof(encryptedcore), 380 "%s/vmcore_encrypted.%s", crashdir, dumpnr) > 0); 381 } 382 383 if (privatekey == NULL || *keyfile == '\0' || *encryptedcore == '\0' || 384 *core == '\0') { 385 usage(); 386 } 387 388 if (usesyslog) 389 pjdlog_mode_set(PJDLOG_MODE_SYSLOG); 390 pjdlog_debug_set(debug); 391 392 if (force && unlink(core) == -1 && errno != ENOENT) { 393 pjdlog_errno(LOG_ERR, "Unable to remove old core"); 394 goto out; 395 } 396 ofd = open(core, O_WRONLY | O_CREAT | O_EXCL, 0600); 397 if (ofd == -1) { 398 pjdlog_errno(LOG_ERR, "Unable to open %s", core); 399 goto out; 400 } 401 402 if (!decrypt(ofd, privatekey, keyfile, encryptedcore)) { 403 if (unlink(core) == -1 && errno != ENOENT) 404 pjdlog_errno(LOG_ERR, "Unable to remove core"); 405 goto out; 406 } 407 408 error = 0; 409 out: 410 pjdlog_fini(); 411 exit(error); 412 } 413