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 EVP_CIPHER_CTX ctx; 124 const EVP_CIPHER *cipher; 125 FILE *fp; 126 struct kerneldumpkey *kdk; 127 RSA *privkey; 128 int ifd, kfd, olen, privkeysize; 129 ssize_t bytes; 130 pid_t pid; 131 132 PJDLOG_ASSERT(ofd >= 0); 133 PJDLOG_ASSERT(privkeyfile != NULL); 134 PJDLOG_ASSERT(keyfile != NULL); 135 PJDLOG_ASSERT(input != NULL); 136 137 privkey = NULL; 138 139 /* 140 * Decrypt a core dump in a child process so we can unlink a partially 141 * decrypted core if the child process fails. 142 */ 143 pid = fork(); 144 if (pid == -1) { 145 pjdlog_errno(LOG_ERR, "Unable to create child process"); 146 close(ofd); 147 return (false); 148 } 149 150 if (pid > 0) { 151 close(ofd); 152 return (wait_for_process(pid) == 0); 153 } 154 155 kfd = open(keyfile, O_RDONLY); 156 if (kfd == -1) { 157 pjdlog_errno(LOG_ERR, "Unable to open %s", keyfile); 158 goto failed; 159 } 160 ifd = open(input, O_RDONLY); 161 if (ifd == -1) { 162 pjdlog_errno(LOG_ERR, "Unable to open %s", input); 163 goto failed; 164 } 165 fp = fopen(privkeyfile, "r"); 166 if (fp == NULL) { 167 pjdlog_errno(LOG_ERR, "Unable to open %s", privkeyfile); 168 goto failed; 169 } 170 171 if (caph_enter() < 0) { 172 pjdlog_errno(LOG_ERR, "Unable to enter capability mode"); 173 goto failed; 174 } 175 176 privkey = RSA_new(); 177 if (privkey == NULL) { 178 pjdlog_error("Unable to allocate an RSA structure: %s", 179 ERR_error_string(ERR_get_error(), NULL)); 180 goto failed; 181 } 182 EVP_CIPHER_CTX_init(&ctx); 183 184 kdk = read_key(kfd); 185 close(kfd); 186 if (kdk == NULL) 187 goto failed; 188 189 privkey = PEM_read_RSAPrivateKey(fp, &privkey, NULL, NULL); 190 fclose(fp); 191 if (privkey == NULL) { 192 pjdlog_error("Unable to read data from %s.", privkeyfile); 193 goto failed; 194 } 195 196 privkeysize = RSA_size(privkey); 197 if (privkeysize != (int)kdk->kdk_encryptedkeysize) { 198 pjdlog_error("RSA modulus size mismatch: equals %db and should be %ub.", 199 8 * privkeysize, 8 * kdk->kdk_encryptedkeysize); 200 goto failed; 201 } 202 203 switch (kdk->kdk_encryption) { 204 case KERNELDUMP_ENC_AES_256_CBC: 205 cipher = EVP_aes_256_cbc(); 206 break; 207 default: 208 pjdlog_error("Invalid encryption algorithm."); 209 goto failed; 210 } 211 212 if (RSA_private_decrypt(kdk->kdk_encryptedkeysize, 213 kdk->kdk_encryptedkey, key, privkey, 214 RSA_PKCS1_PADDING) != sizeof(key)) { 215 pjdlog_error("Unable to decrypt key: %s", 216 ERR_error_string(ERR_get_error(), NULL)); 217 goto failed; 218 } 219 RSA_free(privkey); 220 privkey = NULL; 221 222 EVP_DecryptInit_ex(&ctx, cipher, NULL, key, kdk->kdk_iv); 223 EVP_CIPHER_CTX_set_padding(&ctx, 0); 224 225 explicit_bzero(key, sizeof(key)); 226 227 do { 228 bytes = read(ifd, buf, sizeof(buf)); 229 if (bytes < 0) { 230 pjdlog_errno(LOG_ERR, "Unable to read data from %s", 231 input); 232 goto failed; 233 } 234 235 if (bytes > 0) { 236 if (EVP_DecryptUpdate(&ctx, buf, &olen, buf, 237 bytes) == 0) { 238 pjdlog_error("Unable to decrypt core."); 239 goto failed; 240 } 241 } else { 242 if (EVP_DecryptFinal_ex(&ctx, buf, &olen) == 0) { 243 pjdlog_error("Unable to decrypt core."); 244 goto failed; 245 } 246 } 247 248 if (olen > 0 && write(ofd, buf, olen) != olen) { 249 pjdlog_errno(LOG_ERR, "Unable to write core"); 250 goto failed; 251 } 252 } while (bytes > 0); 253 254 explicit_bzero(buf, sizeof(buf)); 255 EVP_CIPHER_CTX_cleanup(&ctx); 256 exit(0); 257 failed: 258 explicit_bzero(key, sizeof(key)); 259 explicit_bzero(buf, sizeof(buf)); 260 RSA_free(privkey); 261 EVP_CIPHER_CTX_cleanup(&ctx); 262 exit(1); 263 } 264 265 int 266 main(int argc, char **argv) 267 { 268 char core[PATH_MAX], encryptedcore[PATH_MAX], keyfile[PATH_MAX]; 269 const char *crashdir, *dumpnr, *privatekey; 270 int ch, debug, error, ofd; 271 size_t ii; 272 bool force, usesyslog; 273 274 error = 1; 275 276 pjdlog_init(PJDLOG_MODE_STD); 277 pjdlog_prefix_set("(decryptcore) "); 278 279 debug = 0; 280 *core = '\0'; 281 crashdir = NULL; 282 dumpnr = NULL; 283 *encryptedcore = '\0'; 284 force = false; 285 *keyfile = '\0'; 286 privatekey = NULL; 287 usesyslog = false; 288 while ((ch = getopt(argc, argv, "Lc:d:e:fk:n:p:v")) != -1) { 289 switch (ch) { 290 case 'L': 291 usesyslog = true; 292 break; 293 case 'c': 294 if (strlcpy(core, optarg, sizeof(core)) >= sizeof(core)) 295 pjdlog_exitx(1, "Core file path is too long."); 296 break; 297 case 'd': 298 crashdir = optarg; 299 break; 300 case 'e': 301 if (strlcpy(encryptedcore, optarg, 302 sizeof(encryptedcore)) >= sizeof(encryptedcore)) { 303 pjdlog_exitx(1, "Encrypted core file path is too long."); 304 } 305 break; 306 case 'f': 307 force = true; 308 break; 309 case 'k': 310 if (strlcpy(keyfile, optarg, sizeof(keyfile)) >= 311 sizeof(keyfile)) { 312 pjdlog_exitx(1, "Key file path is too long."); 313 } 314 break; 315 case 'n': 316 dumpnr = optarg; 317 break; 318 case 'p': 319 privatekey = optarg; 320 break; 321 case 'v': 322 debug++; 323 break; 324 default: 325 usage(); 326 } 327 } 328 argc -= optind; 329 argv += optind; 330 331 if (argc != 0) 332 usage(); 333 334 /* Verify mutually exclusive options. */ 335 if ((crashdir != NULL || dumpnr != NULL) && 336 (*keyfile != '\0' || *encryptedcore != '\0' || *core != '\0')) { 337 usage(); 338 } 339 340 /* 341 * Set key, encryptedcore and core file names using crashdir and dumpnr. 342 */ 343 if (dumpnr != NULL) { 344 for (ii = 0; ii < strnlen(dumpnr, PATH_MAX); ii++) { 345 if (isdigit((int)dumpnr[ii]) == 0) 346 usage(); 347 } 348 349 if (crashdir == NULL) 350 crashdir = DECRYPTCORE_CRASHDIR; 351 PJDLOG_VERIFY(snprintf(keyfile, sizeof(keyfile), 352 "%s/key.%s", crashdir, dumpnr) > 0); 353 PJDLOG_VERIFY(snprintf(core, sizeof(core), 354 "%s/vmcore.%s", crashdir, dumpnr) > 0); 355 PJDLOG_VERIFY(snprintf(encryptedcore, sizeof(encryptedcore), 356 "%s/vmcore_encrypted.%s", crashdir, dumpnr) > 0); 357 } 358 359 if (privatekey == NULL || *keyfile == '\0' || *encryptedcore == '\0' || 360 *core == '\0') { 361 usage(); 362 } 363 364 if (usesyslog) 365 pjdlog_mode_set(PJDLOG_MODE_SYSLOG); 366 pjdlog_debug_set(debug); 367 368 if (force && unlink(core) == -1 && errno != ENOENT) { 369 pjdlog_errno(LOG_ERR, "Unable to remove old core"); 370 goto out; 371 } 372 ofd = open(core, O_WRONLY | O_CREAT | O_EXCL, 0600); 373 if (ofd == -1) { 374 pjdlog_errno(LOG_ERR, "Unable to open %s", core); 375 goto out; 376 } 377 378 if (!decrypt(ofd, privatekey, keyfile, encryptedcore)) { 379 if (unlink(core) == -1 && errno != ENOENT) 380 pjdlog_errno(LOG_ERR, "Unable to remove core"); 381 goto out; 382 } 383 384 error = 0; 385 out: 386 pjdlog_fini(); 387 exit(error); 388 } 389