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 <fcntl.h> 39 #include <stdbool.h> 40 #include <stdlib.h> 41 #include <string.h> 42 #include <unistd.h> 43 44 #include <openssl/evp.h> 45 #include <openssl/pem.h> 46 #include <openssl/rsa.h> 47 #include <openssl/engine.h> 48 49 #include "pjdlog.h" 50 51 #define DECRYPTCORE_CRASHDIR "/var/crash" 52 53 static void 54 usage(void) 55 { 56 57 pjdlog_exitx(1, 58 "usage: decryptcore [-fLv] -p privatekeyfile -k keyfile -e encryptedcore -c core\n" 59 " decryptcore [-fLv] [-d crashdir] -p privatekeyfile -n dumpnr"); 60 } 61 62 static int 63 wait_for_process(pid_t pid) 64 { 65 int status; 66 67 if (waitpid(pid, &status, WUNTRACED | WEXITED) == -1) { 68 pjdlog_errno(LOG_ERR, "Unable to wait for a child process"); 69 return (1); 70 } 71 72 if (WIFEXITED(status)) 73 return (WEXITSTATUS(status)); 74 75 return (1); 76 } 77 78 static struct kerneldumpkey * 79 read_key(int kfd) 80 { 81 struct kerneldumpkey *kdk; 82 ssize_t size; 83 size_t kdksize; 84 85 PJDLOG_ASSERT(kfd >= 0); 86 87 kdksize = sizeof(*kdk); 88 kdk = calloc(1, kdksize); 89 if (kdk == NULL) { 90 pjdlog_errno(LOG_ERR, "Unable to allocate kernel dump key"); 91 goto failed; 92 } 93 94 size = read(kfd, kdk, kdksize); 95 if (size == (ssize_t)kdksize) { 96 kdk->kdk_encryptedkeysize = dtoh32(kdk->kdk_encryptedkeysize); 97 kdksize += (size_t)kdk->kdk_encryptedkeysize; 98 kdk = realloc(kdk, kdksize); 99 if (kdk == NULL) { 100 pjdlog_errno(LOG_ERR, "Unable to reallocate kernel dump key"); 101 goto failed; 102 } 103 size += read(kfd, &kdk->kdk_encryptedkey, 104 kdk->kdk_encryptedkeysize); 105 } 106 if (size != (ssize_t)kdksize) { 107 pjdlog_errno(LOG_ERR, "Unable to read key"); 108 goto failed; 109 } 110 111 return (kdk); 112 failed: 113 free(kdk); 114 return (NULL); 115 } 116 117 static bool 118 decrypt(int ofd, const char *privkeyfile, const char *keyfile, 119 const char *input) 120 { 121 uint8_t buf[KERNELDUMP_BUFFER_SIZE], key[KERNELDUMP_KEY_MAX_SIZE]; 122 EVP_CIPHER_CTX ctx; 123 const EVP_CIPHER *cipher; 124 FILE *fp; 125 struct kerneldumpkey *kdk; 126 RSA *privkey; 127 int ifd, kfd, olen, privkeysize; 128 ssize_t bytes; 129 pid_t pid; 130 131 PJDLOG_ASSERT(ofd >= 0); 132 PJDLOG_ASSERT(privkeyfile != NULL); 133 PJDLOG_ASSERT(keyfile != NULL); 134 PJDLOG_ASSERT(input != NULL); 135 136 privkey = NULL; 137 138 /* 139 * Decrypt a core dump in a child process so we can unlink a partially 140 * decrypted core if the child process fails. 141 */ 142 pid = fork(); 143 if (pid == -1) { 144 pjdlog_errno(LOG_ERR, "Unable to create child process"); 145 close(ofd); 146 return (false); 147 } 148 149 if (pid > 0) { 150 close(ofd); 151 return (wait_for_process(pid) == 0); 152 } 153 154 kfd = open(keyfile, O_RDONLY); 155 if (kfd == -1) { 156 pjdlog_errno(LOG_ERR, "Unable to open %s", keyfile); 157 goto failed; 158 } 159 ifd = open(input, O_RDONLY); 160 if (ifd == -1) { 161 pjdlog_errno(LOG_ERR, "Unable to open %s", input); 162 goto failed; 163 } 164 fp = fopen(privkeyfile, "r"); 165 if (fp == NULL) { 166 pjdlog_errno(LOG_ERR, "Unable to open %s", privkeyfile); 167 goto failed; 168 } 169 170 if (cap_enter() < 0 && errno != ENOSYS) { 171 pjdlog_errno(LOG_ERR, "Unable to enter capability mode"); 172 goto failed; 173 } 174 175 privkey = RSA_new(); 176 if (privkey == NULL) { 177 pjdlog_error("Unable to allocate an RSA structure: %s", 178 ERR_error_string(ERR_get_error(), NULL)); 179 goto failed; 180 } 181 EVP_CIPHER_CTX_init(&ctx); 182 183 kdk = read_key(kfd); 184 close(kfd); 185 if (kdk == NULL) 186 goto failed; 187 188 privkey = PEM_read_RSAPrivateKey(fp, &privkey, NULL, NULL); 189 fclose(fp); 190 if (privkey == NULL) { 191 pjdlog_error("Unable to read data from %s.", privkeyfile); 192 goto failed; 193 } 194 195 privkeysize = RSA_size(privkey); 196 if (privkeysize != (int)kdk->kdk_encryptedkeysize) { 197 pjdlog_error("RSA modulus size mismatch: equals %db and should be %ub.", 198 8 * privkeysize, 8 * kdk->kdk_encryptedkeysize); 199 goto failed; 200 } 201 202 switch (kdk->kdk_encryption) { 203 case KERNELDUMP_ENC_AES_256_CBC: 204 cipher = EVP_aes_256_cbc(); 205 break; 206 default: 207 pjdlog_error("Invalid encryption algorithm."); 208 goto failed; 209 } 210 211 if (RSA_private_decrypt(kdk->kdk_encryptedkeysize, 212 kdk->kdk_encryptedkey, key, privkey, 213 RSA_PKCS1_PADDING) != sizeof(key)) { 214 pjdlog_error("Unable to decrypt key: %s", 215 ERR_error_string(ERR_get_error(), NULL)); 216 goto failed; 217 } 218 RSA_free(privkey); 219 privkey = NULL; 220 221 EVP_DecryptInit_ex(&ctx, cipher, NULL, key, kdk->kdk_iv); 222 EVP_CIPHER_CTX_set_padding(&ctx, 0); 223 224 explicit_bzero(key, sizeof(key)); 225 226 do { 227 bytes = read(ifd, buf, sizeof(buf)); 228 if (bytes < 0) { 229 pjdlog_errno(LOG_ERR, "Unable to read data from %s", 230 input); 231 goto failed; 232 } 233 234 if (bytes > 0) { 235 if (EVP_DecryptUpdate(&ctx, buf, &olen, buf, 236 bytes) == 0) { 237 pjdlog_error("Unable to decrypt core."); 238 goto failed; 239 } 240 } else { 241 if (EVP_DecryptFinal_ex(&ctx, buf, &olen) == 0) { 242 pjdlog_error("Unable to decrypt core."); 243 goto failed; 244 } 245 } 246 247 if (olen > 0 && write(ofd, buf, olen) != olen) { 248 pjdlog_errno(LOG_ERR, "Unable to write core"); 249 goto failed; 250 } 251 } while (bytes > 0); 252 253 explicit_bzero(buf, sizeof(buf)); 254 EVP_CIPHER_CTX_cleanup(&ctx); 255 exit(0); 256 failed: 257 explicit_bzero(key, sizeof(key)); 258 explicit_bzero(buf, sizeof(buf)); 259 RSA_free(privkey); 260 EVP_CIPHER_CTX_cleanup(&ctx); 261 exit(1); 262 } 263 264 int 265 main(int argc, char **argv) 266 { 267 char core[PATH_MAX], encryptedcore[PATH_MAX], keyfile[PATH_MAX]; 268 const char *crashdir, *dumpnr, *privatekey; 269 int ch, debug, error, ofd; 270 size_t ii; 271 bool force, usesyslog; 272 273 error = 1; 274 275 pjdlog_init(PJDLOG_MODE_STD); 276 pjdlog_prefix_set("(decryptcore) "); 277 278 debug = 0; 279 *core = '\0'; 280 crashdir = NULL; 281 dumpnr = NULL; 282 *encryptedcore = '\0'; 283 force = false; 284 *keyfile = '\0'; 285 privatekey = NULL; 286 usesyslog = false; 287 while ((ch = getopt(argc, argv, "Lc:d:e:fk:n:p:v")) != -1) { 288 switch (ch) { 289 case 'L': 290 usesyslog = true; 291 break; 292 case 'c': 293 if (strlcpy(core, optarg, sizeof(core)) >= sizeof(core)) 294 pjdlog_exitx(1, "Core file path is too long."); 295 break; 296 case 'd': 297 crashdir = optarg; 298 break; 299 case 'e': 300 if (strlcpy(encryptedcore, optarg, 301 sizeof(encryptedcore)) >= sizeof(encryptedcore)) { 302 pjdlog_exitx(1, "Encrypted core file path is too long."); 303 } 304 break; 305 case 'f': 306 force = true; 307 break; 308 case 'k': 309 if (strlcpy(keyfile, optarg, sizeof(keyfile)) >= 310 sizeof(keyfile)) { 311 pjdlog_exitx(1, "Key file path is too long."); 312 } 313 break; 314 case 'n': 315 dumpnr = optarg; 316 break; 317 case 'p': 318 privatekey = optarg; 319 break; 320 case 'v': 321 debug++; 322 break; 323 default: 324 usage(); 325 } 326 } 327 argc -= optind; 328 argv += optind; 329 330 if (argc != 0) 331 usage(); 332 333 /* Verify mutually exclusive options. */ 334 if ((crashdir != NULL || dumpnr != NULL) && 335 (*keyfile != '\0' || *encryptedcore != '\0' || *core != '\0')) { 336 usage(); 337 } 338 339 /* 340 * Set key, encryptedcore and core file names using crashdir and dumpnr. 341 */ 342 if (dumpnr != NULL) { 343 for (ii = 0; ii < strnlen(dumpnr, PATH_MAX); ii++) { 344 if (isdigit((int)dumpnr[ii]) == 0) 345 usage(); 346 } 347 348 if (crashdir == NULL) 349 crashdir = DECRYPTCORE_CRASHDIR; 350 PJDLOG_VERIFY(snprintf(keyfile, sizeof(keyfile), 351 "%s/key.%s", crashdir, dumpnr) > 0); 352 PJDLOG_VERIFY(snprintf(core, sizeof(core), 353 "%s/vmcore.%s", crashdir, dumpnr) > 0); 354 PJDLOG_VERIFY(snprintf(encryptedcore, sizeof(encryptedcore), 355 "%s/vmcore_encrypted.%s", crashdir, dumpnr) > 0); 356 } 357 358 if (privatekey == NULL || *keyfile == '\0' || *encryptedcore == '\0' || 359 *core == '\0') { 360 usage(); 361 } 362 363 if (usesyslog) 364 pjdlog_mode_set(PJDLOG_MODE_SYSLOG); 365 pjdlog_debug_set(debug); 366 367 if (force && unlink(core) == -1 && errno != ENOENT) { 368 pjdlog_errno(LOG_ERR, "Unable to remove old core"); 369 goto out; 370 } 371 ofd = open(core, O_WRONLY | O_CREAT | O_EXCL, 0600); 372 if (ofd == -1) { 373 pjdlog_errno(LOG_ERR, "Unable to open %s", core); 374 goto out; 375 } 376 377 if (!decrypt(ofd, privatekey, keyfile, encryptedcore)) { 378 if (unlink(core) == -1 && errno != ENOENT) 379 pjdlog_errno(LOG_ERR, "Unable to remove core"); 380 goto out; 381 } 382 383 error = 0; 384 out: 385 pjdlog_fini(); 386 exit(error); 387 } 388