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/stat.h> 35 #include <sys/sysctl.h> 36 #include <sys/wait.h> 37 38 #include <ctype.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 [-Lv] -p privatekeyfile -k keyfile -e encryptedcore -c core\n" 60 " decryptcore [-Lv] [-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(const char *privkeyfile, const char *keyfile, const char *input, 120 const char *output) 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, ofd, olen, privkeysize; 129 ssize_t bytes; 130 pid_t pid; 131 132 PJDLOG_ASSERT(privkeyfile != NULL); 133 PJDLOG_ASSERT(keyfile != NULL); 134 PJDLOG_ASSERT(input != NULL); 135 PJDLOG_ASSERT(output != 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 return (false); 147 } 148 149 if (pid > 0) 150 return (wait_for_process(pid) == 0); 151 152 kfd = open(keyfile, O_RDONLY); 153 if (kfd == -1) { 154 pjdlog_errno(LOG_ERR, "Unable to open %s", keyfile); 155 goto failed; 156 } 157 ifd = open(input, O_RDONLY); 158 if (ifd == -1) { 159 pjdlog_errno(LOG_ERR, "Unable to open %s", input); 160 goto failed; 161 } 162 ofd = open(output, O_WRONLY | O_CREAT | O_TRUNC, 0600); 163 if (ofd == -1) { 164 pjdlog_errno(LOG_ERR, "Unable to open %s", output); 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 (cap_enter() < 0 && errno != ENOSYS) { 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 EVP_CIPHER_CTX_init(&ctx); 185 186 kdk = read_key(kfd); 187 close(kfd); 188 if (kdk == NULL) 189 goto failed; 190 191 privkey = PEM_read_RSAPrivateKey(fp, &privkey, NULL, NULL); 192 fclose(fp); 193 if (privkey == NULL) { 194 pjdlog_error("Unable to read data from %s.", privkeyfile); 195 goto failed; 196 } 197 198 privkeysize = RSA_size(privkey); 199 if (privkeysize != (int)kdk->kdk_encryptedkeysize) { 200 pjdlog_error("RSA modulus size mismatch: equals %db and should be %ub.", 201 8 * privkeysize, 8 * kdk->kdk_encryptedkeysize); 202 goto failed; 203 } 204 205 switch (kdk->kdk_encryption) { 206 case KERNELDUMP_ENC_AES_256_CBC: 207 cipher = EVP_aes_256_cbc(); 208 break; 209 default: 210 pjdlog_error("Invalid encryption algorithm."); 211 goto failed; 212 } 213 214 if (RSA_private_decrypt(kdk->kdk_encryptedkeysize, 215 kdk->kdk_encryptedkey, key, privkey, 216 RSA_PKCS1_PADDING) != sizeof(key)) { 217 pjdlog_error("Unable to decrypt key: %s", 218 ERR_error_string(ERR_get_error(), NULL)); 219 goto failed; 220 } 221 RSA_free(privkey); 222 privkey = NULL; 223 224 EVP_DecryptInit_ex(&ctx, cipher, NULL, key, kdk->kdk_iv); 225 EVP_CIPHER_CTX_set_padding(&ctx, 0); 226 227 explicit_bzero(key, sizeof(key)); 228 229 do { 230 bytes = read(ifd, buf, sizeof(buf)); 231 if (bytes < 0) { 232 pjdlog_errno(LOG_ERR, "Unable to read data from %s", 233 input); 234 goto failed; 235 } else if (bytes == 0) { 236 break; 237 } 238 239 if (bytes > 0) { 240 if (EVP_DecryptUpdate(&ctx, buf, &olen, buf, 241 bytes) == 0) { 242 pjdlog_error("Unable to decrypt core."); 243 goto failed; 244 } 245 } else { 246 if (EVP_DecryptFinal_ex(&ctx, buf, &olen) == 0) { 247 pjdlog_error("Unable to decrypt core."); 248 goto failed; 249 } 250 } 251 252 if (olen == 0) 253 continue; 254 255 if (write(ofd, buf, olen) != olen) { 256 pjdlog_errno(LOG_ERR, "Unable to write data to %s", 257 output); 258 goto failed; 259 } 260 } while (bytes > 0); 261 262 explicit_bzero(buf, sizeof(buf)); 263 EVP_CIPHER_CTX_cleanup(&ctx); 264 exit(0); 265 failed: 266 explicit_bzero(key, sizeof(key)); 267 explicit_bzero(buf, sizeof(buf)); 268 RSA_free(privkey); 269 EVP_CIPHER_CTX_cleanup(&ctx); 270 exit(1); 271 } 272 273 int 274 main(int argc, char **argv) 275 { 276 char core[PATH_MAX], encryptedcore[PATH_MAX], keyfile[PATH_MAX]; 277 struct stat sb; 278 const char *crashdir, *dumpnr, *privatekey; 279 int ch, debug; 280 size_t ii; 281 bool usesyslog; 282 283 pjdlog_init(PJDLOG_MODE_STD); 284 pjdlog_prefix_set("(decryptcore) "); 285 286 debug = 0; 287 *core = '\0'; 288 crashdir = NULL; 289 dumpnr = NULL; 290 *encryptedcore = '\0'; 291 *keyfile = '\0'; 292 privatekey = NULL; 293 usesyslog = false; 294 while ((ch = getopt(argc, argv, "Lc:d:e:k:n:p:v")) != -1) { 295 switch (ch) { 296 case 'L': 297 usesyslog = true; 298 break; 299 case 'c': 300 strncpy(core, optarg, sizeof(core)); 301 break; 302 case 'd': 303 crashdir = optarg; 304 break; 305 case 'e': 306 strncpy(encryptedcore, optarg, sizeof(encryptedcore)); 307 break; 308 case 'k': 309 strncpy(keyfile, optarg, sizeof(keyfile)); 310 break; 311 case 'n': 312 dumpnr = optarg; 313 break; 314 case 'p': 315 privatekey = optarg; 316 break; 317 case 'v': 318 debug++; 319 break; 320 default: 321 usage(); 322 } 323 } 324 argc -= optind; 325 argv += optind; 326 327 if (argc != 0) 328 usage(); 329 330 /* Verify mutually exclusive options. */ 331 if ((crashdir != NULL || dumpnr != NULL) && 332 (*keyfile != '\0' || *encryptedcore != '\0' || *core != '\0')) { 333 usage(); 334 } 335 336 /* 337 * Set key, encryptedcore and core file names using crashdir and dumpnr. 338 */ 339 if (dumpnr != NULL) { 340 for (ii = 0; ii < strnlen(dumpnr, PATH_MAX); ii++) { 341 if (isdigit((int)dumpnr[ii]) == 0) 342 usage(); 343 } 344 345 if (crashdir == NULL) 346 crashdir = DECRYPTCORE_CRASHDIR; 347 PJDLOG_VERIFY(snprintf(keyfile, sizeof(keyfile), 348 "%s/key.%s", crashdir, dumpnr) > 0); 349 PJDLOG_VERIFY(snprintf(core, sizeof(core), 350 "%s/vmcore.%s", crashdir, dumpnr) > 0); 351 PJDLOG_VERIFY(snprintf(encryptedcore, sizeof(encryptedcore), 352 "%s/vmcore_encrypted.%s", crashdir, dumpnr) > 0); 353 } 354 355 if (privatekey == NULL || *keyfile == '\0' || *encryptedcore == '\0' || 356 *core == '\0') { 357 usage(); 358 } 359 360 if (usesyslog) 361 pjdlog_mode_set(PJDLOG_MODE_SYSLOG); 362 pjdlog_debug_set(debug); 363 364 if (!decrypt(privatekey, keyfile, encryptedcore, core)) { 365 if (stat(core, &sb) == 0 && unlink(core) != 0) 366 pjdlog_exit(1, "Unable to remove core"); 367 exit(1); 368 } 369 370 pjdlog_fini(); 371 372 exit(0); 373 } 374