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 [-Lv] -p privatekeyfile -k keyfile -e encryptedcore -c core\n" 59 " decryptcore [-Lv] [-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(const char *privkeyfile, const char *keyfile, const char *input, 119 const char *output) 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, ofd, olen, privkeysize; 128 ssize_t bytes; 129 pid_t pid; 130 131 PJDLOG_ASSERT(privkeyfile != NULL); 132 PJDLOG_ASSERT(keyfile != NULL); 133 PJDLOG_ASSERT(input != NULL); 134 PJDLOG_ASSERT(output != 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 return (false); 146 } 147 148 if (pid > 0) 149 return (wait_for_process(pid) == 0); 150 151 kfd = open(keyfile, O_RDONLY); 152 if (kfd == -1) { 153 pjdlog_errno(LOG_ERR, "Unable to open %s", keyfile); 154 goto failed; 155 } 156 ifd = open(input, O_RDONLY); 157 if (ifd == -1) { 158 pjdlog_errno(LOG_ERR, "Unable to open %s", input); 159 goto failed; 160 } 161 ofd = open(output, O_WRONLY | O_CREAT | O_TRUNC, 0600); 162 if (ofd == -1) { 163 pjdlog_errno(LOG_ERR, "Unable to open %s", output); 164 goto failed; 165 } 166 fp = fopen(privkeyfile, "r"); 167 if (fp == NULL) { 168 pjdlog_errno(LOG_ERR, "Unable to open %s", privkeyfile); 169 goto failed; 170 } 171 172 if (cap_enter() < 0 && errno != ENOSYS) { 173 pjdlog_errno(LOG_ERR, "Unable to enter capability mode"); 174 goto failed; 175 } 176 177 privkey = RSA_new(); 178 if (privkey == NULL) { 179 pjdlog_error("Unable to allocate an RSA structure: %s", 180 ERR_error_string(ERR_get_error(), NULL)); 181 goto failed; 182 } 183 EVP_CIPHER_CTX_init(&ctx); 184 185 kdk = read_key(kfd); 186 close(kfd); 187 if (kdk == NULL) 188 goto failed; 189 190 privkey = PEM_read_RSAPrivateKey(fp, &privkey, NULL, NULL); 191 fclose(fp); 192 if (privkey == NULL) { 193 pjdlog_error("Unable to read data from %s.", privkeyfile); 194 goto failed; 195 } 196 197 privkeysize = RSA_size(privkey); 198 if (privkeysize != (int)kdk->kdk_encryptedkeysize) { 199 pjdlog_error("RSA modulus size mismatch: equals %db and should be %ub.", 200 8 * privkeysize, 8 * kdk->kdk_encryptedkeysize); 201 goto failed; 202 } 203 204 switch (kdk->kdk_encryption) { 205 case KERNELDUMP_ENC_AES_256_CBC: 206 cipher = EVP_aes_256_cbc(); 207 break; 208 default: 209 pjdlog_error("Invalid encryption algorithm."); 210 goto failed; 211 } 212 213 if (RSA_private_decrypt(kdk->kdk_encryptedkeysize, 214 kdk->kdk_encryptedkey, key, privkey, 215 RSA_PKCS1_PADDING) != sizeof(key)) { 216 pjdlog_error("Unable to decrypt key: %s", 217 ERR_error_string(ERR_get_error(), NULL)); 218 goto failed; 219 } 220 RSA_free(privkey); 221 privkey = NULL; 222 223 EVP_DecryptInit_ex(&ctx, cipher, NULL, key, kdk->kdk_iv); 224 EVP_CIPHER_CTX_set_padding(&ctx, 0); 225 226 explicit_bzero(key, sizeof(key)); 227 228 do { 229 bytes = read(ifd, buf, sizeof(buf)); 230 if (bytes < 0) { 231 pjdlog_errno(LOG_ERR, "Unable to read data from %s", 232 input); 233 goto failed; 234 } 235 236 if (bytes > 0) { 237 if (EVP_DecryptUpdate(&ctx, buf, &olen, buf, 238 bytes) == 0) { 239 pjdlog_error("Unable to decrypt core."); 240 goto failed; 241 } 242 } else { 243 if (EVP_DecryptFinal_ex(&ctx, buf, &olen) == 0) { 244 pjdlog_error("Unable to decrypt core."); 245 goto failed; 246 } 247 } 248 249 if (olen > 0 && write(ofd, buf, olen) != olen) { 250 pjdlog_errno(LOG_ERR, "Unable to write data to %s", 251 output); 252 goto failed; 253 } 254 } while (bytes > 0); 255 256 explicit_bzero(buf, sizeof(buf)); 257 EVP_CIPHER_CTX_cleanup(&ctx); 258 exit(0); 259 failed: 260 explicit_bzero(key, sizeof(key)); 261 explicit_bzero(buf, sizeof(buf)); 262 RSA_free(privkey); 263 EVP_CIPHER_CTX_cleanup(&ctx); 264 exit(1); 265 } 266 267 int 268 main(int argc, char **argv) 269 { 270 char core[PATH_MAX], encryptedcore[PATH_MAX], keyfile[PATH_MAX]; 271 const char *crashdir, *dumpnr, *privatekey; 272 int ch, debug; 273 size_t ii; 274 bool usesyslog; 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 *keyfile = '\0'; 285 privatekey = NULL; 286 usesyslog = false; 287 while ((ch = getopt(argc, argv, "Lc:d:e:k: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 'k': 306 if (strlcpy(keyfile, optarg, sizeof(keyfile)) >= 307 sizeof(keyfile)) { 308 pjdlog_exitx(1, "Key file path is too long."); 309 } 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 (unlink(core) == -1 && errno != ENOENT) 366 pjdlog_exit(1, "Unable to remove core"); 367 exit(1); 368 } 369 370 pjdlog_fini(); 371 372 exit(0); 373 } 374