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
54static void
55usage(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
63static int
64wait_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
79static struct kerneldumpkey *
80read_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);
113failed:
114	free(kdk);
115	return (NULL);
116}
117
118static bool
119decrypt(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	ctx = NULL;
138	privkey = NULL;
139
140	/*
141	 * Decrypt a core dump in a child process so we can unlink a partially
142	 * decrypted core if the child process fails.
143	 */
144	pid = fork();
145	if (pid == -1) {
146		pjdlog_errno(LOG_ERR, "Unable to create child process");
147		close(ofd);
148		return (false);
149	}
150
151	if (pid > 0) {
152		close(ofd);
153		return (wait_for_process(pid) == 0);
154	}
155
156	kfd = open(keyfile, O_RDONLY);
157	if (kfd == -1) {
158		pjdlog_errno(LOG_ERR, "Unable to open %s", keyfile);
159		goto failed;
160	}
161	ifd = open(input, O_RDONLY);
162	if (ifd == -1) {
163		pjdlog_errno(LOG_ERR, "Unable to open %s", input);
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 (caph_enter() < 0) {
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	ctx = EVP_CIPHER_CTX_new();
184	if (ctx == NULL)
185		goto failed;
186
187	kdk = read_key(kfd);
188	close(kfd);
189	if (kdk == NULL)
190		goto failed;
191
192	privkey = PEM_read_RSAPrivateKey(fp, &privkey, NULL, NULL);
193	fclose(fp);
194	if (privkey == NULL) {
195		pjdlog_error("Unable to read data from %s.", privkeyfile);
196		goto failed;
197	}
198
199	privkeysize = RSA_size(privkey);
200	if (privkeysize != (int)kdk->kdk_encryptedkeysize) {
201		pjdlog_error("RSA modulus size mismatch: equals %db and should be %ub.",
202		    8 * privkeysize, 8 * kdk->kdk_encryptedkeysize);
203		goto failed;
204	}
205
206	switch (kdk->kdk_encryption) {
207	case KERNELDUMP_ENC_AES_256_CBC:
208		cipher = EVP_aes_256_cbc();
209		break;
210	default:
211		pjdlog_error("Invalid encryption algorithm.");
212		goto failed;
213	}
214
215	if (RSA_private_decrypt(kdk->kdk_encryptedkeysize,
216	    kdk->kdk_encryptedkey, key, privkey,
217	    RSA_PKCS1_PADDING) != sizeof(key)) {
218		pjdlog_error("Unable to decrypt key: %s",
219		    ERR_error_string(ERR_get_error(), NULL));
220		goto failed;
221	}
222	RSA_free(privkey);
223	privkey = NULL;
224
225	EVP_DecryptInit_ex(ctx, cipher, NULL, key, kdk->kdk_iv);
226	EVP_CIPHER_CTX_set_padding(ctx, 0);
227
228	explicit_bzero(key, sizeof(key));
229
230	do {
231		bytes = read(ifd, buf, sizeof(buf));
232		if (bytes < 0) {
233			pjdlog_errno(LOG_ERR, "Unable to read data from %s",
234			    input);
235			goto failed;
236		}
237
238		if (bytes > 0) {
239			if (EVP_DecryptUpdate(ctx, buf, &olen, buf,
240			    bytes) == 0) {
241				pjdlog_error("Unable to decrypt core.");
242				goto failed;
243			}
244		} else {
245			if (EVP_DecryptFinal_ex(ctx, buf, &olen) == 0) {
246				pjdlog_error("Unable to decrypt core.");
247				goto failed;
248			}
249		}
250
251		if (olen > 0 && write(ofd, buf, olen) != olen) {
252			pjdlog_errno(LOG_ERR, "Unable to write core");
253			goto failed;
254		}
255	} while (bytes > 0);
256
257	explicit_bzero(buf, sizeof(buf));
258	EVP_CIPHER_CTX_free(ctx);
259	exit(0);
260failed:
261	explicit_bzero(key, sizeof(key));
262	explicit_bzero(buf, sizeof(buf));
263	RSA_free(privkey);
264	if (ctx != NULL)
265		EVP_CIPHER_CTX_free(ctx);
266	exit(1);
267}
268
269int
270main(int argc, char **argv)
271{
272	char core[PATH_MAX], encryptedcore[PATH_MAX], keyfile[PATH_MAX];
273	const char *crashdir, *dumpnr, *privatekey;
274	int ch, debug, error, ofd;
275	size_t ii;
276	bool force, usesyslog;
277
278	error = 1;
279
280	pjdlog_init(PJDLOG_MODE_STD);
281	pjdlog_prefix_set("(decryptcore) ");
282
283	debug = 0;
284	*core = '\0';
285	crashdir = NULL;
286	dumpnr = NULL;
287	*encryptedcore = '\0';
288	force = false;
289	*keyfile = '\0';
290	privatekey = NULL;
291	usesyslog = false;
292	while ((ch = getopt(argc, argv, "Lc:d:e:fk:n:p:v")) != -1) {
293		switch (ch) {
294		case 'L':
295			usesyslog = true;
296			break;
297		case 'c':
298			if (strlcpy(core, optarg, sizeof(core)) >= sizeof(core))
299				pjdlog_exitx(1, "Core file path is too long.");
300			break;
301		case 'd':
302			crashdir = optarg;
303			break;
304		case 'e':
305			if (strlcpy(encryptedcore, optarg,
306			    sizeof(encryptedcore)) >= sizeof(encryptedcore)) {
307				pjdlog_exitx(1, "Encrypted core file path is too long.");
308			}
309			break;
310		case 'f':
311			force = true;
312			break;
313		case 'k':
314			if (strlcpy(keyfile, optarg, sizeof(keyfile)) >=
315			    sizeof(keyfile)) {
316				pjdlog_exitx(1, "Key file path is too long.");
317			}
318			break;
319		case 'n':
320			dumpnr = optarg;
321			break;
322		case 'p':
323			privatekey = optarg;
324			break;
325		case 'v':
326			debug++;
327			break;
328		default:
329			usage();
330		}
331	}
332	argc -= optind;
333	argv += optind;
334
335	if (argc != 0)
336		usage();
337
338	/* Verify mutually exclusive options. */
339	if ((crashdir != NULL || dumpnr != NULL) &&
340	    (*keyfile != '\0' || *encryptedcore != '\0' || *core != '\0')) {
341		usage();
342	}
343
344	/*
345	 * Set key, encryptedcore and core file names using crashdir and dumpnr.
346	 */
347	if (dumpnr != NULL) {
348		for (ii = 0; ii < strnlen(dumpnr, PATH_MAX); ii++) {
349			if (isdigit((int)dumpnr[ii]) == 0)
350				usage();
351		}
352
353		if (crashdir == NULL)
354			crashdir = DECRYPTCORE_CRASHDIR;
355		PJDLOG_VERIFY(snprintf(keyfile, sizeof(keyfile),
356		    "%s/key.%s", crashdir, dumpnr) > 0);
357		PJDLOG_VERIFY(snprintf(core, sizeof(core),
358		    "%s/vmcore.%s", crashdir, dumpnr) > 0);
359		PJDLOG_VERIFY(snprintf(encryptedcore, sizeof(encryptedcore),
360		    "%s/vmcore_encrypted.%s", crashdir, dumpnr) > 0);
361	}
362
363	if (privatekey == NULL || *keyfile == '\0' || *encryptedcore == '\0' ||
364	    *core == '\0') {
365		usage();
366	}
367
368	if (usesyslog)
369		pjdlog_mode_set(PJDLOG_MODE_SYSLOG);
370	pjdlog_debug_set(debug);
371
372	if (force && unlink(core) == -1 && errno != ENOENT) {
373		pjdlog_errno(LOG_ERR, "Unable to remove old core");
374		goto out;
375	}
376	ofd = open(core, O_WRONLY | O_CREAT | O_EXCL, 0600);
377	if (ofd == -1) {
378		pjdlog_errno(LOG_ERR, "Unable to open %s", core);
379		goto out;
380	}
381
382	if (!decrypt(ofd, privatekey, keyfile, encryptedcore)) {
383		if (unlink(core) == -1 && errno != ENOENT)
384			pjdlog_errno(LOG_ERR, "Unable to remove core");
385		goto out;
386	}
387
388	error = 0;
389out:
390	pjdlog_fini();
391	exit(error);
392}
393