bitstream: Improve documentation.
[paraslash.git] / crypt.c
1 /*
2 * Copyright (C) 2005-2014 Andre Noll <maan@systemlinux.org>
3 *
4 * Licensed under the GPL v2. For licencing details see COPYING.
5 */
6
7 /** \file crypt.c Openssl-based encryption/decryption routines. */
8
9 #include <regex.h>
10 #include <sys/types.h>
11 #include <sys/socket.h>
12 #include <openssl/rand.h>
13 #include <openssl/err.h>
14 #include <openssl/rc4.h>
15 #include <openssl/pem.h>
16 #include <openssl/sha.h>
17 #include <openssl/bn.h>
18 #include <openssl/aes.h>
19
20 #include "para.h"
21 #include "error.h"
22 #include "string.h"
23 #include "crypt.h"
24 #include "fd.h"
25 #include "crypt_backend.h"
26
27 struct asymmetric_key {
28 RSA *rsa;
29 };
30
31 void get_random_bytes_or_die(unsigned char *buf, int num)
32 {
33 unsigned long err;
34
35 /* RAND_bytes() returns 1 on success, 0 otherwise. */
36 if (RAND_bytes(buf, num) == 1)
37 return;
38 err = ERR_get_error();
39 PARA_EMERG_LOG("%s\n", ERR_reason_error_string(err));
40 exit(EXIT_FAILURE);
41 }
42
43 /*
44 * Read 64 bytes from /dev/urandom and adds them to the SSL PRNG. Seed the PRNG
45 * used by random() with a random seed obtained from SSL. If /dev/random is not
46 * readable the function calls exit().
47 *
48 * \sa RAND_load_file(3), \ref get_random_bytes_or_die(), srandom(3),
49 * random(3), \ref para_random().
50 */
51 void init_random_seed_or_die(void)
52 {
53 int seed, ret = RAND_load_file("/dev/urandom", 64);
54
55 if (ret != 64) {
56 PARA_EMERG_LOG("could not seed PRNG (ret = %d)\n", ret);
57 exit(EXIT_FAILURE);
58 }
59 get_random_bytes_or_die((unsigned char *)&seed, sizeof(seed));
60 srandom(seed);
61 }
62
63 static EVP_PKEY *load_key(const char *file, int private)
64 {
65 BIO *key;
66 EVP_PKEY *pkey = NULL;
67 int ret = check_key_file(file, private);
68
69 if (ret < 0) {
70 PARA_ERROR_LOG("%s\n", para_strerror(-ret));
71 return NULL;
72 }
73 key = BIO_new(BIO_s_file());
74 if (!key)
75 return NULL;
76 if (BIO_read_filename(key, file) > 0) {
77 if (private == LOAD_PRIVATE_KEY)
78 pkey = PEM_read_bio_PrivateKey(key, NULL, NULL, NULL);
79 else
80 pkey = PEM_read_bio_PUBKEY(key, NULL, NULL, NULL);
81 }
82 BIO_free(key);
83 return pkey;
84 }
85
86 static int get_openssl_key(const char *key_file, RSA **rsa, int private)
87 {
88 EVP_PKEY *key = load_key(key_file, private);
89
90 if (!key)
91 return (private == LOAD_PRIVATE_KEY)? -E_PRIVATE_KEY
92 : -E_PUBLIC_KEY;
93 *rsa = EVP_PKEY_get1_RSA(key);
94 EVP_PKEY_free(key);
95 if (!*rsa)
96 return -E_RSA;
97 return RSA_size(*rsa);
98 }
99
100 /*
101 * The public key loading functions below were inspired by corresponding code
102 * of openssh-5.2p1, Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo,
103 * Finland. However, not much of the original code remains.
104 */
105
106 static int read_bignum(const unsigned char *buf, size_t len, BIGNUM **result)
107 {
108 const unsigned char *p = buf, *end = buf + len;
109 uint32_t bnsize;
110 BIGNUM *bn;
111
112 if (p + 4 < p)
113 return -E_BIGNUM;
114 if (p + 4 > end)
115 return -E_BIGNUM;
116 bnsize = read_ssh_u32(p);
117 PARA_DEBUG_LOG("bnsize: %u\n", bnsize);
118 p += 4;
119 if (p + bnsize < p)
120 return -E_BIGNUM;
121 if (p + bnsize > end)
122 return -E_BIGNUM;
123 if (bnsize > 8192)
124 return -E_BIGNUM;
125 bn = BN_bin2bn(p, bnsize, NULL);
126 if (!bn)
127 return -E_BIGNUM;
128 *result = bn;
129 return bnsize + 4;
130 }
131
132 static int read_rsa_bignums(const unsigned char *blob, int blen, RSA **result)
133 {
134 int ret;
135 RSA *rsa;
136 const unsigned char *p = blob, *end = blob + blen;
137
138 rsa = RSA_new();
139 if (!rsa)
140 return -E_BIGNUM;
141 ret = read_bignum(p, end - p, &rsa->e);
142 if (ret < 0)
143 goto fail;
144 p += ret;
145 ret = read_bignum(p, end - p, &rsa->n);
146 if (ret < 0)
147 goto fail;
148 *result = rsa;
149 return 1;
150 fail:
151 RSA_free(rsa);
152 return ret;
153 }
154
155 int get_asymmetric_key(const char *key_file, int private,
156 struct asymmetric_key **result)
157 {
158 struct asymmetric_key *key = NULL;
159 void *map = NULL;
160 unsigned char *blob = NULL;
161 size_t map_size, blob_size, decoded_size;
162 int ret, ret2;
163 char *cp;
164
165 key = para_malloc(sizeof(*key));
166 if (private) {
167 ret = get_openssl_key(key_file, &key->rsa, LOAD_PRIVATE_KEY);
168 goto out;
169 }
170 ret = mmap_full_file(key_file, O_RDONLY, &map, &map_size, NULL);
171 if (ret < 0)
172 goto out;
173 ret = is_ssh_rsa_key(map, map_size);
174 if (!ret) {
175 ret = para_munmap(map, map_size);
176 map = NULL;
177 if (ret < 0)
178 goto out;
179 ret = get_openssl_key(key_file, &key->rsa, LOAD_PUBLIC_KEY);
180 goto out;
181 }
182 cp = map + ret;
183 PARA_INFO_LOG("decoding public rsa-ssh key %s\n", key_file);
184 ret = -ERRNO_TO_PARA_ERROR(EOVERFLOW);
185 if (map_size > INT_MAX / 4)
186 goto out_unmap;
187 blob_size = 2 * map_size;
188 blob = para_malloc(blob_size);
189 ret = uudecode(cp, blob, blob_size);
190 if (ret < 0)
191 goto out_unmap;
192 decoded_size = ret;
193 ret = check_ssh_key_header(blob, decoded_size);
194 if (ret < 0)
195 goto out_unmap;
196 ret = read_rsa_bignums(blob + ret, decoded_size - ret, &key->rsa);
197 if (ret < 0)
198 goto out_unmap;
199 ret = RSA_size(key->rsa);
200 out_unmap:
201 ret2 = para_munmap(map, map_size);
202 if (ret >= 0 && ret2 < 0)
203 ret = ret2;
204 out:
205 if (ret < 0) {
206 free(key);
207 *result = NULL;
208 PARA_ERROR_LOG("key %s: %s\n", key_file, para_strerror(-ret));
209 } else
210 *result = key;
211 free(blob);
212 return ret;
213 }
214
215 void free_asymmetric_key(struct asymmetric_key *key)
216 {
217 if (!key)
218 return;
219 RSA_free(key->rsa);
220 free(key);
221 }
222
223 int priv_decrypt(const char *key_file, unsigned char *outbuf,
224 unsigned char *inbuf, int inlen)
225 {
226 struct asymmetric_key *priv;
227 int ret;
228
229 if (inlen < 0)
230 return -E_RSA;
231 ret = get_asymmetric_key(key_file, LOAD_PRIVATE_KEY, &priv);
232 if (ret < 0)
233 return ret;
234 /*
235 * RSA is vulnerable to timing attacks. Generate a random blinding
236 * factor to protect against this kind of attack.
237 */
238 ret = -E_BLINDING;
239 if (RSA_blinding_on(priv->rsa, NULL) == 0)
240 goto out;
241 ret = RSA_private_decrypt(inlen, inbuf, outbuf, priv->rsa,
242 RSA_PKCS1_OAEP_PADDING);
243 RSA_blinding_off(priv->rsa);
244 if (ret <= 0)
245 ret = -E_DECRYPT;
246 out:
247 free_asymmetric_key(priv);
248 return ret;
249 }
250
251 int pub_encrypt(struct asymmetric_key *pub, unsigned char *inbuf,
252 unsigned len, unsigned char *outbuf)
253 {
254 int ret, flen = len; /* RSA_public_encrypt expects a signed int */
255
256 if (flen < 0)
257 return -E_ENCRYPT;
258 ret = RSA_public_encrypt(flen, inbuf, outbuf, pub->rsa,
259 RSA_PKCS1_OAEP_PADDING);
260 return ret < 0? -E_ENCRYPT : ret;
261 }
262
263 struct aes_ctr_128_context {
264 AES_KEY key;
265 unsigned char ivec[AES_CRT128_BLOCK_SIZE];
266 unsigned char ecount[AES_CRT128_BLOCK_SIZE];
267 unsigned int num;
268 };
269
270 struct stream_cipher {
271 bool use_aes;
272 union {
273 RC4_KEY rc4_key;
274 struct aes_ctr_128_context aes;
275 } context;
276 };
277
278 struct stream_cipher *sc_new(const unsigned char *data, int len,
279 bool use_aes)
280 {
281 int ret;
282 struct stream_cipher *sc = para_malloc(sizeof(*sc));
283 struct aes_ctr_128_context *aes;
284
285 sc->use_aes = use_aes;
286 if (!use_aes) {
287 RC4_set_key(&sc->context.rc4_key, len, data);
288 return sc;
289 }
290 assert(len >= 2 * AES_CRT128_BLOCK_SIZE);
291 aes = &sc->context.aes;
292 ret = AES_set_encrypt_key(data, AES_CRT128_BLOCK_SIZE * 8 /* bits */,
293 &aes->key);
294 assert(ret == 0);
295 memcpy(aes->ivec, data + AES_CRT128_BLOCK_SIZE, AES_CRT128_BLOCK_SIZE);
296 aes->num = 0;
297 return sc;
298 }
299
300 void sc_free(struct stream_cipher *sc)
301 {
302 free(sc);
303 }
304
305 /**
306 * The RC4() implementation of openssl apparently reads and writes data in
307 * blocks of 8 bytes. So we have to make sure our buffer sizes are a multiple
308 * of this.
309 */
310 #define RC4_ALIGN 8
311
312 static void rc4_crypt(RC4_KEY *key, struct iovec *src, struct iovec *dst)
313 {
314 size_t len = src->iov_len, l1, l2;
315
316 assert(len > 0);
317 assert(len < ((typeof(src->iov_len))-1) / 2);
318 l1 = ROUND_DOWN(len, RC4_ALIGN);
319 l2 = ROUND_UP(len, RC4_ALIGN);
320
321 *dst = (typeof(*dst)) {
322 /* Add one for the terminating zero byte. */
323 .iov_base = para_malloc(l2 + 1),
324 .iov_len = len
325 };
326 RC4(key, l1, src->iov_base, dst->iov_base);
327 if (len > l1) {
328 unsigned char remainder[RC4_ALIGN] = "";
329 memcpy(remainder, src->iov_base + l1, len - l1);
330 RC4(key, len - l1, remainder, dst->iov_base + l1);
331 }
332 ((char *)dst->iov_base)[len] = '\0';
333 }
334
335 static void aes_ctr128_crypt(struct aes_ctr_128_context *aes, struct iovec *src,
336 struct iovec *dst)
337 {
338 size_t len = src->iov_len;
339
340 *dst = (typeof(*dst)) {
341 /* Add one for the terminating zero byte. */
342 .iov_base = para_malloc(len + 1),
343 .iov_len = len
344 };
345 AES_ctr128_encrypt(src->iov_base, dst->iov_base, len,
346 &aes->key, aes->ivec, aes->ecount, &aes->num);
347 ((char *)dst->iov_base)[len] = '\0';
348 }
349
350 void sc_crypt(struct stream_cipher *sc, struct iovec *src, struct iovec *dst)
351 {
352 if (sc->use_aes)
353 return aes_ctr128_crypt(&sc->context.aes, src, dst);
354 return rc4_crypt(&sc->context.rc4_key, src, dst);
355 }
356
357 void hash_function(const char *data, unsigned long len, unsigned char *hash)
358 {
359 SHA_CTX c;
360 SHA1_Init(&c);
361 SHA1_Update(&c, data, len);
362 SHA1_Final(hash, &c);
363 }