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[paraslash.git] / crypt.c
1 /*
2 * Copyright (C) 2005 Andre Noll <maan@tuebingen.mpg.de>
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 #include "base64.h"
27
28 struct asymmetric_key {
29 RSA *rsa;
30 };
31
32 void get_random_bytes_or_die(unsigned char *buf, int num)
33 {
34 unsigned long err;
35
36 /* RAND_bytes() returns 1 on success, 0 otherwise. */
37 if (RAND_bytes(buf, num) == 1)
38 return;
39 err = ERR_get_error();
40 PARA_EMERG_LOG("%s\n", ERR_reason_error_string(err));
41 exit(EXIT_FAILURE);
42 }
43
44 /*
45 * Read 64 bytes from /dev/urandom and adds them to the SSL PRNG. Seed the PRNG
46 * used by random() with a random seed obtained from SSL. If /dev/random is not
47 * readable the function calls exit().
48 *
49 * \sa RAND_load_file(3), \ref get_random_bytes_or_die(), srandom(3),
50 * random(3), \ref para_random().
51 */
52 void init_random_seed_or_die(void)
53 {
54 int seed, ret = RAND_load_file("/dev/urandom", 64);
55
56 if (ret != 64) {
57 PARA_EMERG_LOG("could not seed PRNG (ret = %d)\n", ret);
58 exit(EXIT_FAILURE);
59 }
60 get_random_bytes_or_die((unsigned char *)&seed, sizeof(seed));
61 srandom(seed);
62 }
63
64 static EVP_PKEY *load_key(const char *file, int private)
65 {
66 BIO *key;
67 EVP_PKEY *pkey = NULL;
68 int ret = check_key_file(file, private);
69
70 if (ret < 0) {
71 PARA_ERROR_LOG("%s\n", para_strerror(-ret));
72 return NULL;
73 }
74 key = BIO_new(BIO_s_file());
75 if (!key)
76 return NULL;
77 if (BIO_read_filename(key, file) > 0) {
78 if (private == LOAD_PRIVATE_KEY)
79 pkey = PEM_read_bio_PrivateKey(key, NULL, NULL, NULL);
80 else
81 pkey = PEM_read_bio_PUBKEY(key, NULL, NULL, NULL);
82 }
83 BIO_free(key);
84 return pkey;
85 }
86
87 static int get_openssl_key(const char *key_file, RSA **rsa, int private)
88 {
89 EVP_PKEY *key = load_key(key_file, private);
90
91 if (!key)
92 return (private == LOAD_PRIVATE_KEY)? -E_PRIVATE_KEY
93 : -E_PUBLIC_KEY;
94 *rsa = EVP_PKEY_get1_RSA(key);
95 EVP_PKEY_free(key);
96 if (!*rsa)
97 return -E_RSA;
98 return RSA_size(*rsa);
99 }
100
101 /*
102 * The public key loading functions below were inspired by corresponding code
103 * of openssh-5.2p1, Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo,
104 * Finland. However, not much of the original code remains.
105 */
106
107 static int read_bignum(const unsigned char *buf, size_t len, BIGNUM **result)
108 {
109 const unsigned char *p = buf, *end = buf + len;
110 uint32_t bnsize;
111 BIGNUM *bn;
112
113 if (p + 4 < p)
114 return -E_BIGNUM;
115 if (p + 4 > end)
116 return -E_BIGNUM;
117 bnsize = read_ssh_u32(p);
118 PARA_DEBUG_LOG("bnsize: %u\n", bnsize);
119 p += 4;
120 if (p + bnsize < p)
121 return -E_BIGNUM;
122 if (p + bnsize > end)
123 return -E_BIGNUM;
124 if (bnsize > 8192)
125 return -E_BIGNUM;
126 bn = BN_bin2bn(p, bnsize, NULL);
127 if (!bn)
128 return -E_BIGNUM;
129 *result = bn;
130 return bnsize + 4;
131 }
132
133 static int read_rsa_bignums(const unsigned char *blob, int blen, RSA **result)
134 {
135 int ret;
136 RSA *rsa;
137 const unsigned char *p = blob, *end = blob + blen;
138
139 rsa = RSA_new();
140 if (!rsa)
141 return -E_BIGNUM;
142 ret = read_bignum(p, end - p, &rsa->e);
143 if (ret < 0)
144 goto fail;
145 p += ret;
146 ret = read_bignum(p, end - p, &rsa->n);
147 if (ret < 0)
148 goto fail;
149 *result = rsa;
150 return 1;
151 fail:
152 RSA_free(rsa);
153 return ret;
154 }
155
156 int get_asymmetric_key(const char *key_file, int private,
157 struct asymmetric_key **result)
158 {
159 struct asymmetric_key *key = NULL;
160 void *map = NULL;
161 unsigned char *blob = NULL;
162 size_t map_size, encoded_size, decoded_size;
163 int ret, ret2;
164 char *cp;
165
166 key = para_malloc(sizeof(*key));
167 if (private) {
168 ret = get_openssl_key(key_file, &key->rsa, LOAD_PRIVATE_KEY);
169 goto out;
170 }
171 ret = mmap_full_file(key_file, O_RDONLY, &map, &map_size, NULL);
172 if (ret < 0)
173 goto out;
174 ret = is_ssh_rsa_key(map, map_size);
175 if (!ret) {
176 ret = para_munmap(map, map_size);
177 map = NULL;
178 if (ret < 0)
179 goto out;
180 ret = get_openssl_key(key_file, &key->rsa, LOAD_PUBLIC_KEY);
181 goto out;
182 }
183 cp = map + ret;
184 encoded_size = map_size - ret;
185 PARA_INFO_LOG("decoding public rsa-ssh key %s\n", key_file);
186 ret = uudecode(cp, encoded_size, (char **)&blob, &decoded_size);
187 if (ret < 0)
188 goto out_unmap;
189 ret = check_ssh_key_header(blob, decoded_size);
190 if (ret < 0)
191 goto out_unmap;
192 ret = read_rsa_bignums(blob + ret, decoded_size - ret, &key->rsa);
193 if (ret < 0)
194 goto out_unmap;
195 ret = RSA_size(key->rsa);
196 out_unmap:
197 ret2 = para_munmap(map, map_size);
198 if (ret >= 0 && ret2 < 0)
199 ret = ret2;
200 out:
201 if (ret < 0) {
202 free(key);
203 *result = NULL;
204 PARA_ERROR_LOG("key %s: %s\n", key_file, para_strerror(-ret));
205 } else
206 *result = key;
207 free(blob);
208 return ret;
209 }
210
211 void free_asymmetric_key(struct asymmetric_key *key)
212 {
213 if (!key)
214 return;
215 RSA_free(key->rsa);
216 free(key);
217 }
218
219 int priv_decrypt(const char *key_file, unsigned char *outbuf,
220 unsigned char *inbuf, int inlen)
221 {
222 struct asymmetric_key *priv;
223 int ret;
224
225 if (inlen < 0)
226 return -E_RSA;
227 ret = get_asymmetric_key(key_file, LOAD_PRIVATE_KEY, &priv);
228 if (ret < 0)
229 return ret;
230 /*
231 * RSA is vulnerable to timing attacks. Generate a random blinding
232 * factor to protect against this kind of attack.
233 */
234 ret = -E_BLINDING;
235 if (RSA_blinding_on(priv->rsa, NULL) == 0)
236 goto out;
237 ret = RSA_private_decrypt(inlen, inbuf, outbuf, priv->rsa,
238 RSA_PKCS1_OAEP_PADDING);
239 RSA_blinding_off(priv->rsa);
240 if (ret <= 0)
241 ret = -E_DECRYPT;
242 out:
243 free_asymmetric_key(priv);
244 return ret;
245 }
246
247 int pub_encrypt(struct asymmetric_key *pub, unsigned char *inbuf,
248 unsigned len, unsigned char *outbuf)
249 {
250 int ret, flen = len; /* RSA_public_encrypt expects a signed int */
251
252 if (flen < 0)
253 return -E_ENCRYPT;
254 ret = RSA_public_encrypt(flen, inbuf, outbuf, pub->rsa,
255 RSA_PKCS1_OAEP_PADDING);
256 return ret < 0? -E_ENCRYPT : ret;
257 }
258
259 struct aes_ctr_128_context {
260 AES_KEY key;
261 unsigned char ivec[AES_CRT128_BLOCK_SIZE];
262 unsigned char ecount[AES_CRT128_BLOCK_SIZE];
263 unsigned int num;
264 };
265
266 struct stream_cipher {
267 bool use_aes;
268 union {
269 RC4_KEY rc4_key;
270 struct aes_ctr_128_context aes;
271 } context;
272 };
273
274 struct stream_cipher *sc_new(const unsigned char *data, int len,
275 bool use_aes)
276 {
277 int ret;
278 struct stream_cipher *sc = para_malloc(sizeof(*sc));
279 struct aes_ctr_128_context *aes;
280
281 sc->use_aes = use_aes;
282 if (!use_aes) {
283 RC4_set_key(&sc->context.rc4_key, len, data);
284 return sc;
285 }
286 assert(len >= 2 * AES_CRT128_BLOCK_SIZE);
287 aes = &sc->context.aes;
288 ret = AES_set_encrypt_key(data, AES_CRT128_BLOCK_SIZE * 8 /* bits */,
289 &aes->key);
290 assert(ret == 0);
291 memcpy(aes->ivec, data + AES_CRT128_BLOCK_SIZE, AES_CRT128_BLOCK_SIZE);
292 aes->num = 0;
293 return sc;
294 }
295
296 void sc_free(struct stream_cipher *sc)
297 {
298 free(sc);
299 }
300
301 /**
302 * The RC4() implementation of openssl apparently reads and writes data in
303 * blocks of 8 bytes. So we have to make sure our buffer sizes are a multiple
304 * of this.
305 */
306 #define RC4_ALIGN 8
307
308 static void rc4_crypt(RC4_KEY *key, struct iovec *src, struct iovec *dst)
309 {
310 size_t len = src->iov_len, l1, l2;
311
312 assert(len > 0);
313 assert(len < ((typeof(src->iov_len))-1) / 2);
314 l1 = ROUND_DOWN(len, RC4_ALIGN);
315 l2 = ROUND_UP(len, RC4_ALIGN);
316
317 *dst = (typeof(*dst)) {
318 /* Add one for the terminating zero byte. */
319 .iov_base = para_malloc(l2 + 1),
320 .iov_len = len
321 };
322 RC4(key, l1, src->iov_base, dst->iov_base);
323 if (len > l1) {
324 unsigned char remainder[RC4_ALIGN] = "";
325 memcpy(remainder, src->iov_base + l1, len - l1);
326 RC4(key, len - l1, remainder, dst->iov_base + l1);
327 }
328 ((char *)dst->iov_base)[len] = '\0';
329 }
330
331 static void aes_ctr128_crypt(struct aes_ctr_128_context *aes, struct iovec *src,
332 struct iovec *dst)
333 {
334 size_t len = src->iov_len;
335
336 *dst = (typeof(*dst)) {
337 /* Add one for the terminating zero byte. */
338 .iov_base = para_malloc(len + 1),
339 .iov_len = len
340 };
341 AES_ctr128_encrypt(src->iov_base, dst->iov_base, len,
342 &aes->key, aes->ivec, aes->ecount, &aes->num);
343 ((char *)dst->iov_base)[len] = '\0';
344 }
345
346 void sc_crypt(struct stream_cipher *sc, struct iovec *src, struct iovec *dst)
347 {
348 if (sc->use_aes)
349 return aes_ctr128_crypt(&sc->context.aes, src, dst);
350 return rc4_crypt(&sc->context.rc4_key, src, dst);
351 }
352
353 void hash_function(const char *data, unsigned long len, unsigned char *hash)
354 {
355 SHA_CTX c;
356 SHA1_Init(&c);
357 SHA1_Update(&c, data, len);
358 SHA1_Final(hash, &c);
359 }