Move base64 implementation to own file.
[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, blob_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 PARA_INFO_LOG("decoding public rsa-ssh key %s\n", key_file);
185 ret = -ERRNO_TO_PARA_ERROR(EOVERFLOW);
186 if (map_size > INT_MAX / 4)
187 goto out_unmap;
188 blob_size = 2 * map_size;
189 blob = para_malloc(blob_size);
190 ret = uudecode(cp, blob, blob_size);
191 if (ret < 0)
192 goto out_unmap;
193 decoded_size = ret;
194 ret = check_ssh_key_header(blob, decoded_size);
195 if (ret < 0)
196 goto out_unmap;
197 ret = read_rsa_bignums(blob + ret, decoded_size - ret, &key->rsa);
198 if (ret < 0)
199 goto out_unmap;
200 ret = RSA_size(key->rsa);
201 out_unmap:
202 ret2 = para_munmap(map, map_size);
203 if (ret >= 0 && ret2 < 0)
204 ret = ret2;
205 out:
206 if (ret < 0) {
207 free(key);
208 *result = NULL;
209 PARA_ERROR_LOG("key %s: %s\n", key_file, para_strerror(-ret));
210 } else
211 *result = key;
212 free(blob);
213 return ret;
214 }
215
216 void free_asymmetric_key(struct asymmetric_key *key)
217 {
218 if (!key)
219 return;
220 RSA_free(key->rsa);
221 free(key);
222 }
223
224 int priv_decrypt(const char *key_file, unsigned char *outbuf,
225 unsigned char *inbuf, int inlen)
226 {
227 struct asymmetric_key *priv;
228 int ret;
229
230 if (inlen < 0)
231 return -E_RSA;
232 ret = get_asymmetric_key(key_file, LOAD_PRIVATE_KEY, &priv);
233 if (ret < 0)
234 return ret;
235 /*
236 * RSA is vulnerable to timing attacks. Generate a random blinding
237 * factor to protect against this kind of attack.
238 */
239 ret = -E_BLINDING;
240 if (RSA_blinding_on(priv->rsa, NULL) == 0)
241 goto out;
242 ret = RSA_private_decrypt(inlen, inbuf, outbuf, priv->rsa,
243 RSA_PKCS1_OAEP_PADDING);
244 RSA_blinding_off(priv->rsa);
245 if (ret <= 0)
246 ret = -E_DECRYPT;
247 out:
248 free_asymmetric_key(priv);
249 return ret;
250 }
251
252 int pub_encrypt(struct asymmetric_key *pub, unsigned char *inbuf,
253 unsigned len, unsigned char *outbuf)
254 {
255 int ret, flen = len; /* RSA_public_encrypt expects a signed int */
256
257 if (flen < 0)
258 return -E_ENCRYPT;
259 ret = RSA_public_encrypt(flen, inbuf, outbuf, pub->rsa,
260 RSA_PKCS1_OAEP_PADDING);
261 return ret < 0? -E_ENCRYPT : ret;
262 }
263
264 struct aes_ctr_128_context {
265 AES_KEY key;
266 unsigned char ivec[AES_CRT128_BLOCK_SIZE];
267 unsigned char ecount[AES_CRT128_BLOCK_SIZE];
268 unsigned int num;
269 };
270
271 struct stream_cipher {
272 bool use_aes;
273 union {
274 RC4_KEY rc4_key;
275 struct aes_ctr_128_context aes;
276 } context;
277 };
278
279 struct stream_cipher *sc_new(const unsigned char *data, int len,
280 bool use_aes)
281 {
282 int ret;
283 struct stream_cipher *sc = para_malloc(sizeof(*sc));
284 struct aes_ctr_128_context *aes;
285
286 sc->use_aes = use_aes;
287 if (!use_aes) {
288 RC4_set_key(&sc->context.rc4_key, len, data);
289 return sc;
290 }
291 assert(len >= 2 * AES_CRT128_BLOCK_SIZE);
292 aes = &sc->context.aes;
293 ret = AES_set_encrypt_key(data, AES_CRT128_BLOCK_SIZE * 8 /* bits */,
294 &aes->key);
295 assert(ret == 0);
296 memcpy(aes->ivec, data + AES_CRT128_BLOCK_SIZE, AES_CRT128_BLOCK_SIZE);
297 aes->num = 0;
298 return sc;
299 }
300
301 void sc_free(struct stream_cipher *sc)
302 {
303 free(sc);
304 }
305
306 /**
307 * The RC4() implementation of openssl apparently reads and writes data in
308 * blocks of 8 bytes. So we have to make sure our buffer sizes are a multiple
309 * of this.
310 */
311 #define RC4_ALIGN 8
312
313 static void rc4_crypt(RC4_KEY *key, struct iovec *src, struct iovec *dst)
314 {
315 size_t len = src->iov_len, l1, l2;
316
317 assert(len > 0);
318 assert(len < ((typeof(src->iov_len))-1) / 2);
319 l1 = ROUND_DOWN(len, RC4_ALIGN);
320 l2 = ROUND_UP(len, RC4_ALIGN);
321
322 *dst = (typeof(*dst)) {
323 /* Add one for the terminating zero byte. */
324 .iov_base = para_malloc(l2 + 1),
325 .iov_len = len
326 };
327 RC4(key, l1, src->iov_base, dst->iov_base);
328 if (len > l1) {
329 unsigned char remainder[RC4_ALIGN] = "";
330 memcpy(remainder, src->iov_base + l1, len - l1);
331 RC4(key, len - l1, remainder, dst->iov_base + l1);
332 }
333 ((char *)dst->iov_base)[len] = '\0';
334 }
335
336 static void aes_ctr128_crypt(struct aes_ctr_128_context *aes, struct iovec *src,
337 struct iovec *dst)
338 {
339 size_t len = src->iov_len;
340
341 *dst = (typeof(*dst)) {
342 /* Add one for the terminating zero byte. */
343 .iov_base = para_malloc(len + 1),
344 .iov_len = len
345 };
346 AES_ctr128_encrypt(src->iov_base, dst->iov_base, len,
347 &aes->key, aes->ivec, aes->ecount, &aes->num);
348 ((char *)dst->iov_base)[len] = '\0';
349 }
350
351 void sc_crypt(struct stream_cipher *sc, struct iovec *src, struct iovec *dst)
352 {
353 if (sc->use_aes)
354 return aes_ctr128_crypt(&sc->context.aes, src, dst);
355 return rc4_crypt(&sc->context.rc4_key, src, dst);
356 }
357
358 void hash_function(const char *data, unsigned long len, unsigned char *hash)
359 {
360 SHA_CTX c;
361 SHA1_Init(&c);
362 SHA1_Update(&c, data, len);
363 SHA1_Final(hash, &c);
364 }