Merge branch 't/smaller_tarball'
[paraslash.git] / crypt.c
1 /*
2 * Copyright (C) 2005-2011 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 <stdbool.h>
11 #include <sys/types.h>
12 #include <sys/socket.h>
13 #include <openssl/rand.h>
14 #include <openssl/err.h>
15 #include <openssl/rc4.h>
16 #include <openssl/pem.h>
17 #include <openssl/sha.h>
18 #include <openssl/bn.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 if (rsa)
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;
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;
193 decoded_size = ret;
194 ret = check_ssh_key_header(blob, decoded_size);
195 if (ret < 0)
196 goto out;
197 ret = read_rsa_bignums(blob + ret, decoded_size - ret, &key->rsa);
198 if (ret < 0)
199 goto out;
200 ret = RSA_size(key->rsa);
201 out:
202 ret2 = para_munmap(map, map_size);
203 if (ret >= 0 && ret2 < 0)
204 ret = ret2;
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 stream_cipher {
264 RC4_KEY key;
265 };
266
267 struct stream_cipher *sc_new(const unsigned char *data, int len)
268 {
269 struct stream_cipher *sc = para_malloc(sizeof(*sc));
270 RC4_set_key(&sc->key, len, data);
271 return sc;
272 }
273
274 void sc_free(struct stream_cipher *sc)
275 {
276 free(sc);
277 }
278
279 /**
280 * The RC4() implementation of openssl apparently reads and writes data in
281 * blocks of 8 bytes. So we have to make sure our buffer sizes are a multiple
282 * of this.
283 */
284 #define RC4_ALIGN 8
285
286 int sc_send_bin_buffer(struct stream_cipher_context *scc, char *buf,
287 size_t len)
288 {
289 int ret;
290 unsigned char *tmp;
291 static unsigned char remainder[RC4_ALIGN];
292 size_t l1 = ROUND_DOWN(len, RC4_ALIGN), l2 = ROUND_UP(len, RC4_ALIGN);
293
294 assert(len);
295 tmp = para_malloc(l2);
296 RC4(&scc->send->key, l1, (const unsigned char *)buf, tmp);
297 if (len > l1) {
298 memcpy(remainder, buf + l1, len - l1);
299 RC4(&scc->send->key, len - l1, remainder, tmp + l1);
300 }
301 ret = write_all(scc->fd, (char *)tmp, &len);
302 free(tmp);
303 return ret;
304 }
305
306 int sc_recv_bin_buffer(struct stream_cipher_context *scc, char *buf,
307 size_t size)
308 {
309 unsigned char *tmp = para_malloc(size);
310 ssize_t ret = recv(scc->fd, tmp, size, 0);
311
312 if (ret > 0)
313 RC4(&scc->recv->key, ret, tmp, (unsigned char *)buf);
314 else if (ret < 0)
315 ret = -ERRNO_TO_PARA_ERROR(errno);
316 free(tmp);
317 return ret;
318 }
319
320 void hash_function(const char *data, unsigned long len, unsigned char *hash)
321 {
322 SHA_CTX c;
323 SHA1_Init(&c);
324 SHA1_Update(&c, data, len);
325 SHA1_Final(hash, &c);
326 }