crypt.c: Combine load_key() and get_private_key().
[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 int get_private_key(const char *path, RSA **rsa)
65 {
66 EVP_PKEY *pkey;
67 BIO *bio = BIO_new(BIO_s_file());
68
69 *rsa = NULL;
70 if (!bio)
71 return -E_PRIVATE_KEY;
72 if (BIO_read_filename(bio, path) <= 0)
73 goto bio_free;
74 pkey = PEM_read_bio_PrivateKey(bio, NULL, NULL, NULL);
75 if (!pkey)
76 goto bio_free;
77 *rsa = EVP_PKEY_get1_RSA(pkey);
78 EVP_PKEY_free(pkey);
79 bio_free:
80 BIO_free(bio);
81 return *rsa? RSA_size(*rsa) : -E_PRIVATE_KEY;
82 }
83
84 /*
85 * The public key loading functions below were inspired by corresponding code
86 * of openssh-5.2p1, Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo,
87 * Finland. However, not much of the original code remains.
88 */
89
90 static int read_bignum(const unsigned char *buf, size_t len, BIGNUM **result)
91 {
92 const unsigned char *p = buf, *end = buf + len;
93 uint32_t bnsize;
94 BIGNUM *bn;
95
96 if (p + 4 < p)
97 return -E_BIGNUM;
98 if (p + 4 > end)
99 return -E_BIGNUM;
100 bnsize = read_ssh_u32(p);
101 PARA_DEBUG_LOG("bnsize: %u\n", bnsize);
102 p += 4;
103 if (p + bnsize < p)
104 return -E_BIGNUM;
105 if (p + bnsize > end)
106 return -E_BIGNUM;
107 if (bnsize > 8192)
108 return -E_BIGNUM;
109 bn = BN_bin2bn(p, bnsize, NULL);
110 if (!bn)
111 return -E_BIGNUM;
112 *result = bn;
113 return bnsize + 4;
114 }
115
116 static int read_rsa_bignums(const unsigned char *blob, int blen, RSA **result)
117 {
118 int ret;
119 RSA *rsa;
120 BIGNUM *n, *e;
121 const unsigned char *p = blob, *end = blob + blen;
122
123 rsa = RSA_new();
124 if (!rsa)
125 return -E_BIGNUM;
126 ret = read_bignum(p, end - p, &e);
127 if (ret < 0)
128 goto fail;
129 p += ret;
130 ret = read_bignum(p, end - p, &n);
131 if (ret < 0)
132 goto fail;
133 #ifdef HAVE_RSA_SET0_KEY
134 RSA_set0_key(rsa, n, e, NULL);
135 #else
136 rsa->n = n;
137 rsa->e = e;
138 #endif
139 *result = rsa;
140 return 1;
141 fail:
142 RSA_free(rsa);
143 return ret;
144 }
145
146 int get_public_key(const char *key_file, struct asymmetric_key **result)
147 {
148 struct asymmetric_key *key = NULL;
149 void *map = NULL;
150 unsigned char *blob = NULL;
151 size_t map_size, encoded_size, decoded_size;
152 int ret, ret2;
153 char *cp;
154
155 key = para_malloc(sizeof(*key));
156 ret = mmap_full_file(key_file, O_RDONLY, &map, &map_size, NULL);
157 if (ret < 0)
158 goto out;
159 ret = is_ssh_rsa_key(map, map_size);
160 if (!ret) {
161 para_munmap(map, map_size);
162 return -E_SSH_PARSE;
163 }
164 cp = map + ret;
165 encoded_size = map_size - ret;
166 PARA_INFO_LOG("decoding public rsa-ssh key %s\n", key_file);
167 ret = uudecode(cp, encoded_size, (char **)&blob, &decoded_size);
168 if (ret < 0)
169 goto out_unmap;
170 ret = check_ssh_key_header(blob, decoded_size);
171 if (ret < 0)
172 goto out_unmap;
173 ret = read_rsa_bignums(blob + ret, decoded_size - ret, &key->rsa);
174 if (ret < 0)
175 goto out_unmap;
176 ret = RSA_size(key->rsa);
177 out_unmap:
178 ret2 = para_munmap(map, map_size);
179 if (ret >= 0 && ret2 < 0)
180 ret = ret2;
181 out:
182 if (ret < 0) {
183 free(key);
184 *result = NULL;
185 PARA_ERROR_LOG("key %s: %s\n", key_file, para_strerror(-ret));
186 } else
187 *result = key;
188 free(blob);
189 return ret;
190 }
191
192 void free_public_key(struct asymmetric_key *key)
193 {
194 if (!key)
195 return;
196 RSA_free(key->rsa);
197 free(key);
198 }
199
200 int priv_decrypt(const char *key_file, unsigned char *outbuf,
201 unsigned char *inbuf, int inlen)
202 {
203 struct asymmetric_key *priv;
204 int ret;
205
206 ret = check_private_key_file(key_file);
207 if (ret < 0)
208 return ret;
209 if (inlen < 0)
210 return -E_RSA;
211 priv = para_malloc(sizeof(*priv));
212 ret = get_private_key(key_file, &priv->rsa);
213 if (ret < 0) {
214 free(priv);
215 return ret;
216 }
217 /*
218 * RSA is vulnerable to timing attacks. Generate a random blinding
219 * factor to protect against this kind of attack.
220 */
221 ret = -E_BLINDING;
222 if (RSA_blinding_on(priv->rsa, NULL) == 0)
223 goto out;
224 ret = RSA_private_decrypt(inlen, inbuf, outbuf, priv->rsa,
225 RSA_PKCS1_OAEP_PADDING);
226 RSA_blinding_off(priv->rsa);
227 if (ret <= 0)
228 ret = -E_DECRYPT;
229 out:
230 RSA_free(priv->rsa);
231 free(priv);
232 return ret;
233 }
234
235 int pub_encrypt(struct asymmetric_key *pub, unsigned char *inbuf,
236 unsigned len, unsigned char *outbuf)
237 {
238 int ret, flen = len; /* RSA_public_encrypt expects a signed int */
239
240 if (flen < 0)
241 return -E_ENCRYPT;
242 ret = RSA_public_encrypt(flen, inbuf, outbuf, pub->rsa,
243 RSA_PKCS1_OAEP_PADDING);
244 return ret < 0? -E_ENCRYPT : ret;
245 }
246
247 struct stream_cipher {
248 bool use_aes;
249 union {
250 RC4_KEY rc4_key;
251 EVP_CIPHER_CTX *aes;
252 } context;
253 };
254
255 struct stream_cipher *sc_new(const unsigned char *data, int len,
256 bool use_aes)
257 {
258 struct stream_cipher *sc = para_malloc(sizeof(*sc));
259
260 sc->use_aes = use_aes;
261 if (!use_aes) {
262 RC4_set_key(&sc->context.rc4_key, len, data);
263 return sc;
264 }
265 assert(len >= 2 * AES_CRT128_BLOCK_SIZE);
266 sc->context.aes = EVP_CIPHER_CTX_new();
267 EVP_EncryptInit_ex(sc->context.aes, EVP_aes_128_ctr(), NULL, data,
268 data + AES_CRT128_BLOCK_SIZE);
269 return sc;
270 }
271
272 void sc_free(struct stream_cipher *sc)
273 {
274 if (!sc)
275 return;
276 EVP_CIPHER_CTX_free(sc->context.aes);
277 free(sc);
278 }
279
280 /**
281 * The RC4() implementation of openssl apparently reads and writes data in
282 * blocks of 8 bytes. So we have to make sure our buffer sizes are a multiple
283 * of this.
284 */
285 #define RC4_ALIGN 8
286
287 static void rc4_crypt(RC4_KEY *key, struct iovec *src, struct iovec *dst)
288 {
289 size_t len = src->iov_len, l1, l2;
290
291 assert(len > 0);
292 assert(len < ((typeof(src->iov_len))-1) / 2);
293 l1 = ROUND_DOWN(len, RC4_ALIGN);
294 l2 = ROUND_UP(len, RC4_ALIGN);
295
296 *dst = (typeof(*dst)) {
297 /* Add one for the terminating zero byte. */
298 .iov_base = para_malloc(l2 + 1),
299 .iov_len = len
300 };
301 RC4(key, l1, src->iov_base, dst->iov_base);
302 if (len > l1) {
303 unsigned char remainder[RC4_ALIGN] = "";
304 memcpy(remainder, src->iov_base + l1, len - l1);
305 RC4(key, len - l1, remainder, dst->iov_base + l1);
306 }
307 ((char *)dst->iov_base)[len] = '\0';
308 }
309
310 static void aes_ctr128_crypt(EVP_CIPHER_CTX *ctx, struct iovec *src,
311 struct iovec *dst)
312 {
313 int ret, inlen = src->iov_len, outlen, tmplen;
314
315 *dst = (typeof(*dst)) {
316 /* Add one for the terminating zero byte. */
317 .iov_base = para_malloc(inlen + 1),
318 .iov_len = inlen
319 };
320 ret = EVP_EncryptUpdate(ctx, dst->iov_base, &outlen, src->iov_base, inlen);
321 assert(ret != 0);
322 ret = EVP_EncryptFinal_ex(ctx, dst->iov_base + outlen, &tmplen);
323 assert(ret != 0);
324 outlen += tmplen;
325 ((char *)dst->iov_base)[outlen] = '\0';
326 dst->iov_len = outlen;
327 }
328
329 void sc_crypt(struct stream_cipher *sc, struct iovec *src, struct iovec *dst)
330 {
331 if (sc->use_aes)
332 return aes_ctr128_crypt(sc->context.aes, src, dst);
333 return rc4_crypt(&sc->context.rc4_key, src, dst);
334 }
335
336 void hash_function(const char *data, unsigned long len, unsigned char *hash)
337 {
338 SHA_CTX c;
339 SHA1_Init(&c);
340 SHA1_Update(&c, data, len);
341 SHA1_Final(hash, &c);
342 }