play: Convert com_ls() to lopsub.
[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 BIGNUM *n, *e;
138 const unsigned char *p = blob, *end = blob + blen;
139
140 rsa = RSA_new();
141 if (!rsa)
142 return -E_BIGNUM;
143 ret = read_bignum(p, end - p, &e);
144 if (ret < 0)
145 goto fail;
146 p += ret;
147 ret = read_bignum(p, end - p, &n);
148 if (ret < 0)
149 goto fail;
150 #ifdef HAVE_RSA_SET0_KEY
151 RSA_set0_key(rsa, n, e, NULL);
152 #else
153 rsa->n = n;
154 rsa->e = e;
155 #endif
156 *result = rsa;
157 return 1;
158 fail:
159 RSA_free(rsa);
160 return ret;
161 }
162
163 int get_asymmetric_key(const char *key_file, int private,
164 struct asymmetric_key **result)
165 {
166 struct asymmetric_key *key = NULL;
167 void *map = NULL;
168 unsigned char *blob = NULL;
169 size_t map_size, encoded_size, decoded_size;
170 int ret, ret2;
171 char *cp;
172
173 key = para_malloc(sizeof(*key));
174 if (private) {
175 ret = get_openssl_key(key_file, &key->rsa, LOAD_PRIVATE_KEY);
176 goto out;
177 }
178 ret = mmap_full_file(key_file, O_RDONLY, &map, &map_size, NULL);
179 if (ret < 0)
180 goto out;
181 ret = is_ssh_rsa_key(map, map_size);
182 if (!ret) {
183 ret = para_munmap(map, map_size);
184 map = NULL;
185 if (ret < 0)
186 goto out;
187 ret = get_openssl_key(key_file, &key->rsa, LOAD_PUBLIC_KEY);
188 goto out;
189 }
190 cp = map + ret;
191 encoded_size = map_size - ret;
192 PARA_INFO_LOG("decoding public rsa-ssh key %s\n", key_file);
193 ret = uudecode(cp, encoded_size, (char **)&blob, &decoded_size);
194 if (ret < 0)
195 goto out_unmap;
196 ret = check_ssh_key_header(blob, decoded_size);
197 if (ret < 0)
198 goto out_unmap;
199 ret = read_rsa_bignums(blob + ret, decoded_size - ret, &key->rsa);
200 if (ret < 0)
201 goto out_unmap;
202 ret = RSA_size(key->rsa);
203 out_unmap:
204 ret2 = para_munmap(map, map_size);
205 if (ret >= 0 && ret2 < 0)
206 ret = ret2;
207 out:
208 if (ret < 0) {
209 free(key);
210 *result = NULL;
211 PARA_ERROR_LOG("key %s: %s\n", key_file, para_strerror(-ret));
212 } else
213 *result = key;
214 free(blob);
215 return ret;
216 }
217
218 void free_asymmetric_key(struct asymmetric_key *key)
219 {
220 if (!key)
221 return;
222 RSA_free(key->rsa);
223 free(key);
224 }
225
226 int priv_decrypt(const char *key_file, unsigned char *outbuf,
227 unsigned char *inbuf, int inlen)
228 {
229 struct asymmetric_key *priv;
230 int ret;
231
232 if (inlen < 0)
233 return -E_RSA;
234 ret = get_asymmetric_key(key_file, LOAD_PRIVATE_KEY, &priv);
235 if (ret < 0)
236 return ret;
237 /*
238 * RSA is vulnerable to timing attacks. Generate a random blinding
239 * factor to protect against this kind of attack.
240 */
241 ret = -E_BLINDING;
242 if (RSA_blinding_on(priv->rsa, NULL) == 0)
243 goto out;
244 ret = RSA_private_decrypt(inlen, inbuf, outbuf, priv->rsa,
245 RSA_PKCS1_OAEP_PADDING);
246 RSA_blinding_off(priv->rsa);
247 if (ret <= 0)
248 ret = -E_DECRYPT;
249 out:
250 free_asymmetric_key(priv);
251 return ret;
252 }
253
254 int pub_encrypt(struct asymmetric_key *pub, unsigned char *inbuf,
255 unsigned len, unsigned char *outbuf)
256 {
257 int ret, flen = len; /* RSA_public_encrypt expects a signed int */
258
259 if (flen < 0)
260 return -E_ENCRYPT;
261 ret = RSA_public_encrypt(flen, inbuf, outbuf, pub->rsa,
262 RSA_PKCS1_OAEP_PADDING);
263 return ret < 0? -E_ENCRYPT : ret;
264 }
265
266 struct stream_cipher {
267 bool use_aes;
268 union {
269 RC4_KEY rc4_key;
270 EVP_CIPHER_CTX *aes;
271 } context;
272 };
273
274 struct stream_cipher *sc_new(const unsigned char *data, int len,
275 bool use_aes)
276 {
277 struct stream_cipher *sc = para_malloc(sizeof(*sc));
278
279 sc->use_aes = use_aes;
280 if (!use_aes) {
281 RC4_set_key(&sc->context.rc4_key, len, data);
282 return sc;
283 }
284 assert(len >= 2 * AES_CRT128_BLOCK_SIZE);
285 sc->context.aes = EVP_CIPHER_CTX_new();
286 EVP_EncryptInit_ex(sc->context.aes, EVP_aes_128_ctr(), NULL, data,
287 data + AES_CRT128_BLOCK_SIZE);
288 return sc;
289 }
290
291 void sc_free(struct stream_cipher *sc)
292 {
293 if (!sc)
294 return;
295 EVP_CIPHER_CTX_free(sc->context.aes);
296 free(sc);
297 }
298
299 /**
300 * The RC4() implementation of openssl apparently reads and writes data in
301 * blocks of 8 bytes. So we have to make sure our buffer sizes are a multiple
302 * of this.
303 */
304 #define RC4_ALIGN 8
305
306 static void rc4_crypt(RC4_KEY *key, struct iovec *src, struct iovec *dst)
307 {
308 size_t len = src->iov_len, l1, l2;
309
310 assert(len > 0);
311 assert(len < ((typeof(src->iov_len))-1) / 2);
312 l1 = ROUND_DOWN(len, RC4_ALIGN);
313 l2 = ROUND_UP(len, RC4_ALIGN);
314
315 *dst = (typeof(*dst)) {
316 /* Add one for the terminating zero byte. */
317 .iov_base = para_malloc(l2 + 1),
318 .iov_len = len
319 };
320 RC4(key, l1, src->iov_base, dst->iov_base);
321 if (len > l1) {
322 unsigned char remainder[RC4_ALIGN] = "";
323 memcpy(remainder, src->iov_base + l1, len - l1);
324 RC4(key, len - l1, remainder, dst->iov_base + l1);
325 }
326 ((char *)dst->iov_base)[len] = '\0';
327 }
328
329 static void aes_ctr128_crypt(EVP_CIPHER_CTX *ctx, struct iovec *src,
330 struct iovec *dst)
331 {
332 int ret, inlen = src->iov_len, outlen, tmplen;
333
334 *dst = (typeof(*dst)) {
335 /* Add one for the terminating zero byte. */
336 .iov_base = para_malloc(inlen + 1),
337 .iov_len = inlen
338 };
339 ret = EVP_EncryptUpdate(ctx, dst->iov_base, &outlen, src->iov_base, inlen);
340 assert(ret != 0);
341 ret = EVP_EncryptFinal_ex(ctx, dst->iov_base + outlen, &tmplen);
342 assert(ret != 0);
343 outlen += tmplen;
344 ((char *)dst->iov_base)[outlen] = '\0';
345 dst->iov_len = outlen;
346 }
347
348 void sc_crypt(struct stream_cipher *sc, struct iovec *src, struct iovec *dst)
349 {
350 if (sc->use_aes)
351 return aes_ctr128_crypt(sc->context.aes, src, dst);
352 return rc4_crypt(&sc->context.rc4_key, src, dst);
353 }
354
355 void hash_function(const char *data, unsigned long len, unsigned char *hash)
356 {
357 SHA_CTX c;
358 SHA1_Init(&c);
359 SHA1_Update(&c, data, len);
360 SHA1_Final(hash, &c);
361 }