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b02b720a IJ |
1 | /* |
2 | * eax-transform.c: EAX-Serpent bulk data transformation | |
c215a4bc IJ |
3 | */ |
4 | /* | |
5 | * This file is part of secnet. | |
6 | * See README for full list of copyright holders. | |
b02b720a | 7 | * |
c215a4bc IJ |
8 | * secnet is free software; you can redistribute it and/or modify it |
9 | * under the terms of the GNU General Public License as published by | |
10 | * the Free Software Foundation; either version d of the License, or | |
11 | * (at your option) any later version. | |
12 | * | |
13 | * secnet is distributed in the hope that it will be useful, but | |
14 | * WITHOUT ANY WARRANTY; without even the implied warranty of | |
15 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
16 | * General Public License for more details. | |
17 | * | |
18 | * You should have received a copy of the GNU General Public License | |
19 | * version 3 along with secnet; if not, see | |
20 | * https://www.gnu.org/licenses/gpl.html. | |
21 | */ | |
22 | /* | |
b02b720a IJ |
23 | * We use EAX with the following parameters: |
24 | * | |
25 | * Plaintext: | |
26 | * Concatenation of: | |
27 | * Data packet as supplied to us | |
28 | * Zero or more zero bytes ignored by receiver } padding | |
29 | * One byte padding length } | |
30 | * This is a bit like PKCS#5. It helps disguise message lengths. | |
31 | * It also provides a further room for future expansion. When | |
32 | * transmitting we pad the message to the next multiple of | |
33 | * a configurable rounding factor, 16 bytes by default. | |
34 | * | |
35 | * Transmitted message: | |
36 | * Concatenation of: | |
37 | * EAX ciphertext | |
38 | * 32-bit sequence number (initially zero) | |
39 | * The sequence number allows us to discard far-too-old | |
40 | * packets. | |
41 | * | |
42 | * Nonce: | |
43 | * Concatenation of: | |
44 | * 32-bit sequence number (big endian) | |
45 | * initial value comes from SHA-512 hash (see below) | |
46 | * 1 byte: 0x01 if sender has setup priority, 0x00 if it doesn't | |
47 | * (ie, the direction of data flow) | |
48 | * | |
49 | * Header: None | |
50 | * | |
51 | * Tag length: | |
52 | * 16 bytes (128 bits) by default | |
53 | * | |
54 | * Key: | |
55 | * The first 32 bytes of the SHA-512 hash of the shared secret | |
56 | * from the DH key exchange (the latter being expressed as | |
57 | * the shortest possible big-endian octet string). | |
58 | * | |
59 | * The bytes [32,40> of the hash of the shared secret are used for | |
60 | * initial sequence numbers: [32,36> for those sent by the end without | |
61 | * setup priority, [36,40> for those for the other end. | |
62 | * | |
63 | */ | |
64 | ||
65 | #include "secnet.h" | |
66 | #include "unaligned.h" | |
67 | #include "util.h" | |
68 | #include "serpent.h" | |
69 | #include "sha512.h" | |
70 | #include "transform-common.h" | |
71 | #include "hexdebug.h" | |
72 | ||
73 | #define BLOCK_SIZE 16 | |
74 | #define SEQLEN 4 | |
75 | ||
76 | struct transform_params { | |
35d30aa3 IJ |
77 | SEQNUM_PARAMS_FIELDS; |
78 | uint32_t tag_length, padding_mask; | |
b02b720a IJ |
79 | }; |
80 | ||
81 | struct transform { | |
82 | closure_t cl; | |
83 | struct transform_if ops; | |
84 | struct transform_params p; | |
85 | }; | |
86 | ||
87 | struct transform_inst { | |
88 | struct transform_inst_if ops; | |
89 | struct transform_params p; | |
b02b720a IJ |
90 | /* remaining valid iff keyed */ |
91 | unsigned direction:1; | |
35d30aa3 | 92 | SEQNUM_KEYED_FIELDS; |
b02b720a IJ |
93 | struct keyInstance key; |
94 | uint8_t info_b[BLOCK_SIZE], info_p[BLOCK_SIZE]; | |
95 | }; | |
96 | ||
97 | static void block_encrypt(struct transform_inst *transform_inst, | |
98 | uint8_t dst[BLOCK_SIZE], | |
99 | const uint8_t src[BLOCK_SIZE]) | |
100 | { | |
101 | serpent_encrypt(&transform_inst->key, src, dst); | |
102 | } | |
103 | ||
104 | #define INFO struct transform_inst *transform_inst | |
105 | #define I transform_inst | |
106 | #define EAX_ENTRYPOINT_DECL static | |
107 | #define BLOCK_ENCRYPT(dst,src) block_encrypt(transform_inst,dst,src) | |
108 | #define INFO_B (transform_inst->info_b) | |
109 | #define INFO_P (transform_inst->info_p) | |
110 | ||
111 | #include "eax.c" | |
112 | ||
113 | #if 0 | |
114 | ||
115 | #define TEAX_DEBUG(ary,sz) teax_debug(__func__,__LINE__,#ary,#sz,ary,sz) | |
116 | static void teax_debug(const char *func, int line, | |
117 | const char *aryp, const char *szp, | |
118 | const void *ary, size_t sz) | |
119 | { | |
120 | fprintf(stderr,"TEAX %s:%-3d %10s %15s : ", func,line,aryp,szp); | |
121 | hexdebug(stderr,ary,sz); | |
122 | fprintf(stderr,"\n"); | |
123 | } | |
124 | ||
125 | #else | |
126 | ||
127 | #define TEAX_DEBUG(ary,sz) /* empty */ | |
128 | ||
129 | #endif | |
130 | ||
131 | static bool_t transform_setkey(void *sst, uint8_t *key, int32_t keylen, | |
132 | bool_t direction) | |
133 | { | |
134 | struct transform_inst *ti=sst; | |
135 | struct sha512_ctx hash_ctx; | |
136 | uint8_t hash_out[64]; | |
137 | ||
138 | TEAX_DEBUG(key,keylen); | |
139 | ||
140 | sha512_init_ctx(&hash_ctx); | |
141 | sha512_process_bytes(key, keylen, &hash_ctx); | |
142 | sha512_finish_ctx(&hash_ctx, hash_out); | |
143 | ||
144 | TEAX_DEBUG(hash_out,32); | |
145 | TEAX_DEBUG(hash_out+32,8); | |
146 | ||
147 | ti->direction=direction; | |
b02b720a IJ |
148 | serpent_makekey(&ti->key, 32*8, hash_out); |
149 | eax_setup(ti); | |
35d30aa3 IJ |
150 | SEQNUM_KEYED_INIT(get_uint32(hash_out+32+!direction*4), |
151 | get_uint32(hash_out+32+direction*4)); | |
b02b720a IJ |
152 | |
153 | return True; | |
154 | } | |
155 | ||
156 | TRANSFORM_VALID; | |
157 | ||
158 | TRANSFORM_DESTROY; | |
159 | ||
160 | static void transform_delkey(void *sst) | |
161 | { | |
162 | struct transform_inst *ti=sst; | |
163 | ||
164 | FILLZERO(ti->key); | |
165 | FILLZERO(ti->info_b); | |
166 | FILLZERO(ti->info_p); | |
167 | ti->keyed=False; | |
168 | } | |
169 | ||
170 | static uint32_t transform_forward(void *sst, struct buffer_if *buf, | |
171 | const char **errmsg) | |
172 | { | |
173 | struct transform_inst *ti=sst; | |
174 | ||
175 | KEYED_CHECK; | |
176 | ||
177 | size_t padlen = ti->p.padding_mask - buf->size; | |
178 | padlen &= ti->p.padding_mask; | |
179 | padlen++; | |
180 | ||
181 | uint8_t *pad = buf_append(buf,padlen); | |
182 | memset(pad, 0, padlen-1); | |
183 | pad[padlen-1] = padlen; | |
184 | ||
185 | uint8_t nonce[SEQLEN+1]; | |
186 | put_uint32(nonce,ti->sendseq); | |
187 | nonce[SEQLEN] = ti->direction; | |
188 | ||
189 | TEAX_DEBUG(nonce,sizeof(nonce)); | |
190 | TEAX_DEBUG(buf->start,buf->size); | |
191 | ||
192 | assert(buf_append(buf,ti->p.tag_length)); | |
193 | eax_encrypt(ti, nonce,sizeof(nonce), 0,0, | |
194 | buf->start,buf->size-ti->p.tag_length, | |
195 | ti->p.tag_length, buf->start); | |
196 | ||
197 | TEAX_DEBUG(buf->start,buf->size); | |
198 | ||
4f28e77e | 199 | BUF_ADD_BYTES(append,buf,nonce,SEQLEN); |
b02b720a IJ |
200 | |
201 | TEAX_DEBUG(nonce,SEQLEN); | |
202 | ||
203 | ti->sendseq++; | |
204 | ||
205 | return 0; | |
206 | } | |
207 | ||
208 | static uint32_t transform_reverse(void *sst, struct buffer_if *buf, | |
209 | const char **errmsg) | |
210 | { | |
211 | struct transform_inst *ti=sst; | |
212 | ||
213 | KEYED_CHECK; | |
214 | ||
215 | TEAX_DEBUG(buf->start,buf->size); | |
216 | ||
217 | uint8_t nonce[SEQLEN+1]; | |
218 | const uint8_t *seqp = buf_unappend(buf,SEQLEN); | |
219 | if (!seqp) goto too_short; | |
220 | ||
221 | TEAX_DEBUG(seqp,SEQLEN); | |
222 | ||
223 | uint32_t seqnum = get_uint32(seqp); | |
224 | ||
225 | memcpy(nonce,seqp,SEQLEN); | |
226 | nonce[4] = !ti->direction; | |
227 | ||
228 | TEAX_DEBUG(nonce,sizeof(nonce)); | |
229 | TEAX_DEBUG(buf->start,buf->size); | |
230 | ||
231 | bool_t ok = eax_decrypt(ti, nonce,sizeof(nonce), 0,0, buf->start,buf->size, | |
232 | ti->p.tag_length, buf->start); | |
233 | if (!ok) { | |
234 | TEAX_DEBUG(0,0); | |
235 | *errmsg="EAX decryption failed"; | |
236 | return 1; | |
237 | } | |
238 | assert(buf->size >= (int)ti->p.tag_length); | |
239 | buf->size -= ti->p.tag_length; | |
240 | ||
241 | TEAX_DEBUG(buf->start,buf->size); | |
242 | ||
243 | const uint8_t *padp = buf_unappend(buf,1); | |
244 | if (!padp) goto too_short; | |
245 | ||
246 | TEAX_DEBUG(padp,1); | |
247 | ||
248 | size_t padlen = *padp; | |
249 | if (!buf_unappend(buf,padlen-1)) goto too_short; | |
250 | ||
35d30aa3 | 251 | SEQNUM_CHECK(seqnum, &ti->p); |
b02b720a IJ |
252 | |
253 | TEAX_DEBUG(buf->start,buf->size); | |
254 | ||
255 | return 0; | |
256 | ||
257 | too_short: | |
258 | *errmsg="ciphertext or plaintext too short"; | |
259 | return 1; | |
260 | } | |
261 | ||
262 | static struct transform_inst_if *transform_create(void *sst) | |
263 | { | |
264 | struct transform *st=sst; | |
265 | ||
266 | TRANSFORM_CREATE_CORE; | |
267 | ||
268 | ti->p=st->p; | |
269 | ||
270 | return &ti->ops; | |
271 | } | |
272 | ||
273 | static list_t *transform_apply(closure_t *self, struct cloc loc, | |
274 | dict_t *context, list_t *args) | |
275 | { | |
276 | struct transform *st; | |
277 | item_t *item; | |
278 | dict_t *dict; | |
279 | ||
b7886fd4 | 280 | NEW(st); |
b02b720a IJ |
281 | st->cl.description="eax-serpent"; |
282 | st->cl.type=CL_TRANSFORM; | |
283 | st->cl.apply=NULL; | |
284 | st->cl.interface=&st->ops; | |
285 | st->ops.st=st; | |
286 | ||
287 | /* First parameter must be a dict */ | |
288 | item=list_elem(args,0); | |
289 | if (!item || item->type!=t_dict) | |
290 | cfgfatal(loc,"eax-serpent","parameter must be a dictionary\n"); | |
291 | dict=item->data.dict; | |
292 | ||
5b5f297f IJ |
293 | SET_CAPAB_TRANSFORMNUM(CAPAB_TRANSFORMNUM_EAXSERPENT); |
294 | ||
35d30aa3 | 295 | SEQNUM_PARAMS_INIT(dict,&st->p,"eax-serpent",loc); |
b02b720a IJ |
296 | |
297 | st->p.tag_length=dict_read_number(dict, "tag-length-bytes", | |
298 | False, "eax-serpent", loc, 128/8); | |
299 | if (st->p.tag_length<1 || st->p.tag_length>BLOCK_SIZE) | |
300 | cfgfatal(loc,"eax-serpent","tag-length-bytes out of range 0..%d\n", | |
301 | BLOCK_SIZE); | |
302 | ||
303 | uint32_t padding_round=dict_read_number(dict, "padding-rounding", | |
304 | False, "eax-serpent", loc, 16); | |
305 | if (padding_round & (padding_round-1)) | |
306 | cfgfatal(loc,"eax-serpent","padding-round not a power of two\n"); | |
307 | if (padding_round > 255) | |
308 | cfgfatal(loc,"eax-serpent","padding-round must be 1..128\n"); | |
309 | if (padding_round == 0) | |
310 | padding_round = 1; | |
311 | st->p.padding_mask = padding_round-1; | |
312 | ||
3abd18e8 | 313 | update_max_start_pad(&transform_max_start_pad, 0); |
b02b720a IJ |
314 | |
315 | st->ops.keylen=0; | |
316 | st->ops.create=transform_create; | |
317 | ||
318 | return new_closure(&st->cl); | |
319 | } | |
320 | ||
321 | void transform_eax_module(dict_t *dict) | |
322 | { | |
323 | add_closure(dict,"eax-serpent",transform_apply); | |
324 | } |