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