Commit | Line | Data |
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2fe58dfd SE |
1 | /* Transform module - bulk data transformation */ |
2 | ||
3 | /* For now it's hard-coded to do sequence | |
4 | number/pkcs5/serpent-cbcmac/serpent with a 256 bit key for each | |
5 | instance of serpent. We also require key material for the IVs for | |
6 | cbcmac and cbc. Hack: we're not using full 128-bit IVs, we're just | |
7 | using 32 bits and encrypting to get the full IV to save space in | |
8 | the packets sent over the wire. */ | |
9 | ||
10 | #include <stdio.h> | |
11 | #include "secnet.h" | |
12 | #include "util.h" | |
13 | #include "serpent.h" | |
14 | ||
15 | /* Required key length in bytes */ | |
16 | #define REQUIRED_KEYLEN ((512+64+32)/8) | |
17 | ||
18 | struct transform { | |
19 | closure_t cl; | |
20 | uint32_t line; | |
21 | struct transform_if ops; | |
22 | uint32_t max_seq_skew; | |
23 | }; | |
24 | ||
25 | struct transform_inst { | |
26 | struct transform_inst_if ops; | |
27 | struct keyInstance cryptkey; | |
28 | struct keyInstance mackey; | |
29 | uint32_t cryptiv; | |
30 | uint32_t maciv; | |
31 | uint32_t sendseq; | |
32 | uint32_t lastrecvseq; | |
33 | uint32_t max_skew; | |
34 | bool_t keyed; | |
35 | }; | |
36 | ||
37 | #define PKCS5_MASK 15 | |
38 | ||
39 | static bool_t transform_setkey(void *sst, uint8_t *key, uint32_t keylen) | |
40 | { | |
41 | struct transform_inst *ti=sst; | |
42 | ||
43 | if (keylen<REQUIRED_KEYLEN) { | |
44 | Message(M_ERROR,"transform_create: insufficient key material supplied " | |
45 | "(need %d bytes, got %d)\n",REQUIRED_KEYLEN,keylen); | |
46 | return False; | |
47 | } | |
48 | ||
49 | #if 0 | |
50 | { | |
51 | int i; | |
52 | printf("Setting key to: "); | |
53 | for (i=0; i<keylen; i++) | |
54 | printf("%02x",key[i]); | |
55 | printf("\n"); | |
56 | } | |
57 | #endif /* 0 */ | |
58 | ||
59 | serpent_makekey(&ti->cryptkey,256,key); | |
60 | serpent_makekey(&ti->mackey,256,key+32); | |
61 | ti->cryptiv=*(uint32_t *)(key+64); | |
62 | ti->maciv=*(uint32_t *)(key+68); | |
63 | ti->sendseq=*(uint32_t *)(key+72); | |
64 | ti->lastrecvseq=ti->sendseq; | |
65 | ti->keyed=True; | |
66 | ||
67 | return True; | |
68 | } | |
69 | ||
70 | static void transform_delkey(void *sst) | |
71 | { | |
72 | struct transform_inst *ti=sst; | |
73 | ||
74 | memset(&ti->cryptkey,0,sizeof(ti->cryptkey)); | |
75 | memset(&ti->mackey,0,sizeof(ti->mackey)); | |
76 | ti->keyed=False; | |
77 | } | |
78 | ||
79 | static uint32_t transform_forward(void *sst, struct buffer_if *buf, | |
80 | char **errmsg) | |
81 | { | |
82 | struct transform_inst *ti=sst; | |
83 | uint8_t *padp; | |
84 | int padlen; | |
85 | uint32_t iv[4]; | |
86 | uint32_t macplain[4]; | |
87 | uint32_t macacc[4]; | |
88 | uint32_t *n, *p; | |
89 | ||
90 | if (!ti->keyed) { | |
91 | *errmsg="transform unkeyed"; | |
92 | return 1; | |
93 | } | |
94 | ||
95 | /* Sequence number */ | |
96 | *(uint32_t *)buf_prepend(buf,4)=htonl(ti->sendseq); | |
97 | ti->sendseq++; | |
98 | ||
99 | /* PKCS5, stolen from IWJ */ | |
100 | /* eg with blocksize=4 mask=3 mask+2=5 */ | |
101 | /* msgsize 20 21 22 23 24 */ | |
102 | padlen= PKCS5_MASK-buf->size; /* -17 -18 -19 -16 -17 */ | |
103 | padlen &= PKCS5_MASK; /* 3 2 1 0 3 */ | |
104 | padlen++; /* 4 3 2 1 4 */ | |
105 | ||
106 | padp=buf_append(buf,padlen); | |
107 | memset(padp,padlen,padlen); | |
108 | ||
109 | /* Serpent-CBCMAC. We expand the IV from 32-bit to 128-bit using | |
110 | one encryption. Then we do the MAC and append the result. We don't | |
111 | bother sending the IV - it's the same each time. (If we wanted to send | |
112 | it we've have to add 16 bytes to each message, not 4, so that the | |
113 | message stays a multiple of 16 bytes long.) */ | |
114 | memset(iv,0,16); | |
115 | iv[0]=ti->maciv; | |
116 | serpent_encrypt(&ti->mackey,iv,macacc); | |
117 | ||
118 | /* CBCMAC: encrypt in CBC mode. The MAC is the last encrypted | |
119 | block encrypted once again. */ | |
120 | for (n=(uint32_t *)buf->start; n<(uint32_t *)(buf->start+buf->size); n+=4) | |
121 | { | |
122 | macplain[0]=macacc[0]^n[0]; | |
123 | macplain[1]=macacc[1]^n[1]; | |
124 | macplain[2]=macacc[2]^n[2]; | |
125 | macplain[3]=macacc[3]^n[3]; | |
126 | serpent_encrypt(&ti->mackey,macplain,macacc); | |
127 | } | |
128 | serpent_encrypt(&ti->mackey,macacc,macacc); | |
129 | memcpy(buf_append(buf,16),macacc,16); | |
130 | ||
131 | /* Serpent-CBC. We expand the ID as for CBCMAC, do the encryption, | |
132 | and prepend the IV before increasing it. */ | |
133 | memset(iv,0,16); | |
134 | iv[0]=ti->cryptiv; | |
135 | serpent_encrypt(&ti->cryptkey,iv,iv); | |
136 | ||
137 | /* CBC: each block is XORed with the previous encrypted block (or the IV) | |
138 | before being encrypted. */ | |
139 | p=iv; | |
140 | for (n=(uint32_t *)buf->start; n<(uint32_t *)(buf->start+buf->size); n+=4) | |
141 | { | |
142 | n[0]=p[0]^n[0]; | |
143 | n[1]=p[1]^n[1]; | |
144 | n[2]=p[2]^n[2]; | |
145 | n[3]=p[3]^n[3]; | |
146 | serpent_encrypt(&ti->cryptkey,n,n); | |
147 | p=n; | |
148 | } | |
149 | ||
150 | *(uint32_t *)buf_prepend(buf,4)=ti->cryptiv; | |
151 | ti->cryptiv++; | |
152 | ||
153 | return 0; | |
154 | } | |
155 | ||
156 | static uint32_t transform_reverse(void *sst, struct buffer_if *buf, | |
157 | char **errmsg) | |
158 | { | |
159 | struct transform_inst *ti=sst; | |
160 | uint8_t *padp; | |
161 | unsigned padlen; | |
162 | int i; | |
163 | uint32_t seqnum, skew; | |
164 | uint32_t iv[4]; | |
165 | uint32_t pct[4]; | |
166 | uint32_t macplain[4]; | |
167 | uint32_t macacc[4]; | |
168 | uint32_t *n; | |
169 | uint32_t *macexpected; | |
170 | ||
171 | if (!ti->keyed) { | |
172 | *errmsg="transform unkeyed"; | |
173 | return 1; | |
174 | } | |
175 | ||
176 | /* CBC */ | |
177 | memset(iv,0,16); | |
178 | iv[0]=*(uint32_t *)buf_unprepend(buf,4); | |
179 | serpent_encrypt(&ti->cryptkey,iv,iv); | |
180 | /* XXX assert bufsize is multiple of blocksize */ | |
181 | for (n=(uint32_t *)buf->start; n<(uint32_t *)(buf->start+buf->size); n+=4) | |
182 | { | |
183 | pct[0]=n[0]; pct[1]=n[1]; pct[2]=n[2]; pct[3]=n[3]; | |
184 | serpent_decrypt(&ti->cryptkey,n,n); | |
185 | n[0]=iv[0]^n[0]; | |
186 | n[1]=iv[1]^n[1]; | |
187 | n[2]=iv[2]^n[2]; | |
188 | n[3]=iv[3]^n[3]; | |
189 | iv[0]=pct[0]; iv[1]=pct[1]; iv[2]=pct[2]; iv[3]=pct[3]; | |
190 | } | |
191 | ||
192 | /* CBCMAC */ | |
193 | macexpected=buf_unappend(buf,16); | |
194 | memset(iv,0,16); | |
195 | iv[0]=ti->maciv; | |
196 | serpent_encrypt(&ti->mackey,iv,macacc); | |
197 | ||
198 | /* CBCMAC: encrypt in CBC mode. The MAC is the last encrypted | |
199 | block encrypted once again. */ | |
200 | for (n=(uint32_t *)buf->start; n<(uint32_t *)(buf->start+buf->size); n+=4) | |
201 | { | |
202 | macplain[0]=macacc[0]^n[0]; | |
203 | macplain[1]=macacc[1]^n[1]; | |
204 | macplain[2]=macacc[2]^n[2]; | |
205 | macplain[3]=macacc[3]^n[3]; | |
206 | serpent_encrypt(&ti->mackey,macplain,macacc); | |
207 | } | |
208 | serpent_encrypt(&ti->mackey,macacc,macacc); | |
209 | if (memcmp(macexpected,macacc,16)!=0) { | |
210 | *errmsg="invalid MAC"; | |
211 | return 1; | |
212 | } | |
213 | ||
214 | /* PKCS5, stolen from IWJ */ | |
215 | ||
216 | padp=buf_unappend(buf,1); | |
217 | padlen=*padp; | |
218 | if (!padlen || (padlen > PKCS5_MASK+1)) { | |
219 | *errmsg="pkcs5: invalid length"; | |
220 | return 1; | |
221 | } | |
222 | ||
223 | padp=buf_unappend(buf,padlen-1); | |
224 | for (i=0; i<padlen-1; i++) { | |
225 | if (*++padp != padlen) { | |
226 | *errmsg="pkcs5: corrupted padding"; | |
227 | return 1; | |
228 | } | |
229 | } | |
230 | ||
231 | /* Sequence number must be within max_skew of lastrecvseq; lastrecvseq | |
232 | is only allowed to increase. */ | |
233 | seqnum=ntohl(*(uint32_t *)buf_unprepend(buf,4)); | |
234 | skew=seqnum-ti->lastrecvseq; | |
235 | if (skew<10) { | |
236 | /* Ok */ | |
237 | ti->lastrecvseq=seqnum; | |
238 | } else if ((0-skew)<10) { | |
239 | /* Ok */ | |
240 | } else { | |
241 | /* Too much skew */ | |
242 | *errmsg="seqnum: too much skew"; | |
243 | return 1; | |
244 | } | |
245 | ||
246 | return 0; | |
247 | } | |
248 | ||
249 | static void transform_destroy(void *sst) | |
250 | { | |
251 | struct transform_inst *st=sst; | |
252 | ||
253 | memset(st,0,sizeof(*st)); /* Destroy key material */ | |
254 | free(st); | |
255 | } | |
256 | ||
257 | static struct transform_inst_if *transform_create(void *sst) | |
258 | { | |
259 | struct transform_inst *ti; | |
260 | struct transform *st=sst; | |
261 | ||
262 | ti=safe_malloc(sizeof(*ti),"transform_create"); | |
263 | /* mlock XXX */ | |
264 | ||
265 | ti->ops.st=ti; | |
266 | ti->ops.setkey=transform_setkey; | |
267 | ti->ops.delkey=transform_delkey; | |
268 | ti->ops.forwards=transform_forward; | |
269 | ti->ops.reverse=transform_reverse; | |
270 | ti->ops.destroy=transform_destroy; | |
271 | ti->max_skew=st->max_seq_skew; | |
272 | ti->keyed=False; | |
273 | ||
274 | return &ti->ops; | |
275 | } | |
276 | ||
277 | static list_t *transform_apply(closure_t *self, struct cloc loc, | |
278 | dict_t *context, list_t *args) | |
279 | { | |
280 | struct transform *st; | |
281 | item_t *item; | |
282 | dict_t *dict; | |
283 | ||
284 | st=safe_malloc(sizeof(*st),"serpent"); | |
285 | st->cl.description="serpent-cbc256"; | |
286 | st->cl.type=CL_TRANSFORM; | |
287 | st->cl.apply=NULL; | |
288 | st->cl.interface=&st->ops; | |
289 | st->ops.st=st; | |
290 | st->ops.max_start_pad=28; /* 4byte seqnum, 16byte pad, 4byte MACIV, | |
291 | 4byte IV */ | |
292 | st->ops.max_end_pad=16; /* 16byte CBCMAC */ | |
293 | ||
294 | /* We need 256*2 bits for serpent keys, 32 bits for CBC-IV and 32 bits | |
295 | for CBCMAC-IV, and 32 bits for init sequence number */ | |
296 | st->ops.keylen=REQUIRED_KEYLEN; | |
297 | st->ops.create=transform_create; | |
298 | ||
299 | /* First parameter must be a dict */ | |
300 | item=list_elem(args,0); | |
301 | if (!item || item->type!=t_dict) | |
302 | cfgfatal(loc,"userv-ipif","parameter must be a dictionary\n"); | |
303 | ||
304 | dict=item->data.dict; | |
305 | st->max_seq_skew=dict_read_number(dict, "max-sequence-skew", | |
306 | False, "serpent-cbc256", loc, 10); | |
307 | ||
308 | return new_closure(&st->cl); | |
309 | } | |
310 | ||
311 | init_module transform_module; | |
312 | void transform_module(dict_t *dict) | |
313 | { | |
314 | struct keyInstance k; | |
315 | uint8_t data[32]; | |
316 | uint32_t plaintext[4]; | |
317 | uint32_t ciphertext[4]; | |
318 | ||
319 | /* Serpent self-test */ | |
320 | memset(data,0,32); | |
321 | serpent_makekey(&k,256,data); | |
322 | plaintext[0]=0x00000000; | |
323 | plaintext[1]=0x00000001; | |
324 | plaintext[2]=0x00000002; | |
325 | plaintext[3]=0x00000003; | |
326 | serpent_encrypt(&k,plaintext,ciphertext); | |
327 | if (ciphertext[3]!=0x7ca73bb0 || | |
328 | ciphertext[2]!=0x83C31E69 || | |
329 | ciphertext[1]!=0xec52bd82 || | |
330 | ciphertext[0]!=0x27a46120) { | |
331 | fatal("transform_module: serpent failed self-test (encrypt)\n"); | |
332 | } | |
333 | serpent_decrypt(&k,ciphertext,plaintext); | |
334 | if (plaintext[0]!=0 || | |
335 | plaintext[1]!=1 || | |
336 | plaintext[2]!=2 || | |
337 | plaintext[3]!=3) { | |
338 | fatal("transform_module: serpent failed self-test (decrypt)\n"); | |
339 | } | |
340 | ||
341 | add_closure(dict,"serpent256-cbc",transform_apply); | |
342 | } |