| 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 <string.h> |
| 12 | #include "secnet.h" |
| 13 | #include "util.h" |
| 14 | #include "serpent.h" |
| 15 | #include "unaligned.h" |
| 16 | |
| 17 | /* Required key length in bytes */ |
| 18 | #define REQUIRED_KEYLEN ((512+64+32)/8) |
| 19 | |
| 20 | struct transform { |
| 21 | closure_t cl; |
| 22 | uint32_t line; |
| 23 | struct transform_if ops; |
| 24 | uint32_t max_seq_skew; |
| 25 | }; |
| 26 | |
| 27 | struct transform_inst { |
| 28 | struct transform_inst_if ops; |
| 29 | struct keyInstance cryptkey; |
| 30 | struct keyInstance mackey; |
| 31 | uint32_t cryptiv; |
| 32 | uint32_t maciv; |
| 33 | uint32_t sendseq; |
| 34 | uint32_t lastrecvseq; |
| 35 | uint32_t max_skew; |
| 36 | bool_t keyed; |
| 37 | }; |
| 38 | |
| 39 | #define PKCS5_MASK 15 |
| 40 | |
| 41 | static bool_t transform_setkey(void *sst, uint8_t *key, uint32_t keylen) |
| 42 | { |
| 43 | struct transform_inst *ti=sst; |
| 44 | |
| 45 | if (keylen<REQUIRED_KEYLEN) { |
| 46 | Message(M_ERR,"transform_create: insufficient key material supplied " |
| 47 | "(need %d bytes, got %d)\n",REQUIRED_KEYLEN,keylen); |
| 48 | return False; |
| 49 | } |
| 50 | |
| 51 | #if 0 |
| 52 | { |
| 53 | int i; |
| 54 | printf("Setting key to: "); |
| 55 | for (i=0; i<keylen; i++) |
| 56 | printf("%02x",key[i]); |
| 57 | printf("\n"); |
| 58 | } |
| 59 | #endif /* 0 */ |
| 60 | |
| 61 | serpent_makekey(&ti->cryptkey,256,key); |
| 62 | serpent_makekey(&ti->mackey,256,key+32); |
| 63 | ti->cryptiv=GET_32BIT_MSB_FIRST(key+64); |
| 64 | ti->maciv=GET_32BIT_MSB_FIRST(key+68); |
| 65 | ti->sendseq=GET_32BIT_MSB_FIRST(key+72); |
| 66 | ti->lastrecvseq=ti->sendseq; |
| 67 | ti->keyed=True; |
| 68 | |
| 69 | return True; |
| 70 | } |
| 71 | |
| 72 | static void transform_delkey(void *sst) |
| 73 | { |
| 74 | struct transform_inst *ti=sst; |
| 75 | |
| 76 | memset(&ti->cryptkey,0,sizeof(ti->cryptkey)); |
| 77 | memset(&ti->mackey,0,sizeof(ti->mackey)); |
| 78 | ti->keyed=False; |
| 79 | } |
| 80 | |
| 81 | static uint32_t transform_forward(void *sst, struct buffer_if *buf, |
| 82 | const char **errmsg) |
| 83 | { |
| 84 | struct transform_inst *ti=sst; |
| 85 | uint8_t *padp; |
| 86 | int padlen; |
| 87 | uint8_t iv[16]; |
| 88 | uint8_t macplain[16]; |
| 89 | uint8_t macacc[16]; |
| 90 | uint8_t *p, *n; |
| 91 | int i; |
| 92 | |
| 93 | if (!ti->keyed) { |
| 94 | *errmsg="transform unkeyed"; |
| 95 | return 1; |
| 96 | } |
| 97 | |
| 98 | /* Sequence number */ |
| 99 | buf_prepend_uint32(buf,ti->sendseq); |
| 100 | ti->sendseq++; |
| 101 | |
| 102 | /* PKCS5, stolen from IWJ */ |
| 103 | /* eg with blocksize=4 mask=3 mask+2=5 */ |
| 104 | /* msgsize 20 21 22 23 24 */ |
| 105 | padlen= PKCS5_MASK-buf->size; /* -17 -18 -19 -16 -17 */ |
| 106 | padlen &= PKCS5_MASK; /* 3 2 1 0 3 */ |
| 107 | padlen++; /* 4 3 2 1 4 */ |
| 108 | |
| 109 | padp=buf_append(buf,padlen); |
| 110 | memset(padp,padlen,padlen); |
| 111 | |
| 112 | /* Serpent-CBCMAC. We expand the IV from 32-bit to 128-bit using |
| 113 | one encryption. Then we do the MAC and append the result. We don't |
| 114 | bother sending the IV - it's the same each time. (If we wanted to send |
| 115 | it we've have to add 16 bytes to each message, not 4, so that the |
| 116 | message stays a multiple of 16 bytes long.) */ |
| 117 | memset(iv,0,16); |
| 118 | PUT_32BIT_MSB_FIRST(iv, ti->maciv); |
| 119 | serpent_encrypt(&ti->mackey,iv,macacc); |
| 120 | |
| 121 | /* CBCMAC: encrypt in CBC mode. The MAC is the last encrypted |
| 122 | block encrypted once again. */ |
| 123 | for (n=buf->start; n<buf->start+buf->size; n+=16) |
| 124 | { |
| 125 | for (i = 0; i < 16; i++) |
| 126 | macplain[i] = macacc[i] ^ n[i]; |
| 127 | serpent_encrypt(&ti->mackey,macplain,macacc); |
| 128 | } |
| 129 | serpent_encrypt(&ti->mackey,macacc,macacc); |
| 130 | memcpy(buf_append(buf,16),macacc,16); |
| 131 | |
| 132 | /* Serpent-CBC. We expand the ID as for CBCMAC, do the encryption, |
| 133 | and prepend the IV before increasing it. */ |
| 134 | memset(iv,0,16); |
| 135 | PUT_32BIT_MSB_FIRST(iv, ti->cryptiv); |
| 136 | serpent_encrypt(&ti->cryptkey,iv,iv); |
| 137 | |
| 138 | /* CBC: each block is XORed with the previous encrypted block (or the IV) |
| 139 | before being encrypted. */ |
| 140 | p=iv; |
| 141 | |
| 142 | for (n=buf->start; n<buf->start+buf->size; n+=16) |
| 143 | { |
| 144 | for (i = 0; i < 16; i++) |
| 145 | n[i] ^= p[i]; |
| 146 | serpent_encrypt(&ti->cryptkey,n,n); |
| 147 | p=n; |
| 148 | } |
| 149 | |
| 150 | buf_prepend_uint32(buf,ti->cryptiv); |
| 151 | ti->cryptiv++; |
| 152 | return 0; |
| 153 | } |
| 154 | |
| 155 | static uint32_t transform_reverse(void *sst, struct buffer_if *buf, |
| 156 | const char **errmsg) |
| 157 | { |
| 158 | struct transform_inst *ti=sst; |
| 159 | uint8_t *padp; |
| 160 | unsigned padlen; |
| 161 | int i; |
| 162 | uint32_t seqnum, skew; |
| 163 | uint8_t iv[16]; |
| 164 | uint8_t pct[16]; |
| 165 | uint8_t macplain[16]; |
| 166 | uint8_t macacc[16]; |
| 167 | uint8_t *n; |
| 168 | uint8_t *macexpected; |
| 169 | |
| 170 | if (!ti->keyed) { |
| 171 | *errmsg="transform unkeyed"; |
| 172 | return 1; |
| 173 | } |
| 174 | |
| 175 | |
| 176 | /* CBC */ |
| 177 | memset(iv,0,16); |
| 178 | { |
| 179 | uint32_t ivword = buf_unprepend_uint32(buf); |
| 180 | PUT_32BIT_MSB_FIRST(iv, ivword); |
| 181 | } |
| 182 | /* Assert bufsize is multiple of blocksize */ |
| 183 | if (buf->size&0xf) { |
| 184 | *errmsg="msg not multiple of cipher blocksize"; |
| 185 | } |
| 186 | serpent_encrypt(&ti->cryptkey,iv,iv); |
| 187 | for (n=buf->start; n<buf->start+buf->size; n+=16) |
| 188 | { |
| 189 | for (i = 0; i < 16; i++) |
| 190 | pct[i] = n[i]; |
| 191 | serpent_decrypt(&ti->cryptkey,n,n); |
| 192 | for (i = 0; i < 16; i++) |
| 193 | n[i] ^= iv[i]; |
| 194 | memcpy(iv, pct, 16); |
| 195 | } |
| 196 | |
| 197 | /* CBCMAC */ |
| 198 | macexpected=buf_unappend(buf,16); |
| 199 | memset(iv,0,16); |
| 200 | PUT_32BIT_MSB_FIRST(iv, ti->maciv); |
| 201 | serpent_encrypt(&ti->mackey,iv,macacc); |
| 202 | |
| 203 | /* CBCMAC: encrypt in CBC mode. The MAC is the last encrypted |
| 204 | block encrypted once again. */ |
| 205 | for (n=buf->start; n<buf->start+buf->size; n+=16) |
| 206 | { |
| 207 | for (i = 0; i < 16; i++) |
| 208 | macplain[i] = macacc[i] ^ n[i]; |
| 209 | serpent_encrypt(&ti->mackey,macplain,macacc); |
| 210 | } |
| 211 | serpent_encrypt(&ti->mackey,macacc,macacc); |
| 212 | if (memcmp(macexpected,macacc,16)!=0) { |
| 213 | *errmsg="invalid MAC"; |
| 214 | return 1; |
| 215 | } |
| 216 | |
| 217 | /* PKCS5, stolen from IWJ */ |
| 218 | |
| 219 | padp=buf_unappend(buf,1); |
| 220 | padlen=*padp; |
| 221 | if (!padlen || (padlen > PKCS5_MASK+1)) { |
| 222 | *errmsg="pkcs5: invalid length"; |
| 223 | return 1; |
| 224 | } |
| 225 | |
| 226 | padp=buf_unappend(buf,padlen-1); |
| 227 | for (i=0; i<padlen-1; i++) { |
| 228 | if (*++padp != padlen) { |
| 229 | *errmsg="pkcs5: corrupted padding"; |
| 230 | return 1; |
| 231 | } |
| 232 | } |
| 233 | |
| 234 | /* Sequence number must be within max_skew of lastrecvseq; lastrecvseq |
| 235 | is only allowed to increase. */ |
| 236 | seqnum=buf_unprepend_uint32(buf); |
| 237 | skew=seqnum-ti->lastrecvseq; |
| 238 | if (skew<0x8fffffff) { |
| 239 | /* Ok */ |
| 240 | ti->lastrecvseq=seqnum; |
| 241 | } else if ((0-skew)<ti->max_skew) { |
| 242 | /* Ok */ |
| 243 | } else { |
| 244 | /* Too much skew */ |
| 245 | *errmsg="seqnum: too much skew"; |
| 246 | return 1; |
| 247 | } |
| 248 | |
| 249 | return 0; |
| 250 | } |
| 251 | |
| 252 | static void transform_destroy(void *sst) |
| 253 | { |
| 254 | struct transform_inst *st=sst; |
| 255 | |
| 256 | memset(st,0,sizeof(*st)); /* Destroy key material */ |
| 257 | free(st); |
| 258 | } |
| 259 | |
| 260 | static struct transform_inst_if *transform_create(void *sst) |
| 261 | { |
| 262 | struct transform_inst *ti; |
| 263 | struct transform *st=sst; |
| 264 | |
| 265 | ti=safe_malloc(sizeof(*ti),"transform_create"); |
| 266 | /* mlock XXX */ |
| 267 | |
| 268 | ti->ops.st=ti; |
| 269 | ti->ops.setkey=transform_setkey; |
| 270 | ti->ops.delkey=transform_delkey; |
| 271 | ti->ops.forwards=transform_forward; |
| 272 | ti->ops.reverse=transform_reverse; |
| 273 | ti->ops.destroy=transform_destroy; |
| 274 | ti->max_skew=st->max_seq_skew; |
| 275 | ti->keyed=False; |
| 276 | |
| 277 | return &ti->ops; |
| 278 | } |
| 279 | |
| 280 | static list_t *transform_apply(closure_t *self, struct cloc loc, |
| 281 | dict_t *context, list_t *args) |
| 282 | { |
| 283 | struct transform *st; |
| 284 | item_t *item; |
| 285 | dict_t *dict; |
| 286 | |
| 287 | st=safe_malloc(sizeof(*st),"serpent"); |
| 288 | st->cl.description="serpent-cbc256"; |
| 289 | st->cl.type=CL_TRANSFORM; |
| 290 | st->cl.apply=NULL; |
| 291 | st->cl.interface=&st->ops; |
| 292 | st->ops.st=st; |
| 293 | st->ops.max_start_pad=28; /* 4byte seqnum, 16byte pad, 4byte MACIV, |
| 294 | 4byte IV */ |
| 295 | st->ops.max_end_pad=16; /* 16byte CBCMAC */ |
| 296 | |
| 297 | /* We need 256*2 bits for serpent keys, 32 bits for CBC-IV and 32 bits |
| 298 | for CBCMAC-IV, and 32 bits for init sequence number */ |
| 299 | st->ops.keylen=REQUIRED_KEYLEN; |
| 300 | st->ops.create=transform_create; |
| 301 | |
| 302 | /* First parameter must be a dict */ |
| 303 | item=list_elem(args,0); |
| 304 | if (!item || item->type!=t_dict) |
| 305 | cfgfatal(loc,"userv-ipif","parameter must be a dictionary\n"); |
| 306 | |
| 307 | dict=item->data.dict; |
| 308 | st->max_seq_skew=dict_read_number(dict, "max-sequence-skew", |
| 309 | False, "serpent-cbc256", loc, 10); |
| 310 | |
| 311 | return new_closure(&st->cl); |
| 312 | } |
| 313 | |
| 314 | init_module transform_module; |
| 315 | void transform_module(dict_t *dict) |
| 316 | { |
| 317 | struct keyInstance k; |
| 318 | uint8_t data[32]; |
| 319 | uint8_t plaintext[16]; |
| 320 | uint8_t ciphertext[16]; |
| 321 | |
| 322 | /* |
| 323 | * Serpent self-test. |
| 324 | * |
| 325 | * This test pattern is taken directly from the Serpent test |
| 326 | * vectors, to ensure we have all endianness issues correct. -sgt |
| 327 | */ |
| 328 | |
| 329 | /* Serpent self-test */ |
| 330 | memcpy(data, |
| 331 | "\x00\x11\x22\x33\x44\x55\x66\x77\x88\x99\xaa\xbb\xcc\xdd\xee\xff" |
| 332 | "\xff\xee\xdd\xcc\xbb\xaa\x99\x88\x77\x66\x55\x44\x33\x22\x11\x00", |
| 333 | 32); |
| 334 | serpent_makekey(&k,256,data); |
| 335 | |
| 336 | memcpy(plaintext, |
| 337 | "\x01\x23\x45\x67\x89\xab\xcd\xef\xfe\xdc\xba\x98\x76\x54\x32\x10", |
| 338 | 16); |
| 339 | serpent_encrypt(&k,plaintext,ciphertext); |
| 340 | |
| 341 | if (memcmp(ciphertext, "\xca\x7f\xa1\x93\xe3\xeb\x9e\x99" |
| 342 | "\xbd\x87\xe3\xaf\x3c\x9a\xdf\x93", 16)) { |
| 343 | fatal("transform_module: serpent failed self-test (encrypt)"); |
| 344 | } |
| 345 | serpent_decrypt(&k,ciphertext,plaintext); |
| 346 | if (memcmp(plaintext, "\x01\x23\x45\x67\x89\xab\xcd\xef" |
| 347 | "\xfe\xdc\xba\x98\x76\x54\x32\x10", 16)) { |
| 348 | fatal("transform_module: serpent failed self-test (decrypt)"); |
| 349 | } |
| 350 | |
| 351 | add_closure(dict,"serpent256-cbc",transform_apply); |
| 352 | |
| 353 | #ifdef TEST_WHOLE_TRANSFORM |
| 354 | { |
| 355 | struct transform *tr; |
| 356 | void *ti; |
| 357 | struct buffer_if buf; |
| 358 | const char text[] = "This is a piece of test text."; |
| 359 | char keymaterial[76] = |
| 360 | "Seventy-six bytes i" |
| 361 | "n four rows of 19; " |
| 362 | "this looks almost l" |
| 363 | "ike a poem but not."; |
| 364 | const char *errmsg; |
| 365 | int i; |
| 366 | |
| 367 | tr = malloc(sizeof(struct transform)); |
| 368 | tr->max_seq_skew = 20; |
| 369 | ti = transform_create(tr); |
| 370 | |
| 371 | transform_setkey(ti, keymaterial, 76); |
| 372 | |
| 373 | buf.base = malloc(4096); |
| 374 | buffer_init(&buf, 2048); |
| 375 | memcpy(buf_append(&buf, sizeof(text)), text, sizeof(text)); |
| 376 | if (transform_forward(ti, &buf, &errmsg)) { |
| 377 | fatal("transform_forward test: %s", errmsg); |
| 378 | } |
| 379 | printf("transformed text is:\n"); |
| 380 | for (i = 0; i < buf.size; i++) |
| 381 | printf("%02x%c", buf.start[i], |
| 382 | (i%16==15 || i==buf.size-1 ? '\n' : ' ')); |
| 383 | if (transform_reverse(ti, &buf, &errmsg)) { |
| 384 | fatal("transform_reverse test: %s", errmsg); |
| 385 | } |
| 386 | printf("transform reversal worked OK\n"); |
| 387 | } |
| 388 | #endif |
| 389 | } |