| 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 | } |