curve.c

   1 /*
   2  * netsniff-ng - the packet sniffing beast
   3  * Copyright 2011 - 2013 Daniel Borkmann.
   4  * Subject to the GPL, version 2.
   5  */
   6
   7 #include <stdio.h>
   8 #include <stdlib.h>
   9 #include <stdint.h>
  10 #include <errno.h>
  11 #include <fcntl.h>
  12 #include <syslog.h>
  13 #include <limits.h>
  14 #include <string.h>
  15 #include <sys/types.h>
  16 #include <sys/time.h>
  17 #include <sys/stat.h>
  18
  19 #include "built_in.h"
  20 #include "xmalloc.h"
  21 #include "curve.h"
  22 #include "ioops.h"
  23 #include "rnd.h"
  24 #include "die.h"
  25 #include "str.h"
  26 #include "curvetun.h"
  27 #include "locking.h"
  28 #include "crypto.h"
  29
  30 #define NONCE_LENGTH    (sizeof(struct taia))
  31 #define NONCE_OFFSET    (crypto_box_noncebytes - NONCE_LENGTH)
  32
  33 void curve25519_selftest(void)
  34 {
  35         int i;
  36         unsigned char alicesk[32] = {
  37                 0x77, 0x07, 0x6d, 0x0a, 0x73, 0x18, 0xa5, 0x7d,
  38                 0x3c, 0x16, 0xc1, 0x72, 0x51, 0xb2, 0x66, 0x45,
  39                 0xdf, 0x4c, 0x2f, 0x87, 0xeb, 0xc0, 0x99, 0x2a,
  40                 0xb1, 0x77, 0xfb, 0xa5, 0x1d, 0xb9, 0x2c, 0x2a
  41         };
  42         unsigned char bobpk[32] = {
  43                 0xde, 0x9e, 0xdb, 0x7d, 0x7b, 0x7d, 0xc1, 0xb4,
  44                 0xd3, 0x5b, 0x61, 0xc2, 0xec, 0xe4, 0x35, 0x37,
  45                 0x3f, 0x83, 0x43, 0xc8, 0x5b, 0x78, 0x67, 0x4d,
  46                 0xad, 0xfc, 0x7e, 0x14, 0x6f, 0x88, 0x2b, 0x4f
  47         };
  48         unsigned char nonce[24] = {
  49                 0x69, 0x69, 0x6e, 0xe9, 0x55, 0xb6, 0x2b, 0x73,
  50                 0xcd, 0x62, 0xbd, 0xa8, 0x75, 0xfc, 0x73, 0xd6,
  51                 0x82, 0x19, 0xe0, 0x03, 0x6b, 0x7a, 0x0b, 0x37
  52         };
  53         unsigned char m[163] = {
  54                 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  55                 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  56                 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  57                 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  58                 0xbe, 0x07, 0x5f, 0xc5, 0x3c, 0x81, 0xf2, 0xd5,
  59                 0xcf, 0x14, 0x13, 0x16, 0xeb, 0xeb, 0x0c, 0x7b,
  60                 0x52, 0x28, 0xc5, 0x2a, 0x4c, 0x62, 0xcb, 0xd4,
  61                 0x4b, 0x66, 0x84, 0x9b, 0x64, 0x24, 0x4f, 0xfc,
  62                 0xe5, 0xec, 0xba, 0xaf, 0x33, 0xbd, 0x75, 0x1a,
  63                 0x1a, 0xc7, 0x28, 0xd4, 0x5e, 0x6c, 0x61, 0x29,
  64                 0x6c, 0xdc, 0x3c, 0x01, 0x23, 0x35, 0x61, 0xf4,
  65                 0x1d, 0xb6, 0x6c, 0xce, 0x31, 0x4a, 0xdb, 0x31,
  66                 0x0e, 0x3b, 0xe8, 0x25, 0x0c, 0x46, 0xf0, 0x6d,
  67                 0xce, 0xea, 0x3a, 0x7f, 0xa1, 0x34, 0x80, 0x57,
  68                 0xe2, 0xf6, 0x55, 0x6a, 0xd6, 0xb1, 0x31, 0x8a,
  69                 0x02, 0x4a, 0x83, 0x8f, 0x21, 0xaf, 0x1f, 0xde,
  70                 0x04, 0x89, 0x77, 0xeb, 0x48, 0xf5, 0x9f, 0xfd,
  71                 0x49, 0x24, 0xca, 0x1c, 0x60, 0x90, 0x2e, 0x52,
  72                 0xf0, 0xa0, 0x89, 0xbc, 0x76, 0x89, 0x70, 0x40,
  73                 0xe0, 0x82, 0xf9, 0x37, 0x76, 0x38, 0x48, 0x64,
  74                 0x5e, 0x07, 0x05
  75         };
  76         unsigned char c[163];
  77         unsigned char result[147] = {
  78                 0xf3, 0xff, 0xc7, 0x70, 0x3f, 0x94, 0x00, 0xe5,
  79                 0x2a, 0x7d, 0xfb, 0x4b, 0x3d, 0x33, 0x05, 0xd9,
  80                 0x8e, 0x99, 0x3b, 0x9f, 0x48, 0x68, 0x12, 0x73,
  81                 0xc2, 0x96, 0x50, 0xba, 0x32, 0xfc, 0x76, 0xce,
  82                 0x48, 0x33, 0x2e, 0xa7, 0x16, 0x4d, 0x96, 0xa4,
  83                 0x47, 0x6f, 0xb8, 0xc5, 0x31, 0xa1, 0x18, 0x6a,
  84                 0xc0, 0xdf, 0xc1, 0x7c, 0x98, 0xdc, 0xe8, 0x7b,
  85                 0x4d, 0xa7, 0xf0, 0x11, 0xec, 0x48, 0xc9, 0x72,
  86                 0x71, 0xd2, 0xc2, 0x0f, 0x9b, 0x92, 0x8f, 0xe2,
  87                 0x27, 0x0d, 0x6f, 0xb8, 0x63, 0xd5, 0x17, 0x38,
  88                 0xb4, 0x8e, 0xee, 0xe3, 0x14, 0xa7, 0xcc, 0x8a,
  89                 0xb9, 0x32, 0x16, 0x45, 0x48, 0xe5, 0x26, 0xae,
  90                 0x90, 0x22, 0x43, 0x68, 0x51, 0x7a, 0xcf, 0xea,
  91                 0xbd, 0x6b, 0xb3, 0x73, 0x2b, 0xc0, 0xe9, 0xda,
  92                 0x99, 0x83, 0x2b, 0x61, 0xca, 0x01, 0xb6, 0xde,
  93                 0x56, 0x24, 0x4a, 0x9e, 0x88, 0xd5, 0xf9, 0xb3,
  94                 0x79, 0x73, 0xf6, 0x22, 0xa4, 0x3d, 0x14, 0xa6,
  95                 0x59, 0x9b, 0x1f, 0x65, 0x4c, 0xb4, 0x5a, 0x74,
  96                 0xe3, 0x55, 0xa5
  97         };
  98
  99         bug_on(NONCE_LENGTH != 16);
 100
 101         crypto_box_curve25519xsalsa20poly1305(c, m, 163, nonce, bobpk, alicesk);
 102
 103         for (i = 16; i < 163; ++i) {
 104                 if (c[i] != result[i - 16])
 105                         panic("Crypto selftest failed! :-(\n");
 106         }
 107 }
 108
 109 int curve25519_pubkey_hexparse_32(unsigned char *bin, size_t blen,
 110                                   const char *ascii, size_t alen)
 111 {
 112         int ret = sscanf(ascii,
 113                      "%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:"
 114                      "%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:"
 115                      "%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:"
 116                      "%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:%2hhx",
 117                       &bin[0],  &bin[1],  &bin[2],  &bin[3],  &bin[4],
 118                       &bin[5],  &bin[6],  &bin[7],  &bin[8],  &bin[9],
 119                      &bin[10], &bin[11], &bin[12], &bin[13], &bin[14],
 120                      &bin[15], &bin[16], &bin[17], &bin[18], &bin[19],
 121                      &bin[20], &bin[21], &bin[22], &bin[23], &bin[24],
 122                      &bin[25], &bin[26], &bin[27], &bin[28], &bin[29],
 123                      &bin[30], &bin[31]);
 124         return ret == 32;
 125 }
 126
 127 void curve25519_alloc_or_maybe_die(struct curve25519_struct *curve)
 128 {
 129         curve->enc_buf_size = curve->dec_buf_size = TUNBUFF_SIZ;
 130
 131         curve->enc_buf = xmalloc_aligned(curve->enc_buf_size, 16);
 132         curve->dec_buf = xmalloc_aligned(curve->dec_buf_size, 16);
 133
 134         spinlock_init(&curve->enc_lock);
 135         spinlock_init(&curve->dec_lock);
 136 }
 137
 138 void curve25519_free(void *curvep)
 139 {
 140         struct curve25519_struct *curve = curvep;
 141
 142         memset(curve->enc_buf, 0, curve->enc_buf_size);
 143         memset(curve->dec_buf, 0, curve->dec_buf_size);
 144
 145         xfree(curve->enc_buf);
 146         xfree(curve->dec_buf);
 147
 148         spinlock_destroy(&curve->enc_lock);
 149         spinlock_destroy(&curve->dec_lock);
 150 }
 151
 152 int curve25519_proto_init(struct curve25519_proto *proto, unsigned char *pubkey_remote,
 153                           size_t len, char *home, int server)
 154 {
 155         int fd;
 156         ssize_t ret;
 157         char path[PATH_MAX];
 158         unsigned char secretkey_own[crypto_box_curve25519xsalsa20poly1305_SECRETKEYBYTES];
 159         unsigned char publickey_own[crypto_box_curve25519xsalsa20poly1305_PUBLICKEYBYTES];
 160
 161         fmemset(secretkey_own, 0, sizeof(secretkey_own));
 162         fmemset(publickey_own, 0, sizeof(publickey_own));
 163
 164         if (!pubkey_remote || len != sizeof(publickey_own))
 165                 return -EINVAL;
 166
 167         slprintf(path, sizeof(path), "%s/%s", home, FILE_PRIVKEY);
 168         fd = open_or_die(path, O_RDONLY);
 169
 170         ret = read(fd, secretkey_own, sizeof(secretkey_own));
 171         if (ret != sizeof(secretkey_own)) {
 172                 xmemset(secretkey_own, 0, sizeof(secretkey_own));
 173                 panic("Cannot read private key!\n");
 174         }
 175
 176         close(fd);
 177
 178         crypto_scalarmult_curve25519_base(publickey_own, secretkey_own);
 179
 180         if (!crypto_verify_32(publickey_own, pubkey_remote)) {
 181                 xmemset(secretkey_own, 0, sizeof(secretkey_own));
 182                 xmemset(publickey_own, 0, sizeof(publickey_own));
 183                 panic("PANIC: remote end has same public key as you have!!!\n");
 184         }
 185
 186         crypto_box_beforenm(proto->key, pubkey_remote, secretkey_own);
 187
 188         xmemset(proto->enonce, 0, sizeof(proto->enonce));
 189         xmemset(proto->dnonce, 0, sizeof(proto->dnonce));
 190
 191         xmemset(secretkey_own, 0, sizeof(secretkey_own));
 192         xmemset(publickey_own, 0, sizeof(publickey_own));
 193
 194         return 0;
 195 }
 196
 197 ssize_t curve25519_encode(struct curve25519_struct *curve, struct curve25519_proto *proto,
 198                           unsigned char *plaintext, size_t size, unsigned char **chipertext)
 199 {
 200         int ret, i;
 201         ssize_t done = size;
 202         struct taia packet_taia;
 203
 204         spinlock_lock(&curve->enc_lock);
 205
 206         if (unlikely(size > curve->enc_buf_size)) {
 207                 done = -ENOMEM;
 208                 goto out;
 209         }
 210
 211         taia_now(&packet_taia);
 212         taia_pack(proto->enonce + NONCE_OFFSET, &packet_taia);
 213
 214         memset(curve->enc_buf, 0, curve->enc_buf_size);
 215         ret = crypto_box_afternm(curve->enc_buf, plaintext, size, proto->enonce, proto->key);
 216         if (unlikely(ret)) {
 217                 done = -EIO;
 218                 goto out;
 219         }
 220
 221         fmemcpy(curve->enc_buf + crypto_box_boxzerobytes - NONCE_LENGTH,
 222                proto->enonce + NONCE_OFFSET, NONCE_LENGTH);
 223
 224         for (i = 0; i < crypto_box_boxzerobytes - NONCE_LENGTH; ++i)
 225                 curve->enc_buf[i] = (uint8_t) secrand();
 226
 227         (*chipertext) = curve->enc_buf;
 228 out:
 229         spinlock_unlock(&curve->enc_lock);
 230         return done;
 231 }
 232
 233 ssize_t curve25519_decode(struct curve25519_struct *curve, struct curve25519_proto *proto,
 234                           unsigned char *chipertext, size_t size, unsigned char **plaintext,
 235                           struct taia *arrival_taia)
 236 {
 237         int ret;
 238         ssize_t done = size;
 239         struct taia packet_taia, arrival_taia2;
 240
 241         spinlock_lock(&curve->dec_lock);
 242
 243         if (unlikely(size > curve->dec_buf_size)) {
 244                 done = -ENOMEM;
 245                 goto out;
 246         }
 247         if (unlikely(size < crypto_box_boxzerobytes + NONCE_LENGTH)) {
 248                 done = 0;
 249                 goto out;
 250         }
 251         if (arrival_taia == NULL) {
 252                 taia_now(&arrival_taia2);
 253                 arrival_taia = &arrival_taia2;
 254         }
 255
 256         taia_unpack(chipertext + crypto_box_boxzerobytes - NONCE_LENGTH, &packet_taia);
 257         if (taia_looks_good(arrival_taia, &packet_taia) == 0) {
 258                 syslog(LOG_ERR, "Bad packet time! Dropping connection!\n");
 259                 done = 0;
 260                 goto out;
 261         }
 262
 263         memcpy(proto->dnonce + NONCE_OFFSET, chipertext + crypto_box_boxzerobytes - NONCE_LENGTH, NONCE_LENGTH);
 264         memset(curve->dec_buf, 0, curve->dec_buf_size);
 265
 266         ret = crypto_box_open_afternm(curve->dec_buf, chipertext, size, proto->dnonce, proto->key);
 267         if (unlikely(ret)) {
 268                 done = -EIO;
 269                 goto out;
 270         }
 271
 272         (*plaintext) = curve->dec_buf;
 273 out:
 274         spinlock_unlock(&curve->dec_lock);
 275         return done;
 276 }