curve.c

   1 /*
   2  * netsniff-ng - the packet sniffing beast
   3  * By Daniel Borkmann <daniel@netsniff-ng.org>
   4  * Copyright 2011 - 2013 Daniel Borkmann.
   5  * Subject to the GPL, version 2.
   6  */
   7
   8 #include <stdio.h>
   9 #include <stdlib.h>
  10 #include <stdint.h>
  11 #include <errno.h>
  12 #include <fcntl.h>
  13 #include <syslog.h>
  14 #include <limits.h>
  15 #include <string.h>
  16 #include <sys/types.h>
  17 #include <sys/time.h>
  18 #include <sys/stat.h>
  19
  20 #include "built_in.h"
  21 #include "xmalloc.h"
  22 #include "curve.h"
  23 #include "xutils.h"
  24 #include "xio.h"
  25 #include "die.h"
  26 #include "curvetun.h"
  27 #include "locking.h"
  28 #include "crypto_verify_32.h"
  29 #include "crypto_box_curve25519xsalsa20poly1305.h"
  30 #include "crypto_scalarmult_curve25519.h"
  31
  32 #define crypto_box_beforenm             crypto_box_curve25519xsalsa20poly1305_beforenm
  33 #define crypto_box_afternm              crypto_box_curve25519xsalsa20poly1305_afternm
  34 #define crypto_box_open_afternm         crypto_box_curve25519xsalsa20poly1305_open_afternm
  35
  36 #define NONCE_LENGTH                    16 /* size of taia */
  37 #define NONCE_OFFSET                    (crypto_box_curve25519xsalsa20poly1305_NONCEBYTES - NONCE_LENGTH)
  38
  39 void curve25519_selftest(void)
  40 {
  41         int i;
  42         unsigned char alicesk[32] = {
  43                 0x77, 0x07, 0x6d, 0x0a, 0x73, 0x18, 0xa5, 0x7d,
  44                 0x3c, 0x16, 0xc1, 0x72, 0x51, 0xb2, 0x66, 0x45,
  45                 0xdf, 0x4c, 0x2f, 0x87, 0xeb, 0xc0, 0x99, 0x2a,
  46                 0xb1, 0x77, 0xfb, 0xa5, 0x1d, 0xb9, 0x2c, 0x2a
  47         };
  48         unsigned char bobpk[32] = {
  49                 0xde, 0x9e, 0xdb, 0x7d, 0x7b, 0x7d, 0xc1, 0xb4,
  50                 0xd3, 0x5b, 0x61, 0xc2, 0xec, 0xe4, 0x35, 0x37,
  51                 0x3f, 0x83, 0x43, 0xc8, 0x5b, 0x78, 0x67, 0x4d,
  52                 0xad, 0xfc, 0x7e, 0x14, 0x6f, 0x88, 0x2b, 0x4f
  53         };
  54         unsigned char nonce[24] = {
  55                 0x69, 0x69, 0x6e, 0xe9, 0x55, 0xb6, 0x2b, 0x73,
  56                 0xcd, 0x62, 0xbd, 0xa8, 0x75, 0xfc, 0x73, 0xd6,
  57                 0x82, 0x19, 0xe0, 0x03, 0x6b, 0x7a, 0x0b, 0x37
  58         };
  59         unsigned char m[163] = {
  60                 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  61                 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  62                 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  63                 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  64                 0xbe, 0x07, 0x5f, 0xc5, 0x3c, 0x81, 0xf2, 0xd5,
  65                 0xcf, 0x14, 0x13, 0x16, 0xeb, 0xeb, 0x0c, 0x7b,
  66                 0x52, 0x28, 0xc5, 0x2a, 0x4c, 0x62, 0xcb, 0xd4,
  67                 0x4b, 0x66, 0x84, 0x9b, 0x64, 0x24, 0x4f, 0xfc,
  68                 0xe5, 0xec, 0xba, 0xaf, 0x33, 0xbd, 0x75, 0x1a,
  69                 0x1a, 0xc7, 0x28, 0xd4, 0x5e, 0x6c, 0x61, 0x29,
  70                 0x6c, 0xdc, 0x3c, 0x01, 0x23, 0x35, 0x61, 0xf4,
  71                 0x1d, 0xb6, 0x6c, 0xce, 0x31, 0x4a, 0xdb, 0x31,
  72                 0x0e, 0x3b, 0xe8, 0x25, 0x0c, 0x46, 0xf0, 0x6d,
  73                 0xce, 0xea, 0x3a, 0x7f, 0xa1, 0x34, 0x80, 0x57,
  74                 0xe2, 0xf6, 0x55, 0x6a, 0xd6, 0xb1, 0x31, 0x8a,
  75                 0x02, 0x4a, 0x83, 0x8f, 0x21, 0xaf, 0x1f, 0xde,
  76                 0x04, 0x89, 0x77, 0xeb, 0x48, 0xf5, 0x9f, 0xfd,
  77                 0x49, 0x24, 0xca, 0x1c, 0x60, 0x90, 0x2e, 0x52,
  78                 0xf0, 0xa0, 0x89, 0xbc, 0x76, 0x89, 0x70, 0x40,
  79                 0xe0, 0x82, 0xf9, 0x37, 0x76, 0x38, 0x48, 0x64,
  80                 0x5e, 0x07, 0x05
  81         };
  82         unsigned char c[163];
  83         unsigned char result[147] = {
  84                 0xf3, 0xff, 0xc7, 0x70, 0x3f, 0x94, 0x00, 0xe5,
  85                 0x2a, 0x7d, 0xfb, 0x4b, 0x3d, 0x33, 0x05, 0xd9,
  86                 0x8e, 0x99, 0x3b, 0x9f, 0x48, 0x68, 0x12, 0x73,
  87                 0xc2, 0x96, 0x50, 0xba, 0x32, 0xfc, 0x76, 0xce,
  88                 0x48, 0x33, 0x2e, 0xa7, 0x16, 0x4d, 0x96, 0xa4,
  89                 0x47, 0x6f, 0xb8, 0xc5, 0x31, 0xa1, 0x18, 0x6a,
  90                 0xc0, 0xdf, 0xc1, 0x7c, 0x98, 0xdc, 0xe8, 0x7b,
  91                 0x4d, 0xa7, 0xf0, 0x11, 0xec, 0x48, 0xc9, 0x72,
  92                 0x71, 0xd2, 0xc2, 0x0f, 0x9b, 0x92, 0x8f, 0xe2,
  93                 0x27, 0x0d, 0x6f, 0xb8, 0x63, 0xd5, 0x17, 0x38,
  94                 0xb4, 0x8e, 0xee, 0xe3, 0x14, 0xa7, 0xcc, 0x8a,
  95                 0xb9, 0x32, 0x16, 0x45, 0x48, 0xe5, 0x26, 0xae,
  96                 0x90, 0x22, 0x43, 0x68, 0x51, 0x7a, 0xcf, 0xea,
  97                 0xbd, 0x6b, 0xb3, 0x73, 0x2b, 0xc0, 0xe9, 0xda,
  98                 0x99, 0x83, 0x2b, 0x61, 0xca, 0x01, 0xb6, 0xde,
  99                 0x56, 0x24, 0x4a, 0x9e, 0x88, 0xd5, 0xf9, 0xb3,
 100                 0x79, 0x73, 0xf6, 0x22, 0xa4, 0x3d, 0x14, 0xa6,
 101                 0x59, 0x9b, 0x1f, 0x65, 0x4c, 0xb4, 0x5a, 0x74,
 102                 0xe3, 0x55, 0xa5
 103         };
 104
 105         crypto_box_curve25519xsalsa20poly1305(c, m, 163, nonce, bobpk, alicesk);
 106
 107         for (i = 16; i < 163; ++i) {
 108                 if (c[i] != result[i - 16])
 109                         panic("Crypto selftest failed! :-(\n");
 110         }
 111 }
 112
 113 int curve25519_pubkey_hexparse_32(unsigned char *bin, size_t blen,
 114                                   const char *ascii, size_t alen)
 115 {
 116         int ret = sscanf(ascii,
 117                      "%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:"
 118                      "%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:"
 119                      "%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:"
 120                      "%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:%2hhx",
 121                       &bin[0],  &bin[1],  &bin[2],  &bin[3],  &bin[4],
 122                       &bin[5],  &bin[6],  &bin[7],  &bin[8],  &bin[9],
 123                      &bin[10], &bin[11], &bin[12], &bin[13], &bin[14],
 124                      &bin[15], &bin[16], &bin[17], &bin[18], &bin[19],
 125                      &bin[20], &bin[21], &bin[22], &bin[23], &bin[24],
 126                      &bin[25], &bin[26], &bin[27], &bin[28], &bin[29],
 127                      &bin[30], &bin[31]);
 128         return ret == 32;
 129 }
 130
 131 void curve25519_alloc_or_maybe_die(struct curve25519_struct *curve)
 132 {
 133         curve->enc_buf_size = curve->dec_buf_size = TUNBUFF_SIZ;
 134
 135         curve->enc_buf = xmalloc_aligned(curve->enc_buf_size, 16);
 136         curve->dec_buf = xmalloc_aligned(curve->dec_buf_size, 16);
 137
 138         spinlock_init(&curve->enc_lock);
 139         spinlock_init(&curve->dec_lock);
 140 }
 141
 142 void curve25519_free(void *curvep)
 143 {
 144         struct curve25519_struct *curve = curvep;
 145
 146         memset(curve->enc_buf, 0, curve->enc_buf_size);
 147         memset(curve->dec_buf, 0, curve->dec_buf_size);
 148
 149         xfree(curve->enc_buf);
 150         xfree(curve->dec_buf);
 151
 152         spinlock_destroy(&curve->enc_lock);
 153         spinlock_destroy(&curve->dec_lock);
 154 }
 155
 156 int curve25519_proto_init(struct curve25519_proto *proto, unsigned char *pubkey_remote,
 157                           size_t len, char *home, int server)
 158 {
 159         int fd;
 160         ssize_t ret;
 161         char path[PATH_MAX];
 162         unsigned char secretkey_own[crypto_box_curve25519xsalsa20poly1305_SECRETKEYBYTES];
 163         unsigned char publickey_own[crypto_box_curve25519xsalsa20poly1305_PUBLICKEYBYTES];
 164
 165         fmemset(secretkey_own, 0, sizeof(secretkey_own));
 166         fmemset(publickey_own, 0, sizeof(publickey_own));
 167
 168         if (!pubkey_remote || len != sizeof(publickey_own))
 169                 return -EINVAL;
 170
 171         slprintf(path, sizeof(path), "%s/%s", home, FILE_PRIVKEY);
 172         fd = open_or_die(path, O_RDONLY);
 173
 174         ret = read(fd, secretkey_own, sizeof(secretkey_own));
 175         if (ret != sizeof(secretkey_own)) {
 176                 xmemset(secretkey_own, 0, sizeof(secretkey_own));
 177                 panic("Cannot read private key!\n");
 178         }
 179
 180         close(fd);
 181
 182         crypto_scalarmult_curve25519_base(publickey_own, secretkey_own);
 183
 184         if (!crypto_verify_32(publickey_own, pubkey_remote)) {
 185                 xmemset(secretkey_own, 0, sizeof(secretkey_own));
 186                 xmemset(publickey_own, 0, sizeof(publickey_own));
 187                 panic("PANIC: remote end has same public key as you have!!!\n");
 188         }
 189
 190         crypto_box_beforenm(proto->key, pubkey_remote, secretkey_own);
 191
 192         xmemset(proto->enonce, 0, sizeof(proto->enonce));
 193         xmemset(proto->dnonce, 0, sizeof(proto->dnonce));
 194
 195         xmemset(secretkey_own, 0, sizeof(secretkey_own));
 196         xmemset(publickey_own, 0, sizeof(publickey_own));
 197
 198         return 0;
 199 }
 200
 201 ssize_t curve25519_encode(struct curve25519_struct *curve, struct curve25519_proto *proto,
 202                           unsigned char *plaintext, size_t size, unsigned char **chipertext)
 203 {
 204         int ret, i;
 205         ssize_t done = size;
 206         struct taia packet_taia;
 207
 208         spinlock_lock(&curve->enc_lock);
 209
 210         if (unlikely(size > curve->enc_buf_size)) {
 211                 done = -ENOMEM;
 212                 goto out;
 213         }
 214
 215         taia_now(&packet_taia);
 216         taia_pack(proto->enonce + NONCE_OFFSET, &packet_taia);
 217
 218         memset(curve->enc_buf, 0, curve->enc_buf_size);
 219         ret = crypto_box_afternm(curve->enc_buf, plaintext, size, proto->enonce, proto->key);
 220         if (unlikely(ret)) {
 221                 done = -EIO;
 222                 goto out;
 223         }
 224
 225         fmemcpy(curve->enc_buf + crypto_box_boxzerobytes - NONCE_LENGTH,
 226                proto->enonce + NONCE_OFFSET, NONCE_LENGTH);
 227
 228         for (i = 0; i < crypto_box_boxzerobytes - NONCE_LENGTH; ++i)
 229                 curve->enc_buf[i] = (uint8_t) secrand();
 230
 231         (*chipertext) = curve->enc_buf;
 232 out:
 233         spinlock_unlock(&curve->enc_lock);
 234         return done;
 235 }
 236
 237 ssize_t curve25519_decode(struct curve25519_struct *curve, struct curve25519_proto *proto,
 238                           unsigned char *chipertext, size_t size, unsigned char **plaintext,
 239                           struct taia *arrival_taia)
 240 {
 241         int ret;
 242         ssize_t done = size;
 243         struct taia packet_taia, arrival_taia2;
 244
 245         spinlock_lock(&curve->dec_lock);
 246
 247         if (unlikely(size > curve->dec_buf_size)) {
 248                 done = -ENOMEM;
 249                 goto out;
 250         }
 251         if (unlikely(size < crypto_box_boxzerobytes + NONCE_LENGTH)) {
 252                 done = 0;
 253                 goto out;
 254         }
 255         if (arrival_taia == NULL) {
 256                 taia_now(&arrival_taia2);
 257                 arrival_taia = &arrival_taia2;
 258         }
 259
 260         taia_unpack(chipertext + crypto_box_boxzerobytes - NONCE_LENGTH, &packet_taia);
 261         if (is_good_taia(arrival_taia, &packet_taia) == 0) {
 262                 syslog(LOG_ERR, "Bad packet time! Dropping connection!\n");
 263                 done = 0;
 264                 goto out;
 265         }
 266
 267         memcpy(proto->dnonce + NONCE_OFFSET, chipertext + crypto_box_boxzerobytes - NONCE_LENGTH, NONCE_LENGTH);
 268         memset(curve->dec_buf, 0, curve->dec_buf_size);
 269
 270         ret = crypto_box_open_afternm(curve->dec_buf, chipertext, size, proto->dnonce, proto->key);
 271         if (unlikely(ret)) {
 272                 done = -EIO;
 273                 goto out;
 274         }
 275
 276         (*plaintext) = curve->dec_buf;
 277 out:
 278         spinlock_unlock(&curve->dec_lock);
 279         return done;
 280 }