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 "xutils.h"
  23 #include "xio.h"
  24 #include "die.h"
  25 #include "curvetun.h"
  26 #include "locking.h"
  27 #include "crypto_verify_32.h"
  28 #include "crypto_box_curve25519xsalsa20poly1305.h"
  29 #include "crypto_scalarmult_curve25519.h"
  30
  31 #define crypto_box_beforenm             crypto_box_curve25519xsalsa20poly1305_beforenm
  32 #define crypto_box_afternm              crypto_box_curve25519xsalsa20poly1305_afternm
  33 #define crypto_box_open_afternm         crypto_box_curve25519xsalsa20poly1305_open_afternm
  34
  35 #define NONCE_LENGTH                    (sizeof(struct taia))
  36 #define NONCE_OFFSET                    (crypto_box_curve25519xsalsa20poly1305_NONCEBYTES - NONCE_LENGTH)
  37
  38 void curve25519_selftest(void)
  39 {
  40         int i;
  41         unsigned char alicesk[32] = {
  42                 0x77, 0x07, 0x6d, 0x0a, 0x73, 0x18, 0xa5, 0x7d,
  43                 0x3c, 0x16, 0xc1, 0x72, 0x51, 0xb2, 0x66, 0x45,
  44                 0xdf, 0x4c, 0x2f, 0x87, 0xeb, 0xc0, 0x99, 0x2a,
  45                 0xb1, 0x77, 0xfb, 0xa5, 0x1d, 0xb9, 0x2c, 0x2a
  46         };
  47         unsigned char bobpk[32] = {
  48                 0xde, 0x9e, 0xdb, 0x7d, 0x7b, 0x7d, 0xc1, 0xb4,
  49                 0xd3, 0x5b, 0x61, 0xc2, 0xec, 0xe4, 0x35, 0x37,
  50                 0x3f, 0x83, 0x43, 0xc8, 0x5b, 0x78, 0x67, 0x4d,
  51                 0xad, 0xfc, 0x7e, 0x14, 0x6f, 0x88, 0x2b, 0x4f
  52         };
  53         unsigned char nonce[24] = {
  54                 0x69, 0x69, 0x6e, 0xe9, 0x55, 0xb6, 0x2b, 0x73,
  55                 0xcd, 0x62, 0xbd, 0xa8, 0x75, 0xfc, 0x73, 0xd6,
  56                 0x82, 0x19, 0xe0, 0x03, 0x6b, 0x7a, 0x0b, 0x37
  57         };
  58         unsigned char m[163] = {
  59                 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  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                 0xbe, 0x07, 0x5f, 0xc5, 0x3c, 0x81, 0xf2, 0xd5,
  64                 0xcf, 0x14, 0x13, 0x16, 0xeb, 0xeb, 0x0c, 0x7b,
  65                 0x52, 0x28, 0xc5, 0x2a, 0x4c, 0x62, 0xcb, 0xd4,
  66                 0x4b, 0x66, 0x84, 0x9b, 0x64, 0x24, 0x4f, 0xfc,
  67                 0xe5, 0xec, 0xba, 0xaf, 0x33, 0xbd, 0x75, 0x1a,
  68                 0x1a, 0xc7, 0x28, 0xd4, 0x5e, 0x6c, 0x61, 0x29,
  69                 0x6c, 0xdc, 0x3c, 0x01, 0x23, 0x35, 0x61, 0xf4,
  70                 0x1d, 0xb6, 0x6c, 0xce, 0x31, 0x4a, 0xdb, 0x31,
  71                 0x0e, 0x3b, 0xe8, 0x25, 0x0c, 0x46, 0xf0, 0x6d,
  72                 0xce, 0xea, 0x3a, 0x7f, 0xa1, 0x34, 0x80, 0x57,
  73                 0xe2, 0xf6, 0x55, 0x6a, 0xd6, 0xb1, 0x31, 0x8a,
  74                 0x02, 0x4a, 0x83, 0x8f, 0x21, 0xaf, 0x1f, 0xde,
  75                 0x04, 0x89, 0x77, 0xeb, 0x48, 0xf5, 0x9f, 0xfd,
  76                 0x49, 0x24, 0xca, 0x1c, 0x60, 0x90, 0x2e, 0x52,
  77                 0xf0, 0xa0, 0x89, 0xbc, 0x76, 0x89, 0x70, 0x40,
  78                 0xe0, 0x82, 0xf9, 0x37, 0x76, 0x38, 0x48, 0x64,
  79                 0x5e, 0x07, 0x05
  80         };
  81         unsigned char c[163];
  82         unsigned char result[147] = {
  83                 0xf3, 0xff, 0xc7, 0x70, 0x3f, 0x94, 0x00, 0xe5,
  84                 0x2a, 0x7d, 0xfb, 0x4b, 0x3d, 0x33, 0x05, 0xd9,
  85                 0x8e, 0x99, 0x3b, 0x9f, 0x48, 0x68, 0x12, 0x73,
  86                 0xc2, 0x96, 0x50, 0xba, 0x32, 0xfc, 0x76, 0xce,
  87                 0x48, 0x33, 0x2e, 0xa7, 0x16, 0x4d, 0x96, 0xa4,
  88                 0x47, 0x6f, 0xb8, 0xc5, 0x31, 0xa1, 0x18, 0x6a,
  89                 0xc0, 0xdf, 0xc1, 0x7c, 0x98, 0xdc, 0xe8, 0x7b,
  90                 0x4d, 0xa7, 0xf0, 0x11, 0xec, 0x48, 0xc9, 0x72,
  91                 0x71, 0xd2, 0xc2, 0x0f, 0x9b, 0x92, 0x8f, 0xe2,
  92                 0x27, 0x0d, 0x6f, 0xb8, 0x63, 0xd5, 0x17, 0x38,
  93                 0xb4, 0x8e, 0xee, 0xe3, 0x14, 0xa7, 0xcc, 0x8a,
  94                 0xb9, 0x32, 0x16, 0x45, 0x48, 0xe5, 0x26, 0xae,
  95                 0x90, 0x22, 0x43, 0x68, 0x51, 0x7a, 0xcf, 0xea,
  96                 0xbd, 0x6b, 0xb3, 0x73, 0x2b, 0xc0, 0xe9, 0xda,
  97                 0x99, 0x83, 0x2b, 0x61, 0xca, 0x01, 0xb6, 0xde,
  98                 0x56, 0x24, 0x4a, 0x9e, 0x88, 0xd5, 0xf9, 0xb3,
  99                 0x79, 0x73, 0xf6, 0x22, 0xa4, 0x3d, 0x14, 0xa6,
 100                 0x59, 0x9b, 0x1f, 0x65, 0x4c, 0xb4, 0x5a, 0x74,
 101                 0xe3, 0x55, 0xa5
 102         };
 103
 104         bug_on(NONCE_LENGTH != 16);
 105
 106         crypto_box_curve25519xsalsa20poly1305(c, m, 163, nonce, bobpk, alicesk);
 107
 108         for (i = 16; i < 163; ++i) {
 109                 if (c[i] != result[i - 16])
 110                         panic("Crypto selftest failed! :-(\n");
 111         }
 112 }
 113
 114 int curve25519_pubkey_hexparse_32(unsigned char *bin, size_t blen,
 115                                   const char *ascii, size_t alen)
 116 {
 117         int ret = sscanf(ascii,
 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                      "%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:%2hhx",
 122                       &bin[0],  &bin[1],  &bin[2],  &bin[3],  &bin[4],
 123                       &bin[5],  &bin[6],  &bin[7],  &bin[8],  &bin[9],
 124                      &bin[10], &bin[11], &bin[12], &bin[13], &bin[14],
 125                      &bin[15], &bin[16], &bin[17], &bin[18], &bin[19],
 126                      &bin[20], &bin[21], &bin[22], &bin[23], &bin[24],
 127                      &bin[25], &bin[26], &bin[27], &bin[28], &bin[29],
 128                      &bin[30], &bin[31]);
 129         return ret == 32;
 130 }
 131
 132 void curve25519_alloc_or_maybe_die(struct curve25519_struct *curve)
 133 {
 134         curve->enc_buf_size = curve->dec_buf_size = TUNBUFF_SIZ;
 135
 136         curve->enc_buf = xmalloc_aligned(curve->enc_buf_size, 16);
 137         curve->dec_buf = xmalloc_aligned(curve->dec_buf_size, 16);
 138
 139         spinlock_init(&curve->enc_lock);
 140         spinlock_init(&curve->dec_lock);
 141 }
 142
 143 void curve25519_free(void *curvep)
 144 {
 145         struct curve25519_struct *curve = curvep;
 146
 147         memset(curve->enc_buf, 0, curve->enc_buf_size);
 148         memset(curve->dec_buf, 0, curve->dec_buf_size);
 149
 150         xfree(curve->enc_buf);
 151         xfree(curve->dec_buf);
 152
 153         spinlock_destroy(&curve->enc_lock);
 154         spinlock_destroy(&curve->dec_lock);
 155 }
 156
 157 int curve25519_proto_init(struct curve25519_proto *proto, unsigned char *pubkey_remote,
 158                           size_t len, char *home, int server)
 159 {
 160         int fd;
 161         ssize_t ret;
 162         char path[PATH_MAX];
 163         unsigned char secretkey_own[crypto_box_curve25519xsalsa20poly1305_SECRETKEYBYTES];
 164         unsigned char publickey_own[crypto_box_curve25519xsalsa20poly1305_PUBLICKEYBYTES];
 165
 166         fmemset(secretkey_own, 0, sizeof(secretkey_own));
 167         fmemset(publickey_own, 0, sizeof(publickey_own));
 168
 169         if (!pubkey_remote || len != sizeof(publickey_own))
 170                 return -EINVAL;
 171
 172         slprintf(path, sizeof(path), "%s/%s", home, FILE_PRIVKEY);
 173         fd = open_or_die(path, O_RDONLY);
 174
 175         ret = read(fd, secretkey_own, sizeof(secretkey_own));
 176         if (ret != sizeof(secretkey_own)) {
 177                 xmemset(secretkey_own, 0, sizeof(secretkey_own));
 178                 panic("Cannot read private key!\n");
 179         }
 180
 181         close(fd);
 182
 183         crypto_scalarmult_curve25519_base(publickey_own, secretkey_own);
 184
 185         if (!crypto_verify_32(publickey_own, pubkey_remote)) {
 186                 xmemset(secretkey_own, 0, sizeof(secretkey_own));
 187                 xmemset(publickey_own, 0, sizeof(publickey_own));
 188                 panic("PANIC: remote end has same public key as you have!!!\n");
 189         }
 190
 191         crypto_box_beforenm(proto->key, pubkey_remote, secretkey_own);
 192
 193         xmemset(proto->enonce, 0, sizeof(proto->enonce));
 194         xmemset(proto->dnonce, 0, sizeof(proto->dnonce));
 195
 196         xmemset(secretkey_own, 0, sizeof(secretkey_own));
 197         xmemset(publickey_own, 0, sizeof(publickey_own));
 198
 199         return 0;
 200 }
 201
 202 ssize_t curve25519_encode(struct curve25519_struct *curve, struct curve25519_proto *proto,
 203                           unsigned char *plaintext, size_t size, unsigned char **chipertext)
 204 {
 205         int ret, i;
 206         ssize_t done = size;
 207         struct taia packet_taia;
 208
 209         spinlock_lock(&curve->enc_lock);
 210
 211         if (unlikely(size > curve->enc_buf_size)) {
 212                 done = -ENOMEM;
 213                 goto out;
 214         }
 215
 216         taia_now(&packet_taia);
 217         taia_pack(proto->enonce + NONCE_OFFSET, &packet_taia);
 218
 219         memset(curve->enc_buf, 0, curve->enc_buf_size);
 220         ret = crypto_box_afternm(curve->enc_buf, plaintext, size, proto->enonce, proto->key);
 221         if (unlikely(ret)) {
 222                 done = -EIO;
 223                 goto out;
 224         }
 225
 226         fmemcpy(curve->enc_buf + crypto_box_boxzerobytes - NONCE_LENGTH,
 227                proto->enonce + NONCE_OFFSET, NONCE_LENGTH);
 228
 229         for (i = 0; i < crypto_box_boxzerobytes - NONCE_LENGTH; ++i)
 230                 curve->enc_buf[i] = (uint8_t) secrand();
 231
 232         (*chipertext) = curve->enc_buf;
 233 out:
 234         spinlock_unlock(&curve->enc_lock);
 235         return done;
 236 }
 237
 238 ssize_t curve25519_decode(struct curve25519_struct *curve, struct curve25519_proto *proto,
 239                           unsigned char *chipertext, size_t size, unsigned char **plaintext,
 240                           struct taia *arrival_taia)
 241 {
 242         int ret;
 243         ssize_t done = size;
 244         struct taia packet_taia, arrival_taia2;
 245
 246         spinlock_lock(&curve->dec_lock);
 247
 248         if (unlikely(size > curve->dec_buf_size)) {
 249                 done = -ENOMEM;
 250                 goto out;
 251         }
 252         if (unlikely(size < crypto_box_boxzerobytes + NONCE_LENGTH)) {
 253                 done = 0;
 254                 goto out;
 255         }
 256         if (arrival_taia == NULL) {
 257                 taia_now(&arrival_taia2);
 258                 arrival_taia = &arrival_taia2;
 259         }
 260
 261         taia_unpack(chipertext + crypto_box_boxzerobytes - NONCE_LENGTH, &packet_taia);
 262         if (is_good_taia(arrival_taia, &packet_taia) == 0) {
 263                 syslog(LOG_ERR, "Bad packet time! Dropping connection!\n");
 264                 done = 0;
 265                 goto out;
 266         }
 267
 268         memcpy(proto->dnonce + NONCE_OFFSET, chipertext + crypto_box_boxzerobytes - NONCE_LENGTH, NONCE_LENGTH);
 269         memset(curve->dec_buf, 0, curve->dec_buf_size);
 270
 271         ret = crypto_box_open_afternm(curve->dec_buf, chipertext, size, proto->dnonce, proto->key);
 272         if (unlikely(ret)) {
 273                 done = -EIO;
 274                 goto out;
 275         }
 276
 277         (*plaintext) = curve->dec_buf;
 278 out:
 279         spinlock_unlock(&curve->dec_lock);
 280         return done;
 281 }