src/curve.c

   1 /*
   2  * netsniff-ng - the packet sniffing beast
   3  * By Daniel Borkmann <daniel@netsniff-ng.org>
   4  * Copyright 2011 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 "compiler.h"
  21 #include "xmalloc.h"
  22 #include "curve.h"
  23 #include "xstring.h"
  24 #include "die.h"
  25 #include "mtrand.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 /* Some parts derived from public domain code from curveprotect project */
  33
  34 #define crypto_box_beforenm     crypto_box_curve25519xsalsa20poly1305_beforenm
  35 #define crypto_box_afternm      crypto_box_curve25519xsalsa20poly1305_afternm
  36 #define crypto_box_open_afternm crypto_box_curve25519xsalsa20poly1305_open_afternm
  37
  38 #define NONCE_LENGTH    16      /* size of taia */
  39 #define NONCE_OFFSET    (crypto_box_curve25519xsalsa20poly1305_NONCEBYTES - NONCE_LENGTH)
  40
  41 void curve25519_selftest(void)
  42 {
  43         /* Test from the NaCl library */
  44         int i;
  45         unsigned char alicesk[32] = {
  46                 0x77, 0x07, 0x6d, 0x0a, 0x73, 0x18, 0xa5, 0x7d,
  47                 0x3c, 0x16, 0xc1, 0x72, 0x51, 0xb2, 0x66, 0x45,
  48                 0xdf, 0x4c, 0x2f, 0x87, 0xeb, 0xc0, 0x99, 0x2a,
  49                 0xb1, 0x77, 0xfb, 0xa5, 0x1d, 0xb9, 0x2c, 0x2a
  50         };
  51         unsigned char bobpk[32] = {
  52                 0xde, 0x9e, 0xdb, 0x7d, 0x7b, 0x7d, 0xc1, 0xb4,
  53                 0xd3, 0x5b, 0x61, 0xc2, 0xec, 0xe4, 0x35, 0x37,
  54                 0x3f, 0x83, 0x43, 0xc8, 0x5b, 0x78, 0x67, 0x4d,
  55                 0xad, 0xfc, 0x7e, 0x14, 0x6f, 0x88, 0x2b, 0x4f
  56         };
  57         unsigned char nonce[24] = {
  58                 0x69, 0x69, 0x6e, 0xe9, 0x55, 0xb6, 0x2b, 0x73,
  59                 0xcd, 0x62, 0xbd, 0xa8, 0x75, 0xfc, 0x73, 0xd6,
  60                 0x82, 0x19, 0xe0, 0x03, 0x6b, 0x7a, 0x0b, 0x37
  61         };
  62         /* API requires first 32 bytes to be 0 */
  63         unsigned char m[163] = {
  64                 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  65                 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  66                 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  67                 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  68                 0xbe, 0x07, 0x5f, 0xc5, 0x3c, 0x81, 0xf2, 0xd5,
  69                 0xcf, 0x14, 0x13, 0x16, 0xeb, 0xeb, 0x0c, 0x7b,
  70                 0x52, 0x28, 0xc5, 0x2a, 0x4c, 0x62, 0xcb, 0xd4,
  71                 0x4b, 0x66, 0x84, 0x9b, 0x64, 0x24, 0x4f, 0xfc,
  72                 0xe5, 0xec, 0xba, 0xaf, 0x33, 0xbd, 0x75, 0x1a,
  73                 0x1a, 0xc7, 0x28, 0xd4, 0x5e, 0x6c, 0x61, 0x29,
  74                 0x6c, 0xdc, 0x3c, 0x01, 0x23, 0x35, 0x61, 0xf4,
  75                 0x1d, 0xb6, 0x6c, 0xce, 0x31, 0x4a, 0xdb, 0x31,
  76                 0x0e, 0x3b, 0xe8, 0x25, 0x0c, 0x46, 0xf0, 0x6d,
  77                 0xce, 0xea, 0x3a, 0x7f, 0xa1, 0x34, 0x80, 0x57,
  78                 0xe2, 0xf6, 0x55, 0x6a, 0xd6, 0xb1, 0x31, 0x8a,
  79                 0x02, 0x4a, 0x83, 0x8f, 0x21, 0xaf, 0x1f, 0xde,
  80                 0x04, 0x89, 0x77, 0xeb, 0x48, 0xf5, 0x9f, 0xfd,
  81                 0x49, 0x24, 0xca, 0x1c, 0x60, 0x90, 0x2e, 0x52,
  82                 0xf0, 0xa0, 0x89, 0xbc, 0x76, 0x89, 0x70, 0x40,
  83                 0xe0, 0x82, 0xf9, 0x37, 0x76, 0x38, 0x48, 0x64,
  84                 0x5e, 0x07, 0x05
  85         };
  86         unsigned char c[163];
  87         unsigned char result[147] = {
  88                 0xf3, 0xff, 0xc7, 0x70, 0x3f, 0x94, 0x00, 0xe5,
  89                 0x2a, 0x7d, 0xfb, 0x4b, 0x3d, 0x33, 0x05, 0xd9,
  90                 0x8e, 0x99, 0x3b, 0x9f, 0x48, 0x68, 0x12, 0x73,
  91                 0xc2, 0x96, 0x50, 0xba, 0x32, 0xfc, 0x76, 0xce,
  92                 0x48, 0x33, 0x2e, 0xa7, 0x16, 0x4d, 0x96, 0xa4,
  93                 0x47, 0x6f, 0xb8, 0xc5, 0x31, 0xa1, 0x18, 0x6a,
  94                 0xc0, 0xdf, 0xc1, 0x7c, 0x98, 0xdc, 0xe8, 0x7b,
  95                 0x4d, 0xa7, 0xf0, 0x11, 0xec, 0x48, 0xc9, 0x72,
  96                 0x71, 0xd2, 0xc2, 0x0f, 0x9b, 0x92, 0x8f, 0xe2,
  97                 0x27, 0x0d, 0x6f, 0xb8, 0x63, 0xd5, 0x17, 0x38,
  98                 0xb4, 0x8e, 0xee, 0xe3, 0x14, 0xa7, 0xcc, 0x8a,
  99                 0xb9, 0x32, 0x16, 0x45, 0x48, 0xe5, 0x26, 0xae,
 100                 0x90, 0x22, 0x43, 0x68, 0x51, 0x7a, 0xcf, 0xea,
 101                 0xbd, 0x6b, 0xb3, 0x73, 0x2b, 0xc0, 0xe9, 0xda,
 102                 0x99, 0x83, 0x2b, 0x61, 0xca, 0x01, 0xb6, 0xde,
 103                 0x56, 0x24, 0x4a, 0x9e, 0x88, 0xd5, 0xf9, 0xb3,
 104                 0x79, 0x73, 0xf6, 0x22, 0xa4, 0x3d, 0x14, 0xa6,
 105                 0x59, 0x9b, 0x1f, 0x65, 0x4c, 0xb4, 0x5a, 0x74,
 106                 0xe3, 0x55, 0xa5
 107         };
 108         crypto_box_curve25519xsalsa20poly1305(c, m, 163, nonce, bobpk, alicesk);
 109         for (i = 16; i < 163; ++i) {
 110                 if (c[i] != result[i - 16])
 111                         panic("PANIC: crypto selftest failed at pos %d "
 112                               "(%u != %u)! :-(\n", i, c[i], result[i]);
 113         }
 114 }
 115
 116 static int hexdigit(char x)
 117 {
 118         if (x >= '0' && x <= '9')
 119                 return x - '0';
 120         if (x >= 'a' && x <= 'f')
 121                 return 10 + (x - 'a');
 122         if (x >= 'A' && x <= 'F')
 123                 return 10 + (x - 'A');
 124         return -1;
 125 }
 126
 127 int curve25519_pubkey_hexparse_32(unsigned char *y, size_t ylen,
 128                                   const char *x, size_t len)
 129 {
 130         int seen_digits = 0, seen_colons = 0;
 131         if (!x || !y || ylen != 32)
 132                 return 0;
 133         while (len > 0) {
 134                 int digit0, digit1;
 135                 if (x[0] == '\0')
 136                         break;
 137                 if (x[0] == ':') {
 138                         seen_colons++;
 139                         --len;
 140                         x++;
 141                         continue;
 142                 }
 143                 digit0 = hexdigit(x[0]);
 144                 if (digit0 == -1)
 145                         return 0;
 146                 digit1 = hexdigit(x[1]);
 147                 if (digit1 == -1)
 148                         return 0;
 149                 *y++ = digit1 + 16 * digit0;
 150                 seen_digits++;
 151                 --len;
 152                 x += 2;
 153         }
 154         if (x[0] != '\0' || seen_digits != 32 || seen_colons != 31)
 155                 return 0;
 156         return 1;
 157 }
 158
 159 int curve25519_alloc_or_maybe_die(struct curve25519_struct *c)
 160 {
 161         if (!c)
 162                 return -EINVAL;
 163         c->enc_buf_size = TUNBUFF_SIZ;
 164         c->dec_buf_size = TUNBUFF_SIZ;
 165         c->enc_buf = xmalloc_aligned(c->enc_buf_size, 16);
 166         c->dec_buf = xmalloc_aligned(c->dec_buf_size, 16);
 167         spinlock_init(&c->enc_lock);
 168         spinlock_init(&c->dec_lock);
 169         mt_init_by_seed_rand_array();
 170         return 0;
 171 }
 172
 173 void curve25519_free(void *vc)
 174 {
 175         struct curve25519_struct *c = vc;
 176         if (!c)
 177                 return;
 178         memset(c->enc_buf, 0, c->enc_buf_size);
 179         memset(c->dec_buf, 0, c->dec_buf_size);
 180         xfree(c->enc_buf);
 181         xfree(c->dec_buf);
 182         spinlock_destroy(&c->enc_lock);
 183         spinlock_destroy(&c->dec_lock);
 184 }
 185
 186 int curve25519_proto_init(struct curve25519_proto *p, unsigned char *pubkey_remote,
 187                           size_t len, char *home, int server)
 188 {
 189         int fd;
 190         ssize_t ret;
 191         char path[PATH_MAX];
 192         unsigned char secretkey_own[crypto_box_curve25519xsalsa20poly1305_SECRETKEYBYTES] = { 0 };
 193         unsigned char publickey_own[crypto_box_curve25519xsalsa20poly1305_PUBLICKEYBYTES] = { 0 };
 194         if (!pubkey_remote ||
 195             len != crypto_box_curve25519xsalsa20poly1305_PUBLICKEYBYTES)
 196                 return -EINVAL;
 197         memset(path, 0, sizeof(path));
 198         slprintf(path, sizeof(path), "%s/%s", home, FILE_PRIVKEY);
 199         fd = open(path, O_RDONLY);
 200         if (fd < 0)
 201                 panic("Cannot open privkey file!\n");
 202         ret = read(fd, secretkey_own, sizeof(secretkey_own));
 203         if (ret != sizeof(secretkey_own)) {
 204                 xmemset(secretkey_own, 0, sizeof(secretkey_own));
 205                 panic("Cannot read private key!\n");
 206         }
 207         close(fd);
 208         crypto_scalarmult_curve25519_base(publickey_own, secretkey_own);
 209         if (!crypto_verify_32(publickey_own, pubkey_remote)) {
 210                 xmemset(secretkey_own, 0, sizeof(secretkey_own));
 211                 xmemset(publickey_own, 0, sizeof(publickey_own));
 212                 panic("PANIC: remote end has same public key as you have!!!\n");
 213         }
 214         crypto_box_beforenm(p->key, pubkey_remote, secretkey_own);
 215         xmemset(p->enonce, 0, sizeof(p->enonce));
 216         xmemset(p->dnonce, 0, sizeof(p->dnonce));
 217         xmemset(secretkey_own, 0, sizeof(secretkey_own));
 218         xmemset(publickey_own, 0, sizeof(publickey_own));
 219         return 0;
 220 }
 221
 222 ssize_t curve25519_encode(struct curve25519_struct *c, struct curve25519_proto *p,
 223                           unsigned char *plaintext, size_t size,
 224                           unsigned char **chipertext)
 225 {
 226         int ret, i;
 227         ssize_t done = size;
 228         struct taia packet_taia;
 229         spinlock_lock(&c->enc_lock);
 230         if (unlikely(size > c->enc_buf_size)) {
 231                 spinlock_unlock(&c->enc_lock);
 232                 return -ENOMEM;
 233         }
 234         taia_now(&packet_taia);
 235         taia_pack(p->enonce + NONCE_OFFSET, &packet_taia);
 236         memset(c->enc_buf, 0, c->enc_buf_size);
 237         ret = crypto_box_afternm(c->enc_buf, plaintext, size,
 238                                  p->enonce, p->key);
 239         if (unlikely(ret)) {
 240                 spinlock_unlock(&c->enc_lock);
 241                 return -EIO;
 242         }
 243         memcpy(c->enc_buf + crypto_box_boxzerobytes - NONCE_LENGTH,
 244                p->enonce + NONCE_OFFSET, NONCE_LENGTH);
 245         for (i = 0; i < crypto_box_boxzerobytes - NONCE_LENGTH; ++i)
 246                 c->enc_buf[i] = (uint8_t) mt_rand_int32();
 247         (*chipertext) = c->enc_buf;
 248         spinlock_unlock(&c->enc_lock);
 249         return done;
 250 }
 251
 252 ssize_t curve25519_decode(struct curve25519_struct *c, struct curve25519_proto *p,
 253                           unsigned char *chipertext, size_t size,
 254                           unsigned char **plaintext, struct taia *arrival_taia)
 255 {
 256         int ret;
 257         ssize_t done = size;
 258         struct taia packet_taia, __arrival_taia;
 259         spinlock_lock(&c->dec_lock);
 260         if (unlikely(size > c->dec_buf_size)) {
 261                 spinlock_unlock(&c->dec_lock);
 262                 return -ENOMEM;
 263         }
 264         if (unlikely(size < crypto_box_boxzerobytes + NONCE_LENGTH)) {
 265                 spinlock_unlock(&c->dec_lock);
 266                 return 0;
 267         }
 268         if (arrival_taia == NULL) {
 269                 taia_now(&__arrival_taia);
 270                 arrival_taia = &__arrival_taia;
 271         }
 272         taia_unpack(chipertext + crypto_box_boxzerobytes - NONCE_LENGTH,
 273                     &packet_taia);
 274         if (is_good_taia(arrival_taia, &packet_taia) == 0) {
 275                 /* Ignoring packet */
 276                 spinlock_unlock(&c->dec_lock);
 277                 syslog(LOG_ERR, "Bad packet time! Dropping connection!\n");
 278                 return 0;
 279         }
 280         memcpy(p->dnonce + NONCE_OFFSET,
 281                chipertext + crypto_box_boxzerobytes - NONCE_LENGTH,
 282                NONCE_LENGTH);
 283         memset(c->dec_buf, 0, c->dec_buf_size);
 284         ret = crypto_box_open_afternm(c->dec_buf, chipertext, size,
 285                                       p->dnonce, p->key);
 286         if (unlikely(ret)) {
 287                 spinlock_unlock(&c->enc_lock);
 288                 return -EIO;
 289         }
 290         (*plaintext) = c->dec_buf;
 291         spinlock_unlock(&c->dec_lock);
 292         return done;
 293 }
 294