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 <pwd.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 "ioops.h"
  24 #include "rnd.h"
  25 #include "die.h"
  26 #include "str.h"
  27 #include "curvetun.h"
  28 #include "locking.h"
  29 #include "crypto.h"
  30 #include "config.h"
  31
  32 int curve25519_pubkey_hexparse_32(unsigned char *bin, size_t blen,
  33                                   const char *ascii, size_t alen)
  34 {
  35         int ret = sscanf(ascii,
  36                      "%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:"
  37                      "%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:"
  38                      "%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:"
  39                      "%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:%2hhx:%2hhx",
  40                       &bin[0],  &bin[1],  &bin[2],  &bin[3],  &bin[4],
  41                       &bin[5],  &bin[6],  &bin[7],  &bin[8],  &bin[9],
  42                      &bin[10], &bin[11], &bin[12], &bin[13], &bin[14],
  43                      &bin[15], &bin[16], &bin[17], &bin[18], &bin[19],
  44                      &bin[20], &bin[21], &bin[22], &bin[23], &bin[24],
  45                      &bin[25], &bin[26], &bin[27], &bin[28], &bin[29],
  46                      &bin[30], &bin[31]);
  47         return ret == 32;
  48 }
  49
  50 void curve25519_alloc_or_maybe_die(struct curve25519_struct *curve)
  51 {
  52         curve->enc_size = curve->dec_size = TUNBUFF_SIZ;
  53
  54         curve->enc = xmalloc_aligned(curve->enc_size, 16);
  55         curve->dec = xmalloc_aligned(curve->dec_size, 16);
  56
  57         spinlock_init(&curve->enc_lock);
  58         spinlock_init(&curve->dec_lock);
  59 }
  60
  61 void curve25519_free(void *curvep)
  62 {
  63         struct curve25519_struct *curve = curvep;
  64
  65         xzfree(curve->enc, curve->enc_size);
  66         xzfree(curve->dec, curve->dec_size);
  67
  68         spinlock_destroy(&curve->enc_lock);
  69         spinlock_destroy(&curve->dec_lock);
  70 }
  71
  72 void curve25519_proto_init(struct curve25519_proto *proto,
  73                            unsigned char *pubkey_remote, size_t len)
  74 {
  75         int result;
  76         char file[128];
  77         struct passwd *pw = getpwuid(getuid());
  78         unsigned char secretkey_own[crypto_box_sec_key_size];
  79         unsigned char publickey_own[crypto_box_pub_key_size];
  80
  81         fmemset(secretkey_own, 0, sizeof(secretkey_own));
  82         fmemset(publickey_own, 0, sizeof(publickey_own));
  83
  84         if (unlikely(!pubkey_remote || len != sizeof(publickey_own)))
  85                 panic("Invalid argument on curve25519_proto_init!\n");
  86
  87         slprintf(file, sizeof(file), "%s/%s", pw->pw_dir, FILE_PRIVKEY);
  88         read_blob_or_die(file, secretkey_own, sizeof(secretkey_own));
  89
  90         crypto_scalarmult_curve25519_base(publickey_own, secretkey_own);
  91         result = crypto_verify_32(publickey_own, pubkey_remote);
  92
  93         if (result == 0)
  94                 panic("Remote end has same public key as you have!\n");
  95
  96         crypto_box_beforenm(proto->key, pubkey_remote, secretkey_own);
  97
  98         fmemset(proto->enonce, 0, sizeof(proto->enonce));
  99         fmemset(proto->dnonce, 0, sizeof(proto->dnonce));
 100
 101         xmemset(secretkey_own, 0, sizeof(secretkey_own));
 102         xmemset(publickey_own, 0, sizeof(publickey_own));
 103 }
 104
 105 ssize_t curve25519_encode(struct curve25519_struct *curve,
 106                           struct curve25519_proto *proto,
 107                           unsigned char *plaintext, size_t size,
 108                           unsigned char **ciphertext)
 109 {
 110         int ret, i;
 111         ssize_t done = size;
 112         struct taia packet_taia;
 113
 114         spinlock_lock(&curve->enc_lock);
 115         if (unlikely(size > curve->enc_size)) {
 116                 done = -ENOMEM;
 117                 goto out;
 118         }
 119
 120         taia_now(&packet_taia);
 121         taia_pack(NONCE_EDN_OFFSET(proto->enonce), &packet_taia);
 122
 123         fmemset(curve->enc, 0, curve->enc_size);
 124         ret = crypto_box_afternm(curve->enc, plaintext, size,
 125                                  proto->enonce, proto->key);
 126         if (unlikely(ret)) {
 127                 done = -EIO;
 128                 goto out;
 129         }
 130
 131         fmemcpy(NONCE_PKT_OFFSET(curve->enc),
 132                 NONCE_EDN_OFFSET(proto->enonce), NONCE_LENGTH);
 133         for (i = 0; i < NONCE_RND_LENGTH; ++i)
 134                 curve->enc[i] = (uint8_t) secrand();
 135
 136         (*ciphertext) = curve->enc;
 137 out:
 138         spinlock_unlock(&curve->enc_lock);
 139         return done;
 140 }
 141
 142 ssize_t curve25519_decode(struct curve25519_struct *curve,
 143                           struct curve25519_proto *proto,
 144                           unsigned char *ciphertext, size_t size,
 145                           unsigned char **plaintext,
 146                           struct taia *arrival_taia)
 147 {
 148         int ret;
 149         ssize_t done = size;
 150         struct taia packet_taia, tmp_taia;
 151
 152         spinlock_lock(&curve->dec_lock);
 153         if (unlikely(size > curve->dec_size || size < NONCE_ALL_LENGTH)) {
 154                 done = size < NONCE_ALL_LENGTH ? 0 : -ENOMEM;
 155                 goto out;
 156         }
 157
 158         if (arrival_taia == NULL) {
 159                 taia_now(&tmp_taia);
 160                 arrival_taia = &tmp_taia;
 161         }
 162
 163         taia_unpack(NONCE_PKT_OFFSET(ciphertext), &packet_taia);
 164         if (taia_looks_good(arrival_taia, &packet_taia) == 0) {
 165                 done = 0;
 166                 goto out;
 167         }
 168
 169         fmemcpy(NONCE_EDN_OFFSET(proto->dnonce),
 170                 NONCE_PKT_OFFSET(ciphertext), NONCE_LENGTH);
 171         fmemset(curve->dec, 0, curve->dec_size);
 172
 173         ret = crypto_box_open_afternm(curve->dec, ciphertext, size,
 174                                       proto->dnonce, proto->key);
 175         if (unlikely(ret)) {
 176                 done = -EIO;
 177                 goto out;
 178         }
 179
 180         (*plaintext) = curve->dec;
 181 out:
 182         spinlock_unlock(&curve->dec_lock);
 183         return done;
 184 }