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