mirror of
https://github.com/ntop/n2n.git
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114 lines
4.2 KiB
C
114 lines
4.2 KiB
C
/**
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* (C) 2007-20 - ntop.org and contributors
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not see see <http://www.gnu.org/licenses/>
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*
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*/
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#include "n2n.h"
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#define HASH_FIND_COMMUNITY(head, name, out) HASH_FIND_STR(head, name, out)
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/* ********************************************************************** */
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uint32_t packet_header_decrypt (uint8_t packet[], uint16_t packet_len,
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char * community_name, he_context_t * ctx,
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he_context_t * ctx_iv, uint64_t * stamp, uint16_t * checksum) {
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// assemble IV
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// the last four are ASCII "n2n!" and do not get overwritten
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uint8_t iv[16] = { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
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0x00, 0x00, 0x00, 0x00, 0x6E, 0x32, 0x6E, 0x21 };
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// the first 96 bits of the packet get padded with ASCII "n2n!"
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// to full 128 bit IV
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memcpy (iv, packet, 12);
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// extract time stamp (first 64 bit) and checksum (last 16 bit) blended in IV
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speck_he_iv_decrypt (iv, (speck_context_t*)ctx_iv);
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*checksum = be16toh (((uint16_t*)iv)[5]);
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*stamp = be64toh (((uint64_t*)iv)[0]);
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memcpy (iv, packet, 12);
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// try community name as possible key and check for magic bytes
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uint32_t magic = 0x6E326E00; // ="n2n_"
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uint32_t test_magic;
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// check for magic bytes and reasonable value in header len field
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// so, as a first step, decrypt 4 bytes only starting at byte 12
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speck_he ((uint8_t*)&test_magic, &packet[12], 4, iv, (speck_context_t*)ctx);
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test_magic = be32toh (test_magic);
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if( (((test_magic >> 8) << 8) == magic) // check the thre uppermost bytes
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&& (((uint8_t)test_magic) <= packet_len) // lowest 8 bit of test_magic are header_len
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) {
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// decrypt the complete header
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speck_he (&packet[12], &packet[12], (uint8_t)(test_magic) - 12, iv, (speck_context_t*)ctx);
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// restore original packet order
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memcpy (&packet[0], &packet[16], 4);
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memcpy (&packet[4], community_name, N2N_COMMUNITY_SIZE);
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return (1); // successful
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} else
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return (0); // unsuccessful
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}
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/* ********************************************************************** */
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int32_t packet_header_encrypt (uint8_t packet[], uint8_t header_len, he_context_t * ctx,
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he_context_t * ctx_iv, uint64_t stamp, uint16_t checksum) {
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uint8_t iv[16];
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uint16_t *iv16 = (uint16_t*)&iv;
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uint32_t *iv32 = (uint32_t*)&iv;
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uint64_t *iv64 = (uint64_t*)&iv;
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const uint32_t magic = 0x6E326E21; // = ASCII "n2n!"
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if(header_len < 20) {
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traceEvent(TRACE_DEBUG, "packet_header_encrypt dropped a packet too short to be valid.");
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return (-1);
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}
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memcpy (&packet[16], &packet[00], 4);
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iv64[0] = htobe64 (stamp);
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iv16[4] = n2n_rand ();
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iv16[5] = htobe16 (checksum);
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iv32[3] = htobe32 (magic);
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// blend checksum into 96-bit IV
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speck_he_iv_encrypt (iv, (speck_context_t*)ctx_iv);
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memcpy (packet, iv, 16);
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packet[15] = header_len;
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speck_he (&packet[12], &packet[12], header_len - 12, iv, (speck_context_t*)ctx);
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return (0);
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}
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/* ********************************************************************** */
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void packet_header_setup_key (const char * community_name, he_context_t ** ctx,
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he_context_t ** ctx_iv) {
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uint8_t key[16];
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pearson_hash_128 (key, (uint8_t*)community_name, N2N_COMMUNITY_SIZE);
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*ctx = (he_context_t*)calloc(1, sizeof (speck_context_t));
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speck_expand_key_he (key, (speck_context_t*)*ctx);
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// hash again and use last 96 bit (skipping 4 bytes) as key for IV encryption
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// REMOVE as soon as checksum and replay protection get their own fields
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pearson_hash_128 (key, key, sizeof (key));
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*ctx_iv = (he_context_t*)calloc(1, sizeof (speck_context_t));
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speck_expand_key_he_iv (&key[4], (speck_context_t*)*ctx_iv);
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}
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