mirror of https://github.com/ntop/n2n.git
Luca Deri
4 years ago
committed by
GitHub
GitHub
11 changed files with 402 additions and 28 deletions
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#include "header_encryption.h" |
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#include <string.h> |
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#include "random_numbers.h" |
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#include "pearson.h" |
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#include "portable_endian.h" |
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#define HASH_FIND_COMMUNITY(head, name, out) HASH_FIND_STR(head, name, out) |
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uint32_t packet_header_decrypt (uint8_t packet[], uint8_t packet_len, |
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char * community_name, he_context_t * ctx) { |
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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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// alternatively, consider: pearson_hash_128 (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 resonable value in header len field
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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) == magic) |
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&& ((test_magic >> 24) <= packet_len) // (test_masgic >> 24) is header_len
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) { |
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speck_he (&packet[12], &packet[12], (test_magic >> 24) - 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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int8_t packet_header_decrypt_if_required (uint8_t packet[], uint16_t packet_len, |
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struct sn_community *communities) { |
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struct sn_community *c, *tmp; |
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if (packet_len < 20) |
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return (-1); |
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// first, check if header is unenrypted to put it into the fast-lane then
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// the following check is around 99.99962 percent reliable
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// it heavily relies on the structure of packet's common part
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// changes to wire.c:encode/decode_common need to go together with this code
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if ( (packet[19] == (uint8_t)0x00) // null terminated community name
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&& (packet[00] == N2N_PKT_VERSION) // correct packet version
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// && (packet[01] <= N2N_DEFAULT_TTL) // reasonable TTL -- might interfere with hole-punching-related or cli passed higher values ?!
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&& ((be16toh (*(uint16_t*)&(packet[02])) & N2N_FLAGS_TYPE_MASK ) <= MSG_TYPE_MAX_TYPE ) // message type
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&& ( be16toh (*(uint16_t*)&(packet[02])) < N2N_FLAGS_OPTIONS) // flags
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) { |
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// most probably unencrypted
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// make sure, no downgrading happens here and no unencrypted packets can be
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// injected in a community which definitely deals with encrypted headers
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HASH_FIND_COMMUNITY(communities, (char *)&packet[04], c); |
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if (!c) |
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if (c->header_encryption == HEADER_ENCRYPTION_ENABLED) |
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return (-2); |
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// set 'no encryption' in case it is not set yet
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c->header_encryption = HEADER_ENCRYPTION_NONE; |
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c->header_encryption_ctx = NULL; |
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return (HEADER_ENCRYPTION_NONE); |
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} else { |
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// most probably encrypted
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// cycle through the known communities (as keys) to eventually decrypt
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int32_t ret; |
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HASH_ITER (hh, communities, c, tmp) { |
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// skip the definitely unencrypted communities
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if (c->header_encryption == HEADER_ENCRYPTION_NONE) |
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continue; |
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if ( (ret = packet_header_decrypt (packet, packet_len, c->community, c->header_encryption_ctx)) ) { |
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// set 'encrypted' in case it is not set yet
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c->header_encryption = HEADER_ENCRYPTION_ENABLED; |
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// no need to test further communities
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return (HEADER_ENCRYPTION_ENABLED); |
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} |
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} |
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// no matching key/community
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return (-3); |
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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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if (header_len < 20) |
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return (-1); |
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memcpy (&packet[16], &packet[00], 4); |
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uint8_t iv[16]; |
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((uint64_t*)iv)[0] = n2n_rand (); |
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((uint64_t*)iv)[1] = n2n_rand (); |
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const uint32_t magic = 0x006E326E; |
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((uint32_t*)iv)[3] = htobe32 (magic); |
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iv[12] = 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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void packet_header_setup_key (char * community_name, he_context_t * ctx) { |
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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 = calloc(1, sizeof(speck_context_t)); |
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speck_expand_key_he (key, (speck_context_t*)ctx); |
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} |
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@ -0,0 +1,28 @@ |
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#include <stdint.h> |
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#include "n2n.h" |
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#include "speck.h" |
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typedef struct speck_context_t he_context_t; |
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/* Header encryption indicators */ |
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#define HEADER_ENCRYPTION_UNKNOWN 0 |
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#define HEADER_ENCRYPTION_NONE 1 |
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#define HEADER_ENCRYPTION_ENABLED 2 |
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uint32_t packet_header_decrypt (uint8_t packet[], uint8_t packet_len, |
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char * community_name, he_context_t * ctx); |
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int8_t packet_header_decrypt_if_required (uint8_t packet[], uint16_t packet_len, |
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struct sn_community * communities); |
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int32_t packet_header_encrypt (uint8_t packet[], uint8_t header_len, he_context_t * ctx); |
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void packet_header_setup_key (char * community_name, he_context_t * ctx); |
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