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dnscap/plugins/cryptopan/cryptopan.c
Daniel Baumann 14c3c7c9ac
Merging upstream version 2.1.1. 
Signed-off-by: Daniel Baumann <daniel@debian.org>
2025-02-08 12:06:41 +01:00

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/*
* Copyright (c) 2018-2023, OARC, Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. Neither the name of the copyright holder nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
/*
* Crypto-PAn encryption based on submitted extension by David Stott (Lucent)
* https://www.cc.gatech.edu/computing/Networking/projects/cryptopan/lucent.shtml
*/
#include "config.h"
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include "dnscap_common.h"
#if defined(HAVE_LIBCRYPTO) && defined(HAVE_OPENSSL_CONF_H) && defined(HAVE_OPENSSL_ERR_H) && defined(HAVE_OPENSSL_EVP_H)
#include <openssl/conf.h>
#include <openssl/evp.h>
#include <openssl/err.h>
#define USE_OPENSSL 1
#endif
static set_iaddr_t cryptopan_set_iaddr = 0;
static logerr_t* logerr;
static int only_clients = 0, only_servers = 0, dns_port = 53, encrypt_v6 = 0, decrypt = 0;
static unsigned char key[16];
static unsigned char iv[16];
static unsigned char pad[16];
#ifdef USE_OPENSSL
static EVP_CIPHER_CTX* ctx = 0;
#endif
enum plugin_type cryptopan_type()
{
return plugin_filter;
}
void usage(const char* msg)
{
fprintf(stderr, "cryptopan.so usage error: %s\n", msg);
exit(1);
}
void cryptopan_usage()
{
fprintf(stderr,
"\ncryptopan.so options:\n"
"\t-? print these instructions and exit\n"
"\t-k <key> A 16 character long key\n"
"\t-K <file> Read the 16 first bytes from file and use as key\n"
"\t-i <key> A 16 character long Initialisation Vector (IV)\n"
"\t-I <file> Read the 16 first bytes from file and use as IV\n"
"\t-a <key> A 16 character long padding\n"
"\t-A <file> Read the 16 first bytes from file and use as padding\n"
"\t-D Decrypt IP addresses\n"
"\t-c Only en/de-crypt clients (port != 53)\n"
"\t-s Only en/de-crypt servers (port == 53)\n"
"\t-p <port> Set port for -c/-s, default 53\n"
"\t-6 En/de-crypt IPv6 addresses, not default or recommended\n");
}
void cryptopan_extension(int ext, void* arg)
{
switch (ext) {
case DNSCAP_EXT_SET_IADDR:
cryptopan_set_iaddr = (set_iaddr_t)arg;
break;
}
}
void cryptopan_getopt(int* argc, char** argv[])
{
int c, got_key = 0, got_iv = 0, got_pad = 0;
unsigned long ul;
char* p;
while ((c = getopt(*argc, *argv, "?k:K:i:I:a:A:Dcsp:6")) != EOF) {
switch (c) {
case 'k':
if (strlen(optarg) != 16) {
usage("key must be 16 characters long");
}
memcpy(key, optarg, 16);
got_key = 1;
break;
case 'K': {
int fd;
ssize_t r;
if ((fd = open(optarg, O_RDONLY)) < 0) {
perror("open()");
usage("unable to open key file");
}
if ((r = read(fd, key, 16)) < 0) {
perror("read()");
usage("unable to read from key file");
}
if (r != 16) {
usage("unable to read 16 bytes from key file");
}
close(fd);
got_key = 1;
break;
}
case 'i':
if (strlen(optarg) != 16) {
usage("IV must be 16 characters long");
}
memcpy(iv, optarg, 16);
got_iv = 1;
break;
case 'I': {
int fd;
ssize_t r;
if ((fd = open(optarg, O_RDONLY)) < 0) {
perror("open()");
usage("unable to open IV file");
}
if ((r = read(fd, iv, 16)) < 0) {
perror("read()");
usage("unable to read from IV file");
}
if (r != 16) {
usage("unable to read 16 bytes from IV file");
}
close(fd);
got_iv = 1;
break;
}
case 'a':
if (strlen(optarg) != 16) {
usage("padding must be 16 characters long");
}
memcpy(pad, optarg, 16);
got_pad = 1;
break;
case 'A': {
int fd;
ssize_t r;
if ((fd = open(optarg, O_RDONLY)) < 0) {
perror("open()");
usage("unable to open padding file");
}
if ((r = read(fd, pad, 16)) < 0) {
perror("read()");
usage("unable to read from padding file");
}
if (r != 16) {
usage("unable to read 16 bytes from padding file");
}
close(fd);
got_pad = 1;
break;
}
case 'D':
decrypt = 1;
break;
case 'c':
only_clients = 1;
break;
case 's':
only_servers = 1;
break;
case 'p':
ul = strtoul(optarg, &p, 0);
if (*p != '\0' || ul < 1U || ul > 65535U)
usage("port must be an integer 1..65535");
dns_port = (unsigned)ul;
break;
case '6':
encrypt_v6 = 1;
break;
case '?':
cryptopan_usage();
if (!optopt || optopt == '?') {
exit(0);
}
// fallthrough
default:
exit(1);
}
}
if (!got_key || !got_iv || !got_pad) {
usage("must have key (-k/-K), IV (-i/-I) and padding (-a/-A)");
}
#ifdef USE_OPENSSL
if (!(ctx = EVP_CIPHER_CTX_new())) {
usage("unable to create openssl cipher context");
}
if (!EVP_CipherInit_ex(ctx, EVP_aes_128_ecb(), NULL, key, iv, 1)) {
unsigned long e = ERR_get_error();
fprintf(stderr, "%s:%s:%s\n", ERR_lib_error_string(e), ERR_func_error_string(e), ERR_reason_error_string(e));
usage("unable to initialize AES128 cipher");
}
EVP_CIPHER_CTX_set_padding(ctx, 0);
{
unsigned char outbuf[16 + EVP_MAX_BLOCK_LENGTH];
int outlen = 0;
if (!EVP_CipherUpdate(ctx, outbuf, &outlen, pad, 16)) {
fprintf(stderr, "cryptopan.so: error encrypting padding: %s\n", ERR_reason_error_string(ERR_get_error()));
exit(1);
}
if (outlen != 16) {
fprintf(stderr, "cryptopan.so: error encrypted padding is not 16 bytes\n");
exit(1);
}
memcpy(&pad, outbuf, 16);
}
#else
usage("no openssl support built in, can't encrypt IP addresses");
#endif
if (only_clients && only_servers) {
usage("-c and -s options are mutually exclusive");
}
}
int cryptopan_start(logerr_t* a_logerr)
{
logerr = a_logerr;
return 0;
}
void cryptopan_stop()
{
#ifdef USE_OPENSSL
EVP_CIPHER_CTX_free(ctx);
ctx = 0;
#endif
}
int cryptopan_open(my_bpftimeval ts)
{
return 0;
}
int cryptopan_close(my_bpftimeval ts)
{
return 0;
}
#ifdef USE_OPENSSL
struct input {
union {
unsigned char input[16];
uint32_t ui32;
} u;
};
struct output {
union {
unsigned char outbuf[16 + EVP_MAX_BLOCK_LENGTH];
uint32_t ui32;
} u;
};
static inline void _encrypt(uint32_t* in)
{
struct input input;
struct output output;
int outlen = 0, pos;
uint32_t orig, result = 0, pad4b, mask = 0;
memcpy(input.u.input, pad, 16);
orig = ntohl(*in);
memcpy(&pad4b, pad, 4);
// First pass with padding only
input.u.ui32 = htonl(pad4b);
if (!EVP_CipherUpdate(ctx, output.u.outbuf, &outlen, input.u.input, 16)) {
fprintf(stderr, "cryptopan.so: error encrypting: %s\n", ERR_reason_error_string(ERR_get_error()));
exit(1);
}
if (outlen != 16) {
fprintf(stderr, "cryptopan.so: error encrypted result is not 16 bytes\n");
exit(1);
}
result |= ntohl(output.u.ui32) & 0x80000000;
mask >>= 1;
mask |= 0x80000000;
for (pos = 1; pos < 32; pos++) {
input.u.ui32 = htonl(((pad4b << pos) | (pad4b >> (32 - pos))) ^ (orig & mask));
if (!EVP_CipherUpdate(ctx, output.u.outbuf, &outlen, input.u.input, 16)) {
fprintf(stderr, "cryptopan.so: error encrypting: %s\n", ERR_reason_error_string(ERR_get_error()));
exit(1);
}
if (outlen != 16) {
fprintf(stderr, "cryptopan.so: error encrypted result is not 16 bytes\n");
exit(1);
}
result |= (ntohl(output.u.ui32) & 0x80000000) >> pos;
mask >>= 1;
mask |= 0x80000000;
}
*in = htonl(result ^ orig);
}
static inline void _decrypt(uint32_t* in)
{
struct input input;
struct output output;
int outlen = 0, pos;
uint32_t orig, pad4b, mask = 0;
memcpy(input.u.input, pad, 16);
orig = ntohl(*in);
memcpy(&pad4b, pad, 4);
// First pass with padding only
input.u.ui32 = htonl(pad4b);
if (!EVP_CipherUpdate(ctx, output.u.outbuf, &outlen, input.u.input, 16)) {
fprintf(stderr, "cryptopan.so: error encrypting: %s\n", ERR_reason_error_string(ERR_get_error()));
exit(1);
}
if (outlen != 16) {
fprintf(stderr, "cryptopan.so: error encrypted result is not 16 bytes\n");
exit(1);
}
orig ^= ntohl(output.u.ui32) & 0x80000000;
mask >>= 1;
mask |= 0x80000000;
for (pos = 1; pos < 32; pos++) {
input.u.ui32 = htonl(((pad4b << pos) | (pad4b >> (32 - pos))) ^ (orig & mask));
if (!EVP_CipherUpdate(ctx, output.u.outbuf, &outlen, input.u.input, 16)) {
fprintf(stderr, "cryptopan.so: error encrypting: %s\n", ERR_reason_error_string(ERR_get_error()));
exit(1);
}
if (outlen != 16) {
fprintf(stderr, "cryptopan.so: error encrypted result is not 16 bytes\n");
exit(1);
}
orig ^= (ntohl(output.u.ui32) & 0x80000000) >> pos;
mask >>= 1;
mask |= 0x80000000;
}
*in = htonl(orig);
}
#endif
int cryptopan_filter(const char* descr, iaddr* from, iaddr* to, uint8_t proto, unsigned flags,
unsigned sport, unsigned dport, my_bpftimeval ts,
const u_char* pkt_copy, const unsigned olen,
const u_char* payload, const unsigned payloadlen)
{
#ifdef USE_OPENSSL
for (;;) {
if (only_clients && sport == dns_port) {
if (sport != dport) {
from = 0;
break;
}
}
if (only_servers && sport != dns_port) {
from = 0;
break;
}
switch (from->af) {
case AF_INET:
decrypt ? _decrypt((uint32_t*)&from->u.a4) : _encrypt((uint32_t*)&from->u.a4);
break;
case AF_INET6:
if (encrypt_v6) {
if (decrypt) {
_decrypt((uint32_t*)&from->u.a6);
_decrypt(((uint32_t*)&from->u.a6) + 1); // lgtm [cpp/suspicious-pointer-scaling]
_decrypt(((uint32_t*)&from->u.a6) + 2); // lgtm [cpp/suspicious-pointer-scaling]
_decrypt(((uint32_t*)&from->u.a6) + 3); // lgtm [cpp/suspicious-pointer-scaling]
} else {
_encrypt((uint32_t*)&from->u.a6);
_encrypt(((uint32_t*)&from->u.a6) + 1); // lgtm [cpp/suspicious-pointer-scaling]
_encrypt(((uint32_t*)&from->u.a6) + 2); // lgtm [cpp/suspicious-pointer-scaling]
_encrypt(((uint32_t*)&from->u.a6) + 3); // lgtm [cpp/suspicious-pointer-scaling]
}
break;
}
default:
from = 0;
break;
}
break;
}
for (;;) {
if (only_clients && dport == dns_port) {
if (dport != sport) {
to = 0;
break;
}
}
if (only_servers && dport != dns_port) {
to = 0;
break;
}
switch (to->af) {
case AF_INET:
decrypt ? _decrypt((uint32_t*)&to->u.a4) : _encrypt((uint32_t*)&to->u.a4);
break;
case AF_INET6:
if (encrypt_v6) {
if (decrypt) {
_decrypt((uint32_t*)&to->u.a6);
_decrypt(((uint32_t*)&to->u.a6) + 1); // lgtm [cpp/suspicious-pointer-scaling]
_decrypt(((uint32_t*)&to->u.a6) + 2); // lgtm [cpp/suspicious-pointer-scaling]
_decrypt(((uint32_t*)&to->u.a6) + 3); // lgtm [cpp/suspicious-pointer-scaling]
} else {
_encrypt((uint32_t*)&to->u.a6);
_encrypt(((uint32_t*)&to->u.a6) + 1); // lgtm [cpp/suspicious-pointer-scaling]
_encrypt(((uint32_t*)&to->u.a6) + 2); // lgtm [cpp/suspicious-pointer-scaling]
_encrypt(((uint32_t*)&to->u.a6) + 3); // lgtm [cpp/suspicious-pointer-scaling]
}
break;
}
default:
to = 0;
break;
}
break;
}
if (cryptopan_set_iaddr && (from || to)) {
cryptopan_set_iaddr(from, to);
}
#endif
return 0;
}
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