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/* wsgcrypt.c
* Helper functions for libgcrypt
* By Erik de Jong <erikdejong@gmail.com>
* Copyright 2017 Erik de Jong
*
* Wireshark - Network traffic analyzer
* By Gerald Combs <gerald@wireshark.org>
* Copyright 1998 Gerald Combs
*
* SPDX-License-Identifier: GPL-2.0+
*/
#include "wsgcrypt.h"
gcry_error_t ws_hmac_buffer(int algo, void *digest, const void *buffer, size_t length, const void *key, size_t keylen)
{
gcry_md_hd_t hmac_handle;
gcry_error_t result = gcry_md_open(&hmac_handle, algo, GCRY_MD_FLAG_HMAC);
if (result) {
return result;
}
result = gcry_md_setkey(hmac_handle, key, keylen);
if (result) {
gcry_md_close(hmac_handle);
return result;
}
gcry_md_write(hmac_handle, buffer, length);
memcpy(digest, gcry_md_read(hmac_handle, 0), gcry_md_get_algo_dlen(algo));
gcry_md_close(hmac_handle);
return GPG_ERR_NO_ERROR;
}
void crypt_des_ecb(guint8 *output, const guint8 *buffer, const guint8 *key56)
{
guint8 key64[8];
gcry_cipher_hd_t handle;
memset(output, 0x00, 8);
/* Transform 56 bits key into 64 bits DES key */
key64[0] = key56[0];
key64[1] = (key56[0] << 7) | (key56[1] >> 1);
key64[2] = (key56[1] << 6) | (key56[2] >> 2);
key64[3] = (key56[2] << 5) | (key56[3] >> 3);
key64[4] = (key56[3] << 4) | (key56[4] >> 4);
key64[5] = (key56[4] << 3) | (key56[5] >> 5);
key64[6] = (key56[5] << 2) | (key56[6] >> 6);
key64[7] = (key56[6] << 1);
if (gcry_cipher_open(&handle, GCRY_CIPHER_DES, GCRY_CIPHER_MODE_ECB, 0)) {
return;
}
if (gcry_cipher_setkey(handle, key64, 8)) {
gcry_cipher_close(handle);
return;
}
gcry_cipher_encrypt(handle, output, 8, buffer, 8);
gcry_cipher_close(handle);
}
size_t rsa_decrypt_inplace(const guint len, guchar* data, gcry_sexp_t pk, gboolean pkcs1_padding, char **err)
{
gint rc = 0;
size_t decr_len = 0, i = 0;
gcry_sexp_t s_data = NULL, s_plain = NULL;
gcry_mpi_t encr_mpi = NULL, text = NULL;
*err = NULL;
/* create mpi representation of encrypted data */
rc = gcry_mpi_scan(&encr_mpi, GCRYMPI_FMT_USG, data, len, NULL);
if (rc != 0 ) {
*err = g_strdup_printf("can't convert data to mpi (size %d):%s", len, gcry_strerror(rc));
return 0;
}
/* put the data into a simple list */
rc = gcry_sexp_build(&s_data, NULL, "(enc-val(rsa(a%m)))", encr_mpi);
if (rc != 0) {
*err = g_strdup_printf("can't build encr_sexp:%s", gcry_strerror(rc));
decr_len = 0;
goto out;
}
/* pass it to libgcrypt */
rc = gcry_pk_decrypt(&s_plain, s_data, pk);
if (rc != 0)
{
*err = g_strdup_printf("can't decrypt key:%s", gcry_strerror(rc));
decr_len = 0;
goto out;
}
/* convert plain text sexp to mpi format */
text = gcry_sexp_nth_mpi(s_plain, 0, 0);
if (! text) {
*err = g_strdup("can't convert sexp to mpi");
decr_len = 0;
goto out;
}
/* compute size requested for plaintext buffer */
rc = gcry_mpi_print(GCRYMPI_FMT_USG, NULL, 0, &decr_len, text);
if (rc != 0) {
*err = g_strdup_printf("can't compute decr size:%s", gcry_strerror(rc));
decr_len = 0;
goto out;
}
/* sanity check on out buffer */
if (decr_len > len) {
*err = g_strdup_printf("decrypted data is too long ?!? (%" G_GSIZE_MODIFIER "u max %d)", decr_len, len);
decr_len = 0;
goto out;
}
/* write plain text to newly allocated buffer */
rc = gcry_mpi_print(GCRYMPI_FMT_USG, data, len, &decr_len, text);
if (rc != 0) {
*err = g_strdup_printf("can't print decr data to mpi (size %" G_GSIZE_MODIFIER "u):%s", decr_len, gcry_strerror(rc));
decr_len = 0;
goto out;
}
if (pkcs1_padding) {
/* strip the padding*/
rc = 0;
for (i = 1; i < decr_len; i++) {
if (data[i] == 0) {
rc = (gint) i+1;
break;
}
}
decr_len -= rc;
memmove(data, data+rc, decr_len);
}
out:
gcry_sexp_release(s_data);
gcry_sexp_release(s_plain);
gcry_mpi_release(encr_mpi);
gcry_mpi_release(text);
return decr_len;
}
/*
* Editor modelines - http://www.wireshark.org/tools/modelines.html
*
* Local variables:
* c-basic-offset: 8
* tab-width: 8
* indent-tabs-mode: t
* End:
*
* vi: set shiftwidth=8 tabstop=8 noexpandtab:
* :indentSize=8:tabSize=8:noTabs=false:
*/
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