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/*
* (C) Copyright 2025
* Stefano Babic, stefano.babic@swupdate.org.
*
* SPDX-License-Identifier: GPL-2.0-only
*/
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include "util.h"
#include "generated/autoconf.h"
/*
* key is 256 bit for max aes_256
* or is a pkcs#11 URL
* or a cms key file name
* keylen is the actual aes key length
* ivt is 128 bit
*/
struct decryption_key {
char *key;
char keylen;
unsigned char *ivt;
cipher_t cipher;
};
static struct decryption_key *decrypt_keys = NULL;
int set_filename_as_key(const char *fname, cipher_t cipher)
{
size_t len;
if (!decrypt_keys) {
decrypt_keys = (struct decryption_key *)calloc(1, sizeof(*decrypt_keys));
if (!decrypt_keys)
return -ENOMEM;
}
len = strlen(fname);
if (decrypt_keys->key)
free(decrypt_keys->key);
decrypt_keys->key = calloc(1, len + 1);
if (!decrypt_keys->key)
return -ENOMEM;
decrypt_keys->keylen = len;
strncpy(decrypt_keys->key, fname, len);
decrypt_keys->cipher = cipher;
return 0;
}
int set_aes_key(const char *key, const char *ivt)
{
int ret;
size_t keylen;
bool is_pkcs11 = false;
/*
* Allocates the global structure just once
*/
if (!decrypt_keys) {
decrypt_keys = (struct decryption_key *)calloc(1, sizeof(*decrypt_keys));
if (!decrypt_keys)
return -ENOMEM;
}
if (strlen(ivt) != (AES_BLK_SIZE*2) || !is_hex_str(ivt)) {
ERROR("Invalid ivt");
return -EINVAL;
}
if (decrypt_keys->ivt)
free(decrypt_keys->ivt);
decrypt_keys->ivt = calloc(1, AES_BLK_SIZE);
if (!decrypt_keys->ivt)
return -ENOMEM;
ret = ascii_to_bin(decrypt_keys->ivt, AES_BLK_SIZE, ivt);
keylen = strlen(key);
if (!strcmp("pkcs11", key)) {
is_pkcs11 = true;
decrypt_keys->keylen = keylen;
} else {
switch (keylen) {
case AES_128_KEY_LEN * 2:
case AES_192_KEY_LEN * 2:
case AES_256_KEY_LEN * 2:
// valid hex string size for AES 128/192/256
decrypt_keys->keylen = keylen / 2;
break;
default:
ERROR("Invalid decrypt_keys length");
return -EINVAL;
}
}
decrypt_keys->cipher = AES_CBC;
if (decrypt_keys->key)
free(decrypt_keys->key);
decrypt_keys->key = calloc(1, keylen + 1);
if (!decrypt_keys->key)
return -ENOMEM;
if (is_pkcs11) {
strncpy(decrypt_keys->key, key, keylen);
} else {
ret |= !is_hex_str(key);
ret |= ascii_to_bin((unsigned char *)decrypt_keys->key, decrypt_keys->keylen, key);
}
if (ret) {
ERROR("Invalid decrypt_keys");
return -EINVAL;
}
return 0;
}
int load_decryption_key(char *fname)
{
FILE *fp;
char *b1 = NULL, *b2 = NULL;
int ret;
#ifdef CONFIG_ASYM_ENCRYPTED_SW_DESCRIPTION
return set_filename_as_key(fname, CMS);
#endif
fp = fopen(fname, "r");
if (!fp)
return -EBADF;
ret = fscanf(fp, "%ms %ms", &b1, &b2);
switch (ret) {
case 2:
DEBUG("Read decryption key and initialization vector from file %s.", fname);
break;
default:
if (b1 != NULL)
free(b1);
fprintf(stderr, "File with decryption key is not in the format <key> <ivt>\n");
fclose(fp);
return -EINVAL;
}
fclose(fp);
ret = set_aes_key(b1, b2);
if (b1 != NULL)
free(b1);
if (b2 != NULL)
free(b2);
if (ret) {
fprintf(stderr, "Keys are invalid\n");
return -EINVAL;
}
return 0;
}
char *swupdate_get_decrypt_key(void) {
if (!decrypt_keys)
return NULL;
return decrypt_keys->key;
}
char swupdate_get_decrypt_keylen(void) {
if (!decrypt_keys)
return -1;
return decrypt_keys->keylen;
}
unsigned char *get_aes_ivt(void) {
if (!decrypt_keys)
return NULL;
return decrypt_keys->ivt;
}
cipher_t swupdate_get_decrypt_cipher(void) {
if (!decrypt_keys)
return AES_UNKNOWN;
return decrypt_keys->cipher;
}
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