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#include <crypto/aes_gcm.h>
#include <openssl/evp.h>
#include <openssl/rand.h>
#include <openssl/err.h>
#include <string.h>
b32
aes_gcm_key_init_random(AesGcmKey *key)
{
int success = RAND_priv_bytes(key->buff, sizeof(key->buff));
return success == 1;
}
b32
aes_gcm_iv_init(AesGcmIv *iv)
{
if (RAND_priv_bytes(iv->salt, sizeof(iv->salt)) < 0) {
return false;
}
u32 *counter = (u32*)iv->counter;
assert(sizeof(*counter) == sizeof(iv->counter));
*counter = 0;
return true;
}
void
aes_gcm_iv_advance(AesGcmIv *iv)
{
u32 *counter = (u32*)iv->counter;
assert(sizeof(*counter) == sizeof(iv->counter));
*counter += 1;
if (*counter == U32_MAX) {
exit(0); // Todo: make new keys
}
}
b32
aes_gcm_decrypt(AesGcmKey *key, AesGcmIv *iv,
u8 *plaintext, u8 *ciphertext, i32 ciphertext_len,
u8 *tag, i32 tag_len)
{
EVP_CIPHER_CTX *ctx;
i32 plaintext_len = 0;
i32 len = 0;
ctx = EVP_CIPHER_CTX_new();
if (!ctx) {
printf("EVP_CIPHER_CTX_new() failed\n");
return false;
}
if (EVP_DecryptInit_ex(ctx, EVP_aes_256_gcm(), 0, 0, 0) != 1) {
printf("EVP_DecryptInit_ex() failed\n");
EVP_CIPHER_CTX_free(ctx);
return false;
}
if(EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_SET_IVLEN, 12, 0) != 1) {
printf("EVP_CIPHER_CTX_ctrl setting iv length failed\n");
EVP_CIPHER_CTX_free(ctx);
return false;
}
if(EVP_DecryptInit_ex(ctx, 0, 0, key->buff, (u8*)iv) != 1) {
printf("EVP_DecryptInit_ex with key and iv failed\n");
EVP_CIPHER_CTX_free(ctx);
return false;
}
if (EVP_DecryptUpdate(ctx, plaintext, &len, ciphertext, ciphertext_len) != 1) {
printf("EVP_DecryptUpdate() failed\n");
EVP_CIPHER_CTX_free(ctx);
return false;
}
plaintext_len += len;
if(EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_SET_TAG, tag_len, tag) != 1) {
printf("EVP_CIPHER_CTX_ctrl setting tag failed\n");
EVP_CIPHER_CTX_free(ctx);
return false;
}
if (EVP_DecryptFinal_ex(ctx, plaintext + len, &len) != 1) {
ERR_print_errors_fp(stderr);
printf("EVP_DecryptFinal_ex failed\n");
EVP_CIPHER_CTX_free(ctx);
return false;
}
plaintext_len += len;
if (plaintext_len != ciphertext_len) {
printf("aes_gcm_decrypt failed: decrypted_len != len\n");
EVP_CIPHER_CTX_free(ctx);
return false;
}
EVP_CIPHER_CTX_free(ctx);
aes_gcm_iv_advance(iv);
return true;
}
b32
aes_gcm_encrypt(AesGcmKey *key, AesGcmIv *iv,
u8 *ciphertext, u8 *plaintext, i32 plaintext_len,
u8 *tag_out, i32 tag_out_len)
{
EVP_CIPHER_CTX *ctx;
i32 ciphertext_len = 0;
i32 len = 0;
ctx = EVP_CIPHER_CTX_new();
if (!ctx) {
printf("EVP_CIPHER_CTX_new() failed\n");
return false;
}
if (EVP_EncryptInit_ex(ctx, EVP_aes_256_gcm(), 0, 0, 0) != 1) {
printf("EVP_EncryptInit_ex() failed\n");
EVP_CIPHER_CTX_free(ctx);
return false;
}
if(EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_SET_IVLEN, 12, 0) != 1) {
printf("EVP_CIPHER_CTX_ctrl setting iv length failed\n");
EVP_CIPHER_CTX_free(ctx);
return false;
}
if (EVP_EncryptInit_ex(ctx, EVP_aes_256_gcm(), 0, key->buff, (u8*)iv) != 1) {
printf("EVP_EncryptInit_ex() failed\n");
EVP_CIPHER_CTX_free(ctx);
return false;
}
if (EVP_EncryptUpdate(ctx, ciphertext, &len, plaintext, plaintext_len) != 1) {
printf("EVP_EncryptUpdate failed\n");
EVP_CIPHER_CTX_free(ctx);
return false;
}
ciphertext_len += len;
if (EVP_EncryptFinal_ex(ctx, plaintext + len, &len) != 1) {
printf("EVP_EncryptFinal_ex failed\n");
EVP_CIPHER_CTX_free(ctx);
return false;
}
ciphertext_len += len;
if (ciphertext_len != plaintext_len) {
printf("aes_gcm_encrypt failed: ciphertext_len = %d, plaintext_len = %d\n", ciphertext_len, plaintext_len);
EVP_CIPHER_CTX_free(ctx);
return false;
}
if (EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_GET_TAG, tag_out_len, tag_out) != 1) {
printf("EVP_CIPHER_CTX_ctrl failed\n");
EVP_CIPHER_CTX_free(ctx);
return false;
}
EVP_CIPHER_CTX_free(ctx);
aes_gcm_iv_advance(iv);
return true;
}
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