/*******************************************************************************
*
* VERIFY_BAD_DECRYPTION
*
* Handles block type 2: This is the third of the three routines, called by
* VERIFY_GCM, which reads the "gcm_test_vectors.bin" file block by block.
* It invokes the AES-GCM library "gcm_auth_decrypt" function to decrypt the
* provided ciphertext, then verifies a AUTHENTICATION FAILURE caused by a
* deliberate mismatch in the ciphertext and/or authentication data which was
* provided by the NIST file(s).
*/
int verify_bad_decryption(
const uchar *key, // pointer to the cipher key
size_t key_len, // byte length of the key
const uchar *iv, // pointer to the initialization vector
size_t iv_len, // byte length of the initialization vector
const uchar *aad, // pointer to the non-ciphered additional data
size_t aad_len, // byte length of the additional AEAD data
const uchar *ct, // pointer to the CORRECT cipher data
size_t ct_len, // byte length of the cipher data
const uchar *tag, // pointer to the CORRECT tag to be generated
size_t tag_len ) // byte length of the tag to be generated
{
int ret = 0; // our return value
gcm_context ctx; // includes the AES context structure
uchar pt_buf[256]; // plaintext results for comparison
gcm_setkey( &ctx, key, (const uint)key_len ); // setup our AES-GCM key
// decrypt the NIST-provided ciphertext and auth tag into the local pt_buf
ret = gcm_auth_decrypt( &ctx, iv, iv_len, aad, aad_len,
ct, pt_buf, ct_len, tag, tag_len);
ret ^= GCM_AUTH_FAILURE; // the fucntion SHOULD FAIL and return the
// GCM_AUTH_FAILURE. We XOR it to verify
gcm_zero_ctx( &ctx );
return ( ret ); // return any error 'XOR' generated above
}
/*
* Packet-oriented decryption for AEAD modes
*/
int cipher_auth_decrypt( cipher_context_t *ctx,
const unsigned char *iv, size_t iv_len,
const unsigned char *ad, size_t ad_len,
const unsigned char *input, size_t ilen,
unsigned char *output, size_t *olen,
const unsigned char *tag, size_t tag_len )
{
#if defined(POLARSSL_GCM_C)
if( POLARSSL_MODE_GCM == ctx->cipher_info->mode )
{
int ret;
*olen = ilen;
ret = gcm_auth_decrypt( ctx->cipher_ctx, ilen,
iv, iv_len, ad, ad_len,
tag, tag_len, input, output );
if( ret == POLARSSL_ERR_GCM_AUTH_FAILED )
ret = POLARSSL_ERR_CIPHER_AUTH_FAILED;
return( ret );
}
#endif /* POLARSSL_GCM_C */
#if defined(POLARSSL_CCM_C)
if( POLARSSL_MODE_CCM == ctx->cipher_info->mode )
{
int ret;
*olen = ilen;
ret = ccm_auth_decrypt( ctx->cipher_ctx, ilen,
iv, iv_len, ad, ad_len,
input, output, tag, tag_len );
if( ret == POLARSSL_ERR_CCM_AUTH_FAILED )
ret = POLARSSL_ERR_CIPHER_AUTH_FAILED;
return( ret );
}
#endif /* POLARSSL_CCM_C */
return( POLARSSL_ERR_CIPHER_FEATURE_UNAVAILABLE );
}
/**
* @Brief AES-GCM decrypt, compute authentication tag and compare it to the one provided
*
* @param[in] key Encryption key
* @param[in] keyLength Key buffer length, in bytes, must be 16,24 or 32
* @param[in] cipherText Buffer to be decrypted
* @param[in] cipherTextLength Length in bytes of buffer to be decrypted
* @param[in] authenticatedData Buffer holding additional data to be used in auth tag computation
* @param[in] authenticatedDataLength Additional data length in bytes
* @param[in] initializationVector Buffer holding the initialisation vector
* @param[in] initializationVectorLength Initialisation vector length in bytes
* @param[in] tag Buffer holding the authentication tag
* @param[in] tagLength Length in bytes for the authentication tag
* @param[out] output Buffer holding the output, shall be at least the length of cipherText buffer
*
* @return 0 on succes, BCTBX_ERROR_AUTHENTICATION_FAILED if tag doesn't match or polarssl error code
*/
int32_t bctbx_aes_gcm_decrypt_and_auth(const uint8_t *key, size_t keyLength,
const uint8_t *cipherText, size_t cipherTextLength,
const uint8_t *authenticatedData, size_t authenticatedDataLength,
const uint8_t *initializationVector, size_t initializationVectorLength,
const uint8_t *tag, size_t tagLength,
uint8_t *output) {
gcm_context gcmContext;
int ret;
ret = gcm_init(&gcmContext, key, keyLength*8);
if (ret != 0) return ret;
ret = gcm_auth_decrypt(&gcmContext, cipherTextLength, initializationVector, initializationVectorLength, authenticatedData, authenticatedDataLength, tag, tagLength, cipherText, output);
if (ret == POLARSSL_ERR_GCM_AUTH_FAILED) {
return BCTBX_ERROR_AUTHENTICATION_FAILED;
}
return ret;
}
struct item *symmetric_decryption(struct item *key, struct item *item)
/*@ requires [?f]world(?pub, ?key_clsfy) &*&
item(item, ?enc, pub) &*&
enc == symmetric_encrypted_item(?principal1, ?count1,
?pay, ?ent) &*&
item(key, ?k, pub) &*&
k == symmetric_key_item(?principal2, ?count2); @*/
/*@ ensures [f]world(pub, key_clsfy) &*&
item(item, enc, pub) &*& item(key, k, pub) &*&
item(result, ?dec, pub) &*&
col ? [_]pub(dec) :
switch(pay)
{
case some(dec2):
return principal1 == principal2 &&
count1 == count2 && dec == dec2;
case none:
return false;
}; @*/
{
debug_print("DECRYPTING:\n");
print_item(item);
check_is_symmetric_encrypted(item);
//@ open [f]world(pub, key_clsfy);
struct item* result;
result = malloc(sizeof(struct item));
if (result == 0) abort_crypto_lib("Malloc failed");
{
gcm_context gcm_context;
char *iv;
char iv_buffer[GCM_IV_SIZE];
char *encrypted;
//@ open item(key, k, pub);
//@ assert key->content |-> ?k_cont &*& key->size |-> ?k_size;
check_valid_symmetric_key_item_size(key->size);
//@ open [_]item_constraints(k, ?k_cs0, pub);
//@ assert [_]ic_parts(k)(?k_tag, ?k_cs);
//@ crypto_chars_limits(k_cont);
//@ crypto_chars_split(k_cont, TAG_LENGTH);
//@ WELL_FORMED(k_tag, k_cs, TAG_SYMMETRIC_KEY)
//@ assert crypto_chars(secret, k_cont, TAG_LENGTH, k_tag);
//@ assert crypto_chars(secret, k_cont + TAG_LENGTH, GCM_KEY_SIZE, k_cs);
//@ cryptogram k_cg = cg_symmetric_key(principal2, count2);
//@ if (col) k_cg = chars_for_cg_sur(k_cs, tag_symmetric_key);
//@ if (col) crypto_chars_to_chars(k_cont + TAG_LENGTH, GCM_KEY_SIZE);
//@ if (col) public_chars_extract(k_cont + TAG_LENGTH, k_cg);
//@ if (col) chars_to_secret_crypto_chars(k_cont + TAG_LENGTH, GCM_KEY_SIZE);
//@ close cryptogram(k_cont + TAG_LENGTH, GCM_KEY_SIZE, k_cs, k_cg);
//@ close gcm_context(&gcm_context);
if (gcm_init(&gcm_context, POLARSSL_CIPHER_ID_AES, (key->content + TAG_LENGTH),
(unsigned int) GCM_KEY_SIZE * 8) != 0)
abort_crypto_lib("Init gcm failed");
//@ assert gcm_context_initialized(&gcm_context, ?p, ?c);
//@ assert col || (p == principal2 && c == count2);
//@ open cryptogram(k_cont + TAG_LENGTH, GCM_KEY_SIZE, k_cs, k_cg);
//@ crypto_chars_join(k_cont);
//@ close item(key, k, pub);
//@ open item(item, enc, pub);
//@ assert item->content |-> ?i_cont &*& item->size |-> ?i_size;
//@ open [_]item_constraints(enc, ?cs, pub);
//@ open [_]ic_parts(enc)(?enc_tag, ?enc_cont);
//@ open [_]ic_cg(enc)(_, ?enc_cg);
//@ take_append(TAG_LENGTH, enc_tag, enc_cont);
//@ drop_append(TAG_LENGTH, enc_tag, enc_cont);
//@ open [_]ic_sym_enc(enc)(?enc_iv, ?cg_cs);
//@ assert true == well_formed(cs, nat_length(cs));
//@ close [1/2]hide_crypto_chars(_, i_cont, i_size, cs);
check_valid_symmetric_encrypted_item_size(item->size);
//@ assert length(cs) > TAG_LENGTH + GCM_IV_SIZE;
int size = item->size - TAG_LENGTH - GCM_IV_SIZE - GCM_MAC_SIZE;
if (size <= MINIMAL_STRING_SIZE) abort_crypto_lib("Gcm decryption failed");
//@ crypto_chars_limits(i_cont);
//@ crypto_chars_split(i_cont, TAG_LENGTH);
iv = item->content + TAG_LENGTH;
//@ crypto_chars_split(iv, GCM_IV_SIZE);
//@ assert [1/2]crypto_chars(secret, iv, GCM_IV_SIZE, ?iv_cs);
memcpy(iv_buffer, iv, GCM_IV_SIZE);
//@ assert cs == append(enc_tag, enc_cont);
//@ assert enc_cont == append(iv_cs, cg_cs);
//@ public_crypto_chars(iv, GCM_IV_SIZE);
//@ chars_to_secret_crypto_chars(iv, GCM_IV_SIZE);
encrypted = iv + GCM_IV_SIZE;
//@ crypto_chars_limits(encrypted);
//@ crypto_chars_split(encrypted, GCM_MAC_SIZE);
//@ assert [1/2]crypto_chars(secret, encrypted, GCM_MAC_SIZE, ?mac_cs);
/*@ assert [1/2]crypto_chars(secret, encrypted + GCM_MAC_SIZE,
size, ?enc_cs); @*/
//@ assert cg_cs == append(mac_cs, enc_cs);
result->size = size;
result->content = malloc(size);
if (result->content == 0) abort_crypto_lib("Malloc failed");
//@ assert result->content |-> ?r_cont &*& result->size |-> size;
//@ if (col) enc_cg = chars_for_cg_sur(cg_cs, tag_auth_encrypted);
//@ close exists(enc_cg);
if (gcm_auth_decrypt(&gcm_context, (unsigned int) size,
iv_buffer, GCM_IV_SIZE, NULL, 0, encrypted,
GCM_MAC_SIZE, encrypted + GCM_MAC_SIZE,
result->content) != 0)
abort_crypto_lib("Gcm decryption failed");
//@ assert crypto_chars(secret, r_cont, size, ?dec_cs);
//@ assert col || enc_cg == cg_auth_encrypted(principal1, count1, dec_cs, iv_cs);
//@ crypto_chars_join(encrypted);
//@ crypto_chars_join(iv);
//@ crypto_chars_join(i_cont);
//@ open [1/2]hide_crypto_chars(_, i_cont, i_size, cs);
//@ close item(item, enc, pub);
gcm_free(&gcm_context);
//@ open gcm_context(&gcm_context);
zeroize(iv_buffer, GCM_IV_SIZE);
//@ close [f]world(pub, key_clsfy);
/*@ if (col)
{
crypto_chars_to_chars(r_cont, size);
chars_to_crypto_chars(r_cont, size);
}
else
{
assert enc == symmetric_encrypted_item(principal1, count1,
pay, ent);
assert enc_cg == cg_auth_encrypted(principal1, count1,
dec_cs, enc_iv);
switch(pay)
{
case some(pay1):
assert [_]item_constraints(pay1, dec_cs, pub);
case none:
open [_]ill_formed_item_chars(enc)(dec_cs);
assert [_]public_generated(polarssl_pub(pub))(dec_cs);
public_crypto_chars(r_cont, size);
chars_to_crypto_chars(r_cont, size);
}
}
@*/
parse_item(result->content, size);
/*@ if (col)
{
public_chars(r_cont, size);
chars_to_secret_crypto_chars(r_cont, size);
retreive_proof_obligations();
deserialize_item(dec_cs, pub);
leak proof_obligations(pub);
}
@*/
//@ assert crypto_chars(secret, r_cont, size, dec_cs);
//@ assert [_]item_constraints(?r, dec_cs, pub);
//@ close item(result, r, pub);
}
debug_print("DECRYPTING RESULT:\n");
print_item(result);
return result;
}
int app_receive(char *key, char **message)
/*@ requires [?f0]polarssl_world(sc_auth_polarssl_pub) &*&
[?f1]polarssl_cryptogram(key, KEY_BYTE_SIZE, ?key_cs, ?key_cg) &*&
key_cg == polarssl_symmetric_key(?creator, ?key_id) &*&
pointer(message, _);
@*/
/*@ ensures [f0]polarssl_world(sc_auth_polarssl_pub) &*&
[f1]polarssl_cryptogram(key, KEY_BYTE_SIZE, key_cs, key_cg) &*&
pointer(message, ?message_p) &*&
malloc_block(message_p, result) &*&
chars(message_p, result, ?m_cs) &*&
bad(creator) ?
[_]polarssl_public_generated_chars(sc_auth_polarssl_pub)(m_cs)
:
true == app_send_event(creator, m_cs);
@*/
{
int socket1;
int socket2;
int size;
int result_size;
char buffer[POLARSSL_MAX_MESSAGE_BYTE_SIZE];
char iv[16];
char tag[16];
char* encrypted;
char* decrypted;
// Receive message
if(net_bind(&socket1, NULL, APP_RECEIVE_PORT) != 0)
abort();
if(net_accept(socket1, &socket2, NULL) != 0)
abort();
if(net_set_block(socket2) != 0)
abort();
size = net_recv(&socket2, buffer, POLARSSL_MAX_MESSAGE_BYTE_SIZE);
if (size < 16 + POLARSSL_MIN_ENCRYPTED_BYTE_SIZE + 16)
abort();
//@ open polarssl_public_message(sc_auth_polarssl_pub)(buffer, size, ?cs);
//@ close [1/2]hide_chars(buffer, size, cs);
result_size = size - 16 - 16;
encrypted = malloc(result_size);
if (encrypted == 0) abort();
decrypted = malloc(result_size);
if (decrypted == 0) abort();
// Extract parts of message
memcpy(iv, buffer, 16);
memcpy(encrypted, (void*) buffer + 16, (unsigned int) result_size);
memcpy(tag, (void*) buffer + 16 + result_size, 16);
//@ assert chars(iv, 16, ?iv_cs);
//@ assert chars(encrypted, result_size, ?e_cs);
//@ assert chars(tag, 16, ?t_cs);
//@ chars_join(buffer);
//@ chars_join(buffer);
//@ open [1/2]hide_chars(buffer, size, cs);
//@ close [1/2]hide_chars(buffer, size, cs);
//@ assert cs == append(iv_cs, append(e_cs, t_cs));
// Decrypt message
{
gcm_context gcm_context;
//@ close gcm_context(&gcm_context);
//@ open [f1]polarssl_cryptogram(key, KEY_BYTE_SIZE, key_cs, key_cg);
//@ close polarssl_key_id(creator, key_id);
if (gcm_init(&gcm_context, POLARSSL_AES_CIPHER_ID, key,
(unsigned int) KEY_BYTE_SIZE * 8) != 0) abort();
/*@ assert gcm_context_initialized(&gcm_context,
some(pair(creator, key_id))); @*/
//@ close [f1]polarssl_cryptogram(key, KEY_BYTE_SIZE, key_cs, key_cg);
//@ polarssl_public_generated_chars_split(sc_auth_polarssl_pub, cs, 16);
/*@ polarssl_public_generated_chars_split(
sc_auth_polarssl_pub, append(e_cs, t_cs), result_size); @*/
//@ assert chars(encrypted, result_size, e_cs);
if (gcm_auth_decrypt(&gcm_context, (unsigned int) result_size,
iv, 16, NULL, 0, tag, 16,
encrypted, decrypted) != 0) abort();
gcm_free(&gcm_context);
//@ open gcm_context(&gcm_context);
}
//@ assert chars(decrypted, result_size, ?dec_cs);
//@ chars_join(buffer);
//@ open [1/2]hide_chars(buffer, size, cs);
/*@ polarssl_cryptogram e_cg = polarssl_auth_encrypted(
creator, key_id, t_cs, dec_cs, iv_cs); @*/
//@ assert e_cs == polarssl_chars_for_cryptogram(e_cg);
//@ polarssl_cryptogram_constraints(e_cs, e_cg);
/*@ polarssl_public_generated_chars_extract(
sc_auth_polarssl_pub, e_cs, e_cg); @*/
//@ open [_]sc_auth_polarssl_pub(e_cg);
/*@ if (!bad(creator))
{
assert true == app_send_event(creator, dec_cs);
}
else
{
assert [_]polarssl_public_generated_chars(sc_auth_polarssl_pub)(dec_cs);
}
@*/
net_close(socket1);
net_close(socket2);
free(encrypted);
*message = decrypted;
return result_size;
}
void attacker_send_auth_decrypted(havege_state *havege_state, void* socket)
//@ requires attacker_invariant(?pub, ?pred, ?kc, havege_state, socket, ?attacker);
//@ ensures attacker_invariant(pub, pred, kc, havege_state, socket, attacker);
{
int temp;
int size1;
int size2;
char buffer1[MAX_MESSAGE_SIZE];
char buffer2[MAX_MESSAGE_SIZE];
char buffer3[MAX_MESSAGE_SIZE];
gcm_context gcm_context;
char iv[16];
//@ open attacker_invariant(pub, pred, kc, havege_state, socket, attacker);
size1 = net_recv(socket, buffer1, MAX_MESSAGE_SIZE);
size2 = net_recv(socket, buffer2, MAX_MESSAGE_SIZE);
if (size1 <= 16 || size2 <= 16 ||
(size1 != 16 && size1 != 24 && size1 != 32))
{
//@ close attacker_invariant(pub, pred, kc, havege_state, socket, attacker);
return;
}
//@ close gcm_context(&gcm_context);
//@ interpret_symmetric_key(buffer1, size1);
//@ assert cryptogram(buffer1, size1, ?ccs1, ?cg_key);
//@ assert cg_key == cg_symmetric_key(?p, ?c);
if (gcm_init(&gcm_context, POLARSSL_CIPHER_ID_AES,
buffer1, (unsigned int) size1 * 8) == 0)
{
if (get_iv(havege_state, iv) == 0)
{
//@ assert crypto_chars(normal, iv, 16, ?ccs_iv);
//@ assert chars(buffer2, size2, ?cs2);
//@ interpret_auth_encrypted(buffer2, size2);
//@ open cryptogram(buffer2, size2, ?ccs2, ?cg_enc);
//@ cs_to_ccs_crypto_chars(buffer2, cs2);
//@ chars_to_crypto_chars(buffer2, size2);
//@ close exists(cg_enc);
//@ assert cg_enc == cg_auth_encrypted(?p2, ?c2, ?ccs_output2, ?ccs_iv2);
//@ crypto_chars_split(buffer2, 16);
if (gcm_auth_decrypt(&gcm_context, (unsigned int) size2 - 16,
iv, 16, NULL, 0, buffer2, 16,
(void*) buffer2 + 16, buffer3) == 0)
{
/*@ if (!col)
{
assert crypto_chars(secret, buffer3, size2 - 16, ?ccs_output);
ccs_output == ccs_output2;
ccs_iv == ccs_iv2;
assert ccs2 == ccs_for_cg(cg_enc);
assert [_]pub(cg_enc);
assert is_public_auth_decryption_is_public(?proof3, pub, pred);
proof3(cg_key, cg_enc);
public_crypto_chars(buffer3, size2 - 16);
chars_to_crypto_chars(buffer3, size2 - 16);
}
@*/
zeroize(iv, 16);
//@ chars_to_crypto_chars(iv, 16);
}
//@ crypto_chars_to_chars(buffer3, size2 - 16);
net_send(socket, buffer3, (unsigned int) size2 - 16);
//@ crypto_chars_to_chars(buffer2, 16);
//@ crypto_chars_to_chars((void*) buffer2 + 16, size2 - 16);
//@ chars_join(buffer2);
}
//@ crypto_chars_to_chars(iv, 16);
gcm_free(&gcm_context);
}
//@ open gcm_context(&gcm_context);
//@ close attacker_invariant(pub, pred, kc, havege_state, socket, attacker);
//@ public_cryptogram(buffer1, cg_key);
}
