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AES-CBC needs PKCS#7 padding.

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This commit is contained in:
Maarten Billemont 2017-09-24 13:06:19 -04:00
parent b4c2a393f1
commit 0a024b2594
3 changed files with 30 additions and 17 deletions
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10
core/c/mpw-algorithm_v0.c
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@ -165,7 +165,7 @@ static const char *mpw_sitePasswordFromCrypt_v0(
// Base64-decode // Base64-decode
uint8_t *cipherBuf = calloc( 1, mpw_base64_decode_max( cipherText ) ); uint8_t *cipherBuf = calloc( 1, mpw_base64_decode_max( cipherText ) );
size_t bufSize = (size_t)mpw_base64_decode( cipherBuf, cipherText ); size_t bufSize = (size_t)mpw_base64_decode( cipherBuf, cipherText ), cipherBufSize = bufSize;
if ((int)bufSize < 0) { if ((int)bufSize < 0) {
err( "Base64 decoding error." ); err( "Base64 decoding error." );
mpw_free( &cipherBuf, mpw_base64_decode_max( cipherText ) ); mpw_free( &cipherBuf, mpw_base64_decode_max( cipherText ) );
@ -174,13 +174,13 @@ static const char *mpw_sitePasswordFromCrypt_v0(
trc( "b64 decoded: %zu bytes = %s\n", bufSize, mpw_hex( cipherBuf, bufSize ) ); trc( "b64 decoded: %zu bytes = %s\n", bufSize, mpw_hex( cipherBuf, bufSize ) );
// Decrypt // Decrypt
const uint8_t *plainBytes = mpw_aes_decrypt( masterKey, MPMasterKeySize, cipherBuf, bufSize ); const uint8_t *plainBytes = mpw_aes_decrypt( masterKey, MPMasterKeySize, cipherBuf, &bufSize );
mpw_free( &cipherBuf, bufSize ); mpw_free( &cipherBuf, cipherBufSize );
const char *plainText = strndup( (char *)plainBytes, bufSize ); const char *plainText = strndup( (char *)plainBytes, bufSize );
mpw_free( &plainBytes, bufSize ); mpw_free( &plainBytes, bufSize );
if (!plainText) if (!plainText)
err( "AES decryption error: %s\n", strerror( errno ) ); err( "AES decryption error: %s\n", strerror( errno ) );
trc( "decrypted -> plainText: %zu bytes = %s = %s\n", sizeof( plainText ), plainText, mpw_hex( plainText, sizeof( plainText ) ) ); trc( "decrypted -> plainText: %zu bytes = %s = %s\n", strlen( plainText ), plainText, mpw_hex( plainText, strlen( plainText ) ) );
return plainText; return plainText;
} }
@ -235,7 +235,7 @@ static const char *mpw_siteState_v0(
// Encrypt // Encrypt
size_t bufSize = strlen( plainText ); size_t bufSize = strlen( plainText );
const uint8_t *cipherBuf = mpw_aes_encrypt( masterKey, MPMasterKeySize, (const uint8_t *)plainText, bufSize ); const uint8_t *cipherBuf = mpw_aes_encrypt( masterKey, MPMasterKeySize, (const uint8_t *)plainText, &bufSize );
if (!cipherBuf) { if (!cipherBuf) {
err( "AES encryption error: %s\n", strerror( errno ) ); err( "AES encryption error: %s\n", strerror( errno ) );
return NULL; return NULL;

33
core/c/mpw-util.c
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@ -267,33 +267,46 @@ uint8_t const *mpw_hash_hmac_sha256(const uint8_t *key, const size_t keySize, co
return mac; return mac;
} }
static uint8_t const *mpw_aes(bool encrypt, const uint8_t *key, const size_t keySize, const uint8_t *buf, const size_t bufSize) { static uint8_t const *mpw_aes(bool encrypt, const uint8_t *key, const size_t keySize, const uint8_t *buf, size_t *bufSize) {
if (!key || keySize < 16) if (!key || keySize < 16)
return NULL; return NULL;
// IV = zero
uint8_t iv[16]; uint8_t iv[16];
bzero( (void *)iv, sizeof( iv ) ); bzero( (void *)iv, sizeof( iv ) );
uint8_t aesBuf[bufSize];
memcpy( aesBuf, buf, bufSize ); // Add PKCS#7 padding
uint8_t *resultBuf = malloc( bufSize ); uint32_t aesSize = (uint32_t)*bufSize;
if (encrypt)
aesSize = (aesSize / 16) * 16 + 16;
uint8_t aesBuf[aesSize];
memcpy( aesBuf, buf, *bufSize );
memset( aesBuf + *bufSize, aesSize - *bufSize, aesSize - *bufSize );
uint8_t *resultBuf = malloc( aesSize );
if (encrypt) if (encrypt)
AES_CBC_encrypt_buffer( resultBuf, aesBuf, (uint32_t)bufSize, key, iv ); AES_CBC_encrypt_buffer( resultBuf, aesBuf, aesSize, key, iv );
else else
AES_CBC_decrypt_buffer( resultBuf, aesBuf, (uint32_t)bufSize, key, iv ); AES_CBC_decrypt_buffer( resultBuf, aesBuf, aesSize, key, iv );
bzero( aesBuf, bufSize ); bzero( aesBuf, aesSize );
bzero( iv, bufSize ); bzero( iv, 16 );
// Truncate PKCS#7 padding
if (encrypt)
*bufSize = aesSize;
else
*bufSize -= resultBuf[aesSize - 1];
return resultBuf; return resultBuf;
} }
uint8_t const *mpw_aes_encrypt(const uint8_t *key, const size_t keySize, const uint8_t *plainBuf, const size_t bufSize) { uint8_t const *mpw_aes_encrypt(const uint8_t *key, const size_t keySize, const uint8_t *plainBuf, size_t *bufSize) {
return mpw_aes( true, key, keySize, plainBuf, bufSize ); return mpw_aes( true, key, keySize, plainBuf, bufSize );
} }
uint8_t const *mpw_aes_decrypt(const uint8_t *key, const size_t keySize, const uint8_t *cipherBuf, const size_t bufSize) { uint8_t const *mpw_aes_decrypt(const uint8_t *key, const size_t keySize, const uint8_t *cipherBuf, size_t *bufSize) {
return mpw_aes( false, key, keySize, cipherBuf, bufSize ); return mpw_aes( false, key, keySize, cipherBuf, bufSize );
} }

4
core/c/mpw-util.h
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@ -173,11 +173,11 @@ uint8_t const *mpw_hash_hmac_sha256(
/** Encrypt a plainBuf with the given key using AES-128-CBC. /** Encrypt a plainBuf with the given key using AES-128-CBC.
* @return A new bufSize allocated buffer containing the cipherBuf. */ * @return A new bufSize allocated buffer containing the cipherBuf. */
uint8_t const *mpw_aes_encrypt( uint8_t const *mpw_aes_encrypt(
const uint8_t *key, const size_t keySize, const uint8_t *plainBuf, const size_t bufSize); const uint8_t *key, const size_t keySize, const uint8_t *plainBuf, size_t *bufSize);
/** Decrypt a cipherBuf with the given key using AES-128-CBC. /** Decrypt a cipherBuf with the given key using AES-128-CBC.
* @return A new bufSize allocated buffer containing the plainBuf. */ * @return A new bufSize allocated buffer containing the plainBuf. */
uint8_t const *mpw_aes_decrypt( uint8_t const *mpw_aes_decrypt(
const uint8_t *key, const size_t keySize, const uint8_t *cipherBuf, const size_t bufSize); const uint8_t *key, const size_t keySize, const uint8_t *cipherBuf, size_t *bufSize);
/** Calculate an OTP using RFC-4226. /** Calculate an OTP using RFC-4226.
* @return A newly allocated string containing exactly `digits` decimal OTP digits. */ * @return A newly allocated string containing exactly `digits` decimal OTP digits. */
#if UNUSED #if UNUSED