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important fix (last 16 decrypted bytes were missing in each audio packet)

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fduncanh
2021-11-03 00:29:16 -04:00
parent 23164acf05
commit 57b158478c
1 changed files with 14 additions and 3 deletions
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17
lib/raop_buffer.c
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@@ -170,12 +170,23 @@ raop_buffer_decrypt(raop_buffer_t *raop_buffer, unsigned char *data, unsigned ch
fwrite(&data[12], payloadsize, 1, file_source);
}
#endif
/* Need to be initialized externally */
aes_ctx_t *aes_ctx_audio = aes_cbc_init(raop_buffer->aeskey, raop_buffer->aesiv, AES_DECRYPT);
encryptedlen = (payload_size / 16) * 16;
memset(output, 0, payload_size);
// Need to be initialized internally
aes_ctx_t *aes_ctx_audio = aes_cbc_init(raop_buffer->aeskey, raop_buffer->aesiv, AES_DECRYPT);
aes_cbc_decrypt(aes_ctx_audio, &data[12], output, encryptedlen);
/* Adding 15 to encryptedlen in the call to aes_cbc_decrypt is a fix (hack) to ensure that */
/* all encryptedlen encrypted bytes are decrypted .*/
/* The implementation of aes_cbc_decrypt in crypto.c calls OpenSSL function EVP_EncryptUpdate */
/* but does not call EVP_EncryptFinal_ex to finalize the decryption of the packet. */
/* Without the fix, the last 16 encrypted bytes are lost; */
/* with the fix all (encryptedlen + 15) /16 * 16 = encryptedlen encrypted bytes are written into output,*/
/* with no risk of buffer overflow */
aes_cbc_decrypt(aes_ctx_audio, &data[12], output, encryptedlen + 15);
aes_cbc_destroy(aes_ctx_audio);
memcpy(output + encryptedlen, &data[12 + encryptedlen], payload_size - encryptedlen);