Reading arbitrary stack memory in aes_gcm_openssl_set_aad()

[ukreator]

OpenSSL function call at aes_gcm_ossl.c:261 can sometimes read more than is pointed by aad function argument. For example, if called from srtp.c:2415. In this case tseq is 4 bytes long, but 8 bytes is read.

Fix could be to use aad_len instead of c->tag_len when calling EVP_CIPHER_CTX_ctrl, but I'm not sure about it.

[jfigus]

Based on my understanding of OpenSSL, this is benign. Line 261 is simply setting the tag length for the upcoming decrypt operation, which is specified by c->tag_len. While the OpenSSL code does read from memory pointed by by *aad, the data that is read is irrelevant. The true processing on *aad is done on line 263 during the call to EVP_Cipher(). This is one of the joys of working with the OpenSSL API. Work with it enough and one will learn to dislike it.

[jfigus]

Closing this issue due to inactivity.