576984 - libssl: When decompressing, ssl3_HandleRecord doesn't zero-out plaintext buffer before freeing it

Status: RESOLVED INVALID

(NSS :: Libraries, defect)

Description

[Brian Smith (:briansmith, :bsmith, use NEEDINFO?)]

AFAICT, every buffer in libssl that may contain plaintext application data is supposed to be zeroed out. However, the temporary buffer used for decompression isn't zeroed out in ssl_HandleRecord.

The fix is to change the PORT_Free(plaintext->buf) to PORT_ZFree(plaintext->buf) everywhere in ssl3_HandleRecord.

Comment 1

[Brian Smith (:briansmith, :bsmith, use NEEDINFO?)]

The patch for bug 576902 contains a fix for this bug.

Comment 2

[Leander Schwarz]

As of TLS 1.3 compression is removed[RFC8446, Section 1.2] and also not supported by the NSS implementation.

Generally the gather plaintext buffer is allocated and freed on the ssl socket creation and destruction, more specifically by calls to ssl3gthr.c - ssl3_InitGather() and ssl3_DestroyGather(). The buffer is zeroed-out at freeing.