In the defined AEAD modes, SRTP packets must always be encrypted and
authenticated, but SRTCP packets may be only authenticated. It's
possible, therefore, for us to end up in `srtp_protect_aead()` without
the `sec_serv_conf` bit being set. We should just ignore this and
encrypt the RTP packet anyway.
What we are doing instead is encrypting the packet anyway, but setting
`enc_start` to NULL first. This causes `aad_len` to underflow which
will cause us to over-read in `cipher_set_aad()`.
If we could get past that, we would try to read and write memory
starting at 0x0 down in `cipher_encrypt()`.
This commit causes us to not check the `sec_serv_conf` bit and never
set `enc_start` to NULL in `srtp_protect_aead()`.
`srtp_unprotect_aead()` does not contain a similar error.
When computing the start address of the RTP data to encrypt or SRTP
data to decrypt (`enc_start`), we are using `hdr->cc` (the CSRC
count), which is untrusted data from the packet, and the length field
of an RTP header extension, which is also untrusted and unchecked data
from the packet.
This value then pollutes our calculation of how much data we'll be
encrypting or decrypting (`enc_octet_len`), possibly causing us to
underflow.
We'll then call `cipher_encrypt()` or `cipher_decrypt()` with these
two values, causing us to read from and write to arbitrary addresses
in memory.
(In the AEAD functions, we'd also pollute `aad_len`, which would cause
us to read undefined memory in `cipher_set_aad`.)
This commit adds checks to verify that the `enc_start` we calculate is
sane based on the actual packet length.
What we momentarily called log-uuid-chars is now better called
log-uuid-length. Setting log-uuid-length will specify a truncation
length for UUIDs displayed by setting log-uuid.
If log-uuid-short is set, or -S is passed to fs_cli, we only display
the first 8 hex digits of the UUID. The log-uuid-chars option may
instead be set to specify some other truncation length for the UUID.
Travis Cross