Wireshark-bugs: [Wireshark-bugs] [Bug 4838] New: AES-CTR decoding not working, (dissectors/packe
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From: bugzilla-daemon@xxxxxxxxxxxxx
Date: Thu, 3 Jun 2010 14:52:02 -0700 (PDT)
https://bugs.wireshark.org/bugzilla/show_bug.cgi?id=4838

           Summary: AES-CTR decoding not working,
                    (dissectors/packet_ipsec.c using gcrypt)
           Product: Wireshark
           Version: 1.2.8
          Platform: Other
        OS/Version: All
            Status: NEW
          Severity: Normal
          Priority: Low
         Component: Wireshark
        AssignedTo: wireshark-bugs@xxxxxxxxxxxxx
        ReportedBy: john_fitzgibbon@xxxxxxxxx


Build Information:
wireshark 1.2.8

Copyright 1998-2010 Gerald Combs <gerald@xxxxxxxxxxxxx> and contributors.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Compiled with GTK+ 2.10.4, (32-bit) with GLib 2.12.3, with libpcap 0.9.4, with
libz 1.2.3, with POSIX capabilities (Linux), with libpcre 6.6, with SMI 0.4.5,
without c-ares, with ADNS, with Lua 5.1, with GnuTLS 1.4.1, with Gcrypt 1.4.4,
with MIT Kerberos, without GeoIP, without PortAudio, without AirPcap.

Running on Linux 2.6.18-194.3.1.el5, with libpcap version 0.9.4, GnuTLS 1.4.1,
Gcrypt 1.4.4.

Built using gcc 4.1.2 20080704 (Red Hat 4.1.2-48).

--
Decoding IPsec (ESP) using AES-CTR fails.

When specifying SA keys for AES-CTR, wireshark expects a key length of 160, 224
or 288 bits, (i.e. 128, 192 or 256 bits, followed by the 32 bit nonce value),
but gcry_cipher_setkey() in packet_ipsec.c fails, as it expects 128, 192 or 256
bits.

Omitting the nonce won't work -- even if wireshark liked those key lengths,
gcrypt wouldn't be able to decrypt without it.

Looking at gcrypt.h, I'm guessing what's missing may be a call to
gcry_cipher_setctr()? Once gcrypt has the nonce, the key len could be
decremented by 4, (32 bits), for the call to gcry_cipher_setkey() and things
should work from there.

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