Wireshark · Wireshark-dev: Re: [Wireshark-dev] epan_base64_decode(): failure when string contains a NUL character

[Jakub Zawadzki <darkjames-ws@xxxxxxxxxxxx>]

Hi,

On Wed, Apr 17, 2013 at 10:27:42PM +0200, Uli Heilmeier wrote:
> With the PLAIN mechanism the packet has a base64 encoded string containing:
> [authorization user](\x00)[authentication user](\x00)[password]
> 
> For example:
> dGVzdAB0ZXN0ADEyMzQ= contains test(NUL)test(NUL)1234
> 
> I tried to decode the base64 string with the epan_base64_decode() function
> (from epan/base64.h). Unfortunately this fails. I only get a wrong three
> bytes long string.
> I guess the problem is the NUL character as a delimiter.
> 
> Do you have an idea if this is bug in the epan_base64_decode() function or
> do I have to do the decoding another way?

>From C interactive shell (gdb):

(gdb) call $x = (char *) strdup("dGVzdAB0ZXN0ADEyMzQ=")
$1 = 0x65b0e0 "dGVzdAB0ZXN0ADEyMzQ="
(gdb) call epan_base64_decode($x)
$2 = 14

(gdb) x/14c $x
0x65b0e0:       116 't' 101 'e' 115 's' 116 't' 0 '\000'        116 't' 101 'e' 115 's'
0x65b0e8:       116 't' 0 '\000'        49 '1'  50 '2'  51 '3'  52 '4'

(gdb) call $x
$3 = 0x65b0e0 "test"
(gdb) call $x + 5
$4 = 0x65b0e5 "test"
(gdb) call $x + 5 + 5
$5 = 0x65b0ea "1234"

Seems to be working ok, can you attach your code?

Regards,
Jakub Zawadzki