[asterisk-bugs] [JIRA] (ASTERISK-22432) Async AGI crashes Asterisk when issuing "set variable" command without args

[Antoine Pitrou (JIRA)]

Antoine Pitrou created ASTERISK-22432:
-----------------------------------------

             Summary: Async AGI crashes Asterisk when issuing "set variable" command without args
                 Key: ASTERISK-22432
                 URL: https://issues.asterisk.org/jira/browse/ASTERISK-22432
             Project: Asterisk
          Issue Type: Bug
      Security Level: None
          Components: Resources/res_agi
         Environment: Fresh install of squeeze-xivo-skaro-13.16.iso
            Reporter: Antoine Pitrou


Banner is the following:
11.5.0+pf.xivo.13.16~20130722.141054.2668289,

Actions to reproduce: open an AMI session using telnet, trigger an async AGI session and then type:

action: agi
actionid: FOOBAR.568
CommandID: 124
command: set variable
Channel: <AGI channel name>

Response: Success
ActionID: FOOBAR.568
Message: Added AGI command to queue


At this point Asterisk crashes (the AMI connection is closed).


gdb stack trace:
(gdb) bt
#0  0xb767e073 in strlen () from /lib/libc.so.6
#1  0x0818c754 in pbx_builtin_setvar_helper ()
#2  0xb6e87b57 in ?? () from /usr/lib/asterisk/modules/res_agi.so
#3  0xb6e8d053 in ?? () from /usr/lib/asterisk/modules/res_agi.so
#4  0xb6e8f7dd in ?? () from /usr/lib/asterisk/modules/res_agi.so
#5  0x08184eca in pbx_exec ()
#6  0x081916a6 in ?? ()
#7  0x08199087 in ?? ()
#8  0x0819b390 in ?? ()
#9  0x081e222b in ?? ()
#10 0xb72937b0 in start_thread () from /lib/libpthread.so.0
#11 0xb76d6cde in clone () from /lib/libc.so.6


I've made a SVN checkout of Asterisk and identified the likely cause of the problem:

in res/res_agi.c, handle_setvariable() calls pbx_builtin_setvar_helper(chan, argv[2], argv[3]).
However, if "set variable" is called with too few arguments, argv[2] and argv[3] may be unitialized.
Then pbx_builtin_setvar_helper() calls strlen(argv[2]) and crashes.


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