gdb.debug() appends an extra line to the passed gdbscript, resulting in symbol resolution errors

[numin0us]

Pwntools Issue Template

• Version: Latest version of the dev3 branch
• OS: Ubuntu 18.04/Kali 2019.3
• GDB Version: 8.3
• Python Version: 3.7.4

When using the gdb.debug() feature of pwntools an extra line is appended to the the passed gdbscript which in some cases can prevent proper symbol resolution.

root@kali:~/Downloads/crackmes# ptpython                                                                                                                                                                          
>>> from pwn import *                                                                                                                                                                                             
>>> context.log_level = "DEBUG"                                                                                                                                                                                   
>>> p = gdb.debug('./crackme01.64')                                                                      
...
[DEBUG] Wrote gdb script to '/tmp/pwnxnkmbope.gdb'
    file "./crackme01.64"
    target remote 127.0.0.1:38677
    file "./crackme01.64"

and on gdb..

Reading symbols from ./crackme01.64...(no debugging symbols found)...done.
Reading /lib64/ld-linux-x86-64.so.2 from remote target...
warning: File transfers from remote targets can be slow. Use "set sysroot" to access files locally instead.
Reading /lib64/ld-linux-x86-64.so.2 from remote target...
Reading /lib64/ld-2.27.so from remote target...
Reading /lib64/.debug/ld-2.27.so from remote target...
0x00007f16e2289090 in ?? () from target:/lib64/ld-linux-x86-64.so.2

(gdb) disass main
Dump of assembler code for function main:
   0x00000000000006aa <+0>:     Cannot access memory at address 0x6aa

The issue stems from the fact that in the new version of gdb, when you run file after attaching to a remote target, it replaces the symbols in the current context. I downloaded and edited a local version of pwntools to remove that final line of the gdbscript and it seems to work fine.

...
[DEBUG] Wrote gdb script to '/tmp/pwnva62cw6s.gdb'
    file "./crackme01.64"
    target remote 127.0.0.1:34373

on GDB

(gdb) disass main
Dump of assembler code for function main:
   0x0000557f59b586aa <+0>:     push   %rbx
   0x0000557f59b586ab <+1>:     cmp    $0x2,%edi
   0x0000557f59b586ae <+4>:     jne    0x557f59b586ec <main+66>

This issue does not appear to happen on the pwntools container from Dockerhub. I believe that may be due to it using an older version of GDB (7.x), but I have not performed enough testing to determine that. In my own pwntools module I hacked together a solution, I am not familiar enough with the codebase to submit a pull request.

[numin0us]

Updated initial submission with more diagnostic information.

[bet4it]

I'm trying to fix it in #1323

[Arusekk]

Closed via #1323