GDB api not functionnal for GDB 8.3+

[SecT0uch]

I'm having an issue when I want to Use GDB api.

Using:

• OS: Manjaro X64
• GNU gdb (GDB) 15.1
• python 3.12.5
• Pwntools v4.13.0
• rpyc 6.0.0

Issue

Sample script:

from pwn import context, gdb

context.binary = "bin.elf"
context.terminal = "wezterm"

p = context.binary.process()
gdb.attach(p, api=True)

And the error:

[x] Starting local process '/usr/bin/gdb' argv=[b'/usr/bin/gdb', b'--nx', b'-bat[◢] Starting local process '/usr/bin/gdb' argv=[b'/usr/bin/gdb', b'--nx', b'-bat[+]  b'-ex', b'python import rpyc; import sys; sys.exit(123)'] : pid 49447
[*] Process '/usr/bin/gdb' stopped with exit code 1 (pid 49447)
[ERROR] Failed to connect to GDB: rpyc is not installed
Traceback (most recent call last):
  File "/home/user/file.py", line 23, in <module>
    gdb.attach(p, api=True)
  File "/usr/lib/python3.12/site-packages/pwnlib/context/__init__.py", line 1582, in setter
    return function(*a, **kw)
           ^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/site-packages/pwnlib/gdb.py", line 1251, in attach
    log.error('Failed to connect to GDB: rpyc is not installed')
  File "/usr/lib/python3.12/site-packages/pwnlib/log.py", line 439, in error
    raise PwnlibException(message % args)
pwnlib.exception.PwnlibException: Failed to connect to GDB: rpyc is not installed
[*] Stopped process '/home/user/bin.elf' (pid 49429)

Analysis

Upon analyzing whats happening I can see how the check is done:

pwntools/pwnlib/gdb.py

Lines 1277 to 1281 in d7817a7

	rpyc_check = [gdb_binary, '--nx', '-batch', '-ex',
	'python import rpyc; import sys; sys.exit(123)']
	if 123 != tubes.process.process(rpyc_check).poll(block=True):
	log.error('Failed to connect to GDB: rpyc is not installed')

I tried running the command in the terminal directly:

# Using bash shell
gdb --nx -batch -ex 'python import rpyc; import sys; sys.exit(123)'; echo $?
Python Exception <class 'SystemExit'>: 123
Error occurred in Python: 123
1

Gdb seems to exit with an error code of 1.
And indeed in the GDB 8.3 changelog we have GDB in batch mode now exits with status 1 if the last command to be executed failed.

I wonder how come this has not been spotted since then ?
Am I really the only one wanting to use the GDB api through pwnlib ?

[Arusekk]

Idea: we can probably switch to os.exit. Email z środy 11 września 2024 od Jordana ERNSTa:

…

I'm having an issue when I want to Use GDB api. Using: - OS: Manjaro X64 - GNU gdb (GDB) 15.1 - python 3.12.5 - Pwntools v4.13.0 - rpyc 6.0.0 ## Issue Sample script: ```python from pwn import context, gdb context.binary = "bin.elf" context.terminal = "wezterm" p = context.binary.process() gdb.attach(p, api=True) ``` And the error: ```text [x] Starting local process '/usr/bin/gdb' argv=[b'/usr/bin/gdb', b'--nx', b'-bat[◢] Starting local process '/usr/bin/gdb' argv=[b'/usr/bin/gdb', b'--nx', b'-bat[+] b'-ex', b'python import rpyc; import sys; sys.exit(123)'] : pid 49447 [*] Process '/usr/bin/gdb' stopped with exit code 1 (pid 49447) [ERROR] Failed to connect to GDB: rpyc is not installed Traceback (most recent call last): File "/home/user/file.py", line 23, in <module> gdb.attach(p, api=True) File "/usr/lib/python3.12/site-packages/pwnlib/context/__init__.py", line 1582, in setter return function(*a, **kw) ^^^^^^^^^^^^^^^^^^ File "/usr/lib/python3.12/site-packages/pwnlib/gdb.py", line 1251, in attach log.error('Failed to connect to GDB: rpyc is not installed') File "/usr/lib/python3.12/site-packages/pwnlib/log.py", line 439, in error raise PwnlibException(message % args) pwnlib.exception.PwnlibException: Failed to connect to GDB: rpyc is not installed [*] Stopped process '/home/user/bin.elf' (pid 49429) ``` ## Analysis Upon analyzing whats happening I can see how the check is done: https://github.com/Gallopsled/pwntools/blob/d7817a7eaccb9baacb121131ec913cf0a14a1f05/pwnlib/gdb.py#L1277-L1281 I tried running the command in the terminal directly: ```bash # Using bash shell gdb --nx -batch -ex 'python import rpyc; import sys; sys.exit(123)'; echo $? Python Exception <class 'SystemExit'>: 123 Error occurred in Python: 123 1 ``` Gdb seems to exit with an error code of `1`. And indeed in DGB 8.3 changelog we have `GDB in batch mode now exits with status 1 if the last command to be executed failed.` I wonder how come this has not been spotted since then ? Am I really the only one wanting tu use theGDB api through pwnlib ? -- Reply to this email directly or view it on GitHub: #2458 You are receiving this because you are subscribed to this thread. Message ID: ***@***.***

-- Wysłane z mojego urządzenia Sailfish

[SecT0uch]

I confirm this would work:

gdb --nx -batch -ex 'python import rpyc; import os; os._exit(123)'; echo $?
123

[peace-maker]

This isn't a problem with gdb 8.3 but with GDB 15.1 packaged in Ubuntu 24.04 now.
https://sourceware.org/bugzilla/show_bug.cgi?id=31946

Our tests run on Ubuntu 22.04 which is why this wasn't spotted yet.