Depends

1. GDB
2. Python

How to use?

1. Launch wechat linux client 4.1.10(Latest)
2. Don't Login(Need logged in before)
3. Run this Python script.(Waiting one seconde)
4. Do Login
5. Come back to Script console, The key will print.

Code

import gdb
import re
import time
import sys
sys.stdout = sys.stderr
relative = "0x658FC90"
base = next(line.split()[0] for line in gdb.execute("info proc mapping", to_string=True).splitlines() if line.strip().endswith('/wechat'))
print(f"base = {base}, relative = {relative}")
bp = gdb.Breakpoint(f"* {base} + {relative}")
print("breakpoint has been set, please login wechat")
gdb.execute("continue") # wait to breakpoint
print(f"hit_count = {bp.hit_count}, now, reading memory")
assert gdb.execute("x/1gx $rsi+16", to_string=True).strip().endswith('0x0000000000000020'), "expect size == 0x20 == 32 bytes"
key = re.compile(r"^.*?:\s*|0x|\s+", re.MULTILINE).sub("", gdb.execute("x/32bx *(void**)($rsi+8)", to_string=True))
print(f"key = {key}")
time.sleep(1)
exit(0)
# sudo gdb --pid=$(pgrep wechat) --batch-silent --command=wechat_gdb.py