From 68b09cdb8ca13ab4141e763793ab0145b78b255f Mon Sep 17 00:00:00 2001
From: Pavel 'LEdoian' Turinsky <ledoian@matfyz.cz>
Date: Sun, 14 Jan 2024 17:57:08 +0100
Subject: [PATCH] Implement basic introspection into what is passed.

---
 sopass.py | 84 ++++++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 80 insertions(+), 4 deletions(-)

diff --git a/sopass.py b/sopass.py
index 0afbb6a..7d4b6c8 100755
--- a/sopass.py
+++ b/sopass.py
@@ -9,6 +9,7 @@ import selectors
 from dataclasses import dataclass
 import logging as log
 import math
+import termcolor # external dep, TODO
 # Note: get/setrlimit are in resource module
 
 def setup_logging():
@@ -36,9 +37,30 @@ def hexdump(data: bytes) -> list[str]: # We will be prefixing the lines with sig
 		result.append(line)
 	return result
 
+# fd types from inode(7)
+fdtypes = {
+	S_IFSOCK:	'socket',
+	S_IFLNK:	'symlink',
+	S_IFREG:	'regular file',
+	S_IFBLK:	'blockdev',
+	S_IFDIR:	'directory',
+	S_IFCHR:	'chardev',
+	S_IFIFO:	'fifo',
+	}
+
 def fdinfo(fd: int) -> str:
+	result = []
 	stat = os.fstat(fd)
-	# TODO: return something
+	type = S_IFMT(stat.st_mode)
+	result.append(f'type: {fdtypes.get(type, f"UNKNOWN: {type}")}')
+	if S_ISREG(stat.st_mode):
+		result.append(f'size: {stat.st_size}')
+		orig_offset = os.lseek(fd, 0, os.SEEK_CUR)
+		os.lseek(fd, 0, os.SEEK_SET)
+		head = os.read(fd, 256)
+		result.extend(hexdump(head))
+		os.lseek(fd, orig_offset, os.SEEK_SET)
+	return result
 
 def fd_readlink(fd: int, pid: int | None =None) -> str:
 	if pid is None:
@@ -49,12 +71,66 @@ def fd_readlink(fd: int, pid: int | None =None) -> str:
 	except OSError as e:
 		return f"Could not read {fd_link}: {e.strerror} (errno {e.errno})"
 
+def dirprintlines(dir: Direction, lines, file=sys.stdout, indent=''):
+	if isinstance(lines, str): lines = [lines]
+	lines_to_print = [f'{dir.sigil} {indent}{line}' for line in lines]
+	if True or COLOR:
+		lines_to_print = [termcolor.colored(line, dir.color) for line in lines_to_print]
+	print(*lines_to_print, sep='\n', file=file)
+
+def show_fd(dir, fd, /, indent='    '):
+	# Here we decide what to show and format it. We leave any particular
+	# decisions on other functions.
+	dirprintlines(dir, f'link: {fd_readlink(fd)}', indent=indent)
+	dirprintlines(dir, fdinfo(fd), indent=indent)
+
+# Maps from integers to symbolic names, acc to unix(7)
+sockopts = {getattr(sk, name): name for name in(
+	'SO_PASSCRED',
+	'SO_PASSSEC',
+#	'SO_PEEK_OFF', # wtf python does not have this
+	'SO_PEERCRED',
+	'SO_PEERSEC',
+	)}
+anclevels = {getattr(sk, name): name for name in(
+	'SOL_SOCKET',
+	)}
+anctypes = {getattr(sk, name): name for name in(
+	'SCM_RIGHTS',
+	'SCM_CREDENTIALS',
+#	'SCM_SECURITY', # wtf python does not have this
+	)}
+
+
+def show_anc(dir, a, /, indent='  ') -> list[int]:
+	"returns a possible list of file descriptors"
+	result = []
+	level, type, data = a
+	if level == sk.SOL_SOCKET and type == sk.SCM_RIGHTS:
+		# A file descriptor
+		fds = array('i')
+		fds.frombytes(data)
+		dirprintlines(dir, f'Received {len(fds)} file descriptor{"s"*(len(fds)!=1)}', indent=indent)
+		result = list(fds)
+		for fd in fds:
+			show_fd(dir, fd, indent=2*indent)
+	else:
+		dirprintlines(dir, 'Cannot show details.', indent=indent)
+	return result
+
 def fwd_traffic(frm: sk.socket, to: sk.socket, dir: Direction):
-	print(f'{dir.sigil} there be data from {frm}')
 	chunk_size = 640*1024 # … idk, ought to be enough for anyone…
-	data, anc, flags, _addr = frm.recvmsg(chunk_size, chunk_size)
-	# TODO: inspect
+	fds = [] # potential fds
+	data, anc, flags, addr = frm.recvmsg(chunk_size, chunk_size)
+	dirprintlines(dir, f'Forwarding {len(data)} bytes and {len(anc)} ancillary from {addr} to {to}')
+	dirprintlines(dir, hexdump(data), indent='  ')
+	for i,a in enumerate(anc):
+		anclevel, anctype, _ancdata = a
+		dirprintlines(dir, f'Ancillary #{i}: level {anclevels[anclevel]}, type {anctypes[anctype]}')
+		fds = show_anc(dir, a)
 	to.sendmsg([data], anc, flags)
+	if fds: log.debug(f'Closing fds: {fds}')
+	for fd in fds: os.close(fd)
 
 def main():
 	setup_logging()