fishdescriptor: new approach

[chiark-utils.git] / fishdescriptor / py / fishdescriptor / fish.py

diff --git a/fishdescriptor/py/fishdescriptor/fish.py b/fishdescriptor/py/fishdescriptor/fish.py
index 101a461f7c1e52be2f1487be03a6061787e8d288..95694ff2eaceac3eb59c1b0d672eadf9405c0885 100644 (file)
--- a/fishdescriptor/py/fishdescriptor/fish.py
+++ b/fishdescriptor/py/fishdescriptor/fish.py
@@ -2,38 +2,132 @@
 
 import socket
 import subprocess
+import os
+import pwd
+
+def _shuffle_fd3():
+    os.dup(1,3)
+    os.dup(2,1)
 
 class Donor():
-    def __init__(s):
-        pass
+    def __init__(d, pid):
+        d._pid = pid
+        d._sp = subprocess.Popen(
+            preexec_fn = _suffle_fd3,
+            stdin = subprocess.PIPE,
+            stdout = subprocess.PIPE,
+            close_fds = False,
+            args = ['gdb', '-p', pid, '-batch', '-ex'
+                    'python import fishdescriptor.indonor as id;'+
+                    ' id.DonorImplementation().eval_loop()'
+                ]
+        )            
 
-    def _ancilmsg(fds):
-        '''
+    def _eval_integer(d, expr):
+        l = d._sp.stdin.readline()
+        if l != '!\n': raise RuntimeError("indonor said %s" % repr(l))
+        d._sp.stdout.write(expr + '\n')
+        d._sp.stdout.flush()
+        l = d._sp.stdin.readline().rstrip('\n')
+        return int(l)
+
+    def _eval_success(d, expr):
+        r = d._eval_integer(expr)
+        if r != 1: raise RuntimeError("eval of %s gave %d" % (expr, r))
+
+    def _geteuid(d):
+        return d._eval_integer('di.geteuid()')
+
+    def _ancilmsg(d, fds):
+        perl_script = '''
+            use strict;
             use Socket;
             use Socket::MsgHdr;
             my $fds = pack "i*", @ARGV;
             my $m = Socket::MsgHdr::pack_cmsghdr SOL_SOCKET, SCM_RIGHTS, $fds;
-            print join ", ", unpack "C*", $m
+            print join ", ", unpack "C*", $m;
         '''
+        ap = subprocess.Popen(
+            stdin = subprocess.DEVNULL,
+            stdout = subprocess.PIPE,
+            args = ['perl','-we',perl_script] + fds
+        )
+        (output, dummy) = ap.communicate()
+        return output
+
+    def donate(d, path, fds):
+        ancil = d._ancilmsg(fds)
+        d._eval_success('di.donate(%s, %s)'
+                        % (repr(path), ancil))
+        return len(ancil.split(','))
+
+    def mkdir(d, path):
+        d._eval_integer('di.mkdir(%s)'
+                        % (repr(path)))
+
+    def _exists(d, path):
+        try:
+            os.stat(path)
+            return True
+        except OSError as oe:
+            if oe.errno != os.errno.ENOENT: raise oe
+            return False
+
+    def _sock_dir(d, target_euid):
+        run_dir = '/run/user/%d' % target_euid
+        if d._exists(run_dir):
+            return run_dir + 'fishdescriptor'
+
+        try:
+            pw = pwd.getpwuid(target_euid)
+            return pw.pw_dir + '.fishdescriptor'
+        except KeyError:
+            pass
+
+        raise RuntimeError(
+ 'cannot find good socket path - no /run/user/UID nor pw entry for target process euid %d'
+            % target_euid
+        )
+
+    def fish(d, fds):
+        # -> list of fds in our process
+
+        euid = d._geteuid()
+        sockdir = d._sock_dir(euid)
+        d.mkdir(sockdir)
+
+        sockname = '%s/%s,%d' % (sockdir, os.uname().nodename, d._pid)
+
+        target_root = '/proc/%d/root/' % d._pid
+        if not d._exists(target_root):
+            target_root = ''
+
+        our_sockname = target_root + sockname
+
+        s = None
+        s2 = None
+
+        try:
+            try: os.remove(our_sockname)
+            except FileNotFoundError: pass
+
+            s = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+            s.bind(our_sockname)
+            s.listen(1)
+
+            ancil_len = d.donate(our_sockname, fds)
+            s2 = s.accept()
+            (msg, ancil, flags, sender) = s2.recvmsg(1, ancil_len)
+
+            got_fds = [ ]
+
+            for clvl, ctype, cdata in ancil:
+                if clvl == socket.SOL_SOCKET and ctype == socket.SCM_RIGHTS:
+                    got_fds += cdata # need to trim any surplus, and unpack
+
+        finally:
+            if s is not None: s.close()
+            if s2 is not None: s2.close()
 
-def _geteuid(pid):
-    def _shuffle_fd3():
-        dup(1,3)
-        dup(2,1)
-    sp = subprocess.Popen(preexec_fn = _suffle_fd3,
-          stdin = subprocess.DEVNULL, stdout = subprocess.PIPE,
-          close_fds = False,
-          args = ['gdb', '-p', pid, '-batch', '-ex'
-                  'python import os; os.fdopen(30,"w").write("%d\n" % '
-                  +'gdb.parse_and_eval("(uid_t)geteuid()"))'])
-    (output, dummy) = sp.communicate()
-    
-2009
-
-def fish(pid, fds):
-    # -> list of fds in our process
-    sockname = '/run/user/' + 
-    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
-
-def deliver(pid, fds, path):
-    gdb -batch -p %d -ex '
+            try: os.remove(our_sockname)
+            except FileNotFoundError: pass