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Re: Re : breakage in emacsclient

From: Andrew Eggenberger
Subject: Re: Re : breakage in emacsclient
Date: Tue, 10 Nov 2020 21:24:27 -0600

Hi Sam,

I made a patch based on your advice that solves the issue for me. Any feedback
would be appreciated. Thanks for your help.

diff --git a/pflocal/io.c b/pflocal/io.c
index 23e71ea4..2a6b104c 100644
--- a/pflocal/io.c
+++ b/pflocal/io.c
@@ -327,6 +327,8 @@ S_io_stat (struct sock_user *user, struct stat *st)
   st->st_ino = sock->id;
   /* As we try to be clever with large transfers, ask for them. */
   st->st_blksize = vm_page_size * 16;
+  st->st_uid = sock->uid;
+  st->st_gid = sock->gid;
   pthread_mutex_lock (&sock->lock); /* Make sure the pipes don't go away...  */
diff --git a/pflocal/mig-mutate.h b/pflocal/mig-mutate.h
index 0743f336..88c9d7da 100644
--- a/pflocal/mig-mutate.h
+++ b/pflocal/mig-mutate.h
@@ -39,4 +39,10 @@
 #define ADDRPORT_INTRAN_PAYLOAD addr_t begin_using_addr_payload
 #define ADDRPORT_DESTRUCTOR end_using_addr_port (addr_t)
-#define SOCKET_IMPORTS import "mig-decls.h";
+  import "mig-decls.h"; \
+  import "../libtrivfs/mig-decls.h"; \
+#define PF_INTRAN trivfs_protid_t trivfs_begin_using_protid (pf_t)
+#define PF_INTRAN_PAYLOAD trivfs_protid_t trivfs_begin_using_protid_payload
+#define PF_DESTRUCTOR trivfs_end_using_protid (trivfs_protid_t)
diff --git a/pflocal/pf.c b/pflocal/pf.c
index 35b3d8c3..c905f3bf 100644
--- a/pflocal/pf.c
+++ b/pflocal/pf.c
@@ -21,6 +21,7 @@
 #include <stddef.h>
 #include <sys/socket.h>
 #include <hurd/pipe.h>
+#include <hurd/trivfs.h>
 #include "sock.h"
@@ -29,7 +30,7 @@
 /* Create a new socket.  Sock type is, for example, SOCK_STREAM,
    SOCK_DGRAM, or some such.  */
-S_socket_create (mach_port_t pf,
+S_socket_create (trivfs_protid_t pf,
   int sock_type, int protocol,
   mach_port_t *port, mach_msg_type_name_t *port_type)
@@ -77,6 +78,11 @@ S_socket_create (mach_port_t pf,
  *port_type = MACH_MSG_TYPE_MAKE_SEND;
+  if (pf->user->uids->num > 0)
+    sock->uid = pf->user->uids->ids[0];
+  if (pf->user->gids->num > 0)
+    sock->gid = pf->user->gids->ids[0];
   return err;
diff --git a/pflocal/sock.c b/pflocal/sock.c
index 89ba16e2..e39e2932 100644
--- a/pflocal/sock.c
+++ b/pflocal/sock.c
@@ -123,6 +123,8 @@ sock_create (struct pipe_class *pipe_class, mode_t mode, struct sock **sock)
   new->connect_queue = NULL;
   new->pipe_class = pipe_class;
   new->addr = NULL;
+  new->uid = 0;
+  new->gid = 0;
   memset (&new->change_time, 0, sizeof (new->change_time));
   pthread_mutex_init (&new->lock, NULL);
diff --git a/pflocal/sock.h b/pflocal/sock.h
index c1e73f9b..c3061246 100644
--- a/pflocal/sock.h
+++ b/pflocal/sock.h
@@ -85,6 +85,10 @@ struct sock
   /* A connection queue we're attempting to connect through; a socket may
      only be attempting one connection at a time.  */
   struct connq *connect_queue;
+  uid_t uid;
+  gid_t gid;
 /* Socket flags */

Andrew Eggenberger

On Mon, Nov 9, 2020 at 2:53 PM Samuel Thibault <samuel.thibault@gnu.org> wrote:
Andrew Eggenberger, le jeu. 29 oct. 2020 16:12:47 -0500, a ecrit:
>     I think the problem is with the pflocal/io.c implementation of S_io_stat.
>     calling fstat on the 
>     file descriptor of a socket created with cloexec_socket (AF_UNIX,
>     SOCK_STREAM, 0);. But S_io_stat doesn't set uid.

Indeed.  The more complete story is that

- on the application side, socket() calls _hurd_socket_server, which
  opens /servers/socket/1
- on the pflocal side, that translates to calling trivfs_S_dir_lookup,
  which does receive the user credentials in its cred parameter, and
  calls trivfs_open that creates a struct trivfs_peropen and struct
  trivfs_protid in which the user field points to the credentials.

- then on the application side, socket() calls __socket_create
- on the pflocal side, that translates to calling S_socket_create.
  There, the pf port is for now untranslated (showing up as a
  mach_port_t), but you can add to pflocal/mig-mutate.h the same
  pfinet/mig-mutate.h, so that S_socket_create (and others in the same
  file) get the translated port (showing up as a struct trivfs_protid
  *master). Then you have access to the credential, and can record
  uid/gid in a new field of struct sock.

> The problem is that /hurd/pflocal is owned by and in
> the group root,

Well, that's unrelated. io_stat memsets the struct stat to 0 anyway.


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