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unix.7: Move discussion on pathname socket permissions to DESCRIPTION 

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This commit is contained in:
Michael Kerrisk 2016-06-20 11:14:27 +02:00
parent b2bbcdb6ac
commit 9f213833a4
1 changed files with 29 additions and 28 deletions
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man7/unix.7
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@ -223,6 +223,35 @@ if the output value exceeds the input value,
then there is no guarantee that a null terminator is present in
.IR sun_path .
(See BUGS.)
.\"
.SS Pathname socket ownership and permissions
In the Linux implementation,
pathname sockets honor the permissions of the directory they are in.
Creation of a new socket will fail if the process does not have write and
search (execute) permission on the directory in which the socket is created.
On Linux,
connecting to a stream socket object requires write permission on that socket;
sending a datagram to a datagram socket likewise
requires write permission on that socket.
POSIX does not make any statement about the effect of the permissions
on a socket file, and on many systems (e.g., several BSD derivatives),
the socket permissions are ignored.
Portable programs should not rely on
this feature for security.
When creating a new socket, the owner and group of the socket file
are set according to the usual rules.
The socket file has all permissions enabled,
other than those that are turned off by the process
.BR umask (2).
The owner, group, and permissions of a pathname socket can be changed (using
.BR chown (2)
and
.BR chmod (2)).
.\" However, fchown() and fchmod() do not seem to have an effect
.\"
.SS Socket options
For historical reasons, these socket options are specified with a
.B SOL_SOCKET
@ -522,34 +551,6 @@ call.
UNIX domain stream sockets do not support the notion of out-of-band data.
.\"
.SS Socket ownership and permissions
In the Linux implementation,
pathname sockets honor the permissions of the directory they are in.
Creation of a new socket will fail if the process does not have write and
search (execute) permission on the directory in which the socket is created.
On Linux,
connecting to a stream socket object requires write permission on that socket;
sending a datagram to a datagram socket likewise
requires write permission on that socket.
POSIX does not make any statement about the effect of the permissions
on a socket file, and on many systems (e.g., several BSD derivatives),
the socket permissions are ignored.
Portable programs should not rely on
this feature for security.
When creating a new socket, the owner and group of the socket file
are set according to the usual rules.
The socket file has all permissions enabled,
other than those that are turned off by the process
.BR umask (2).
The owner, group, and permissions of a pathname socket can be changed (using
.BR chown (2)
and
.BR chmod (2)).
.\" However, fchown() and fchmod() do not seem to have an effect
.\"
.SH BUGS
When binding a socket to an address,
Linux is one of the implementations that appends a null terminator