Fix unpack of abstract socket addrs with nul byte

Addresses of Linux abstract namespace sockets are not nul-terminated C
strings, but rather an arbitrary character arrays. According to unix(7)
documentation from Linux, "Null bytes in the name have  no special
significance."

unpack_sockaddr_un() was just throwing the initial nul byte away and
then treating the rest like ordinary C string when computing the length
of the address, which was wrong. This fix utilizes the length of the PV
for addresses starting with nul instead.

The regression test was extended with check for the problem.

diff --git a/ext/Socket/Socket.xs b/ext/Socket/Socket.xs
index d46a6b9..3820225 100644 (file)
--- a/ext/Socket/Socket.xs
+++ b/ext/Socket/Socket.xs
@@ -363,7 +363,7 @@ unpack_sockaddr_un(sun_sv)
        struct sockaddr_un addr;
        STRLEN sockaddrlen;
        char * sun_ad = SvPVbyte(sun_sv,sockaddrlen);
-       char * e;
+       int addr_len;
 #   ifndef __linux__
        /* On Linux sockaddrlen on sockets returned by accept, recvfrom,
           getpeername and getsockname is not equal to sizeof(addr). */
@@ -382,13 +382,17 @@ unpack_sockaddr_un(sun_sv)
                        addr.sun_family,
                        AF_UNIX);
        }
-       e = (char*)addr.sun_path;
-       /* On Linux, the name of abstract unix domain sockets begins
-        * with a '\0', so allow this. */
-       while ((*e || (e == addr.sun_path && e[1] && sockaddrlen > 1))
-               && e < (char*)addr.sun_path + sizeof addr.sun_path)
-           ++e;
-       ST(0) = sv_2mortal(newSVpvn(addr.sun_path, e - (char*)addr.sun_path));
+
+       if (addr.sun_path[0] == '\0') {
+               /* Linux-style abstract socket address begins with a nul
+                * and can contain nuls. */
+               addr_len = (void *)&addr - (void *)&addr.sun_path + sockaddrlen;
+       } else {
+               for (addr_len = 0; addr.sun_path[addr_len]
+                    && addr_len < sizeof addr.sun_path; addr_len++);
+       }
+
+       ST(0) = sv_2mortal(newSVpvn(addr.sun_path, addr_len));
 #else
        ST(0) = (SV *) not_here("unpack_sockaddr_un");
 #endif

diff --git a/ext/Socket/t/Socket.t b/ext/Socket/t/Socket.t
old mode 100644 (file)
new mode 100755 (executable)
index ac50cbe..9a6d31f
--- a/ext/Socket/t/Socket.t
+++ b/ext/Socket/t/Socket.t
@@ -150,7 +150,7 @@ print (($@ =~ /^Bad arg length for Socket::sockaddr_family, length is 0, should
 
 if ($^O eq 'linux') {
     # see if we can handle abstract sockets
-    my $test_abstract_socket = chr(0) . '/tmp/test-perl-socket';
+    my $test_abstract_socket = chr(0) . '/org/perl/hello'. chr(0) . 'world';
     my $addr = sockaddr_un ($test_abstract_socket);
     my ($path) = sockaddr_un ($addr);
     if ($test_abstract_socket eq $path) {