nfs-utils: add and use nfs_authsys_create

The current mount, umount and showmount code uses
authunix_create_default to get an auth handle. The one provided by glibc
returned a truncated list of groups when there were more than 16 groups.
libtirpc however currently does an abort() in this case, which causes
the program to crash and dump core.

nfs-utils just uses these auth handles for the MNT protocol, so the
group list doesn't make a lot of difference here. Add a new function
that creates an auth handle with a supplemental gids list that consists
only of the primary gid. Have nfs-utils use that function anywhere that
it currently uses authunix_create_default. Also, have the caller
properly check for a NULL return from that function.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve Dickson <steved@redhat.com>

2 files changed, 24 insertions, 0 deletions

diff --git a/support/include/nfsrpc.h b/support/include/nfsrpc.h
index 4db35ab..6ebefca 100644
--- a/support/include/nfsrpc.h
+++ b/support/include/nfsrpc.h
@@ -160,4 +160,7 @@ extern int		nfs_rpc_ping(const struct sockaddr *sap,
 				const unsigned short protocol,
 				const struct timeval *timeout);
 
+/* create AUTH_SYS handle with no supplemental groups */
+extern AUTH *			 nfs_authsys_create(void);
+
 #endif	/* !__NFS_UTILS_NFSRPC_H */
diff --git a/support/nfs/rpc_socket.c b/support/nfs/rpc_socket.c
index 0e20824..aa6a205 100644
--- a/support/nfs/rpc_socket.c
+++ b/support/nfs/rpc_socket.c
@@ -557,3 +557,24 @@ rpcprog_t nfs_getrpcbyname(const rpcprog_t program, const char *table[])
 
 	return program;
 }
+
+/*
+ * AUTH_SYS doesn't allow more than 16 gids in the supplemental group list.
+ * If there are more than that, trying to determine which ones to include
+ * in the list is problematic. This function creates an auth handle that
+ * only has the primary gid in the supplemental gids list. It's intended to
+ * be used for protocols where credentials really don't matter much (the MNT
+ * protocol, for instance).
+ */
+AUTH *
+nfs_authsys_create(void)
+{
+	char machname[MAXHOSTNAMELEN + 1];
+	uid_t	uid = geteuid();
+	gid_t	gid = getegid();
+
+	if (gethostname(machname, sizeof(machname)) == -1)
+		return NULL;
+
+	return authsys_create(machname, uid, gid, 1, &gid);
+}