[PATCH] mount.cifs: check access of credential files before opening

[Jeff Layton]

It's possible for an unprivileged user to pass a setuid mount.cifs a
credential or password file to which he does not have access. This can cause
mount.cifs to open the file on his behalf and possibly leak the info in the
first few lines of the file.

Check the access permissions of the file before opening it.

Reported-by: Ronald Volgers <r.c.volgers at student.utwente.nl>
Signed-off-by: Jeff Layton <jlayton at redhat.com>
Acked-by: Steve French <sfrench at us.ibm.com>
---
 source/client/mount.cifs.c |   11 +++++++++++
 1 files changed, 11 insertions(+), 0 deletions(-)

diff --git a/source/client/mount.cifs.c b/source/client/mount.cifs.c
index d05115b..cee9188 100644
--- a/source/client/mount.cifs.c
+++ b/source/client/mount.cifs.c
@@ -199,6 +199,11 @@ static int open_cred_file(char * file_name)
 	char * temp_val;
 	FILE * fs;
 	int i, length;
+
+	i = access(file_name, R_OK);
+	if (i)
+		return i;
+
 	fs = fopen(file_name,"r");
 	if(fs == NULL)
 		return errno;
@@ -321,6 +326,12 @@ static int get_password_from_file(int file_descript, char * filename)
 	}
 
 	if(filename != NULL) {
+		rc = access(filename, R_OK);
+		if (rc) {
+			fprintf(stderr, "mount.cifs failed: access check of %s failed: %s\n",
+					filename, strerror(errno));
+			exit(2);
+		}
 		file_descript = open(filename, O_RDONLY);
 		if(file_descript < 0) {
 			printf("mount.cifs failed. %s attempting to open password file %s\n",
-- 
1.6.0.6


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