Fix script so that it doesn't constantly concatenate.

BUG=b/300016454
TEST=None
RELEASE_NOTE=None

cos-patch: bug
Change-Id: I884fcc6c49d5fc3af80bfe2a8d3388d5f7e8d29b

alphabet-compliance/scripts/5330-password-reuse-limited.sh

diff --git a/alphabet-compliance/scripts/5330-password-reuse-limited.sh b/alphabet-compliance/scripts/5330-password-reuse-limited.sh
index f5372eb..a2822f9 100644
--- a/alphabet-compliance/scripts/5330-password-reuse-limited.sh
+++ b/alphabet-compliance/scripts/5330-password-reuse-limited.sh
@@ -14,6 +14,16 @@
 # limitations under the License.
 
 ## Section: 5.3.3 Ensure password reuse is limited (Not Scored) ##
-sed -i '0,/password/s//password        required        pam_pwhistory.so remember=5\n&/' \
-  /etc/pam.d/system-auth
-sed -i 's/password.*pam_unix.so/& remember=5/' /etc/pam.d/system-auth
+# Check if the changes have already been made
+if ! grep -q \
+  "password[[:space:]]*required[[:space:]]*pam_pwhistory.so[[:space:]]*remember=5" \
+  /etc/pam.d/system-auth; then
+  sed -i \
+    '0,/password/s//password        required        pam_pwhistory.so remember=5\n&/' \
+    /etc/pam.d/system-auth
+fi
+if ! grep -q \
+  "password[[:space:]]*required[[:space:]]*pam_unix.so[[:space:]]*remember=5" \
+  /etc/pam.d/system-auth; then
+  sed -i 's/password.*pam_unix.so/& remember=5/' /etc/pam.d/system-auth
+fi