Fix: Fixed issue while installing debian credentials (#1987)

Fixed issue in .deb credential script that throws an error when running script twice for a username to replace a credential

---------

Co-authored-by: Joseph Lee <joseph.lee.esl@gmail.com>

tools/gvm-lsc-deb-creator

@@ -30,6 +30,7 @@ TEMP_DIR="$3"
 OUTPUT_PATH=$4
 MAINTAINER_EMAIL="$5"
 
+# Verify required args
 if [ -z "${USERNAME}" ]
 then
   echo "No username given" >&2
@@ -38,7 +39,7 @@ fi
 
 if [ -z "${PUBKEY_FILE}" ]
 then
-  echo "No pubkey path given" >&2
+  echo "No pubkey at given path" >&2
   exit 1
 fi
 
@@ -54,6 +55,7 @@ then
   exit 1
 fi
 
+# Ensure maintainer email
 if [ -z "${MAINTAINER_EMAIL}" ]
 then
   MAINTAINER_HOSTNAME="$(hostname)"
@@ -71,7 +73,7 @@ PACKAGE_VERSION="0.5-1"
 PACKAGE_NAME_VERSION="${PACKAGE_NAME}_${PACKAGE_VERSION}"
 MAINTAINER="Greenbone Vulnerability Manager  <${MAINTAINER_EMAIL}>"
 PACKAGE_DATE=$(date "+%a, %d %b %Y %H:%M:%S %z")
-
+# Used for identifying username entry in /etc/passwd
 USER_COMMENT="GVM Local Security Checks"
 USER_COMMENT_GREP="GVM\\ Local\\ Security\\ Checks"
 
@@ -194,6 +196,9 @@ chmod "0755" "${PREINST_FILE}"
 {
   echo "#!/bin/sh"
   echo "set -e  # abort on errors"
+  echo "# Delete GVM Local Security Checks user by username and comment identifier"
+  echo "grep \"${USERNAME}.*${USER_COMMENT_GREP}\" /etc/passwd && userdel -fr ${USERNAME}"
+  echo "# GVM Local Security Checks user and create home directory"
   echo "useradd -c \"${USER_COMMENT}\" -d /home/${USERNAME} -m -s /bin/bash ${USERNAME}"
 } > "${PREINST_FILE}"
 
@@ -204,6 +209,7 @@ chmod "0755" "${POSTINST_FILE}"
 {
   echo "#!/bin/sh"
   echo "set -e  # abort on errors"
+  echo "# Change file permissions"
   echo "chown -R ${USERNAME}:${USERNAME} /home/${USERNAME}"
   echo "chmod 500 /home/${USERNAME}/.ssh"
   echo "chmod 400 /home/${USERNAME}/.ssh/authorized_keys"
@@ -215,13 +221,15 @@ touch "${POSTRM_FILE}"
 chmod "0755" "${POSTRM_FILE}"
 {
   echo "#!/bin/sh"
-  echo "# Remove user only if it was created by this package."
+  echo "# Remove user only if it was created by this package and only"
+  echo "# if postrm is not called when reinstalling the same package."
   echo "# The debian package will run the postun script in case of errors"
   echo "# (e.g. user already existed)."
   echo "# Delete the user only if /etc/passwd lists content that suggests"
   echo "# that the user was created by this package."
   # echo "set -e  # abort on errors"
-  echo "grep \"${USERNAME}.*${USER_COMMENT_GREP}\" /etc/passwd && userdel -fr ${USERNAME}"
+  echo "if [ \$1 != \"upgrade\" ]; then grep \"${USERNAME}.*${USER_COMMENT_GREP}\" /etc/passwd && userdel -fr ${USERNAME}; fi"
+  echo "exit 0"
 } > "${POSTRM_FILE}"
 
 # Calculate md5 checksums