From 8296051653a8187374ad51a3a487315767b73a19 Mon Sep 17 00:00:00 2001
From: Dennis Camera <dennis.camera@ssrq-sds-fds.ch>
Date: Fri, 16 Apr 2021 19:22:58 +0200
Subject: [PATCH] [type/__postgres_extension] Add state explorer

---
 .../type/__postgres_extension/explorer/state  | 41 ++++++++++++++
 .../type/__postgres_extension/gencode-remote  | 44 ++++++++++-----
 cdist/conf/type/__postgres_extension/man.rst  | 55 +++++++++++--------
 3 files changed, 104 insertions(+), 36 deletions(-)
 create mode 100644 cdist/conf/type/__postgres_extension/explorer/state

diff --git a/cdist/conf/type/__postgres_extension/explorer/state b/cdist/conf/type/__postgres_extension/explorer/state
new file mode 100644
index 00000000..9d156be7
--- /dev/null
+++ b/cdist/conf/type/__postgres_extension/explorer/state
@@ -0,0 +1,41 @@
+#!/bin/sh -e
+# -*- mode: sh; indent-tabs-mode: t -*-
+#
+# 2021 Dennis Camera (dennis.camera at ssrq-sds-fds.ch)
+#
+# This file is part of cdist.
+#
+# cdist is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# cdist is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with cdist. If not, see <http://www.gnu.org/licenses/>.
+#
+# Prints "present" if the extension is currently installed.
+# "absent" otherwise.
+
+quote() { printf '%s\n' "$*" | sed "s/'/'\\\\''/g;1s/^/'/;\$s/\$/'/"; }
+
+postgres_user=$("${__type_explorer:?}/postgres_user")
+
+IFS=: read -r dbname extname <<EOF
+${__object_id:?}
+EOF
+
+psql_exec() {
+	su - "${postgres_user}" -c "psql $(quote "$1") -twAc $(quote "$2")"
+}
+
+if psql_exec "${dbname}" 'SELECT extname FROM pg_extension' | grep -qFx "${extname}"
+then
+	echo present
+else
+	echo absent
+fi
diff --git a/cdist/conf/type/__postgres_extension/gencode-remote b/cdist/conf/type/__postgres_extension/gencode-remote
index a1c84828..4ce72622 100755
--- a/cdist/conf/type/__postgres_extension/gencode-remote
+++ b/cdist/conf/type/__postgres_extension/gencode-remote
@@ -2,9 +2,10 @@
 #
 # 2011 Steven Armstrong (steven-cdist at armstrong.cc)
 # 2013 Tomas Pospisek (tpo_deb at sourcepole.ch)
+# 2021 Dennis Camera (dennis.camera at ssrq-sds-fds.ch)
 #
 # This type was created by Tomas Pospisek based on the
-#__postgres_role type by Steven Armstrong
+# __postgres_role type by Steven Armstrong.
 #
 # This file is part of cdist.
 #
@@ -24,19 +25,36 @@
 
 postgres_user=$(cat "${__object:?}/explorer/postgres_user")
 
+quote() { printf '%s\n' "$*" | sed "s/'/'\\\\''/g;1s/^/'/;\$s/\$/'/"; }
+psql_cmd() {
+	printf 'su - %s -c %s\n' \
+		"$(quote "${postgres_user}")" \
+		"$(quote psql "$(quote "$1")" -c "$(quote "$2")")"
+}
 
-dbname=$(    echo "$__object_id" | cut -d":" -f1 )
-extension=$( echo "$__object_id" | cut -d":" -f2 )
 
-state_should=$( cat "$__object/parameter/state" )
+IFS=: read -r dbname extname <<EOF
+${__object_id:?}
+EOF
 
-case "$state_should" in
-    present)
-         cmd="CREATE EXTENSION IF NOT EXISTS $extension"
-         echo "su - '$postgres_user' -c 'psql -c \"$cmd\" \"$dbname\"'"
-    ;;
-    absent)
-         cmd="DROP EXTENSION IF EXISTS $extension"
-         echo "su - '$postgres_user' -c 'psql -c \"$cmd\" \"$dbname\"'"
-    ;;
+state_is=$(cat "${__object:?}/explorer/state")
+state_should=$(cat "${__object:?}/parameter/state")
+
+if test "${state_is}" = "${state_should}"
+then
+	exit 0
+fi
+
+case ${state_should}
+in
+	(present)
+		psql_cmd "${dbname}" "CREATE EXTENSION ${extname}"
+		;;
+	(absent)
+		psql_cmd "${dbname}" "DROP EXTENSION ${extname}"
+		;;
+	(*)
+		printf 'Invalid --state: %s\n' "${state_should}" >&2
+		exit 1
+		;;
 esac
diff --git a/cdist/conf/type/__postgres_extension/man.rst b/cdist/conf/type/__postgres_extension/man.rst
index 79645b2b..442239f6 100644
--- a/cdist/conf/type/__postgres_extension/man.rst
+++ b/cdist/conf/type/__postgres_extension/man.rst
@@ -3,32 +3,36 @@ cdist-type__postgres_extension(7)
 
 NAME
 ----
-cdist-type__postgres_extension - manage postgres extensions
+cdist-type__postgres_extension - Manage PostgreSQL extensions
 
 
 DESCRIPTION
 -----------
-This cdist type allows you to create or drop postgres extensions.
+This cdist type allows you to manage PostgreSQL extensions.
 
-The object you need to pass to __postgres_extension consists of
-the database name and the extension name joined by a colon in the
-following form:
-
-.. code-block:: sh
-
-    dbname:extension
-
-f.ex.
+The ``__object_id`` to pass to ``__postgres_extension`` is of the form
+``dbname:extension``, e.g.:
 
 .. code-block:: sh
 
     rails_test:unaccent
 
 
+**CAUTION!** Be careful when installing extensions from (untrusted) third-party
+sources:
+
+   | Installing an extension as superuser requires trusting that the extension's
+     author wrote the extension installation script in a secure fashion. It is
+     not terribly difficult for a malicious user to create trojan-horse objects
+     that will compromise later execution of a carelessly-written extension
+     script, allowing that user to acquire superuser privileges.
+   | – `<https://www.postgresql.org/docs/13/sql-createextension.html#id-1.9.3.64.7>`_
+
+
 OPTIONAL PARAMETERS
 -------------------
 state
-    either "present" or "absent", defaults to "present"
+    either ``present`` or ``absent``, defaults to ``present``.
 
 
 EXAMPLES
@@ -36,24 +40,29 @@ EXAMPLES
 
 .. code-block:: sh
 
-    __postgres_extension           rails_test:unaccent
-    __postgres_extension --present rails_test:unaccent
-    __postgres_extension --absent  rails_test:unaccent
+   # Install extension unaccent into database rails_test
+   __postgres_extension rails_test:unaccent
+
+   # Drop extension unaccent from database fails_test
+   __postgres_extension rails_test:unaccent --state absent
 
 
 SEE ALSO
 --------
-:strong:`cdist-type__postgre_database`\ (7)
+- :strong:`cdist-type__postgres_database`\ (7)
+- PostgreSQL "CREATE EXTENSION" documentation at:
+  `<http://www.postgresql.org/docs/current/static/sql-createextension.html>`_.
 
-Postgres "Create Extension" documentation at: <http://www.postgresql.org/docs/current/static/sql-createextension.html>.
 
-AUTHOR
+AUTHORS
 -------
-Tomas Pospisek <tpo_deb--@--sourcepole.ch>
+| Tomas Pospisek <tpo_deb--@--sourcepole.ch>
+| Dennis Camera <dennis.camera--@--ssrq-sds-fds.ch>
+
 
 COPYING
 -------
-Copyright \(C) 2014 Tomas Pospisek. You can redistribute it
-and/or modify it under the terms of the GNU General Public License as
-published by the Free Software Foundation, either version 3 of the
-License, or (at your option) any later version.
+Copyright \(C) 2014 Tomas Pospisek, 2021 Dennis Camera.
+You can redistribute it and/or modify it under the terms of the GNU General
+Public License as published by the Free Software Foundation, either version 3 of
+the License, or (at your option) any later version.