Adds block-outdated-clients pre-receive hook

pre-receive-hooks/block-outdated-clients.sh

@@ -0,0 +1,140 @@
+#!/usr/bin/env bash
+
+#
+# Git Block Outdated Clients pre-receive hook
+#
+# Minimum required version of GHES: 2.22
+# This is an implementation of a pre-receive hook for GHES that checks if the current version from the
+# user is older than the current version.
+#
+# If the version is outdated it prints a message encouraging the user to update the client. However if this
+# version has a minor diff greater than max_minor_diff the hook fails and
+# the user cannot push the changes. You can also block specific versions by adding them to the
+# block_list.
+#
+# Test this locally setting $GIT_USER_AGENT. ex. GIT_USER_AGENT=git/2.2.23 and exporting it.
+# Also add to the $GH_TOKEN a personal access token for adding more authentication requests on getting the version
+# if you want it dynamically:
+# ```
+# $ GIT_USER_AGENT=git/2.2.23
+# $ GH_TOKEN=token
+# $ export GH_TOKEN
+# $ export GIT_USER_AGENT
+# $ sh git_hook_outdated_clients.sh
+# ```
+#
+# Edit this variables to set the policy for the git version
+#
+# max_minor_diff: the number of git versions allowed from the latest one.
+# block_list: a list containing specific versions that are blocked by policy
+max_minor_diff=3
+block_list=(
+)
+
+# Edit this variables to get the right version to compare as latest
+# latest_version: add the latest version to check or leave it empty to let the script get it dynamically
+# authentication: provide a PAT on the environment if you want to execute the request to get the version without triggering the rate limit.
+# If you don't provide the latest version we strongly recommend to add a GH_TOKEN to the environment. It requires jq as dependency
+latest_version=""
+authentication=$GH_TOKEN
+
+DEBUG=1
+
+function block_version {
+  echo "#########################################"
+  echo "##     Outdated git version $1     ##"
+  echo "#########################################"
+  echo ""
+  echo "Update the git version to a newest one: https://git-scm.com/downloads"
+
+  exit 1;
+}
+
+#################################
+# Parse the version from the user
+# agent
+#################################
+user_version=$GIT_USER_AGENT
+if [[ $user_version =~ [0-9]+\.[0-9]+\.[0-9]+ ]]; then
+  version=${BASH_REMATCH[0]}
+  echo "Current git version: $version"
+else
+  echo "The user agent used is not supported as it doesn't provide the version it is using"
+  exit 1;
+fi
+
+#################################
+# Check if the version belongs to
+# the block list
+#################################
+for i in "${block_list[@]}"
+do
+  if [ "$i" == "$version" ]; then
+    echo "The version $i is blocked by policy for security reasons. Please update"
+    block_version "$version"
+  fi
+done
+
+#################################
+# Get the latest version from an
+# external source if not available
+# and validate it
+#################################
+if [ "$latest_version" == "" ]; then
+  latest_version=$(curl -s -X GET -H "Authorization: token $authentication" https://api.github.com/repos/git/git/tags \
+    | jq ".[0].name")
+    if [[ $latest_version =~ [0-9]+\.[0-9]+\.[0-9]+ ]]; then
+      latest_version=${BASH_REMATCH[0]}
+    else
+      echo "Something went wrong getting the latest version. Try it again in a few moments"
+      exit 1;
+    fi
+fi
+
+if ! [[ $latest_version =~ [0-9]+\.[0-9]+\.[0-9]+ ]]; then
+  echo "The latest version $latest_version doesn't match the version pattern. Review the parameter latest_version and
+  add a version following semantic versioning"
+  exit 1;
+fi
+
+echo "Latest certified git version: $latest_version"
+IFS="." read -r -a version_match <<< "$latest_version"
+latest_major="${version_match[0]}"
+latest_minor="${version_match[1]}"
+
+#################################
+# Parse the versions
+#################################
+IFS="." read -r -a version_match <<< "$version"
+major="${version_match[0]}"
+minor="${version_match[1]}"
+
+if [ $DEBUG -eq 0 ]; then
+  echo "
+  Current version
+  =====================
+  Major: $major
+  Minor: $minor
+
+  Latest version
+  =====================
+  Major: $latest_major
+  Minor: $latest_minor
+  "
+fi
+
+#################################
+# Check for the version policies
+#################################
+# Major versions should be always updated if there is a new one
+if [ "$major" != "$latest_major" ]; then
+  block_version "$version"
+fi
+
+# Minor versions can be checked by max_minor_diff
+allowed_minor=$((minor + max_minor_diff))
+if [ "$allowed_minor" -lt "$latest_minor" ]; then
+  block_version "$version"
+fi
+
+exit 0;