Resolve slow key retrieval when some GPG key servers are not reachable (#1016)

* Reduce timeout to GPG key servers for Python feature

* Dynamically find out reachable GPG servers

* Apply fix to other features

* Fix build issues

* Fix shellcheck SC2068 by quoting array expansion

* Bump up patch version for affected features

* improve readability for keyservers_curl_map

src/git-lfs/devcontainer-feature.json

 {
     "id": "git-lfs",
-    "version": "1.2.1",
+    "version": "1.2.2",
     "name": "Git Large File Support (LFS)",
     "documentationURL": "https://github.com/devcontainers/features/tree/main/src/git-lfs",
     "description": "Installs Git Large File Support (Git LFS) along with needed dependencies. Useful for base Dockerfiles that often are missing required install dependencies like git and curl.",

src/git-lfs/install.sh

@@ -15,10 +15,6 @@ GIT_LFS_ARCHIVE_GPG_KEY_URI="https://packagecloud.io/github/git-lfs/gpgkey"
 GIT_LFS_ARCHIVE_ARCHITECTURES="amd64 arm64"
 GIT_LFS_ARCHIVE_VERSION_CODENAMES="stretch buster bullseye bionic focal jammy"
 GIT_LFS_CHECKSUM_GPG_KEYS="0x88ace9b29196305ba9947552f1ba225c0223b187 0x86cd3297749375bcf8206715f54fe648088335a9 0xaa3b3450295830d2de6db90caba67be5a5795889"
-GPG_KEY_SERVERS="keyserver hkp://keyserver.ubuntu.com
-keyserver hkp://keyserver.ubuntu.com:80
-keyserver hkps://keys.openpgp.org
-keyserver hkp://keyserver.pgp.com"
 
 set -e
 
@@ -64,15 +60,52 @@ find_version_from_git_tags() {
     echo "${variable_name}=${!variable_name}"
 }
 
+# Get the list of GPG key servers that are reachable
+get_gpg_key_servers() {
+    declare -A keyservers_curl_map=(
+        ["hkp://keyserver.ubuntu.com"]="http://keyserver.ubuntu.com:11371"
+        ["hkp://keyserver.ubuntu.com:80"]="http://keyserver.ubuntu.com"
+        ["hkps://keys.openpgp.org"]="https://keys.openpgp.org"
+        ["hkp://keyserver.pgp.com"]="http://keyserver.pgp.com:11371"
+    )
+
+    local curl_args=""
+    local keyserver_reachable=false  # Flag to indicate if any keyserver is reachable
+
+    if [ ! -z "${KEYSERVER_PROXY}" ]; then
+        curl_args="--proxy ${KEYSERVER_PROXY}"
+    fi
+
+    for keyserver in "${!keyservers_curl_map[@]}"; do
+        local keyserver_curl_url="${keyservers_curl_map[${keyserver}]}"
+        if curl -s ${curl_args} --max-time 5 ${keyserver_curl_url} > /dev/null; then
+            echo "keyserver ${keyserver}"
+            keyserver_reachable=true
+        else
+            echo "(*) Keyserver ${keyserver} is not reachable." >&2
+        fi
+    done
+
+    if ! $keyserver_reachable; then
+        echo "(!) No keyserver is reachable." >&2
+        exit 1
+    fi
+}
+
 # Import the specified key in a variable name passed in as 
 receive_gpg_keys() {
     local keys=${!1}
 
+    # Install curl
+    if ! type curl > /dev/null 2>&1; then
+        check_packages curl
+    fi
+
     # Use a temporary location for gpg keys to avoid polluting image
     export GNUPGHOME="/tmp/tmp-gnupg"
     mkdir -p ${GNUPGHOME}
     chmod 700 ${GNUPGHOME}
-    echo -e "disable-ipv6\n${GPG_KEY_SERVERS}" > ${GNUPGHOME}/dirmngr.conf
+    echo -e "disable-ipv6\n$(get_gpg_key_servers)" > ${GNUPGHOME}/dirmngr.conf
     # GPG key download sometimes fails for some reason and retrying fixes it.
     local retry_count=0
     local gpg_ok="false"

src/git/devcontainer-feature.json

 {
     "id": "git",
-    "version": "1.3.0",
+    "version": "1.3.1",
     "name": "Git (from source)",
     "documentationURL": "https://github.com/devcontainers/features/tree/main/src/git",
     "description": "Install an up-to-date version of Git, built from source as needed. Useful for when you want the latest and greatest features. Auto-detects latest stable version and installs needed dependencies.",

src/git/install.sh

@@ -11,10 +11,6 @@ GIT_VERSION=${VERSION} # 'system' checks the base image first, else installs 'la
 USE_PPA_IF_AVAILABLE=${PPA}
 
 GIT_CORE_PPA_ARCHIVE_GPG_KEY=E1DD270288B4E6030699E45FA1715D88E1DF1F24
-GPG_KEY_SERVERS="keyserver hkp://keyserver.ubuntu.com
-keyserver hkp://keyserver.ubuntu.com:80
-keyserver hkps://keys.openpgp.org
-keyserver hkp://keyserver.pgp.com"
 
 if [ "$(id -u)" -ne 0 ]; then
     echo -e 'Script must be run as root. Use sudo, su, or add "USER root" to your Dockerfile before running this script.'
@@ -68,6 +64,38 @@ clean_up() {
 }
 clean_up
 
+# Get the list of GPG key servers that are reachable
+get_gpg_key_servers() {
+    declare -A keyservers_curl_map=(
+        ["hkp://keyserver.ubuntu.com"]="http://keyserver.ubuntu.com:11371"
+        ["hkp://keyserver.ubuntu.com:80"]="http://keyserver.ubuntu.com"
+        ["hkps://keys.openpgp.org"]="https://keys.openpgp.org"
+        ["hkp://keyserver.pgp.com"]="http://keyserver.pgp.com:11371"
+    )
+
+    local curl_args=""
+    local keyserver_reachable=false  # Flag to indicate if any keyserver is reachable
+
+    if [ ! -z "${KEYSERVER_PROXY}" ]; then
+        curl_args="--proxy ${KEYSERVER_PROXY}"
+    fi
+
+    for keyserver in "${!keyservers_curl_map[@]}"; do
+        local keyserver_curl_url="${keyservers_curl_map[${keyserver}]}"
+        if curl -s ${curl_args} --max-time 5 ${keyserver_curl_url} > /dev/null; then
+            echo "keyserver ${keyserver}"
+            keyserver_reachable=true
+        else
+            echo "(*) Keyserver ${keyserver} is not reachable." >&2
+        fi
+    done
+
+    if ! $keyserver_reachable; then
+        echo "(!) No keyserver is reachable." >&2
+        exit 1
+    fi
+}
+
 # Import the specified key in a variable name passed in as 
 receive_gpg_keys() {
     local keys=${!1}
@@ -77,11 +105,16 @@ receive_gpg_keys() {
         keyring_args="--no-default-keyring --keyring $2"
     fi
 
+    # Install curl
+    if ! type curl > /dev/null 2>&1; then
+        check_packages curl
+    fi
+    
     # Use a temporary location for gpg keys to avoid polluting image
     export GNUPGHOME="/tmp/tmp-gnupg"
     mkdir -p ${GNUPGHOME}
     chmod 700 ${GNUPGHOME}
-    echo -e "disable-ipv6\n${GPG_KEY_SERVERS}" > ${GNUPGHOME}/dirmngr.conf
+    echo -e "disable-ipv6\n$(get_gpg_key_servers)" > ${GNUPGHOME}/dirmngr.conf
     # GPG key download sometimes fails for some reason and retrying fixes it.
     local retry_count=0
     local gpg_ok="false"

src/github-cli/devcontainer-feature.json

 {
     "id": "github-cli",
-    "version": "1.0.12",
+    "version": "1.0.13",
     "name": "GitHub CLI",
     "documentationURL": "https://github.com/devcontainers/features/tree/main/src/github-cli",
     "description": "Installs the GitHub CLI. Auto-detects latest version and installs needed dependencies.",

src/github-cli/install.sh

@@ -11,10 +11,6 @@ CLI_VERSION=${VERSION:-"latest"}
 INSTALL_DIRECTLY_FROM_GITHUB_RELEASE=${INSTALLDIRECTLYFROMGITHUBRELEASE:-"true"}
 
 GITHUB_CLI_ARCHIVE_GPG_KEY=23F3D4EA75716059
-GPG_KEY_SERVERS="keyserver hkp://keyserver.ubuntu.com
-keyserver hkp://keyserver.ubuntu.com:80
-keyserver hkps://keys.openpgp.org
-keyserver hkp://keyserver.pgp.com"
 
 set -e
 
@@ -26,6 +22,37 @@ if [ "$(id -u)" -ne 0 ]; then
     exit 1
 fi
 
+# Get the list of GPG key servers that are reachable
+get_gpg_key_servers() {
+    declare -A keyservers_curl_map=(
+        ["hkp://keyserver.ubuntu.com"]="http://keyserver.ubuntu.com:11371"
+        ["hkp://keyserver.ubuntu.com:80"]="http://keyserver.ubuntu.com"
+        ["hkps://keys.openpgp.org"]="https://keys.openpgp.org"
+        ["hkp://keyserver.pgp.com"]="http://keyserver.pgp.com:11371"
+    )
+
+    local curl_args=""
+    local keyserver_reachable=false  # Flag to indicate if any keyserver is reachable
+
+    if [ ! -z "${KEYSERVER_PROXY}" ]; then
+        curl_args="--proxy ${KEYSERVER_PROXY}"
+    fi
+
+    for keyserver in "${!keyservers_curl_map[@]}"; do
+        local keyserver_curl_url="${keyservers_curl_map[${keyserver}]}"
+        if curl -s ${curl_args} --max-time 5 ${keyserver_curl_url} > /dev/null; then
+            echo "keyserver ${keyserver}"
+            keyserver_reachable=true
+        else
+            echo "(*) Keyserver ${keyserver} is not reachable." >&2
+        fi
+    done
+
+    if ! $keyserver_reachable; then
+        echo "(!) No keyserver is reachable." >&2
+        exit 1
+    fi
+}
 
 # Import the specified key in a variable name passed in as 
 receive_gpg_keys() {
@@ -35,11 +62,16 @@ receive_gpg_keys() {
         keyring_args="--no-default-keyring --keyring $2"
     fi
 
+    # Install curl
+    if ! type curl > /dev/null 2>&1; then
+        check_packages curl
+    fi
+
     # Use a temporary location for gpg keys to avoid polluting image
     export GNUPGHOME="/tmp/tmp-gnupg"
     mkdir -p ${GNUPGHOME}
     chmod 700 ${GNUPGHOME}
-    echo -e "disable-ipv6\n${GPG_KEY_SERVERS}" > ${GNUPGHOME}/dirmngr.conf
+    echo -e "disable-ipv6\n$(get_gpg_key_servers)" > ${GNUPGHOME}/dirmngr.conf
     # GPG key download sometimes fails for some reason and retrying fixes it.
     local retry_count=0
     local gpg_ok="false"

src/kubectl-helm-minikube/devcontainer-feature.json

 {
     "id": "kubectl-helm-minikube",
-    "version": "1.1.9",
+    "version": "1.1.10",
     "name": "Kubectl, Helm, and Minikube",
     "documentationURL": "https://github.com/devcontainers/features/tree/main/src/kubectl-helm-minikube",
     "description": "Installs latest version of kubectl, Helm, and optionally minikube. Auto-detects latest versions and installs needed dependencies.",

src/kubectl-helm-minikube/install.sh

@@ -22,10 +22,6 @@ MINIKUBE_SHA256="${MINIKUBE_SHA256:-"automatic"}"
 USERNAME="${USERNAME:-"${_REMOTE_USER:-"automatic"}"}"
 
 HELM_GPG_KEYS_URI="https://raw.githubusercontent.com/helm/helm/main/KEYS"
-GPG_KEY_SERVERS="keyserver hkp://keyserver.ubuntu.com
-keyserver hkp://keyserver.ubuntu.com:80
-keyserver hkps://keys.openpgp.org
-keyserver hkp://keyserver.pgp.com"
 
 if [ "$(id -u)" -ne 0 ]; then
     echo -e 'Script must be run as root. Use sudo, su, or add "USER root" to your Dockerfile before running this script.'
@@ -234,6 +230,38 @@ get_helm() {
     curl -sSL "https://github.com/helm/helm/releases/download/${HELM_VERSION}/${helm_filename}.asc" -o "${tmp_helm_filename}.asc"
 }
 
+# Get the list of GPG key servers that are reachable
+get_gpg_key_servers() {
+    declare -A keyservers_curl_map=(
+        ["hkp://keyserver.ubuntu.com"]="http://keyserver.ubuntu.com:11371"
+        ["hkp://keyserver.ubuntu.com:80"]="http://keyserver.ubuntu.com"
+        ["hkps://keys.openpgp.org"]="https://keys.openpgp.org"
+        ["hkp://keyserver.pgp.com"]="http://keyserver.pgp.com:11371"
+    )
+
+    local curl_args=""
+    local keyserver_reachable=false  # Flag to indicate if any keyserver is reachable
+
+    if [ ! -z "${KEYSERVER_PROXY}" ]; then
+        curl_args="--proxy ${KEYSERVER_PROXY}"
+    fi
+
+    for keyserver in "${!keyservers_curl_map[@]}"; do
+        local keyserver_curl_url="${keyservers_curl_map[${keyserver}]}"
+        if curl -s ${curl_args} --max-time 5 ${keyserver_curl_url} > /dev/null; then
+            echo "keyserver ${keyserver}"
+            keyserver_reachable=true
+        else
+            echo "(*) Keyserver ${keyserver} is not reachable." >&2
+        fi
+    done
+
+    if ! $keyserver_reachable; then
+        echo "(!) No keyserver is reachable." >&2
+        exit 1
+    fi
+}
+
 if [ ${HELM_VERSION} != "none" ]; then
     # Install Helm, verify signature and checksum
     echo "Downloading Helm..."
@@ -255,7 +283,7 @@ if [ ${HELM_VERSION} != "none" ]; then
     mkdir -p "${GNUPGHOME}"
     chmod 700 ${GNUPGHOME}
     curl -sSL "${HELM_GPG_KEYS_URI}" -o /tmp/helm/KEYS
-    echo -e "disable-ipv6\n${GPG_KEY_SERVERS}" > ${GNUPGHOME}/dirmngr.conf
+    echo -e "disable-ipv6\n$(get_gpg_key_servers)" > ${GNUPGHOME}/dirmngr.conf
     gpg -q --import "/tmp/helm/KEYS"
     if ! gpg --verify "${tmp_helm_filename}.asc" > ${GNUPGHOME}/verify.log 2>&1; then
         echo "Verification failed!"

src/python/devcontainer-feature.json

 {
   "id": "python",
-  "version": "1.6.2",
+  "version": "1.6.3",
   "name": "Python",
   "documentationURL": "https://github.com/devcontainers/features/tree/main/src/python",
   "description": "Installs the provided version of Python, as well as PIPX, and other common Python utilities.  JupyterLab is conditionally installed with the python feature. Note: May require source code compilation.",

src/python/install.sh

@@ -31,12 +31,7 @@ ADDITIONAL_VERSIONS="${ADDITIONALVERSIONS:-""}"
 # Comma-separated list of additional tools to be installed via pipx.
 IFS="," read -r -a DEFAULT_UTILS <<< "${TOOLSTOINSTALL:-flake8,autopep8,black,yapf,mypy,pydocstyle,pycodestyle,bandit,pipenv,virtualenv,pytest}"
 
-
 PYTHON_SOURCE_GPG_KEYS="64E628F8D684696D B26995E310250568 2D347EA6AA65421D FB9921286F5E1540 3A5CA953F73C700D 04C367C218ADD4FF 0EDDC5F26A45C816 6AF053F07D9DC8D2 C9BE28DEE6DF025C 126EB563A74B06BF D9866941EA5BBD71 ED9D77D5 A821E680E5FA6305"
-GPG_KEY_SERVERS="keyserver hkp://keyserver.ubuntu.com
-keyserver hkp://keyserver.ubuntu.com:80
-keyserver hkps://keys.openpgp.org
-keyserver hkp://keyserver.pgp.com"
 
 KEYSERVER_PROXY="${HTTPPROXY:-"${HTTP_PROXY:-""}"}"
 
@@ -130,6 +125,38 @@ updaterc() {
     fi
 }
 
+# Get the list of GPG key servers that are reachable
+get_gpg_key_servers() {
+    declare -A keyservers_curl_map=(
+        ["hkp://keyserver.ubuntu.com"]="http://keyserver.ubuntu.com:11371"
+        ["hkp://keyserver.ubuntu.com:80"]="http://keyserver.ubuntu.com"
+        ["hkps://keys.openpgp.org"]="https://keys.openpgp.org"
+        ["hkp://keyserver.pgp.com"]="http://keyserver.pgp.com:11371"
+    )
+
+    local curl_args=""
+    local keyserver_reachable=false  # Flag to indicate if any keyserver is reachable
+
+    if [ ! -z "${KEYSERVER_PROXY}" ]; then
+        curl_args="--proxy ${KEYSERVER_PROXY}"
+    fi
+
+    for keyserver in "${!keyservers_curl_map[@]}"; do
+        local keyserver_curl_url="${keyservers_curl_map[${keyserver}]}"
+        if curl -s ${curl_args} --max-time 5 ${keyserver_curl_url} > /dev/null; then
+            echo "keyserver ${keyserver}"
+            keyserver_reachable=true
+        else
+            echo "(*) Keyserver ${keyserver} is not reachable." >&2
+        fi
+    done
+
+    if ! $keyserver_reachable; then
+        echo "(!) No keyserver is reachable." >&2
+        exit 1
+    fi
+}
+
 # Import the specified key in a variable name passed in as
 receive_gpg_keys() {
     local keys=${!1}
@@ -143,11 +170,16 @@ receive_gpg_keys() {
         keyring_args="${keyring_args} --keyserver-options http-proxy=${KEYSERVER_PROXY}"
     fi
 
+    # Install curl
+    if ! type curl > /dev/null 2>&1; then
+        check_packages curl
+    fi
+
     # Use a temporary location for gpg keys to avoid polluting image
     export GNUPGHOME="/tmp/tmp-gnupg"
     mkdir -p ${GNUPGHOME}
     chmod 700 ${GNUPGHOME}
-    echo -e "disable-ipv6\n${GPG_KEY_SERVERS}" > ${GNUPGHOME}/dirmngr.conf
+    echo -e "disable-ipv6\n$(get_gpg_key_servers)" > ${GNUPGHOME}/dirmngr.conf
     # GPG key download sometimes fails for some reason and retrying fixes it.
     local retry_count=0
     local gpg_ok="false"
@@ -182,6 +214,11 @@ receive_gpg_keys_centos7() {
         keyring_args="${keyring_args} --keyserver-options http-proxy=${KEYSERVER_PROXY}"
     fi
 
+    # Install curl
+    if ! type curl > /dev/null 2>&1; then
+        check_packages curl
+    fi
+
     # Use a temporary location for gpg keys to avoid polluting image
     export GNUPGHOME="/tmp/tmp-gnupg"
     mkdir -p ${GNUPGHOME}
@@ -193,7 +230,7 @@ receive_gpg_keys_centos7() {
     set +e
         echo "(*) Downloading GPG keys..."
         until [ "${gpg_ok}" = "true" ] || [ "${retry_count}" -eq "5" ]; do
-            for keyserver in $(echo "${GPG_KEY_SERVERS}" | sed 's/keyserver //'); do
+            for keyserver in $(echo "$(get_gpg_key_servers)" | sed 's/keyserver //'); do
                 ( echo "${keys}" | xargs -n 1 gpg -q ${keyring_args} --recv-keys --keyserver=${keyserver} ) 2>&1
                 downloaded_keys=$(gpg --list-keys | grep ^pub | wc -l)
                 if [[ ${num_keys} = ${downloaded_keys} ]]; then

src/ruby/devcontainer-feature.json

 {
     "id": "ruby",
-    "version": "1.2.2",
+    "version": "1.2.3",
     "name": "Ruby (via rvm)",
     "documentationURL": "https://github.com/devcontainers/features/tree/main/src/ruby",
     "description": "Installs Ruby, rvm, rbenv, common Ruby utilities, and needed dependencies.",

src/ruby/install.sh

@@ -23,10 +23,6 @@ ADDITIONAL_VERSIONS="${ADDITIONALVERSIONS:-""}"
 DEFAULT_GEMS="rake"
 
 RVM_GPG_KEYS="409B6B1796C275462A1703113804BB82D39DC0E3 7D2BAF1CF37B13E2069D6956105BD0E739499BDB"
-GPG_KEY_SERVERS="keyserver hkp://keyserver.ubuntu.com
-keyserver hkp://keyserver.ubuntu.com:80
-keyserver hkps://keys.openpgp.org
-keyserver hkp://keyserver.pgp.com"
 
 set -e
 
@@ -72,6 +68,38 @@ updaterc() {
     fi
 }
 
+# Get the list of GPG key servers that are reachable
+get_gpg_key_servers() {
+    declare -A keyservers_curl_map=(
+        ["hkp://keyserver.ubuntu.com"]="http://keyserver.ubuntu.com:11371"
+        ["hkp://keyserver.ubuntu.com:80"]="http://keyserver.ubuntu.com"
+        ["hkps://keys.openpgp.org"]="https://keys.openpgp.org"
+        ["hkp://keyserver.pgp.com"]="http://keyserver.pgp.com:11371"
+    )
+
+    local curl_args=""
+    local keyserver_reachable=false  # Flag to indicate if any keyserver is reachable
+
+    if [ ! -z "${KEYSERVER_PROXY}" ]; then
+        curl_args="--proxy ${KEYSERVER_PROXY}"
+    fi
+
+    for keyserver in "${!keyservers_curl_map[@]}"; do
+        local keyserver_curl_url="${keyservers_curl_map[${keyserver}]}"
+        if curl -s ${curl_args} --max-time 5 ${keyserver_curl_url} > /dev/null; then
+            echo "keyserver ${keyserver}"
+            keyserver_reachable=true
+        else
+            echo "(*) Keyserver ${keyserver} is not reachable." >&2
+        fi
+    done
+
+    if ! $keyserver_reachable; then
+        echo "(!) No keyserver is reachable." >&2
+        exit 1
+    fi
+}
+
 # Import the specified key in a variable name passed in as 
 receive_gpg_keys() {
     local keys=${!1}
@@ -80,11 +108,16 @@ receive_gpg_keys() {
         keyring_args="--no-default-keyring --keyring \"$2\""
     fi
 
+    # Install curl
+    if ! type curl > /dev/null 2>&1; then
+        check_packages curl
+    fi
+
     # Use a temporary location for gpg keys to avoid polluting image
     export GNUPGHOME="/tmp/tmp-gnupg"
     mkdir -p ${GNUPGHOME}
     chmod 700 ${GNUPGHOME}
-    echo -e "disable-ipv6\n${GPG_KEY_SERVERS}" > ${GNUPGHOME}/dirmngr.conf
+    echo -e "disable-ipv6\n$(get_gpg_key_servers)" > ${GNUPGHOME}/dirmngr.conf
     # GPG key download sometimes fails for some reason and retrying fixes it.
     local retry_count=0
     local gpg_ok="false"

src/terraform/devcontainer-feature.json

 {
     "id": "terraform",
-    "version": "1.3.7",
+    "version": "1.3.8",
     "name": "Terraform, tflint, and TFGrunt",
     "documentationURL": "https://github.com/devcontainers/features/tree/main/src/terraform",
     "description": "Installs the Terraform CLI and optionally TFLint and Terragrunt. Auto-detects latest version and installs needed dependencies.",

src/terraform/install.sh

@@ -28,9 +28,6 @@ TERRAFORM_DOCS_SHA256="${TERRAFORM_DOCS_SHA256:-"automatic"}"
 
 TERRAFORM_GPG_KEY="72D7468F"
 TFLINT_GPG_KEY_URI="https://raw.githubusercontent.com/terraform-linters/tflint/v0.46.1/8CE69160EB3F2FE9.key"
-GPG_KEY_SERVERS="keyserver hkps://keyserver.ubuntu.com
-keyserver hkps://keys.openpgp.org
-keyserver hkps://keyserver.pgp.com"
 KEYSERVER_PROXY="${HTTPPROXY:-"${HTTP_PROXY:-""}"}"
 
 architecture="$(uname -m)"
@@ -47,6 +44,37 @@ if [ "$(id -u)" -ne 0 ]; then
     exit 1
 fi
 
+# Get the list of GPG key servers that are reachable
+get_gpg_key_servers() {
+    declare -A keyservers_curl_map=(
+        ["hkps://keyserver.ubuntu.com"]="https://keyserver.ubuntu.com"
+        ["hkps://keys.openpgp.org"]="https://keys.openpgp.org"
+        ["hkps://keyserver.pgp.com"]="https://keyserver.pgp.com"
+    )
+
+    local curl_args=""
+    local keyserver_reachable=false  # Flag to indicate if any keyserver is reachable
+
+    if [ ! -z "${KEYSERVER_PROXY}" ]; then
+        curl_args="--proxy ${KEYSERVER_PROXY}"
+    fi
+
+    for keyserver in "${!keyservers_curl_map[@]}"; do
+        local keyserver_curl_url="${keyservers_curl_map[${keyserver}]}"
+        if curl -s ${curl_args} --max-time 5 ${keyserver_curl_url} > /dev/null; then
+            echo "keyserver ${keyserver}"
+            keyserver_reachable=true
+        else
+            echo "(*) Keyserver ${keyserver} is not reachable." >&2
+        fi
+    done
+
+    if ! $keyserver_reachable; then
+        echo "(!) No keyserver is reachable." >&2
+        exit 1
+    fi
+}
+
 # Import the specified key in a variable name passed in as 
 receive_gpg_keys() {
     local keys=${!1}
@@ -58,11 +86,16 @@ receive_gpg_keys() {
 	keyring_args="${keyring_args} --keyserver-options http-proxy=${KEYSERVER_PROXY}"
     fi
 
+    # Install curl
+    if ! type curl > /dev/null 2>&1; then
+        check_packages curl
+    fi
+
     # Use a temporary location for gpg keys to avoid polluting image
     export GNUPGHOME="/tmp/tmp-gnupg"
     mkdir -p ${GNUPGHOME}
     chmod 700 ${GNUPGHOME}
-    echo -e "disable-ipv6\n${GPG_KEY_SERVERS}" > ${GNUPGHOME}/dirmngr.conf
+    echo -e "disable-ipv6\n$(get_gpg_key_servers)" > ${GNUPGHOME}/dirmngr.conf
     # GPG key download sometimes fails for some reason and retrying fixes it.
     local retry_count=0
     local gpg_ok="false"

test/python/install_cpython_fallback_prev_version_test.sh

@@ -93,6 +93,38 @@ check_packages() {
     esac
 }
 
+# Get the list of GPG key servers that are reachable
+get_gpg_key_servers() {
+    declare -A keyservers_curl_map=(
+        ["hkp://keyserver.ubuntu.com"]="http://keyserver.ubuntu.com:11371"
+        ["hkp://keyserver.ubuntu.com:80"]="http://keyserver.ubuntu.com"
+        ["hkps://keys.openpgp.org"]="https://keys.openpgp.org"
+        ["hkp://keyserver.pgp.com"]="http://keyserver.pgp.com:11371"
+    )
+
+    local curl_args=""
+    local keyserver_reachable=false  # Flag to indicate if any keyserver is reachable
+
+    if [ ! -z "${KEYSERVER_PROXY}" ]; then
+        curl_args="--proxy ${KEYSERVER_PROXY}"
+    fi
+
+    for keyserver in "${!keyservers_curl_map[@]}"; do
+        local keyserver_curl_url="${keyservers_curl_map[${keyserver}]}"
+        if curl -s ${curl_args} --max-time 5 ${keyserver_curl_url} > /dev/null; then
+            echo "keyserver ${keyserver}"
+            keyserver_reachable=true
+        else
+            echo "(*) Keyserver ${keyserver} is not reachable." >&2
+        fi
+    done
+
+    if ! $keyserver_reachable; then
+        echo "(!) No keyserver is reachable." >&2
+        exit 1
+    fi
+}
+
 # Import the specified key in a variable name passed in as 
 receive_gpg_keys() {
     local keys=${!1}
@@ -106,11 +138,16 @@ receive_gpg_keys() {
         keyring_args="${keyring_args} --keyserver-options http-proxy=${KEYSERVER_PROXY}"
     fi
 
+    # Install curl
+    if ! type curl > /dev/null 2>&1; then
+        check_packages curl
+    fi
+
     # Use a temporary location for gpg keys to avoid polluting image
     export GNUPGHOME="/tmp/tmp-gnupg"
     mkdir -p ${GNUPGHOME}
     chmod 700 ${GNUPGHOME}
-    echo -e "disable-ipv6\n${GPG_KEY_SERVERS}" > ${GNUPGHOME}/dirmngr.conf
+    echo -e "disable-ipv6\n$(get_gpg_key_servers)" > ${GNUPGHOME}/dirmngr.conf
     # GPG key download sometimes fails for some reason and retrying fixes it.
     local retry_count=0
     local gpg_ok="false"
@@ -145,6 +182,11 @@ receive_gpg_keys_centos7() {
         keyring_args="${keyring_args} --keyserver-options http-proxy=${KEYSERVER_PROXY}"
     fi
 
+    # Install curl
+    if ! type curl > /dev/null 2>&1; then
+        check_packages curl
+    fi
+
     # Use a temporary location for gpg keys to avoid polluting image
     export GNUPGHOME="/tmp/tmp-gnupg"
     mkdir -p ${GNUPGHOME}
@@ -156,7 +198,7 @@ receive_gpg_keys_centos7() {
     set +e
         echo "(*) Downloading GPG keys..."
         until [ "${gpg_ok}" = "true" ] || [ "${retry_count}" -eq "5" ]; do
-            for keyserver in $(echo "${GPG_KEY_SERVERS}" | sed 's/keyserver //'); do
+            for keyserver in $(echo "$(get_gpg_key_servers)" | sed 's/keyserver //'); do
                 ( echo "${keys}" | xargs -n 1 gpg -q ${keyring_args} --recv-keys --keyserver=${keyserver} ) 2>&1
                 downloaded_keys=$(gpg --list-keys | grep ^pub | wc -l)
                 if [[ ${num_keys} = ${downloaded_keys} ]]; then

test/ruby/ruby_fallback_test.sh

@@ -13,10 +13,6 @@ check "ruby" ruby -v
 trap 'echo "Last executed command failed at line ${LINENO}"' ERR
 
 RVM_GPG_KEYS="409B6B1796C275462A1703113804BB82D39DC0E3 7D2BAF1CF37B13E2069D6956105BD0E739499BDB"
-GPG_KEY_SERVERS="keyserver hkp://keyserver.ubuntu.com
-keyserver hkp://keyserver.ubuntu.com:80
-keyserver hkps://keys.openpgp.org
-keyserver hkp://keyserver.pgp.com"
 
 # Clean up
 rm -rf /var/lib/apt/lists/*
@@ -63,6 +59,38 @@ check_packages() {
     fi
 }
 
+# Get the list of GPG key servers that are reachable
+get_gpg_key_servers() {
+    declare -A keyservers_curl_map=(
+        ["hkp://keyserver.ubuntu.com"]="http://keyserver.ubuntu.com:11371"
+        ["hkp://keyserver.ubuntu.com:80"]="http://keyserver.ubuntu.com"
+        ["hkps://keys.openpgp.org"]="https://keys.openpgp.org"
+        ["hkp://keyserver.pgp.com"]="http://keyserver.pgp.com:11371"
+    )
+
+    local curl_args=""
+    local keyserver_reachable=false  # Flag to indicate if any keyserver is reachable
+
+    if [ ! -z "${KEYSERVER_PROXY}" ]; then
+        curl_args="--proxy ${KEYSERVER_PROXY}"
+    fi
+
+    for keyserver in "${!keyservers_curl_map[@]}"; do
+        local keyserver_curl_url="${keyservers_curl_map[${keyserver}]}"
+        if curl -s ${curl_args} --max-time 5 ${keyserver_curl_url} > /dev/null; then
+            echo "keyserver ${keyserver}"
+            keyserver_reachable=true
+        else
+            echo "(*) Keyserver ${keyserver} is not reachable." >&2
+        fi
+    done
+
+    if ! $keyserver_reachable; then
+        echo "(!) No keyserver is reachable." >&2
+        exit 1
+    fi
+}
+
 # Import the specified key in a variable name passed in as 
 receive_gpg_keys() {
     local keys=${!1}
@@ -71,11 +99,16 @@ receive_gpg_keys() {
         keyring_args="--no-default-keyring --keyring \"$2\""
     fi
 
+    # Install curl
+    if ! type curl > /dev/null 2>&1; then
+        check_packages curl
+    fi
+
     # Use a temporary location for gpg keys to avoid polluting image
     export GNUPGHOME="/tmp/tmp-gnupg"
     mkdir -p ${GNUPGHOME}
     chmod 700 ${GNUPGHOME}
-    echo -e "disable-ipv6\n${GPG_KEY_SERVERS}" | tee ${GNUPGHOME}/dirmngr.conf > /dev/null
+    echo -e "disable-ipv6\n$(get_gpg_key_servers)" | tee ${GNUPGHOME}/dirmngr.conf > /dev/null
     # GPG key download sometimes fails for some reason and retrying fixes it.
     local retry_count=0
     local gpg_ok="false"