Added certificate install script check for missing certificates

Necessary to ensure the script fails when no certificates can be found. This'll help in situations where the install failed, the user has misconfigured where these files are located, or the user has completely wiped out all files.

Issue: 337
Milestone: minor

scripts/docker/install-certificates

@@ -7,9 +7,10 @@ set -o errexit
 set -o pipefail
 IFS=$'\n\t'
 
-CERT_DIR="/usr/local/share/ca-certificates"
+DEFAULT_ROOT="/etc/ssl/certs"
+CUSTOM_ROOT="/usr/local/share/ca-certificates"
 
-if [ -z "${CERTIFICATE_URLS:-}" ]; then
+if [[ -z "${CERTIFICATE_URLS:-}" ]]; then
   printf "%s: Skipped, CERTIFICATE_URLS is empty.\n" "${0}"
   exit 0
 fi
@@ -28,18 +29,24 @@ for url in "${urls[@]}"; do
 
   printf "%s\n" "Downloading certificate: ${url}."
 
-  filename=$(basename "${url}")
+  base_name=$(basename "${url}")
+  file_name="${base_name%.*}.crt"
+  install_path="${CUSTOM_ROOT}/${file_name}"
 
-  # Change extension to .crt (required by update-ca-certificates).
-  cert_name="${filename%.*}.crt"
-
-  if curl --fail --silent --show-error --location "${url}" --output "${CERT_DIR}/${cert_name}"; then
-    printf "%s\n" "Downloaded ${url} to ${CERT_DIR}/${cert_name}."
+  if curl --fail --silent --show-error --location "${url}" --output "$install_path"; then
+    printf "%s\n" "Downloaded ${url} to $install_path."
   else
     printf "%s\n" "ERROR: Failed to download from ${url}."
+    exit 1
   fi
 done
 
 printf "%s\n" "Updating CA certificates..."
 update-ca-certificates
+
+if [[ -d "$DEFAULT_ROOT" && -z "$(ls -A "$DEFAULT_ROOT")" ]]; then
+  printf "%s\n" "ERROR: No certificates exist!"
+  exit 1
+fi
+
 printf "%s\n" "Custom SSL certificates installed successfully."