160 lines
4.1 KiB
Bash
Executable File
160 lines
4.1 KiB
Bash
Executable File
#!/usr/bin/env bash
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# Script to perform verified file downloads.
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# Exit codes:
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# 0 - File downloaded successfully and verified
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# 1 - Failed to download requested file
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# 2 - Failed to download sha256sums file
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# 3 - Failed to download sha256sums.gpg file
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# 4 - GnuPG is available but fails to verify the signature (missing pubkey, file integrity error, ...)
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# 5 - The checksums do not match
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# 6 - Unable to copy the requested file to its final destination
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# 254 - The script got interrupted by a signal
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# 255 - A suitable download or checksum utility is missing
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[ -n "$1" ] || {
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echo "$0 - Download and verify build artifacts"
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echo "Usage: $0 <url>" >&2
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exit 1
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}
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finish() {
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[ -e "/tmp/verify.$$" ] && {
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echo "Cleaning up."
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rm -r "/tmp/verify.$$"
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}
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exit "$1"
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}
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trap "finish 254" INT TERM
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destdir="$(pwd)"
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image_url="$1"
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image_file="${image_url##*/}"
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sha256_url="${image_url%/*}/sha256sums"
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gpgsig_url="${image_url%/*}/sha256sums.asc"
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keyserver_url="hkp://keyserver.ubuntu.com"
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# Find a suitable download utility
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if which curl >/dev/null; then
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download() { curl --progress-bar -o "$1" "$2"; }
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elif which wget >/dev/null; then
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download() { wget -O "$1" "$2"; }
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elif which fetch >/dev/null; then
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download() { fetch -o "$1" "$2"; }
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else
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echo "No suitable download utility found, cannot download files!" >&2
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finish 255
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fi
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# Find a suitable checksum utility
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if which sha256sum >/dev/null; then
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checksum() { sha256sum -c --ignore-missing "sha256sums"; }
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elif which shasum >/dev/null; then
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checksum() {
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local sum
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sum="$(shasum -a 256 "$image_file")";
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grep -xF "${sum%% *} *$image_file" "sha256sums";
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}
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else
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echo "No SHA256 checksum executable installed, cannot verify checksums!" >&2
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finish 255
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fi
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# Check for gpg availability
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if which gpg >/dev/null; then
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runpgp() { gpg "$@"; }
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else
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runpgp() {
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echo "WARNING: No GnuPG installed, cannot verify digital signature!" >&2
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return 0
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}
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fi
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tmpdir="$(mktemp -d)"
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cd "$tmpdir" || {
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echo "Failed to create temporary directory!" >&2
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finish 255
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}
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echo ""
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echo "1) Downloading artifact file"
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echo "========================="
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download "$image_file" "$image_url" || {
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echo "Failed to download image file!" >&2
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finish 1
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}
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echo ""
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echo "2) Downloading checksum file"
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echo "============================"
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download "sha256sums" "$sha256_url" || {
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echo "Failed to download checksum file!" >&2
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finish 2
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}
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echo ""
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echo "3) Downloading the GPG signature"
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echo "================================"
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download "sha256sums.gpg" "$gpgsig_url" || {
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echo "Failed to download GPG signature!" >&2
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finish 3
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}
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echo ""
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echo "4) Verifying GPG signature"
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echo "=========================="
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missing_key=$(runpgp --status-fd 1 --with-fingerprint --verify \
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"sha256sums.gpg" "sha256sums" 2>/dev/null | sed -ne 's!^.* NO_PUBKEY !!p')
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if [ -n "$missing_key" ]; then
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echo "The signature was signed by a public key with the id $missing_key" >&2
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echo "which is not present on this system." >&2
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echo "" >&2
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echo "Provide a public keyserver url below or press enter to accept the" >&2
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echo "default suggestion. Hit Ctrl-C to abort the operation." >&2
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echo "" >&2
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while true; do
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printf 'Keyserver to use? [%s] > ' "$keyserver_url"
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read -r url; case "${url:-$keyserver_url}" in
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hkp://*)
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gpg --keyserver "${url:-$keyserver_url}" --recv-keys "$missing_key" || {
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echo "Failed to download public key." >&2
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finish 7
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}
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break
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;;
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*)
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echo "Expecting a key server url in the form 'hkp://hostname'." >&2
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;;
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esac
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done
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fi
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runpgp --with-fingerprint --verify "sha256sums.gpg" "sha256sums" || {
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echo "Failed to verify checksum file with GPG signature!" >&2
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finish 4
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}
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echo ""
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echo "5) Verifying SHA256 checksum"
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echo "============================"
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checksum || {
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echo "Checksums do not match!" >&2
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finish 5
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}
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cp "$image_file" "$destdir/$image_file" || {
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echo "Failed to write '$destdir/$image_file'" >&2
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finish 6
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}
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echo ""
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echo "Verification done!"
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echo "=================="
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echo "Downloaded artifact placed in '$destdir/$image_file'."
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echo ""
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finish 0
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