feat(riot): add GPG agent forwarding

Signed-off-by: Dict Xiong <me@beardic.cn>

scripts/riot

@@ -5,6 +5,7 @@ source "$THIS_DIR/../tools/common.sh"
 RIOT_TRUST_CLIENT=${RIOT_TRUST_CLIENT:-${DFS_TRUST:-0}}
 RIOT_TRUST_SERVER=${RIOT_TRUST_SERVER:-0}
 EXTRA_SSH_OPTIONS=()
+GPG_FORWARD=0
 
 # config
 RIOT_CONFIG_FILES=(
@@ -135,6 +136,129 @@ parse_remote() {
     fi
 }
 
+check_local_gpg_agent() {
+    LOCAL_GPG_EXTRA_SOCKET=""
+    GPG_FORWARD_ERROR=""
+
+    if ! command -v gpgconf > /dev/null 2>&1 || ! command -v gpg-connect-agent > /dev/null 2>&1; then
+        GPG_FORWARD_ERROR="gpgconf or gpg-connect-agent is not available"
+        return 1
+    fi
+
+    local agent_info
+    agent_info=$(gpg-connect-agent --no-autostart 'GETINFO pid' /bye 2>/dev/null || true)
+    if ! grep -qE '^D [1-9][0-9]*$' <<< "$agent_info"; then
+        GPG_FORWARD_ERROR="local gpg-agent is not running"
+        return 1
+    fi
+
+    LOCAL_GPG_EXTRA_SOCKET=$(gpgconf --list-dirs agent-extra-socket 2>/dev/null || true)
+    if [[ -z "$LOCAL_GPG_EXTRA_SOCKET" || "$LOCAL_GPG_EXTRA_SOCKET" != /* \
+        || "$LOCAL_GPG_EXTRA_SOCKET" == *:* || "$LOCAL_GPG_EXTRA_SOCKET" == *$'\r'* \
+        || "$LOCAL_GPG_EXTRA_SOCKET" == *$'\n'* || ! -S "$LOCAL_GPG_EXTRA_SOCKET" ]]; then
+        GPG_FORWARD_ERROR="local gpg-agent extra socket is unavailable"
+        return 1
+    fi
+
+    local extra_info
+    extra_info=$(gpg-connect-agent --raw-socket "$LOCAL_GPG_EXTRA_SOCKET" 'GETINFO version' /bye 2>/dev/null || true)
+    if ! grep -qE '^D [^[:space:]]+' <<< "$extra_info"; then
+        GPG_FORWARD_ERROR="local gpg-agent extra socket exists but is not accepting connections"
+        return 1
+    fi
+}
+
+probe_remote_gpg_socket() {
+    REMOTE_GPG_SOCKET=""
+
+    # The probe must be an independent connection: reusing or creating a
+    # multiplex master here races with the immediately following login.
+    local query_cmd=(ssh "-S" "none" "-o" "ClearAllForwardings=yes" "-o" "RequestTTY=no")
+    if [[ -n "$PORT" ]]; then
+        query_cmd+=("-p" "$PORT")
+    fi
+    query_cmd+=(
+        "${SSH_OPTIONS[@]}"
+        "${EXTRA_SSH_OPTIONS[@]}"
+        "-T"
+        "$USERNAME${USERNAME:+@}$SERVER"
+        'socket=$(gpgconf --list-dirs agent-socket 2>/dev/null) || exit 10
+case "$socket" in /*/S.gpg-agent) ;; *) exit 11;; esac
+case "$socket" in *:*) exit 11;; esac
+case "$socket" in *"
+"*) exit 11;; esac
+carriage_return=$(printf "\r")
+case "$socket" in *"$carriage_return"*) exit 11;; esac
+if [ -e "$socket" ] && [ ! -S "$socket" ]; then exit 12; fi
+if [ -S "$socket" ] && command -v gpg-connect-agent >/dev/null 2>&1; then
+    agent_mode=$(gpg-connect-agent --raw-socket "$socket" "GETINFO restricted" /bye 2>/dev/null || true)
+    case "$agent_mode" in *"D 1"*) exit 13;; esac
+fi
+systemd_socket=0
+if command -v systemctl >/dev/null 2>&1 && systemctl --user is-active --quiet gpg-agent.socket >/dev/null 2>&1; then
+    systemd_socket=1
+fi
+gpgconf --kill gpg-agent >/dev/null 2>&1 || exit 14
+rm -f "$socket" || exit 15
+printf "%s\n%s\n" "$socket" "$systemd_socket"'
+    )
+
+    local output status
+    if output=$("${query_cmd[@]}"); then
+        status=0
+    else
+        status=$?
+    fi
+    case "$status" in
+    0) ;;
+    10) GPG_FORWARD_ERROR="gpgconf is unavailable on the remote host" ;;
+    11) GPG_FORWARD_ERROR="remote gpgconf returned an invalid agent socket" ;;
+    12) GPG_FORWARD_ERROR="refusing to remove the non-socket remote gpg-agent path" ;;
+    13) GPG_FORWARD_ERROR="another forwarded gpg-agent is already using the remote socket; close that session first" ;;
+    14) GPG_FORWARD_ERROR="failed to stop the remote gpg-agent (the socket may belong to another forwarding session)" ;;
+    15) GPG_FORWARD_ERROR="failed to remove the stale remote gpg-agent socket" ;;
+    *) GPG_FORWARD_ERROR="failed to query or clean the remote gpg-agent socket (ssh status $status)" ;;
+    esac
+    if [[ "$status" != "0" ]]; then
+        return 1
+    fi
+
+    local remote_systemd_socket
+    REMOTE_GPG_SOCKET=${output%%$'\n'*}
+    remote_systemd_socket=${output#*$'\n'}
+    if [[ -z "$REMOTE_GPG_SOCKET" || "$REMOTE_GPG_SOCKET" == *$'\r'* || "$REMOTE_GPG_SOCKET" == *$'\n'* \
+        || "$REMOTE_GPG_SOCKET" != /*/S.gpg-agent || "$REMOTE_GPG_SOCKET" == *:* \
+        || "$remote_systemd_socket" != "0" && "$remote_systemd_socket" != "1" ]]; then
+        GPG_FORWARD_ERROR="remote gpgconf returned an invalid agent socket: $output"
+        return 1
+    fi
+    if [[ "$remote_systemd_socket" == "1" ]]; then
+        fmt_warning "remote gpg-agent.socket is active and may race with GPG forwarding; consider disabling its socket activation"
+    fi
+}
+
+prepare_gpg_forwarding() {
+    if [[ "$DFS_DRY_RUN" == "1" ]]; then
+        REMOTE_GPG_SOCKET="<remote-gpg-agent-socket>"
+        LOCAL_GPG_EXTRA_SOCKET="<local-gpg-agent-extra-socket>"
+    else
+        if ! check_local_gpg_agent; then
+            fmt_fatal "cannot forward gpg-agent: $GPG_FORWARD_ERROR"
+        fi
+        if ! probe_remote_gpg_socket; then
+            fmt_fatal "cannot forward gpg-agent: $GPG_FORWARD_ERROR"
+        fi
+    fi
+
+    SSH_OPTIONS+=(
+        # The probe already removed the old socket. Do not let the main SSH
+        # connection unlink a path recreated during the gap between them.
+        "-o" "StreamLocalBindUnlink=no"
+        "-o" "ExitOnForwardFailure=yes"
+        "-R" "$REMOTE_GPG_SOCKET:$LOCAL_GPG_EXTRA_SOCKET"
+    )
+}
+
 print_cmd() {
     local output=""
     for s in "${CMD[@]}"; do
@@ -303,8 +427,10 @@ remove_hostkey() {
 # main
 print_help()
 {
-    fmt_info "usage: $0 [-Ddhlqt] [--dry-run] [--dev] [--help] [--lite] [--quite] [--trust] [--tmux] [--password] [[-o ssh-option]...] remote [command] [--] [command-args]"
+    fmt_info "usage: $0 [-Ddghlqt] [--dry-run] [--dev] [--gpg] [--help] [--lite] [--quite] [--trust] [--tmux] [--password] [[-o ssh-option]...] remote [command] [--] [command-args]"
     cat <<EOF
+  options:
+  - -g, --gpg: forward the local GPG agent during an interactive SSH login (trusted remotes only)
   available commands:
   - ssh [ssh-command-args] (default)
   - tmux [ssh-command-args] (run ssh in multiple tmux windows)
@@ -330,6 +456,9 @@ router() {
             -t|--trust )
                 RIOT_TRUST_SERVER=1
                 ;;
+            -g|--gpg )
+                GPG_FORWARD=1
+                ;;
             --tmux )
                 USE_TMUX=1
                 ;;
@@ -369,6 +498,11 @@ router() {
         print_help
         exit 1
     fi
+    if [[ "$GPG_FORWARD" == "1" && ( \
+        ( "${positional[1]}" != "" && "${positional[1]}" != "ssh" && "${positional[1]}" != "tmux" ) \
+        || "${#positional[@]}" -gt 2 ) ]]; then
+        fmt_fatal "gpg-agent forwarding is only supported for interactive SSH login"
+    fi
     for i in ${!remotes[@]}; do
         remote="${remotes[i]}"
         local batch_func="${remote}.batch"
@@ -380,6 +514,9 @@ router() {
         case "${positional[1]}" in
             ssh|tmux|"" )
                 [[ "${positional[1]}" == tmux ]] && USE_TMUX=1
+                if [[ "$GPG_FORWARD" == "1" ]]; then
+                    prepare_gpg_forwarding
+                fi
                 run_ssh ssh "${positional[@]:2}"
                 ;;
             git )

tools/test-riot-gpg.sh

@@ -0,0 +1,130 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+THIS_DIR=$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)
+RIOT="$THIS_DIR/../scripts/riot"
+TEST_DIR=$(mktemp -d /tmp/riot-gpg.XXXXXX)
+trap 'rm -rf "$TEST_DIR"' EXIT
+
+MOCK_BIN="$TEST_DIR/bin"
+MOCK_HOME="$TEST_DIR/home"
+MOCK_LOCAL_SOCKET="$TEST_DIR/local/S.gpg-agent.extra"
+MOCK_REMOTE_SOCKET="$TEST_DIR/remote/S.gpg-agent"
+MOCK_GPG_LOG="$TEST_DIR/gpg.log"
+MOCK_SSH_LOG="$TEST_DIR/ssh.log"
+mkdir -p "$MOCK_BIN" "$MOCK_HOME" "${MOCK_LOCAL_SOCKET%/*}" "${MOCK_REMOTE_SOCKET%/*}"
+export MOCK_LOCAL_SOCKET MOCK_REMOTE_SOCKET MOCK_GPG_LOG MOCK_SSH_LOG
+
+make_stale_socket() {
+    rm -f "$1"
+    python3 - "$1" <<'PY'
+import socket
+import sys
+
+sock = socket.socket(socket.AF_UNIX)
+sock.bind(sys.argv[1])
+sock.close()
+PY
+}
+
+cat > "$MOCK_BIN/gpgconf" <<'EOF'
+#!/usr/bin/env bash
+printf 'gpgconf %s\n' "$*" >> "$MOCK_GPG_LOG"
+case "$*" in
+    '--list-dirs agent-extra-socket') printf '%s\n' "$MOCK_LOCAL_SOCKET" ;;
+    '--list-dirs agent-socket') printf '%s\n' "$MOCK_REMOTE_SOCKET" ;;
+    '--kill gpg-agent') exit "${MOCK_KILL_STATUS:-0}" ;;
+    *) exit 1 ;;
+esac
+EOF
+
+cat > "$MOCK_BIN/gpg-connect-agent" <<'EOF'
+#!/usr/bin/env bash
+printf 'gpg-connect-agent %s\n' "$*" >> "$MOCK_GPG_LOG"
+case "$*" in
+    *'GETINFO pid'*) printf 'D 123\nOK\n' ;;
+    *'GETINFO version'*)
+        [[ "${MOCK_LOCAL_LIVE:-1}" == 1 ]] || exit 1
+        printf 'D 2.4.0\nOK\n'
+        ;;
+    *'GETINFO restricted'*) printf 'D %s\nOK\n' "${MOCK_REMOTE_RESTRICTED:-0}" ;;
+    *) exit 1 ;;
+esac
+EOF
+
+cat > "$MOCK_BIN/systemctl" <<'EOF'
+#!/usr/bin/env bash
+[[ "${MOCK_SYSTEMD_ACTIVE:-0}" == 1 ]]
+EOF
+
+cat > "$MOCK_BIN/ssh" <<'EOF'
+#!/usr/bin/env bash
+{
+    printf 'CALL\n'
+    printf 'ARG=%s\n' "$@"
+} >> "$MOCK_SSH_LOG"
+
+is_probe=0
+last_arg=''
+for arg in "$@"; do
+    [[ "$arg" == '-T' ]] && is_probe=1
+    last_arg=$arg
+done
+if [[ "$is_probe" == 1 ]]; then
+    sh -c "$last_arg"
+fi
+EOF
+
+chmod +x "$MOCK_BIN/gpgconf" "$MOCK_BIN/gpg-connect-agent" "$MOCK_BIN/systemctl" "$MOCK_BIN/ssh"
+
+run_riot() {
+    HOME="$MOCK_HOME" RIOT_TRUST_CLIENT=0 PATH="$MOCK_BIN:$PATH" "$RIOT" "$@"
+}
+
+expect_failure() {
+    local expected=$1
+    shift
+    if run_riot "$@" > "$TEST_DIR/out" 2> "$TEST_DIR/err"; then
+        echo "expected riot to fail: $*" >&2
+        exit 1
+    fi
+    grep -Fq "$expected" "$TEST_DIR/err"
+}
+
+# Dry-run must not inspect or mutate either host.
+: > "$MOCK_GPG_LOG"
+: > "$MOCK_SSH_LOG"
+DFS_DRY_RUN=1 run_riot -g example.test > "$TEST_DIR/out" 2> "$TEST_DIR/err"
+grep -Fq '<remote-gpg-agent-socket>:<local-gpg-agent-extra-socket>' "$TEST_DIR/out"
+[[ ! -s "$MOCK_GPG_LOG" && ! -s "$MOCK_SSH_LOG" ]]
+
+# A socket inode without a listener must be rejected locally.
+make_stale_socket "$MOCK_LOCAL_SOCKET"
+MOCK_LOCAL_LIVE=0 expect_failure 'extra socket exists but is not accepting connections' -g example.test
+
+# -g is valid only for an interactive SSH login.
+expect_failure 'only supported for interactive SSH login' -g example.test scp ./a ./b
+expect_failure 'only supported for interactive SSH login' -g example.test ssh -- true
+
+# Never remove a regular file merely because it has the expected basename.
+MOCK_LOCAL_LIVE=1
+printf 'keep me\n' > "$MOCK_REMOTE_SOCKET"
+expect_failure 'refusing to remove the non-socket remote gpg-agent path' -g example.test
+grep -Fqx 'keep me' "$MOCK_REMOTE_SOCKET"
+
+# A restricted agent at the remote socket represents another forwarding session.
+make_stale_socket "$MOCK_REMOTE_SOCKET"
+MOCK_REMOTE_RESTRICTED=1 expect_failure 'another forwarded gpg-agent is already using the remote socket' -g example.test
+
+# A normal remote agent can be cleaned up; systemd activation is reported.
+make_stale_socket "$MOCK_REMOTE_SOCKET"
+: > "$MOCK_SSH_LOG"
+MOCK_REMOTE_RESTRICTED=0 MOCK_SYSTEMD_ACTIVE=1 run_riot -g example.test > "$TEST_DIR/out" 2> "$TEST_DIR/err"
+grep -Fq 'remote gpg-agent.socket is active' "$TEST_DIR/err"
+grep -Fq 'ARG=none' "$MOCK_SSH_LOG"
+grep -Fq 'ARG=ClearAllForwardings=yes' "$MOCK_SSH_LOG"
+grep -Fq 'ARG=StreamLocalBindUnlink=no' "$MOCK_SSH_LOG"
+grep -Fq "ARG=$MOCK_REMOTE_SOCKET:$MOCK_LOCAL_SOCKET" "$MOCK_SSH_LOG"
+[[ ! -e "$MOCK_REMOTE_SOCKET" ]]
+
+echo 'riot gpg forwarding tests passed'

tools/test.zsh

@@ -34,6 +34,7 @@ dogo
 doll
 dfs cd
 tools/test-getopts.sh
+tools/test-riot-gpg.sh
 tools/common.sh get_os_name
 test $(echo y | tools/common.sh ask_for_yN "test") = "1"
 test $(echo n | tools/common.sh ask_for_yN "test") = "0"