359 lines
12 KiB
Bash
359 lines
12 KiB
Bash
#!/usr/bin/env bash
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#
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# sshuser -- manage SSH users on a hardened Alpine box.
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#
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# Two roles, matching harden-jumphost.sh:
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# admin -> group ssh-admins, shell /bin/ash (full shell)
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# jumper -> group ssh-jumpers, shell /sbin/nologin (ProxyJump only)
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#
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# Two modes:
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# - TUI (gum) : run with no command, or any command with missing args
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# - CLI flags : full automation, suitable for shell scripts and CI
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#
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# Install:
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# install -m 0755 sshuser.sh /usr/local/bin/sshuser
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# apk add gum # only needed for TUI mode
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#
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# Usage:
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# sshuser # interactive TUI
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# sshuser add -u alice -r jumper -f alice.pub
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# sshuser add -u bob -r admin -k "ssh-ed25519 AAA..."
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# sshuser edit -u alice --add-key "ssh-ed25519 BBB..."
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# sshuser edit -u alice --remove-key "comment-substring"
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# sshuser edit -u alice --role admin
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# sshuser remove -u alice -y
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# sshuser list
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# sshuser list -r jumper
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# sshuser show -u alice
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set -euo pipefail
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ADMIN_GROUP="ssh-admins"
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JUMPER_GROUP="ssh-jumpers"
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ADMIN_SHELL="/bin/ash"
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JUMPER_SHELL="/sbin/nologin"
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# ---------------------------------------------------------------------------
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# Helpers
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# ---------------------------------------------------------------------------
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err() { printf '\033[1;31m[x]\033[0m %s\n' "$*" >&2; exit 1; }
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warn() { printf '\033[1;33m[!]\033[0m %s\n' "$*" >&2; }
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log() { printf '\033[1;32m[+]\033[0m %s\n' "$*"; }
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have_gum() { command -v gum >/dev/null 2>&1; }
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require_root() {
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[[ $EUID -eq 0 ]] || err "Run as root."
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}
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require_groups() {
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getent group "$ADMIN_GROUP" >/dev/null || err "Group $ADMIN_GROUP missing -- run harden-jumphost.sh first."
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getent group "$JUMPER_GROUP" >/dev/null || err "Group $JUMPER_GROUP missing -- run harden-jumphost.sh first."
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}
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confirm() {
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# confirm "Prompt" -- returns 0 if yes, 1 if no.
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local prompt="$1"
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if [[ "${YES:-0}" == "1" ]]; then return 0; fi
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if have_gum; then
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gum confirm "$prompt"
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else
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read -r -p "$prompt [y/N] " ans
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[[ "${ans,,}" == "y" || "${ans,,}" == "yes" ]]
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fi
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}
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ask() {
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# ask "Prompt" [default] -- prints user input.
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local prompt="$1"
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local default="${2:-}"
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if have_gum; then
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gum input --prompt "$prompt: " --placeholder "$default"
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else
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local ans
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read -r -p "$prompt${default:+ [$default]}: " ans
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echo "${ans:-$default}"
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fi
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}
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choose() {
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# choose "Prompt" opt1 opt2 ... -- prints chosen.
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local prompt="$1"; shift
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if have_gum; then
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gum choose --header "$prompt" "$@"
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else
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printf '%s\n' "$prompt" >&2
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local i=1; for o in "$@"; do printf ' %d) %s\n' "$i" "$o" >&2; ((i++)); done
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local n; read -r -p "Choice: " n
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echo "${!n}"
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fi
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}
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valid_pubkey() {
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# Quick sanity check: starts with a known algo prefix.
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[[ "$1" =~ ^(ssh-ed25519|ssh-rsa|sk-ssh-ed25519@openssh\.com|ecdsa-sha2-)[[:space:]]+[A-Za-z0-9+/=]+ ]]
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}
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resolve_role() {
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# Map role -> group + shell. echoes "GROUP SHELL".
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case "$1" in
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admin) echo "$ADMIN_GROUP $ADMIN_SHELL" ;;
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jumper) echo "$JUMPER_GROUP $JUMPER_SHELL" ;;
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*) err "Unknown role: $1 (must be admin|jumper)" ;;
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esac
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}
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ssh_dir_setup() {
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# Ensure ~user/.ssh exists with correct perms and ownership.
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local user="$1"
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local home; home=$(getent passwd "$user" | cut -d: -f6)
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[[ -n "$home" ]] || err "User $user has no home directory."
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install -d -m 0700 -o "$user" -g "$user" "$home/.ssh"
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install -m 0600 -o "$user" -g "$user" /dev/null "$home/.ssh/authorized_keys" 2>/dev/null || \
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touch "$home/.ssh/authorized_keys"
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chown "$user:$user" "$home/.ssh/authorized_keys"
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chmod 600 "$home/.ssh/authorized_keys"
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echo "$home/.ssh/authorized_keys"
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}
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# ---------------------------------------------------------------------------
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# Commands
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# ---------------------------------------------------------------------------
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cmd_add() {
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local user="${USER_ARG:-}" role="${ROLE_ARG:-}" key="${KEY_ARG:-}"
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[[ -z "$user" ]] && user=$(ask "Username")
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[[ -z "$user" ]] && err "Username required."
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if id "$user" >/dev/null 2>&1; then
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err "User $user already exists. Use 'sshuser edit' instead."
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fi
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[[ -z "$role" ]] && role=$(choose "Role" admin jumper)
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read -r group shell <<<"$(resolve_role "$role")"
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if [[ -z "$key" ]]; then
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if [[ -n "${KEY_FILE_ARG:-}" ]]; then
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[[ -f "$KEY_FILE_ARG" ]] || err "Key file not found: $KEY_FILE_ARG"
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key=$(<"$KEY_FILE_ARG")
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elif have_gum; then
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key=$(gum input --prompt "SSH public key (paste full line, blank to skip): " --width 200)
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else
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read -r -p "SSH public key (paste full line, blank to skip): " key
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fi
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fi
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if [[ -n "$key" ]]; then
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valid_pubkey "$key" || err "That doesn't look like a valid SSH public key."
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fi
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confirm "Create user $user as $role (group $group, shell $shell)?" || { warn "Aborted."; exit 1; }
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log "Creating $user..."
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adduser -D -s "$shell" -g "" "$user"
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adduser "$user" "$group"
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if [[ -n "$key" ]]; then
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local ak; ak=$(ssh_dir_setup "$user")
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if grep -qxF "$key" "$ak" 2>/dev/null; then
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warn "Key already present, skipping."
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else
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echo "$key" >> "$ak"
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log "Added SSH key to $ak"
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fi
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else
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warn "No SSH key added. User cannot log in until 'sshuser edit -u $user --add-key ...' is run."
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fi
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log "Done."
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}
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cmd_edit() {
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local user="${USER_ARG:-}"
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[[ -z "$user" ]] && user=$(ask "Username to edit")
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id "$user" >/dev/null 2>&1 || err "No such user: $user"
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# If no specific edit flag, prompt for action.
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local has_action=0
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[[ -n "${ADD_KEY_ARG:-}" ]] && has_action=1
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[[ -n "${REMOVE_KEY_ARG:-}" ]] && has_action=1
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[[ -n "${ROLE_ARG:-}" ]] && has_action=1
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[[ -n "${SHELL_ARG:-}" ]] && has_action=1
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if [[ $has_action -eq 0 ]]; then
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local action
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action=$(choose "What to do for $user?" \
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"add ssh key" "remove ssh key" "change role" "change shell" "cancel")
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case "$action" in
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"add ssh key") ADD_KEY_ARG=$(ask "Paste SSH public key") ;;
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"remove ssh key") REMOVE_KEY_ARG=$(ask "Substring of key to remove (comment is fine)") ;;
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"change role") ROLE_ARG=$(choose "New role" admin jumper) ;;
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"change shell") SHELL_ARG=$(ask "New shell" "/bin/ash") ;;
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*) warn "Cancelled."; return 0 ;;
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esac
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fi
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if [[ -n "${ROLE_ARG:-}" ]]; then
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read -r new_group new_shell <<<"$(resolve_role "$ROLE_ARG")"
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log "Setting $user role to $ROLE_ARG (group $new_group, shell $new_shell)"
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# Remove from the other ssh group, add to the target.
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local other
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[[ "$new_group" == "$ADMIN_GROUP" ]] && other="$JUMPER_GROUP" || other="$ADMIN_GROUP"
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deluser "$user" "$other" 2>/dev/null || true
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adduser "$user" "$new_group" 2>/dev/null || true
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usermod -s "$new_shell" "$user" 2>/dev/null || \
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sed -i "s|^\($user:.*:\)[^:]*$|\1$new_shell|" /etc/passwd
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fi
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if [[ -n "${SHELL_ARG:-}" ]]; then
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log "Setting $user shell to $SHELL_ARG"
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usermod -s "$SHELL_ARG" "$user" 2>/dev/null || \
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sed -i "s|^\($user:.*:\)[^:]*$|\1$SHELL_ARG|" /etc/passwd
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fi
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if [[ -n "${ADD_KEY_ARG:-}" ]]; then
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valid_pubkey "$ADD_KEY_ARG" || err "Invalid pubkey."
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local ak; ak=$(ssh_dir_setup "$user")
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if grep -qxF "$ADD_KEY_ARG" "$ak" 2>/dev/null; then
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warn "Key already present."
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else
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echo "$ADD_KEY_ARG" >> "$ak"
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log "Added key to $ak"
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fi
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fi
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if [[ -n "${REMOVE_KEY_ARG:-}" ]]; then
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local ak; ak=$(ssh_dir_setup "$user")
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local before after
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before=$(wc -l <"$ak")
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# Remove any line containing the substring (safe escape for sed).
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local pat; pat=$(printf '%s\n' "$REMOVE_KEY_ARG" | sed 's/[][\.*^$/]/\\&/g')
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sed -i "/$pat/d" "$ak"
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after=$(wc -l <"$ak")
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log "Removed $((before - after)) key line(s) from $ak"
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fi
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}
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cmd_remove() {
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local user="${USER_ARG:-}"
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[[ -z "$user" ]] && user=$(ask "Username to remove")
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id "$user" >/dev/null 2>&1 || err "No such user: $user"
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[[ "$user" == "root" ]] && err "Refusing to remove root."
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confirm "DELETE user $user and their home directory?" || { warn "Aborted."; exit 1; }
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log "Deleting $user..."
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deluser --remove-home "$user" 2>/dev/null || deluser "$user"
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log "Done."
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}
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cmd_list() {
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local role="${ROLE_ARG:-}"
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local groups=()
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case "$role" in
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admin) groups=("$ADMIN_GROUP") ;;
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jumper) groups=("$JUMPER_GROUP") ;;
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"") groups=("$ADMIN_GROUP" "$JUMPER_GROUP") ;;
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*) err "Unknown role: $role" ;;
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esac
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printf '%-20s %-15s %-20s %s\n' "USER" "ROLE" "SHELL" "KEYS"
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printf '%-20s %-15s %-20s %s\n' "----" "----" "-----" "----"
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for g in "${groups[@]}"; do
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local label="admin"
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[[ "$g" == "$JUMPER_GROUP" ]] && label="jumper"
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# getent group returns: groupname:x:gid:user1,user2,...
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local members; members=$(getent group "$g" | awk -F: '{print $4}' | tr ',' ' ')
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for u in $members; do
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[[ -z "$u" ]] && continue
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local home; home=$(getent passwd "$u" | cut -d: -f6)
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local shell; shell=$(getent passwd "$u" | cut -d: -f7)
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local nkeys=0
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[[ -f "$home/.ssh/authorized_keys" ]] && nkeys=$(grep -cv '^\s*$\|^\s*#' "$home/.ssh/authorized_keys" 2>/dev/null || echo 0)
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printf '%-20s %-15s %-20s %s\n' "$u" "$label" "$shell" "$nkeys"
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done
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done
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}
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cmd_show() {
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local user="${USER_ARG:-}"
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[[ -z "$user" ]] && user=$(ask "Username")
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id "$user" >/dev/null 2>&1 || err "No such user: $user"
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local home; home=$(getent passwd "$user" | cut -d: -f6)
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local shell; shell=$(getent passwd "$user" | cut -d: -f7)
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local groups; groups=$(id -nG "$user" | tr ' ' ',')
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echo "user: $user"
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echo "home: $home"
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echo "shell: $shell"
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echo "groups: $groups"
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echo "keys:"
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if [[ -f "$home/.ssh/authorized_keys" ]]; then
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awk 'NF && !/^#/ {
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n=split($0, p, " ");
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type=p[1]; comment=(n>=3 ? p[n] : "(no comment)");
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printf " - %s %s\n", type, comment
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}' "$home/.ssh/authorized_keys"
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else
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echo " (none)"
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fi
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}
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cmd_tui() {
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have_gum || err "TUI mode requires gum: 'apk add gum'. Or use CLI flags (sshuser --help)."
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local action
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action=$(choose "What do you want to do?" \
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"add user" "edit user" "remove user" "list users" "show user" "quit")
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case "$action" in
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"add user") cmd_add ;;
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"edit user") cmd_edit ;;
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"remove user") cmd_remove ;;
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"list users") cmd_list ;;
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"show user") cmd_show ;;
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*) ;;
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esac
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}
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# ---------------------------------------------------------------------------
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# Argument parsing
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# ---------------------------------------------------------------------------
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usage() {
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sed -n '2,30p' "$0" | sed 's/^# \{0,1\}//'
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}
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CMD=""
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USER_ARG=""
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ROLE_ARG=""
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KEY_ARG=""
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KEY_FILE_ARG=""
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ADD_KEY_ARG=""
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REMOVE_KEY_ARG=""
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SHELL_ARG=""
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YES=0
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if [[ $# -gt 0 && "$1" != -* ]]; then
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CMD="$1"; shift
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fi
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while [[ $# -gt 0 ]]; do
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case "$1" in
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-u|--user) USER_ARG="$2"; shift 2 ;;
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-r|--role) ROLE_ARG="$2"; shift 2 ;;
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-k|--key) KEY_ARG="$2"; shift 2 ;;
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-f|--key-file) KEY_FILE_ARG="$2"; shift 2 ;;
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--add-key) ADD_KEY_ARG="$2"; shift 2 ;;
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--remove-key) REMOVE_KEY_ARG="$2"; shift 2 ;;
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--shell) SHELL_ARG="$2"; shift 2 ;;
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-y|--yes) YES=1; shift ;;
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-h|--help) usage; exit 0 ;;
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*) err "Unknown flag: $1" ;;
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esac
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done
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require_root
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require_groups
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case "$CMD" in
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add) cmd_add ;;
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edit) cmd_edit ;;
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remove|rm|del) cmd_remove ;;
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list|ls) cmd_list ;;
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show) cmd_show ;;
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"") cmd_tui ;;
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*) err "Unknown command: $CMD (try: add edit remove list show)" ;;
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esac
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