nixos-servers/scripts/vault-fetch/vault-fetch.sh

#!/usr/bin/env bash
set -euo pipefail

# vault-fetch: Fetch secrets from OpenBao/Vault and write to filesystem
#
# Usage: vault-fetch <secret-path> <output-directory> [cache-directory]
#
# Example: vault-fetch hosts/monitoring01/grafana-admin /run/secrets/grafana /var/lib/vault/cache/grafana
#
# This script:
# 1. Authenticates to Vault using AppRole credentials from /var/lib/vault/approle/
# 2. Fetches secrets from the specified path
# 3. Writes each secret key as an individual file in the output directory
# 4. Updates cache for fallback when Vault is unreachable
# 5. Falls back to cache if Vault authentication fails or is unreachable

# Parse arguments
if [ $# -lt 2 ]; then
    echo "Usage: vault-fetch <secret-path> <output-directory> [cache-directory]" >&2
    echo "Example: vault-fetch hosts/monitoring01/grafana /run/secrets/grafana /var/lib/vault/cache/grafana" >&2
    exit 1
fi

SECRET_PATH="$1"
OUTPUT_DIR="$2"
CACHE_DIR="${3:-/var/lib/vault/cache/$(basename "$OUTPUT_DIR")}"

# Vault configuration
VAULT_ADDR="${VAULT_ADDR:-https://vault01.home.2rjus.net:8200}"
VAULT_SKIP_VERIFY="${VAULT_SKIP_VERIFY:-1}"
APPROLE_DIR="/var/lib/vault/approle"

# TLS verification flag for curl
if [ "$VAULT_SKIP_VERIFY" = "1" ]; then
    CURL_TLS_FLAG="-k"
else
    CURL_TLS_FLAG=""
fi

# Logging helper
log() {
    echo "[vault-fetch] $*" >&2
}

# Error handler
error() {
    log "ERROR: $*"
    exit 1
}

# Check if cache is available
has_cache() {
    [ -d "$CACHE_DIR" ] && [ -n "$(ls -A "$CACHE_DIR" 2>/dev/null)" ]
}

# Use cached secrets
use_cache() {
    if ! has_cache; then
        error "No cache available and Vault is unreachable"
    fi

    log "WARNING: Using cached secrets from $CACHE_DIR"
    mkdir -p "$OUTPUT_DIR"
    cp -r "$CACHE_DIR"/* "$OUTPUT_DIR/"
    chmod -R u=rw,go= "$OUTPUT_DIR"/*
}

# Fetch secrets from Vault
fetch_from_vault() {
    # Read AppRole credentials
    if [ ! -f "$APPROLE_DIR/role-id" ] || [ ! -f "$APPROLE_DIR/secret-id" ]; then
        log "WARNING: AppRole credentials not found at $APPROLE_DIR"
        use_cache
        return
    fi

    ROLE_ID=$(cat "$APPROLE_DIR/role-id")
    SECRET_ID=$(cat "$APPROLE_DIR/secret-id")

    # Authenticate to Vault
    log "Authenticating to Vault at $VAULT_ADDR"
    AUTH_RESPONSE=$(curl -s $CURL_TLS_FLAG -X POST \
        -d "{\"role_id\":\"$ROLE_ID\",\"secret_id\":\"$SECRET_ID\"}" \
        "$VAULT_ADDR/v1/auth/approle/login" 2>&1) || {
        log "WARNING: Failed to connect to Vault"
        use_cache
        return
    }

    # Check for errors in response
    if echo "$AUTH_RESPONSE" | jq -e '.errors' >/dev/null 2>&1; then
        ERRORS=$(echo "$AUTH_RESPONSE" | jq -r '.errors[]' 2>/dev/null || echo "Unknown error")
        log "WARNING: Vault authentication failed: $ERRORS"
        use_cache
        return
    fi

    # Extract token
    VAULT_TOKEN=$(echo "$AUTH_RESPONSE" | jq -r '.auth.client_token' 2>/dev/null)
    if [ -z "$VAULT_TOKEN" ] || [ "$VAULT_TOKEN" = "null" ]; then
        log "WARNING: Failed to extract Vault token from response"
        use_cache
        return
    fi

    log "Successfully authenticated to Vault"

    # Fetch secret
    log "Fetching secret from path: $SECRET_PATH"
    SECRET_RESPONSE=$(curl -s $CURL_TLS_FLAG \
        -H "X-Vault-Token: $VAULT_TOKEN" \
        "$VAULT_ADDR/v1/secret/data/$SECRET_PATH" 2>&1) || {
        log "WARNING: Failed to fetch secret from Vault"
        use_cache
        return
    }

    # Check for errors
    if echo "$SECRET_RESPONSE" | jq -e '.errors' >/dev/null 2>&1; then
        ERRORS=$(echo "$SECRET_RESPONSE" | jq -r '.errors[]' 2>/dev/null || echo "Unknown error")
        log "WARNING: Failed to fetch secret: $ERRORS"
        use_cache
        return
    fi

    # Extract secret data
    SECRET_DATA=$(echo "$SECRET_RESPONSE" | jq -r '.data.data' 2>/dev/null)
    if [ -z "$SECRET_DATA" ] || [ "$SECRET_DATA" = "null" ]; then
        log "WARNING: No secret data found at path $SECRET_PATH"
        use_cache
        return
    fi

    # Create output and cache directories
    mkdir -p "$OUTPUT_DIR"
    mkdir -p "$CACHE_DIR"

    # Write each secret key to a separate file
    log "Writing secrets to $OUTPUT_DIR"
    for key in $(echo "$SECRET_DATA" | jq -r 'keys[]'); do
        echo "$SECRET_DATA" | jq -j --arg k "$key" '.[$k]' > "$OUTPUT_DIR/$key"
        echo "$SECRET_DATA" | jq -j --arg k "$key" '.[$k]' > "$CACHE_DIR/$key"
        chmod 600 "$OUTPUT_DIR/$key"
        chmod 600 "$CACHE_DIR/$key"
        log "  - Wrote secret key: $key"
    done

    log "Successfully fetched and cached secrets"
}

# Main execution
fetch_from_vault