openpgp_ca_lib/

lib.rs

// SPDX-FileCopyrightText: 2019-2023 Heiko Schaefer <heiko@schaefer.name>
// SPDX-License-Identifier: GPL-3.0-or-later
//
// This file is part of OpenPGP CA
// https://gitlab.com/openpgp-ca/openpgp-ca

//! OpenPGP CA functionality as a library
//!
//! Example usage:
//! ```
//! # use openpgp_ca_lib::Uninit;
//! # use tempfile;
//! // all state of an OpenPGP CA instance is persisted in one SQLite database
//! let db_filename = "/tmp/openpgp-ca.sqlite";
//! # // for Doc-tests we need a random database filename
//! # let file = tempfile::NamedTempFile::new().unwrap();
//! # let db_filename = file.path().to_str().unwrap();
//!
//! // Set up a new, uninitialized OpenPGP CA database
//! // (implicitly creates the database file).
//! let ca_uninit = Uninit::new(Some(db_filename)).expect("Failed to set up CA");
//!
//! // Initialize the CA, create the CA key (with domain name and descriptive name)
//! let ca = ca_uninit
//!     .init_softkey("example.org", Some("Example Org OpenPGP CA Key"), None)
//!     .unwrap();
//!
//! // Create a new user, certified by the CA, and a trust signature by the user
//! // key on the CA key.
//! //
//! // The new private key for the user is printed to stdout and needs to be manually
//! // processed from there.
//! ca.user_new(
//!     Some(&"Alice"),
//!     &["alice@example.org"],
//!     None,
//!     false,
//!     None,
//!     false,
//!     None,
//!     true,
//!     true,
//!     false,
//! )
//! .unwrap();
//! ```

// FIXME: cleanup
#![allow(non_local_definitions)]

#[macro_use]
extern crate diesel;

#[macro_use]
extern crate diesel_migrations;

/// The version of this crate.
pub const VERSION: &str = env!("CARGO_PKG_VERSION");

mod backend;
mod bridge;
mod cert;
pub mod db;
mod export;
pub mod pgp;
mod revocation;
mod secret;
mod storage;
pub mod types;
mod update;

use std::collections::HashMap;
use std::env;
use std::path::{Path, PathBuf};
use std::rc::Rc;
use std::str::FromStr;
use std::time::SystemTime;

use anyhow::{Context, Result};
use chrono::offset::Utc;
use chrono::DateTime;
use openpgp_card::algorithm::AlgoSimple;
use openpgp_card_pcsc::PcscBackend;
use openpgp_card_sequoia::{state::Open, Card};
use sequoia_openpgp::packet::{Signature, UserID};
use sequoia_openpgp::parse::Parse;
use sequoia_openpgp::Cert;

use crate::backend::card::{check_card_empty, CardBackend};
use crate::backend::softkey::SoftkeyBackend;
use crate::backend::split::SplitCa;
use crate::backend::{card, split, Backend};
use crate::db::models;
use crate::db::models::NewCacert;
use crate::db::OcaDb;
use crate::pgp::CipherSuite;
use crate::secret::{CaSec, CaSecCB};
use crate::storage::{CaStorageRW, DbCa, UninitDb};
use crate::types::CertificationStatus;

/// List of cards that are blank (no fingerprint in any slot)
pub fn blank_cards() -> Result<Vec<String>> {
    let mut idents = vec![];

    for backend in PcscBackend::cards(None)? {
        let mut card: Card<Open> = backend.into();
        let transaction = card.transaction()?;

        if check_card_empty(&transaction)? {
            idents.push(transaction.application_identifier()?.ident());
        }
    }

    Ok(idents)
}

/// List of cards that match the CA cert `cert`
pub fn matching_cards(ca_cert: &[u8]) -> Result<Vec<String>> {
    let ca_cert = Cert::from_bytes(ca_cert).context("Cert::from_bytes failed")?;

    let mut idents = vec![];

    for backend in PcscBackend::cards(None)? {
        let mut card: Card<Open> = backend.into();
        let mut transaction = card.transaction()?;

        if card::card_matches(&mut transaction, &ca_cert).is_ok() {
            idents.push(transaction.application_identifier()?.ident());
        }
    }

    Ok(idents)
}

/// A CA instance that has a database, which is (possibly) not initialized yet.
/// No backend for private key operations is available at this stage.
pub struct Uninit {
    storage: UninitDb,
}

/// An initialized OpenPGP CA instance, with a configured backend.
/// Oca exposes the main functionality of OpenPGP CA.
pub struct Oca {
    storage: Box<dyn CaStorageRW>,
    secret: Box<dyn CaSec>,

    backend: Backend,
    domainname: String,
}

impl Uninit {
    /// Instantiate a new Uninit object (with db, but without private key backend).
    ///
    /// This CA may be fully uninitialized and not be linked to a CA key yet.
    ///
    /// The SQLite backend filename can be configured:
    /// - explicitly via the db_url parameter, or
    /// - the environment variable OPENPGP_CA_DB.
    pub fn new(db_url: Option<&str>) -> Result<Self> {
        let db_url = if let Some(url) = db_url {
            url.to_owned()
        } else if let Ok(database) = env::var("OPENPGP_CA_DB") {
            database
        } else {
            return Err(anyhow::anyhow!("ERROR: no database configuration found"));
        };

        let db = Rc::new(OcaDb::new(&db_url)?);
        db.diesel_migrations_run();

        let storage = UninitDb::new(db);

        Ok(Self { storage })
    }

    /// Check if domainname is legal according to Mozilla's Public Suffix List
    fn check_domainname(domainname: &str) -> Result<()> {
        // domainname syntax check
        use addr::parser::DomainName;
        use addr::psl::List;
        if List.parse_domain_name(domainname).is_err() {
            return Err(anyhow::anyhow!("Invalid domainname: '{}'", domainname));
        }

        Ok(())
    }

    /// Init CA with softkey backend.
    ///
    /// This generates a new OpenPGP Key for the Admin role and stores the
    /// private Key in the OpenPGP CA database.
    ///
    /// `domainname` is the domain that this CA Admin is in charge of,
    /// `name` is a descriptive name for the CA Admin
    pub fn init_softkey(
        self,
        domainname: &str,
        name: Option<&str>,
        cipher_suite: Option<CipherSuite>,
    ) -> Result<Oca> {
        Self::check_domainname(domainname)?;
        let (cert, _) = pgp::make_ca_cert(domainname, name, cipher_suite)?;

        self.storage
            .transaction(|| self.storage.ca_init_softkey(domainname, &cert))?;

        self.init_from_db_state()
    }

    /// Init CA with OpenPGP card backend. Generate key material on the card.
    ///
    /// This assumes that:
    /// - all key slots on the card are currently empty
    /// - the PINs are set to their default values (User PIN is '123456', Admin PIN is '12345678')
    ///
    /// The User PIN is changed to a new, random 8-digit value and persisted in the CA database.
    ///
    /// The user is encouraged to change the Admin PIN to a different setting.
    pub fn init_card_generate_on_card(
        self,
        ident: &str,
        domain: &str,
        name: Option<&str>,
        algo: Option<AlgoSimple>,
    ) -> Result<Oca> {
        // The CA database must be uninitialized!
        if self.storage.is_ca_initialized()? {
            return Err(anyhow::anyhow!("CA database is already initialized"));
        }

        let email = format!("openpgp-ca@{domain}");
        let uid = pgp::ca_user_id(&email, name);
        let uid = String::from_utf8_lossy(uid.value()).to_string();

        // Generate key material on card, get the public key,
        // initialize the CA with these artifacts.
        let (ca_cert, user_pin) = card::generate_on_card(ident, domain, uid, algo)?;

        self.ca_init_card(ident, &user_pin, domain, &ca_cert)
    }

    pub fn init_card_generate_on_host(
        self,
        ident: &str,
        domain: &str,
        name: Option<&str>,
        cipher_suite: Option<CipherSuite>,
    ) -> Result<(Oca, String)> {
        // The CA database must be uninitialized!
        if self.storage.is_ca_initialized()? {
            return Err(anyhow::anyhow!("CA database is already initialized"));
        }

        // Generate a new CA private key
        let (ca_key, _) = pgp::make_ca_cert(domain, name, cipher_suite)?;

        // Import key material to card.
        let user_pin = card::import_to_card(ident, &ca_key)?;

        // Private key material will get stripped implicitly by ca_init_card()
        let ca = self.ca_init_card(ident, &user_pin, domain, &ca_key)?;

        // return private key (unencrypted)
        let key = pgp::cert_to_armored_private_key(&ca_key)?;

        Ok((ca, key))
    }

    /// Import the CA's public key and use it with a pre-initialized OpenPGP card.
    pub fn init_card_import_card(
        self,
        card_ident: &str,
        user_pin: &str,
        domain: &str,
        ca_cert: &[u8],
    ) -> Result<Oca> {
        let ca_cert = Cert::from_bytes(ca_cert).context("Cert::from_bytes failed")?;

        // Check if user-supplied PIN is accepted by the card
        card::verify_user_pin(card_ident, user_pin)?;

        // FIXME: could add checks if the cert and the keys on the card really correspond?
        // (e.g.: could perform crypto operations on the card and test against cert?
        // however, this might surprisingly require touch confirmation!)

        self.ca_init_card(card_ident, user_pin, domain, &ca_cert)
    }

    /// Import existing CA private key onto a blank OpenPGP card.
    pub fn init_card_import_key(
        self,
        card_ident: &str,
        domain: &str,
        ca_key: &[u8],
    ) -> Result<Oca> {
        let ca_key = Cert::from_bytes(ca_key).context("Cert::from_bytes failed")?;
        if !ca_key.is_tsk() {
            return Err(anyhow::anyhow!(
                "No private key material found in file. Can't import to OpenPGP card."
            ));
        }

        // FIXME: handle password protected key file?

        // Import key material to card.
        let user_pin = card::import_to_card(card_ident, &ca_key)?;

        // Private key material will get stripped implicitly by ca_init_card()
        self.ca_init_card(card_ident, &user_pin, domain, &ca_key)
    }

    /// Migrate an existing softkey CA onto a blank OpenPGP card.
    ///
    /// Caution: If you want to keep a backup of your CA private key material,
    /// you need to make it before calling this!
    ///
    /// 1. The private CA key material gets imported to the blank OpenPGP card.
    ///
    /// 2. The CA is then switched from the softkey backend to the card backend. The CA private
    ///    key material in the database is replaced with the CA public key material.
    ///
    /// 3. "VACUUM" is called on the database after removing the CA private key from the database.
    ///    According to SQLite documentation, this will remove any traces of the key material from
    ///    the database (however, no guarantees can be made about the underlying storage!).
    pub fn migrate_card_import_key(self, card_ident: &str) -> Result<Oca> {
        self.storage.transaction(|| {
            let ca_key = self.storage.ca_get_cert_private()?;
            if !ca_key.is_tsk() {
                return Err(anyhow::anyhow!(
                    "No private key material in CA database. Can't migrate to OpenPGP card."
                ));
            }

            // Import key material to card.
            let user_pin = card::import_to_card(card_ident, &ca_key)?;

            // Switch cacert in db
            let ca_pub = pgp::cert_to_armored(&ca_key.strip_secret_key_material())?;
            CardBackend::ca_replace_in_place(&self.storage, card_ident, &user_pin, &ca_pub)?;

            Ok(())
        })?;

        // Run VACUUM on sqlite.
        // SQLite guarantees that this removes remaining private key fragments from the database file.
        self.storage.vacuum()?;

        self.init_from_db_state()
    }

    /// Init with OpenPGP card backend
    fn ca_init_card(
        self,
        card_ident: &str,
        pin: &str,
        domainname: &str,
        ca_cert: &Cert,
    ) -> Result<Oca> {
        Self::check_domainname(domainname)?;

        self.storage.transaction(|| {
            // The CA database must be uninitialized!
            if self.storage.is_ca_initialized()? {
                return Err(anyhow::anyhow!("CA database is already initialized"));
            }

            let pubkey = card::check_if_card_matches(card_ident, ca_cert)?;

            CardBackend::ca_init(
                &self.storage,
                domainname,
                card_ident,
                pin,
                &pubkey,
                &ca_cert.fingerprint().to_hex(),
            )
        })?;

        self.init_from_db_state()
    }

    /// Initialize OpenpgpCa object - this assumes a backend has previously been configured.
    fn init_from_db_state(self) -> Result<Oca> {
        // check database state of this CA
        let (ca, cacert) = self.storage.ca_cert()?;

        let backend = Backend::from_config(cacert.backend.as_deref())?;
        let domainname = ca.domainname;

        match &backend {
            Backend::Softkey => {
                let softkey = SoftkeyBackend::new(self.storage.ca_get_cert_private()?);

                let ca_cert_pub = self.storage.ca_get_cert_pub()?;
                let ca_sec = CaSecCB::new(Rc::new(softkey), ca_cert_pub);

                let storage = Box::new(DbCa::new(self.storage.db()));

                Ok(Oca {
                    storage,
                    secret: Box::new(ca_sec),
                    backend,
                    domainname,
                })
            }
            Backend::Card(card) => {
                let card_ca = CardBackend::new(&card.ident, &card.user_pin)?;

                let ca_cert = self.storage.ca_get_cert_pub()?;
                let ca_sec = CaSecCB::new(Rc::new(card_ca), ca_cert);

                let storage = Box::new(DbCa::new(self.storage.db()));

                Ok(Oca {
                    storage,
                    secret: Box::new(ca_sec),
                    backend,
                    domainname,
                })
            }
            Backend::SplitFront => {
                let oca_db = self.storage.db();

                let storage = Box::new(DbCa::new(oca_db.clone()));
                let secret = Box::new(SplitCa::new(oca_db)?);

                Ok(Oca {
                    storage,
                    secret,
                    backend,
                    domainname,
                })
            }
            Backend::SplitBack(inner) => {
                let secret: Box<dyn CaSec> = match &**inner {
                    Backend::Softkey => {
                        let softkey = SoftkeyBackend::new(self.storage.ca_get_cert_private()?);
                        let ca_cert_pub = self.storage.ca_get_cert_pub()?;
                        Box::new(CaSecCB::new(Rc::new(softkey), ca_cert_pub))
                    }
                    Backend::Card(card) => {
                        let card_ca = CardBackend::new(&card.ident, &card.user_pin)?;

                        let ca_cert = self.storage.ca_get_cert_pub()?;
                        Box::new(CaSecCB::new(Rc::new(card_ca), ca_cert))
                    }

                    _ => return Err(anyhow::anyhow!("Illegal inner backend: {}", inner)),
                };

                let db = match env::var("OPENPGP_CA_FRONT_DB") {
                    Ok(readonly) => {
                        println!("Using {readonly} as r/o online datasource");

                        let ocadb = OcaDb::new(&readonly)?;
                        split::SplitBackDb::new(Some(Rc::new(ocadb)))
                    }
                    Err(_e) => split::SplitBackDb::new(None),
                };

                let storage = Box::new(db);

                Ok(Oca {
                    storage,
                    secret,
                    backend,
                    domainname,
                })
            }
        }
    }
}

impl Oca {
    /// Open an initialized Oca instance.
    ///
    /// The SQLite backend filename can be configured:
    /// - explicitly via the db_url parameter, or
    /// - the environment variable OPENPGP_CA_DB.
    pub fn open(db_url: Option<&str>) -> Result<Self> {
        let cau = Uninit::new(db_url)?;
        cau.init_from_db_state()
    }

    pub fn domainname(&self) -> &str {
        &self.domainname
    }

    pub(crate) fn backend(&self) -> &Backend {
        &self.backend
    }

    /// Get the CaSec implementation to run operations that need CA
    /// private key material.
    pub(crate) fn secret(&self) -> &dyn CaSec {
        &*self.secret
    }

    /// Change which card backs an OpenPGP CA instance
    /// (e.g. to switch to a replacement for a broken card).
    pub fn set_card_backend(self, card_ident: &str, user_pin: &str) -> Result<()> {
        let cacert = self.storage.cacert()?;

        let b = Backend::from_config(cacert.backend.as_deref())?;
        match b {
            Backend::Card(_c) => {
                // For now, we only allow switches from card-backend to card-backend

                // Check if user-supplied PIN is accepted by the card
                card::verify_user_pin(card_ident, user_pin)?;

                // Check if the card exists and contains the correct CA key
                let ca_cert = self.ca_get_cert_pub()?;
                let _pubkey = card::check_if_card_matches(card_ident, &ca_cert)?;

                // Update backend configuration in database
                let ca_pub = pgp::cert_to_armored(&ca_cert)?;

                let db = self.storage.into_uninit();
                CardBackend::ca_replace_in_place(&db, card_ident, user_pin, &ca_pub)?;

                Ok(())
            }
            Backend::Softkey => Err(anyhow::anyhow!(
                "Setting card backend from softkey is not supported."
            )),
            Backend::SplitFront | Backend::SplitBack(_) => Err(anyhow::anyhow!(
                "Setting card backend from split mode is not supported."
            )),
        }
    }

    // -------- CA

    /// Generate revocations for the CA key, write to output file.
    pub fn ca_generate_revocations(&self, output: PathBuf) -> Result<()> {
        self.secret.ca_generate_revocations(output)
    }

    /// Ingest/merge in any new tsigs for our CA certificate from 'cert'
    pub fn ca_import_tsig(&self, cert: &[u8]) -> Result<()> {
        self.storage.ca_import_tsig(cert)
    }

    /// Get current CA certificate from storage.
    /// This representation of the CA cert includes user certifications.
    ///
    /// Get from database storage, if possible - the cert will then contain all certifications
    /// we know of. However, on split-mode backends, we don't rely on storage, unless we get
    /// a readonly copy of the online CA. In this case, the CA certificate may lack some or all
    /// certifications.
    pub fn ca_get_cert_pub(&self) -> Result<Cert> {
        match self.backend {
            // In a split-mode backend instance, we can't rely on having an up-to-date copy
            // of the CA certificate in storage.
            Backend::SplitBack(_) => {
                if let Ok(ca_cert) = self.storage.ca_get_cert_pub() {
                    // If readonly front database is available, get CA cert from there
                    Ok(ca_cert)
                } else {
                    // If not: get CA cert from secret backend
                    self.secret.cert()
                }
            }
            _ => self.storage.ca_get_cert_pub(),
        }
    }

    /// Returns the public key of the CA as an armored String (see [Self::ca_get_cert_pub]).
    pub fn ca_get_pubkey_armored(&self) -> Result<String> {
        let cert = self.ca_get_cert_pub()?;

        let ca_pub =
            pgp::cert_to_armored(&cert).context("Failed to transform CA key to armored pubkey")?;

        Ok(ca_pub)
    }

    /// Get the User ID of this CA
    pub(crate) fn get_ca_userid(&self) -> Result<UserID> {
        let cert = self.ca_get_cert_pub()?;
        let uids: Vec<_> = cert.userids().collect();

        if uids.len() != 1 {
            return Err(anyhow::anyhow!("ERROR: CA has != 1 user_id"));
        }

        Ok(uids[0].userid().clone())
    }

    /// Get the email of this CA
    pub fn get_ca_email(&self) -> Result<String> {
        let uid = self.get_ca_userid()?;
        let email = uid.email2()?;

        if let Some(email) = email {
            Ok(email.to_string())
        } else {
            Err(anyhow::anyhow!("CA user_id has no email"))
        }
    }

    /// Print information about the Ca to stdout.
    ///
    /// This shows the domainname, fingerprint and creation time of this OpenPGP CA instance.
    pub fn ca_show(&self) -> Result<()> {
        let cert = self.secret().cert()?;

        let created = cert.primary_key().key().creation_time();
        let created: DateTime<Utc> = created.into();

        println!("    CA Domain: {}", self.domainname());
        println!("  Fingerprint: {}", cert.fingerprint());
        println!("Creation time: {}", created.format("%F %T %Z"));

        let backend = self.backend();
        println!("   CA Backend: {backend}");

        Ok(())
    }

    /// Print private key of the Ca to stdout.
    ///
    /// This operation is only supported for Softkey and SplitBack+Softkey instances.
    pub fn ca_print_private(&self) -> Result<()> {
        match &self.backend {
            Backend::Softkey => {
                // OK
            }
            Backend::SplitBack(inner) => match **inner {
                Backend::Softkey => {
                    // OK
                }
                _ => {
                    // SplitBack instance that is not Softkey-based
                    return Err(anyhow::anyhow!(
                        "Operation unsupported for this backend type"
                    ));
                }
            },
            _ => {
                return Err(anyhow::anyhow!(
                    "Operation unsupported for this backend type"
                ));
            }
        }

        let ca_cert = self
            .storage
            .cacert()
            .context("failed to load CA from database")?;
        println!("{}", ca_cert.priv_cert);

        Ok(())
    }

    /// Find all User IDs that have been certified by `ca_cert_old` and re-certify them
    /// with the current CA key.
    ///
    /// This can be useful after CA key rotation: when the CA has a new key, `ca_re_certify` issues
    /// fresh certifications for all previously CA-certified user certs.
    pub fn ca_re_certify(&self, ca_cert_old: &[u8], validity_days: u64) -> Result<()> {
        let ca_cert_old = pgp::to_cert(ca_cert_old)?;

        cert::certs_re_certify(self, ca_cert_old, validity_days)
    }

    /// Split a CA instance into a pair of "front" and "back" CA instances.
    ///
    /// This operation is currently supported for softkey or card-backed CAs.
    pub fn ca_split_into(self, front: &Path, back: &Path) -> Result<()> {
        match self.backend {
            Backend::Softkey | Backend::Card(_) => {
                let uninit_orig = self.storage.into_uninit();
                let (orig_ca, orig_cacert) = uninit_orig.ca_cert()?;

                let cert = Cert::from_str(&orig_cacert.priv_cert)?;
                let pub_ca_cert = pgp::cert_to_armored(&cert)?;

                let fp = cert.fingerprint().to_hex();

                let db = uninit_orig.db();
                let db_url = db.url();

                // The front instance gets all user/cert data (but no CA private key/card config).

                // - Assert that all references from users to 'ca_id' point to "1"
                for user in db.users_sorted_by_name()? {
                    if user.ca_id != 1 {
                        return Err(anyhow::anyhow!(
                            "Splitting a multi-CA setup is not currently supported"
                        ));
                    }
                }

                // - Copy the database file to "front" CA file
                std::fs::copy(db_url, front)?;

                if let Some(url) = front.to_str() {
                    let front = OcaDb::new(url)?;

                    // - Remove cacerts and add a new one ('ca' entry stays unchanged)
                    front.cacerts_delete()?;

                    let backend = Backend::SplitFront.to_config();

                    let new_ca_cert = NewCacert {
                        active: true,
                        ca_id: orig_ca.id,
                        priv_cert: pub_ca_cert,
                        fingerprint: &fp,
                        backend: backend.as_deref(),
                    };
                    front.cacert_insert(&new_ca_cert)?;

                    // - Vacuum (to remove traces of private key material, if any)
                    front.vacuum()?;
                } else {
                    return Err(anyhow::anyhow!("Illegal front filename"));
                }

                // The back instance is a new, bare database that just gets the CA
                // softkey (or card config)
                let orig_back = Backend::from_config(orig_cacert.backend.as_deref())?;

                let backend = Backend::SplitBack(Box::new(orig_back));

                if let Some(url) = back.to_str() {
                    let back = Uninit::new(Some(url))?;

                    back.storage.ca_insert(
                        &orig_ca.domainname,
                        &orig_cacert.priv_cert,
                        &fp,
                        backend.to_config().as_deref(),
                    )?;
                } else {
                    return Err(anyhow::anyhow!("Illegal back filename"));
                }

                Ok(())
            }
            _ => Err(anyhow::anyhow!(
                "Splitting operation not supported for this backend type"
            )),
        }
    }

    /// Merge a back CA into a front CA instance, resulting in a regular ("non-split") CA.
    pub fn ca_merge_split(self, back: &Path) -> Result<()> {
        match self.backend {
            Backend::SplitFront => {
                // get inner backend and cacert data from the back instance
                if let Some(url) = back.to_str() {
                    let back = OcaDb::new(url)?;
                    let (_back_ca, back_cacert) = back.get_ca()?;

                    let orig_back = Backend::from_config(back_cacert.backend.as_deref())?;
                    if let Backend::SplitBack(inner) = orig_back {
                        // update backend and cacert in front database

                        let mut front_cacert = self.storage.cacert()?;

                        if front_cacert.fingerprint != back_cacert.fingerprint {
                            return Err(anyhow::anyhow!(
                                "Front {} and back {} instance use different CA fingerprints",
                                front_cacert.fingerprint,
                                back_cacert.fingerprint
                            ));
                        }

                        // The back CA contains private key material (in softkey mode).
                        // Start from the back CA Cert, merge in the public material from the front CA.
                        // Use the resulting merged cert for the newly merged CA.
                        let back_cert = pgp::to_cert(back_cacert.priv_cert.as_bytes())?;
                        let front_cert = pgp::to_cert(front_cacert.priv_cert.as_bytes())?;

                        let ca_merged = back_cert.merge_public(front_cert)?;

                        front_cacert.priv_cert = pgp::cert_to_armored_private_key(&ca_merged)?;

                        // The backend config of the merged CA is the "inner" backend type of the back instance
                        front_cacert.backend = inner.to_config();

                        let db = self.storage;
                        db.cacert_update(&front_cacert)?;
                    }

                    Ok(())
                } else {
                    Err(anyhow::anyhow!(
                        "Failed to use back instance path ({:?})",
                        back
                    ))
                }
            }

            _ => Err(anyhow::anyhow!(
                "Merge operation not supported for this backend type"
            )),
        }
    }

    /// Export certification requests for the backing CA in a simple human-readable output format
    /// (inspired by <https://github.com/wiktor-k/airsigner/>, but with some adjustments!).
    ///
    /// The output file is a tar-archive:
    /// - The archive contains a top-level file "csr.txt", which lists User IDs that should be
    ///   certified.
    /// - Current versions of all certs are provided in the tar in armored format, as individual
    ///   files "certs/*fingerprint*".
    ///
    /// One design goal of this format is to make it easy to implement small (and thus more easily
    /// auditable) certification services, which may use arbitrary underlying mechanisms
    /// (and/or PGP implementations) for signing.
    pub fn ca_split_export(&self, file: PathBuf) -> Result<()> {
        match self.backend {
            Backend::SplitFront => {
                let cacert = self.storage.cacert()?;

                let queue = self.storage.queue_not_done()?;
                SplitCa::export_csr_queue(file, queue, &cacert.fingerprint)?;

                Ok(())
            }
            _ => Err(anyhow::anyhow!(
                "Operation is only supported on split mode front instances."
            )),
        }
    }

    /// Process certification requests in a SplitBack instance
    ///
    /// When "batch" is false, this fn is interactive.
    ///
    /// In interactive mode, it reads KeyEvents for user feedback
    /// about certification operations.
    pub fn ca_split_certify(&self, import: PathBuf, export: PathBuf, batch: bool) -> Result<()> {
        match self.backend {
            Backend::SplitBack(_) => split::certify(&*self.secret, import, export, batch),
            _ => Err(anyhow::anyhow!(
                "Operation is only supported on split mode back instances."
            )),
        }
    }

    /// Ingest the certifications that were generated by the split backend
    pub fn ca_split_import(&self, file: PathBuf) -> Result<()> {
        match self.backend {
            Backend::SplitFront => split::ca_split_import(&*self.storage, file),
            _ => Err(anyhow::anyhow!(
                "Operation is only supported on split mode front instances."
            )),
        }
    }

    /// Show the currently not done entries in the queue of a split mode front instance
    pub fn ca_split_show_queue(&self) -> Result<()> {
        match self.backend {
            Backend::SplitFront => split::ca_split_show_queue(&*self.storage),
            _ => Err(anyhow::anyhow!(
                "Operation is only supported on split mode front instances."
            )),
        }
    }

    // -------- users / certs

    /// Get a list of all User Certs
    pub fn user_certs_get_all(&self) -> Result<Vec<models::Cert>> {
        let users = self.storage.users_sorted_by_name()?;
        let mut user_certs = Vec::new();
        for user in users {
            user_certs.append(&mut self.get_certs_by_user(&user)?);
        }
        Ok(user_certs)
    }

    /// Which certs will be expired in 'days' days?
    ///
    /// If a cert is not "alive" now, it will not get returned as expiring
    /// (otherwise old/abandoned certs would clutter the results)
    pub fn certs_expired(&self, days: u64) -> Result<HashMap<models::Cert, Option<SystemTime>>> {
        cert::certs_expired(self, days)
    }

    /// Check if this Cert has been certified by the CA Key, returns all
    /// certified User IDs
    pub fn cert_check_ca_sig(&self, cert: &models::Cert) -> Result<CertificationStatus> {
        cert::cert_check_ca_sig(self, cert).context("Failed while checking CA sig")
    }

    /// Check if this Cert has tsigned the CA Key
    pub fn cert_check_tsig_on_ca(&self, cert: &models::Cert) -> Result<bool> {
        cert::cert_check_tsig_on_ca(self, cert).context("Failed while checking tsig on CA")
    }

    /// Check if this CA has tsigned the bridge cert
    pub fn check_tsig_on_bridge(&self, bridge: &models::Bridge) -> Result<bool> {
        let ca = self.ca_get_cert_pub()?;

        if let Some(br) = self.storage.cert_by_id(bridge.cert_id)? {
            let bridge_cert = pgp::to_cert(br.pub_cert.as_bytes())?;

            Ok(cert::check_tsig_on_cert(&ca, &bridge_cert)?)
        } else {
            Err(anyhow::anyhow!(
                "No public key found for bridge to '{}'",
                bridge.email
            ))
        }
    }

    /// Check all Certs for certifications from the CA. If a certification
    /// expires in less than `threshold_days` and it is not marked as
    /// 'inactive', make a new certification that is good for
    /// `validity_days` and update the Cert.
    pub fn certs_refresh_ca_certifications(
        &self,
        threshold_days: u64,
        validity_days: u64,
    ) -> Result<()> {
        cert::certs_refresh_ca_certifications(self, threshold_days, validity_days)
    }

    /// Create a new OpenPGP CA User.
    /// ("Centralized key creation workflow")
    ///
    /// This generates a fresh OpenPGP key for the new User.
    /// The private key is printed to stdout and NOT stored in OpenPGP CA.
    /// The public key material (Cert) is stored in the OpenPGP CA database.
    ///
    /// The CA Cert is trust-signed by this new user key and the user
    /// Cert is certified by the CA.
    #[allow(clippy::too_many_arguments)]
    pub fn user_new(
        &self,
        name: Option<&str>,
        emails: &[&str],
        duration_days: Option<u64>,
        password: bool,
        password_file: Option<String>,
        output_format_minimal: bool,
        cipher_suite: Option<CipherSuite>,
        enable_encryption_subkey: bool,
        enable_signing_subkey: bool,
        enable_authentication_subkey: bool,
    ) -> Result<()> {
        // storage: ca_import_tsig + user_add
        cert::user_new(
            self,
            name,
            emails,
            duration_days,
            password,
            password_file,
            output_format_minimal,
            cipher_suite,
            enable_encryption_subkey,
            enable_signing_subkey,
            enable_authentication_subkey,
        )
    }

    /// Import an existing OpenPGP Cert (public key) as a new OpenPGP CA user.
    ///
    /// The `cert` parameter accepts the user's armored public key.
    ///
    /// User IDs that correspond to `emails` will be signed by the CA.
    ///
    /// A symbolic `name` and a list of `emails` for this User can
    /// optionally be supplied. If those are not set, emails are taken from
    /// the list of User IDs in the public key. If the key has exactly one
    /// User ID, the symbolic name is taken from that User ID.
    ///
    /// Optionally, revocation certificates can be supplied for storage in
    /// OpenPGP CA.
    pub fn cert_import_new(
        &self,
        cert: &[u8],
        revoc_certs: &[&[u8]],
        name: Option<&str>,
        emails: &[&str],
        duration_days: Option<u64>,
    ) -> Result<()> {
        cert::cert_import_new(self, cert, revoc_certs, name, emails, duration_days)
    }

    /// Update existing Cert in database (e.g. if the user has extended
    /// the expiry date)
    pub fn cert_import_update(&self, cert: &[u8]) -> Result<()> {
        cert::cert_import_update(self, cert)
    }

    /// Mark a cert as "delisted" in the OpenPGP CA database.
    /// As a result, the cert will not be exported to WKD anymore.
    ///
    /// Note: existing CA certifications will still get renewed for delisted
    /// certs, but as the cert is not published via WKD, third parties might not
    /// learn about refreshed certifications.
    ///
    /// CAUTION:
    /// This method is probably rarely appropriate. In most cases, it's better
    /// to "deactivate" a cert (in almost all cases, it is best to continually
    /// serve the latest version of a cert to third parties, so they can learn
    /// about e.g. revocations on the cert)
    pub fn cert_delist(&self, fp: &str) -> Result<()> {
        self.storage.cert_delist(fp)
    }

    /// Mark a certificate as "deactivated".
    /// It will continue to be listed and exported to WKD.
    /// However, the certification by our CA will expire and not get renewed.
    ///
    /// This approach is probably appropriate in most cases to phase out a
    /// certificate.
    pub fn cert_deactivate(&self, fp: &str) -> Result<()> {
        self.storage.cert_deactivate(fp)
    }

    /// Get Cert by fingerprint.
    ///
    /// The fingerprint parameter is normalized (e.g. if it contains
    /// spaces, they will be filtered out).
    pub fn cert_get_by_fingerprint(&self, fingerprint: &str) -> Result<Option<models::Cert>> {
        let fp = pgp::normalize_fp(fingerprint)?;

        self.storage.cert_by_fp(&fp)
    }

    /// Get a list of all Certs for one User
    pub fn get_certs_by_user(&self, user: &models::User) -> Result<Vec<models::Cert>> {
        self.storage.certs_by_user(user)
    }

    /// Get a list of all Users, ordered by name
    pub fn users_get_all(&self) -> Result<Vec<models::User>> {
        self.storage.users_sorted_by_name()
    }

    /// Get a list of the Certs that are associated with `email`
    pub fn certs_by_email(&self, email: &str) -> Result<Vec<models::Cert>> {
        self.storage.certs_by_email(email)
    }

    /// Get database User(s) for database Cert
    pub fn cert_get_users(&self, cert: &models::Cert) -> Result<Option<models::User>> {
        self.storage.user_by_cert(cert)
    }

    /// Get the username that is associated with this Cert.
    ///
    /// The name is only for display purposes, it is set to "*no name*" if
    /// no name can be found, or to "*multiple users*" if the Cert is
    /// associated with more than one User.
    pub fn cert_get_name(&self, cert: &models::Cert) -> Result<String> {
        if let Some(user) = self.cert_get_users(cert)? {
            Ok(user.name.unwrap_or_else(|| "<no name>".to_string()))
        } else {
            Ok("<no name>".to_string())
        }
    }

    pub fn print_certifications_status(&self) -> Result<()> {
        let mut count_ok = 0;

        let db_users = self.users_get_all()?;
        for db_user in &db_users {
            for db_cert in self.get_certs_by_user(db_user)? {
                let sigs_by_ca = self.cert_check_ca_sig(&db_cert)?;
                let tsig_on_ca = self.cert_check_tsig_on_ca(&db_cert)?;

                let sig_by_ca = !sigs_by_ca.certified.is_empty();

                if sig_by_ca && tsig_on_ca {
                    count_ok += 1;
                } else {
                    println!(
                        "No mutual certification for {}{}:",
                        db_cert.fingerprint,
                        db_user
                            .name
                            .as_deref()
                            .map(|s| format!(" ({s})"))
                            .unwrap_or_else(|| "".to_string()),
                    );

                    if !sig_by_ca {
                        println!("  No CA certification on any User ID");
                    }

                    if !tsig_on_ca {
                        println!("  Has not tsigned CA key.");
                    };

                    println!();
                }
            }
        }

        println!(
            "Checked {} user keys, {} of them have mutual certifications.",
            db_users.len(),
            count_ok
        );

        Ok(())
    }

    pub fn print_expiry_status(&self, exp_days: u64) -> Result<()> {
        let expiries = self.certs_expired(exp_days)?;

        if expiries.is_empty() {
            println!("No certificates will expire in the next {exp_days} days.");
        } else {
            println!(
                "The following {} certificate{} will expire in the next {} days.",
                expiries.len(),
                if expiries.len() == 1 { "" } else { "s" },
                exp_days
            );
            println!();
        }

        for (db_cert, expiry) in expiries {
            let name = self.cert_get_name(&db_cert)?;
            println!("name {}, fingerprint {}", name, db_cert.fingerprint);

            if let Some(exp) = expiry {
                let datetime: DateTime<Utc> = exp.into();
                println!(" expires: {}", datetime.format("%d/%m/%Y"));
            } else {
                println!(" no expiration date is set for this user key");
            }

            println!();
        }

        Ok(())
    }

    pub fn print_users(&self) -> Result<()> {
        for db_user in self.users_get_all()? {
            for db_cert in self.get_certs_by_user(&db_user)? {
                let sig_by_ca = self.cert_check_ca_sig(&db_cert)?;
                let tsig_on_ca = self.cert_check_tsig_on_ca(&db_cert)?;

                println!("OpenPGP certificate {}", db_cert.fingerprint);
                if let Some(name) = &db_user.name {
                    println!(" User '{name}'");
                }

                if !sig_by_ca.certified.is_empty() {
                    println!(" Identities certified by this CA:");
                    for uid in sig_by_ca.certified {
                        println!(" - '{uid}'");
                    }
                }

                if tsig_on_ca {
                    println!(" Has trust-signed this CA");
                }

                let c = pgp::to_cert(db_cert.pub_cert.as_bytes())?;

                match pgp::get_expiry(&c) {
                    Ok(Some(exp)) => {
                        let datetime: DateTime<Utc> = exp.into();
                        println!(" Expiration {}", datetime.format("%d/%m/%Y"));
                    }
                    Ok(None) => println!(" No expiration is set"),
                    Err(e) => println!(" Expiration unknown ({e})"),
                }

                let revs = self.revocations_get(&db_cert)?;
                if !revs.is_empty() {
                    println!(" {} revocations available", revs.len());
                }

                if pgp::is_possibly_revoked(&c) {
                    println!(" This certificate has (possibly) been REVOKED");
                }
                println!();
            }
        }

        Ok(())
    }

    // -------- revocations

    /// Get a list of all Revocations for a cert
    pub fn revocations_get(&self, cert: &models::Cert) -> Result<Vec<models::Revocation>> {
        self.storage.revocations_by_cert(cert)
    }

    /// Add a revocation certificate to the OpenPGP CA database.
    ///
    /// The matching cert is looked up by issuer Fingerprint, if
    /// possible - or by exhaustive search otherwise.
    ///
    /// Verifies that applying the revocation cert can be validated by the
    /// cert. Only if this is successful is the revocation stored.
    pub fn revocation_add(&self, revoc_cert: &[u8]) -> Result<()> {
        self.storage.revocation_add(revoc_cert)
    }

    /// Add a revocation certificate to the OpenPGP CA database (from a file).
    pub fn revocation_add_from_file(&self, filename: &Path) -> Result<()> {
        let rev = std::fs::read(filename)?;

        self.revocation_add(&rev)
    }

    /// Get a Revocation by hash
    pub fn revocation_get_by_hash(&self, hash: &str) -> Result<models::Revocation> {
        if let Some(rev) = self.storage.revocation_by_hash(hash)? {
            Ok(rev)
        } else {
            Err(anyhow::anyhow!("No revocation found for {}", hash))
        }
    }

    /// Apply a revocation.
    ///
    /// The revocation is merged into out copy of the OpenPGP Cert.
    pub fn revocation_apply(&self, revoc: models::Revocation) -> Result<()> {
        self.storage.revocation_apply(revoc)
    }

    /// Get reason and creation time for a Revocation
    pub fn revocation_details(
        revocation: &models::Revocation,
    ) -> Result<(String, Option<SystemTime>)> {
        let rev = pgp::to_signature(revocation.revocation.as_bytes())?;

        let creation = rev.signature_creation_time();

        if let Some((code, reason)) = rev.reason_for_revocation() {
            let reason = String::from_utf8(reason.to_vec())?;
            Ok((format!("{code} ({reason})"), creation))
        } else {
            Ok(("Revocation reason unknown".to_string(), creation))
        }
    }

    /// Get an armored representation of a revocation certificate
    pub fn revoc_to_armored(sig: &Signature) -> Result<String> {
        pgp::revoc_to_armored(sig, None)
    }

    pub fn print_revocations(&self, email: &str) -> Result<()> {
        let certs = self.certs_by_email(email)?;
        if certs.is_empty() {
            println!("No OpenPGP keys found");
        } else {
            for cert in certs {
                let name = self.cert_get_name(&cert)?;

                println!(
                    "Revocations for OpenPGP key {}, user \"{}\"",
                    cert.fingerprint, name
                );
                let revoc = self.revocations_get(&cert)?;
                for r in revoc {
                    let (reason, time) = Self::revocation_details(&r)?;
                    let time = if let Some(time) = time {
                        let datetime: DateTime<Utc> = time.into();
                        format!("{}", datetime.format("%d/%m/%Y"))
                    } else {
                        "".to_string()
                    };
                    println!(" - revocation id {}: {} ({})", r.hash, reason, time);
                    if r.published {
                        println!("   this revocation has been APPLIED");
                    }

                    println!();
                }
            }
        }
        Ok(())
    }

    // -------- emails

    /// Get all Emails for a Cert
    pub fn emails_get(&self, cert: &models::Cert) -> Result<Vec<models::CertEmail>> {
        self.storage.emails_by_cert(cert)
    }

    /// Get all Emails
    pub fn get_emails_all(&self) -> Result<Vec<models::CertEmail>> {
        self.storage.emails()
    }

    // --------- bridges

    /// Get a list of Bridges
    pub fn bridges_get(&self) -> Result<Vec<models::Bridge>> {
        self.storage.list_bridges()
    }

    /// Get a specific Bridge
    pub fn bridges_search(&self, email: &str) -> Result<models::Bridge> {
        if let Some(bridge) = self.storage.bridge_by_email(email)? {
            Ok(bridge)
        } else {
            Err(anyhow::anyhow!("Bridge not found"))
        }
    }

    /// Get the Cert row for a Bridge
    pub fn bridge_get_cert(&self, bridge: &models::Bridge) -> Result<models::Cert> {
        if let Some(cert) = self.storage.cert_by_id(bridge.cert_id)? {
            Ok(cert)
        } else {
            Err(anyhow::anyhow!("No cert found for bridge {}", bridge.id))
        }
    }

    pub fn add_bridge(
        &self,
        email: Option<&str>,
        key_file: &Path,
        scope: Option<&str>,
        unscoped: bool,
    ) -> Result<(String, String)> {
        let (bridge, fingerprint) = bridge::bridge_new(self, key_file, email, scope, unscoped)?;

        Ok((bridge.email, fingerprint.to_string()))
    }

    /// Create a revocation Certificate for a Bridge and apply it the our
    /// copy of the remote CA's public key.
    ///
    /// Both the revoked remote public key and the revocation cert are
    /// printed to stdout.
    pub fn bridge_revoke(&self, email: &str) -> Result<()> {
        bridge::bridge_revoke(self, email)
    }

    pub fn print_bridges(&self, email: Option<String>) -> Result<()> {
        let bridges = if let Some(email) = email {
            vec![self.bridges_search(&email)?]
        } else {
            self.bridges_get()?
        };

        for bridge in bridges {
            println!("Bridge to '{}'", bridge.email);
            if let Some(db_cert) = self.storage.cert_by_id(bridge.cert_id)? {
                println!("{}", db_cert.pub_cert);
            }
            println!();
        }

        Ok(())
    }

    pub fn list_bridges(&self) -> Result<()> {
        for bridge in self.bridges_get()? {
            let tsigned = self.check_tsig_on_bridge(&bridge)?;

            println!(
                "Bridge to '{}'{}, (scope: '{}')",
                bridge.email,
                if !tsigned {
                    " [no trust signature]"
                } else {
                    ""
                },
                bridge.scope,
            )
        }

        Ok(())
    }

    // -------- export

    /// Export all user keys (that have a userid in `domain`) and the CA key
    /// into a wkd directory structure
    ///
    /// <https://tools.ietf.org/html/draft-koch-openpgp-webkey-service-08>
    pub fn export_wkd(&self, domain: &str, path: &Path) -> Result<()> {
        export::wkd_export(self, domain, path)
    }

    /// Export the contents of a CA in Keylist format.
    ///
    /// <https://code.firstlook.media/keylist-rfc-explainer>
    ///
    /// `path`: filesystem path into which the exported keylist and signature
    /// files will be written.
    ///
    /// `signature_uri`: the https address from which the signature file will
    /// be retrievable
    ///
    /// `force`: by default, this fn fails if the files exist; when force is
    /// true, overwrite.
    pub fn export_keylist(&self, path: PathBuf, signature_uri: String, force: bool) -> Result<()> {
        export::export_keylist(self, path, signature_uri, force)
    }

    /// Export Certs from this CA into files, with filenames based on email
    /// addresses of user ids.
    pub fn export_certs_as_files(&self, email_filter: Option<String>, path: &str) -> Result<()> {
        export::export_certs_as_files(self, email_filter, path)
    }

    pub fn print_certring(&self, email_filter: Option<String>) -> Result<()> {
        export::print_certring(self, email_filter)
    }

    // -------- Update certs from public sources

    /// Pull updates for all certs from WKD and merge them into our local
    /// storage.
    pub fn update_from_wkd(&self) -> Result<()> {
        for c in self.user_certs_get_all()? {
            match update::update_from_wkd(self, &c) {
                Ok(true) => {
                    println!("Got update for cert {}", c.fingerprint);
                }
                Ok(false) => {
                    println!("No changes for cert {}", c.fingerprint);
                }
                Err(e) => {
                    eprintln!("Failed to update cert {}: {}", c.fingerprint, e);
                }
            }
        }
        Ok(())
    }

    /// Update all certs from the hagrid keyserver (<https://keys.openpgp.org/>)
    /// and merge any updates into our local storage for this cert.
    pub fn update_from_keyserver(&self) -> Result<()> {
        for c in self.user_certs_get_all()? {
            match update::update_from_hagrid(self, &c) {
                Ok(true) => {
                    println!("Got update for cert {}", c.fingerprint);
                }
                Ok(false) => {
                    println!("No changes for cert {}", c.fingerprint);
                }
                Err(e) => {
                    eprintln!("Failed to update cert {}: {}", c.fingerprint, e);
                }
            }
        }
        Ok(())
    }
}