krill 0.16.0

use std::sync::Arc;
use std::{collections::HashMap, sync::RwLock};

#[cfg(feature = "hsm")]
use log::{debug, error, info, trace};
use rpki::crypto::{
    signer::KeyError, KeyIdentifier, PublicKey, PublicKeyFormat, Signature,
    SignatureAlgorithm, Signer, SigningError,
};

use crate::commons::{
    crypto::{
        dispatch::{
            signerinfo::SignerMapper, signerprovider::SignerProvider,
        },
        signers::error::SignerError,
        SignerHandle,
    },
    error::Error,
    KrillResult,
};

#[cfg(feature = "hsm")]
use crate::commons::crypto::dispatch::error::ErrorString;

/// Manages multiple Signers and routes requests to the appropriate Signer.
///
/// SignerRouter:
///   - Creates the appropriate [Signer] implementations according to
///     configuration.
///   - Handles registration of [Signer] instances with the [SignerMapper].
///   - Dispatches requests to the correct [Signer] instance, either because
///     the request specified a [KeyIdentifier] which is owned by a particular
///     [Signer] instance, or because the kind of request dictates the kind of
///     [Signer] that should handle it (e.g. one-off signing may be handled by
///     a different [Signer] than handles new key creation).
///
/// Note: If the `hsm` feature is not enabled all requests are routed to an
/// instance of the [`OpenSslSigner`][crate::commons::crypto::OpenSslSigner]
/// for backward compatibility with the
/// behaviour of Krill before the introduction of the feature and the
/// [SignerMapper] is not created.
///
/// To avoid the complexities of dynamic dispatch in Rust we use enum based
/// dispatch instead, as we know at compile time which implementations of the
/// [Signer] trait exist. The code noise caused by doing enum based dispatch
/// is wrapped up in the [SignerProvider] struct so we can focus on the
/// business logic here instead.
///
/// [SignerProvider] instances are wrapped in [Arc] so that we can "assign"
/// the same signer to multiple different "roles" (default signer, one-off
/// signer, etc).
///
/// Additional complexity is introduced by the need to wrap the [Signer]s in a
/// lock due to the use of `&mut` by the [Signer] trait on the `create_key()`
/// and `destroy_key()` functions. The latest, not yet released, version of
/// the `rpki-rs` crate which defines the [Signer] trait removes the `&mut`
/// from the trait and so we will be able to remove these locks and instead
/// use interior mutability inside the [Signer] implementations as
/// appropriate/necessary rather than lock the entire [Signer]. Even if that
/// is released we will not make those changes in the current code however as that will introduce too many changes in one PR. See <https://github.com/NLnetLabs/rpki-rs/issues/161> and
/// <https://github.com/NLnetLabs/rpki-rs/pull/162> for more information.
///
/// Further, a signer may not be available at the time we wish to use it,
/// perhaps it is down or being slow or a network or configuration issue
/// prevents us connecting to it at that time. Signers are therefore
/// maintained in two distinct sets: pending and active. Signers start in the
/// pending set and are promoted to the active set once we are able to
/// verify that we can connect to and use them and determine which
/// [SignerMapper] [SignerHandle] they should be assigned.
#[derive(Debug)]
pub struct SignerRouter {
    /// The signer to use for creating new keys.
    ///
    /// Exceptions:
    ///   - One-off signing keys are NOT created by the default signer. See
    ///     `one_off_signer` below.
    ///   - Random numbers are always generated using OpenSSL.
    default_signer: Arc<SignerProvider>,

    /// The signer to create, sign with and destroy a one-off key.
    ///
    /// As the security of a HSM isn't needed for one-off keys, and HSMs are
    /// slow, by default this should be an instance of
    /// `OpenSslSigner`, However, if users think the perceived extra security
    /// is warranted let them use a different signer for one-off keys if
    /// that's what they want.
    one_off_signer: Arc<SignerProvider>,

    /// A mechanism for identifying the [`SignerHandle`] that owns the key
    /// with a particular [KeyIdentifier].
    ///
    /// Used to route requests to the signer that possesses the key. If a key
    /// was created using a signer that is no longer present in the
    /// config file then the [SignerMapper] may return a [`SignerHandle`]
    /// which is not present in the `active_signers` set (see below) and thus
    /// for which we thus have no way of using the key.
    ///
    /// Conversely, if a key was deleted from the signer/HSM by an external
    /// entity without our knowledge then the [SignerMapper] may return a
    /// [`SignerHandle`] for a signer which no longer possesses the key.
    ///
    /// A reference to the [SignerMapper] is also given to each [Signer] so
    /// that it can register the mapping of newly created keys by their
    /// [KeyIdentifier] to their [Signer] implementation specific internal
    /// key identifier, and in reverse to lookup the internal key
    /// identifier from A given [KeyIdentifier].
    signer_mapper: Option<Arc<SignerMapper>>,

    /// A lookup table for resolving a [`SignerHandle`] to its associated
    /// [SignerProvider] instance.
    ///
    /// Used for any operation which must be routed to the signer that owns
    /// the key, e.g. key deletion and signing (except one-off signing).
    /// First the []
    ///
    /// If a signer was used in the past to create a key but that signer is
    /// no longer present in the Krill config file it will not be present
    /// in this map and will thus not be usable. While we could keep a record
    /// of connection details for used signers even once they are removed
    /// from the config file we don't do that, the operator must
    /// ensure correct connection details are present in the config file.
    /// There are multiple reasons for this: connection details likely
    /// include secrets such as client certificates, keys, usernames and
    /// passwords; an operator may no longer wish to or have the right to
    /// use a particular signer/HSM; once we support multi-node
    /// deployment connection details to the signer/HSM may vary from one
    /// node to another so there is no single correct set of connection
    /// details to store in the history, e.g. if the HSM is clustered and
    /// each Krill node uses its nearest/same subnet HSM instance which
    /// has a different IP address from the HSM instance used by another
    /// Krill node in another subnet).
    ///
    /// This lookup table includes at least the default and one off signers
    /// and may also include other signers defined in the config file
    /// which were used to create keys in the past which are still in use.
    ///
    /// [SignerProvider] instances are moved to this set from the
    /// `pending_signers` set once we are able to confirm that
    /// we can connect to them and can identify the correct [`SignerHandle`]
    /// used by the [SignerMapper] to associate with keys created by that
    /// signer.
    active_signers: RwLock<HashMap<SignerHandle, Arc<SignerProvider>>>,

    /// The set of [SignerProvider] instances that are configured but not yet
    /// confirmed to be usable. All signers start off in this set and are
    /// moved to the `active_signers` set as soon as we are able to confirm
    /// them. See `active_signers` above.
    #[cfg(feature = "hsm")]
    pending_signers: RwLock<Vec<Arc<SignerProvider>>>,
}

impl SignerRouter {
    pub fn build(
        signer_mapper: Option<Arc<SignerMapper>>,
        mut signers: Vec<SignerProvider>,
    ) -> KrillResult<Self> {
        // Keep a mapping of signer mapper handle to signer provider. Fill it
        // in as and when signers become ready at which point their
        // signer mapper handle will be known.
        let active_signers = RwLock::new(HashMap::new());

        // One and only one signer should be the default. The default signer
        // is used for operations that don't concern an existing key,
        // i.e. key creation and one-off signing. Create the signers
        let mut default_signer: Option<Arc<SignerProvider>> = None;
        let mut one_off_signer: Option<Arc<SignerProvider>> = None;
        let mut all_signers = Vec::new();

        for signer in signers.drain(..) {
            let signer = Arc::new(signer);
            if signer.is_default_signer() {
                Self::set_once(&mut default_signer, signer.clone()).map_err(
                    |_| {
                        Error::ConfigError(
                            "There must only be one default signer"
                                .to_string(),
                        )
                    },
                )?;
            } else if signer.is_one_off_signer() {
                Self::set_once(&mut one_off_signer, signer.clone()).map_err(
                    |_| {
                        Error::ConfigError(
                            "There must only be one one-off signer"
                                .to_string(),
                        )
                    },
                )?;
            }
            all_signers.push(signer.clone());
        }

        let default_signer = default_signer.unwrap();

        #[cfg(feature = "hsm")]
        let pending_signers = RwLock::new(all_signers);

        Ok(SignerRouter {
            default_signer: default_signer.clone(),
            one_off_signer: one_off_signer
                .unwrap_or_else(|| default_signer.clone()),
            active_signers,
            #[cfg(feature = "hsm")]
            pending_signers,
            signer_mapper,
        })
    }

    pub fn get_mapper(&self) -> Option<Arc<SignerMapper>> {
        self.signer_mapper.clone()
    }

    pub fn get_active_signers(
        &self,
    ) -> HashMap<SignerHandle, Arc<SignerProvider>> {
        self.active_signers.read().unwrap().clone()
    }

    /// Locate the [SignerProvider] that owns a given [KeyIdentifier], if the
    /// signer is active.
    ///
    /// If the signer that owns the key has not yet been promoted from the
    /// pending set to the active set or if no the key was not created by
    /// us or was not registered with the [SignerMapper] then this lookup will
    /// fail with [SignerError::KeyNotFound].
    fn get_signer_for_key(
        &self,
        key_id: &KeyIdentifier,
    ) -> Result<Arc<SignerProvider>, SignerError> {
        match &self.signer_mapper {
            None => Ok(self.default_signer.clone()),
            Some(mapper) => {
                // Get the signer handle for the key
                let signer_handle = mapper
                    .get_signer_for_key(key_id)
                    .map_err(|_| SignerError::KeyNotFound)?;

                // Get the SignerProvider for the handle, if the signer is
                // active
                let signer = self
                    .active_signers
                    .read()
                    .unwrap()
                    .get(&signer_handle)
                    .cloned();

                signer.ok_or(SignerError::KeyNotFound)
            }
        }
    }

    fn set_once(
        to_be_set: &mut Option<Arc<SignerProvider>>,
        new_value: Arc<SignerProvider>,
    ) -> Result<(), ()> {
        let old_value = to_be_set.replace(new_value);
        if old_value.is_some() {
            Err(())
        } else {
            Ok(())
        }
    }

    /// Import an existing private RSA key. Will only work for the
    /// OpenSslSigner. Returns an error if another signer is used.
    pub fn import_key(
        &self,
        pem: &str,
    ) -> Result<KeyIdentifier, SignerError> {
        self.bind_ready_signers();
        self.default_signer.import_key(pem)
    }
}

/// When the "hsm" feature is enabled we can no longer assume that signers are
/// immediately and always available as was the case without the "hsm" feature
/// when only the OpenSslSigner was supported. We therefore keep created
/// signers on standby in a "pending" set until we can verify that they are
/// reachable and usable and can determine which [SignerMapper]
/// [SignerHandle] to assign to them.
///
/// The Krill configuration file defines named signers with a type (openssl,
/// kmip or pkcs#11) and type specific settings (key dir path, hostname, port
/// number, TLS certificate paths, username, password, slot id, etc) and
/// assigns signers one or more roles (default signer or one-off signer)
/// either explicitly or by default.
///
/// Keys created using signers in a previous Krill process MUST have been
/// registered by the signer with the [SignerMapper] to indicate that the
/// signer owns/possesses the key, and how to map from the [KeyIdentifier] to
/// any internal signer specific key id. When a new Krill process starts it
/// will need to know for any given [KeyIdentifier] which signer that was
/// created should be used to work with the key. Rather than rely on operator
/// supplied signer names being stable or requiring operators to also maintain
/// a stable signer id in the config, we instead "bind" the signer backend to
/// the signer handle that owns the set of keys stored in the [SignerMapper].
///
/// Binding is done by asking the signer on first use to create a new key pair
/// for which we save the public key and the signer specific internal private
/// key identifier and combine them into a unique [SignerHandle] for use by the
/// signer with the [SignerMapper]. We also store some metadata about the
/// signer backend with the [SignerHandle] in the [SignerMapper] which allows
/// us to see if the configuration and/or backend properties change over time.
///
/// On subsequent bindings we determine which signer maps to which
/// [SignerMapper] [SignerHandle] by extracting the private key signer specific
/// internal id from the handle and asking each signer to sign a challenge
/// using that key. We then verify the signature using the saved public key.
/// If the signer doesn't know the internal private key id or produces
/// an incorrect signature we know that the signer doesn't possess the binding
/// key and thus likely isn't the signer we should go to for the keys mapped
/// to the [SignerMapper] handle corresponding to the binding key.
///
/// By binding this way we both verify that the signer is usable (at least for
/// key pair creation and signing) and that we are using a signer that should
/// have the keys we expect it to possess.
#[cfg(feature = "hsm")]
enum IdentifyResult {
    Unavailable,
    Corrupt,
    Identified(SignerHandle),
    Unusable,
    Unidentified,
}

#[cfg(feature = "hsm")]
enum RegisterResult {
    NotReady,
    ReadyVerified(SignerHandle),
    ReadyUnusable(String),
}

#[cfg(not(feature = "hsm"))]
impl SignerRouter {
    fn bind_ready_signers(&self) {}
}

#[cfg(feature = "hsm")]
impl SignerRouter {
    /// Check for and bind any ready signers.
    ///
    /// This function should return as quickly as possible. Newly bound
    /// signers will be moved from the pending set to the active set and
    /// be available immediately for use by the caller.
    ///
    /// This function should be invoked prior to attempting a signing
    /// operation so that the required signer is ready to handle the
    /// request. On error we log but do not return an error to the caller
    /// because the signer required by the caller may have been previously
    /// bound and this binding error may relate to a different signer. There's
    /// also nothing the caller can do if a binding failure occurs so
    /// receiving an error wouldn't be useful.
    ///
    /// If all signers have either already been bound or deemed to be
    /// permanently broken then this function will return immediately. In
    /// cases of temporary connectivity issues the signer handling code may
    /// deem it worth trying again but in such cases should implement
    /// retry and backoff such that not every attempt to use the signer is
    /// blocked trying to connect to the backend. Instead most attempts to
    /// use a temporarily unavailable signer should fail very quickly
    /// because the signer handling code is "sleeping" between binding
    /// attempts.
    fn bind_ready_signers(&self) {
        if let Err(err) = self.do_ready_signer_binding() {
            error!("Internal error: Unable to bind ready signers: {err}");
        }
    }

    /// Attempt to bind pending signers.
    fn do_ready_signer_binding(&self) -> Result<(), String> {
        let num_pending_signers = self.pending_signers.read().unwrap().len();
        if num_pending_signers > 0 {
            trace!(
                "Attempting to bind {num_pending_signers} pending signers"
            );

            // Fetch the handle of every signer previously created in the
            // [SignerMapper] to see if any of the pending signers
            // is actually one of these or is a new signer that we haven't
            // seen before.
            let candidate_handles = self.get_candidate_signer_handles()?;
            trace!(
                "{} signers were previously registered",
                candidate_handles.len()
            );

            // Block until we can get a write lock on the set of
            // pending_signers as we will hopefully remove one or
            // more items from the set. Standard practice in Krill is to panic
            // if a lock cannot be obtained.
            let mut pending_signers = self.pending_signers.write().unwrap();

            let mut abort_flag = false;

            // For each pending signer see if we can verify it and if so move
            // it from the pending set to the active set.
            pending_signers.retain(|signer_provider| -> bool {
                if abort_flag {
                    return true;
                }

                let signer_name = signer_provider.get_name().to_string();

                // See if this is a known signer that whose signature matches the public key stored in the
                // [SignerMapper] for the signer.
                self.identify_signer(signer_provider, &candidate_handles)
                    .and_then(|verify_result| match verify_result {
                        IdentifyResult::Unavailable => {
                            // Signer isn't ready yet, leave it in the pending set and try again next time.
                            trace!("Signer '{signer_name}' is unavailable");
                            Ok(true)
                        }
                        IdentifyResult::Identified(signer_handle) => {
                            // Signer is ready and verified, add it to the active set.
                            self.active_signers
                                .write()
                                .unwrap()
                                .insert(signer_handle, signer_provider.clone());
                            info!("Signer '{signer_name}' is ready for use");
                            // And remove it from the pending set
                            Ok(false)
                        }
                        IdentifyResult::Unidentified => {
                            // Signer is ready and new, register it and move it to the active set
                            self.register_new_signer(signer_provider)
                                .map(|register_result| match register_result {
                                    RegisterResult::NotReady => {
                                        // Strange, it was ready just now when we verified it ... leave it in the
                                        // pending set and try again next time.
                                        trace!("Signer '{signer_name}' is not ready");
                                        true
                                    }
                                    RegisterResult::ReadyVerified(signer_handle) => {
                                        // Signer is ready and verified, add it to the active set.
                                        self.active_signers
                                            .write()
                                            .unwrap()
                                            .insert(signer_handle, signer_provider.clone());
                                        info!("Signer '{signer_name}' is ready for use");
                                        // And remove it from the pending set
                                        false
                                    }
                                    RegisterResult::ReadyUnusable(err) => {
                                        // Signer registration failed, remove it from the pending set
                                        error!(
                                            "Signer '{signer_name}' could not be registered: signer is not usable: {err}"
                                        );
                                        false
                                    }
                                })
                        }
                        IdentifyResult::Unusable => {
                            // Signer is ready and unusable, remove it from the pending set
                            error!("Signer '{signer_name}' could not be identified: signer is not usable");
                            Ok(false)
                        }
                        IdentifyResult::Corrupt => {
                            // This case should never happen as this variant is handled in the called code
                            Err(ErrorString::new("Internal error: invalid handle"))
                        }
                    })
                    .unwrap_or_else(|err| {
                        error!("Signer '{}' could not be bound: {}. Aborting.", signer_name, *err);
                        abort_flag = true;
                        true
                    })
            });
        }

        Ok(())
    }

    /// Retrieves the set of signer handles known to the signer mapper.
    fn get_candidate_signer_handles(
        &self,
    ) -> Result<Vec<SignerHandle>, String> {
        // TODO: Filter out already bound signers?
        self.signer_mapper
            .as_ref()
            .unwrap()
            .get_signer_handles()
            .map_err(|err| format!("Failed to get signer handles: {err}"))
    }

    /// Checks if the signer identity can be shown to match one of the known
    /// signer public keys.
    fn identify_signer(
        &self,
        signer_provider: &Arc<SignerProvider>,
        candidate_handles: &[SignerHandle],
    ) -> Result<IdentifyResult, ErrorString> {
        let config_signer_name = signer_provider.get_name().to_string();

        // First try any candidate handle whose signer name matches the name
        // of the signer provider then fall back to trying other
        // candidate handles, as perhaps the signer was renamed in the config
        // file and no longer matches by name but can still be matched
        // by verifying a new signing signature with the stored public key of
        // the other candidate handles.
        let mut ordered_candidate_handles = Vec::new();
        for candidate_handle in candidate_handles {
            let stored_signer_name = self
                .signer_mapper
                .as_ref()
                .unwrap()
                .get_signer_name(candidate_handle)?;
            if stored_signer_name == config_signer_name {
                ordered_candidate_handles.insert(0, candidate_handle);
            } else {
                ordered_candidate_handles.push(candidate_handle);
            }
        }

        for candidate_handle in ordered_candidate_handles {
            let res = self.is_signer_identified_by_handle(
                signer_provider,
                candidate_handle,
            )?;
            match res {
                IdentifyResult::Unidentified => {
                    // Signer was contacted and no errors were encountered but
                    // it doesn't know the key encoded in the
                    // given handle. Try again with the next handle.
                    continue;
                }
                IdentifyResult::Corrupt => {
                    // The candidate handle or signer public key is invalid so
                    // no key could be extracted to present to
                    // the signer. Try again with the next handle.
                    continue;
                }
                IdentifyResult::Unavailable
                | IdentifyResult::Unusable
                | IdentifyResult::Identified(_) => {
                    // No need to try the next candidate key, let the caller
                    // process the result.
                    return Ok(res);
                }
            }
        }

        // No errors occurred while contacting the signer but it doesn't know
        // any of our candidate keys so this must be a new signer that
        // should be registered.
        Ok(IdentifyResult::Unidentified)
    }

    /// Checks if the signer identity matches the signer public key associated
    /// with a given signer handle.
    ///
    /// To match the signer backend must have access to a key whose signer
    /// internal key ID matches one we stored when the signer was
    /// previously registered, and when used to sign a challenge the signature
    /// must match the public key we have on record (also stored when the
    /// signer was previously registered).
    fn is_signer_identified_by_handle(
        &self,
        signer_provider: &Arc<SignerProvider>,
        candidate_handle: &SignerHandle,
    ) -> Result<IdentifyResult, ErrorString> {
        let handle_name = self
            .signer_mapper
            .as_ref()
            .unwrap()
            .get_signer_name(candidate_handle)?;
        let signer_name = signer_provider.get_name().to_string();
        trace!(
            "Attempting to identify signer '{signer_name}' using identity key stored for signer '{handle_name}'"
        );

        let public_key = match self
            .signer_mapper
            .as_ref()
            .unwrap()
            .get_signer_public_key(candidate_handle)
        {
            Ok(res) => Ok(res),
            Err(err) => match err {
                crate::commons::error::Error::SignerError(err) => {
                    error!(
                        "Internal error: Identity public key for signer '{handle_name}' is invalid: {err}"
                    );
                    return Ok(IdentifyResult::Corrupt);
                }
                err => Err(err),
            },
        }?;

        let signer_private_key_id = self
            .signer_mapper
            .as_ref()
            .unwrap()
            .get_signer_private_key_internal_id(candidate_handle)?;

        let challenge = "Krill signer verification challenge".as_bytes();
        let signature = match signer_provider
            .sign_registration_challenge(&signer_private_key_id, challenge)
        {
            Err(SignerError::TemporarilyUnavailable) => {
                debug!("Signer '{signer_name}' could not be contacted");
                return Ok(IdentifyResult::Unavailable);
            }
            Err(SignerError::KeyNotFound) => {
                debug!(
                    "Signer '{signer_name}' not matched: private key id '{signer_private_key_id}' not found"
                );
                return Ok(IdentifyResult::Unidentified);
            }
            Err(err) => {
                error!("Signer '{signer_name}' is unusable: {err}");
                return Ok(IdentifyResult::Unusable);
            }
            Ok(res) => res,
        };

        if public_key.verify(challenge, &signature).is_ok() {
            debug!("Signer '{signer_name}' is ready and known, binding");
            let signer_info = signer_provider
                .get_info()
                .unwrap_or_else(|| "No signer info".to_string());

            signer_provider.set_handle(candidate_handle.clone());

            if let Err(err) = self
                .signer_mapper
                .as_ref()
                .unwrap()
                .change_signer_name(candidate_handle, &signer_name)
            {
                // This is unexpected and perhaps indicative of a deeper
                // problem but log and keep going.
                error!(
                    "Internal error: Failed to change name of signer to '{signer_name}': {err}"
                );
            }
            if let Err(err) = self
                .signer_mapper
                .as_ref()
                .unwrap()
                .change_signer_info(candidate_handle, &signer_info)
            {
                // This is unexpected and perhaps indicative of a deeper
                // problem but log and keep going.
                error!(
                    "Internal error: Failed to change info for signer '{signer_name}' to '{signer_info}': {err}"
                );
            }

            debug!(
                "Signer '{signer_name}' bound to signer mapper handle '{candidate_handle}'"
            );
        } else {
            debug!(
                "Signer '{signer_name}' not matched: incorrect signature created with private key '{signer_private_key_id}'"
            );
        }

        Ok(IdentifyResult::Identified(candidate_handle.clone()))
    }

    /// Register a signer backend so that we can identify it later.
    ///
    /// Registration creates a key pair in the signer backend and stores the
    /// signer specific internal ID of the created private key and the
    /// content of the created public key. Registration also verifies that the
    /// signer is able to sign using the newly created private key such
    /// that the created signature matches the created public key.
    fn register_new_signer(
        &self,
        signer_provider: &Arc<SignerProvider>,
    ) -> Result<RegisterResult, ErrorString> {
        let signer_name = signer_provider.get_name().to_string();

        trace!("Attempting to register signer '{signer_name}'");

        let (public_key, signer_private_key_id) =
            match signer_provider.create_registration_key() {
                Err(SignerError::TemporarilyUnavailable) => {
                    return Ok(RegisterResult::NotReady)
                }
                Err(err) => {
                    return Ok(RegisterResult::ReadyUnusable(err.to_string()))
                }
                Ok(res) => res,
            };

        let challenge = "Krill signer verification challenge".as_bytes();
        let signature = match signer_provider
            .sign_registration_challenge(&signer_private_key_id, challenge)
        {
            Err(SignerError::TemporarilyUnavailable) => {
                return Ok(RegisterResult::NotReady)
            }
            Err(err) => {
                return Ok(RegisterResult::ReadyUnusable(err.to_string()))
            }
            Ok(res) => res,
        };

        if public_key.verify(challenge, &signature).is_err() {
            return Ok(RegisterResult::ReadyUnusable(
                "Challenge signature is invalid".to_string(),
            ));
        }

        debug!("Signer '{signer_name}' is ready and new, binding");

        let signer_info = signer_provider
            .get_info()
            .unwrap_or_else(|| "No signer info".to_string());

        let signer_handle = self.signer_mapper.as_ref().unwrap().add_signer(
            &signer_name,
            &signer_info,
            &public_key,
            &signer_private_key_id,
        )?;

        signer_provider.set_handle(signer_handle.clone());

        debug!(
            "Signer '{signer_name}' bound to signer handle '{signer_handle}'"
        );
        Ok(RegisterResult::ReadyVerified(signer_handle))
    }
}

impl Signer for SignerRouter {
    type KeyId = KeyIdentifier;
    type Error = SignerError;

    fn create_key(
        &self,
        algorithm: PublicKeyFormat,
    ) -> Result<Self::KeyId, Self::Error> {
        self.bind_ready_signers();
        self.default_signer.create_key(algorithm)
    }

    fn get_key_info(
        &self,
        key_id: &KeyIdentifier,
    ) -> Result<PublicKey, KeyError<Self::Error>> {
        self.bind_ready_signers();
        self.get_signer_for_key(key_id)?.get_key_info(key_id)
    }

    fn destroy_key(
        &self,
        key_id: &KeyIdentifier,
    ) -> Result<(), KeyError<Self::Error>> {
        self.bind_ready_signers();
        self.get_signer_for_key(key_id)?.destroy_key(key_id)
    }

    fn sign<Alg: SignatureAlgorithm, D: AsRef<[u8]> + ?Sized>(
        &self,
        key_id: &KeyIdentifier,
        algorithm: Alg,
        data: &D,
    ) -> Result<Signature<Alg>, SigningError<Self::Error>> {
        self.bind_ready_signers();
        self.get_signer_for_key(key_id)?
            .sign(key_id, algorithm, data)
    }

    fn sign_one_off<Alg: SignatureAlgorithm, D: AsRef<[u8]> + ?Sized>(
        &self,
        algorithm: Alg,
        data: &D,
    ) -> Result<(Signature<Alg>, PublicKey), Self::Error> {
        self.bind_ready_signers();
        self.one_off_signer.sign_one_off(algorithm, data)
    }

    fn rand(&self, target: &mut [u8]) -> Result<(), Self::Error> {
        self.bind_ready_signers();
        openssl::rand::rand_bytes(target).map_err(SignerError::OpenSslError)
    }
}

#[cfg(all(test, feature = "hsm"))]
pub mod tests {
    use std::slice;
    use rpki::crypto::RpkiSignatureAlgorithm;

    use crate::{
        commons::crypto::{
            dispatch::signerprovider::SignerFlags,
            signers::mocksigner::{
                CreateRegistrationKeyErrorCb, FnIdx, MockSigner,
                MockSignerCallCounts, SignRegistrationChallengeErrorCb,
            },
        },
        commons::test,
    };

    use super::*;

    fn create_signer_router(
        all_signers: &[Arc<SignerProvider>],
        signer_mapper: Arc<SignerMapper>,
    ) -> SignerRouter {
        SignerRouter {
            default_signer: all_signers[0].clone(),
            one_off_signer: all_signers[0].clone(),
            signer_mapper: Some(signer_mapper),
            active_signers: RwLock::new(HashMap::new()),
            pending_signers: RwLock::new(all_signers.to_vec()),
        }
    }

    #[test]
    pub fn verify_that_a_usable_signer_is_registered_and_can_be_used() {
        test::test_in_memory(|storage_uri| {
            #[allow(non_snake_case)]
            let DEF_SIG_ALG = RpkiSignatureAlgorithm::default();

            // Build a mock signer that is contactable and usable for the
            // SignerRouter
            let call_counts = Arc::new(MockSignerCallCounts::new());
            let signer_mapper =
                Arc::new(SignerMapper::build(storage_uri).unwrap());
            let mock_signer = MockSigner::new(
                "mock signer",
                signer_mapper.clone(),
                call_counts.clone(),
                None,
                None,
            );
            let mock_signer = Arc::new(SignerProvider::Mock(
                SignerFlags::default(),
                mock_signer,
            ));

            // Create a SignerRouter that uses the mock signer with the mock
            // signer starting in the pending signer set.
            let router = create_signer_router(
                slice::from_ref(&mock_signer),
                signer_mapper.clone(),
            );

            // No signers have been registered with the SignerMapper yet
            assert_eq!(0, signer_mapper.get_signer_handles().unwrap().len());

            // Verify that initially none of the functions in the mock signer
            // have been called
            assert_eq!(0, call_counts.get(FnIdx::CreateRegistrationKey));
            assert_eq!(0, call_counts.get(FnIdx::SignRegistrationChallenge));
            assert_eq!(0, call_counts.get(FnIdx::GetInfo));
            assert_eq!(0, call_counts.get(FnIdx::SetHandle));
            assert_eq!(0, call_counts.get(FnIdx::CreateKey));
            assert_eq!(0, call_counts.get(FnIdx::Sign));
            assert_eq!(0, call_counts.get(FnIdx::DestroyKey));

            // Try to use the SignerRouter to generate a random value. This
            // should cause the SignerRouter to contact
            // the mock signer, ask it to create a registration key, verify
            // that it can sign correctly with that key,
            // assign a signer mapper handle to the signer, then check for
            // random number generation support and finally
            // actually generate the random number.
            let mut out_buf: [u8; 1] = [0; 1];
            router.rand(&mut out_buf).unwrap();
            assert_eq!(1, call_counts.get(FnIdx::CreateRegistrationKey));
            assert_eq!(1, call_counts.get(FnIdx::SignRegistrationChallenge));
            assert_eq!(1, call_counts.get(FnIdx::GetInfo));
            assert_eq!(1, call_counts.get(FnIdx::SetHandle));

            // One signer has been registered with the SignerMapper now
            assert_eq!(1, signer_mapper.get_signer_handles().unwrap().len());

            // Ask for another random number. This time none of the
            // registration steps should be performed as the signer
            // is already registered and active.
            router.rand(&mut out_buf).unwrap();

            // Check that we can create a new key with the mock signer via the
            // SignerRouter and that the key gets registered with
            // the signer mapper.
            let key_identifier =
                router.create_key(PublicKeyFormat::Rsa).unwrap();
            assert!(signer_mapper
                .get_signer_for_key(&key_identifier)
                .is_ok());
            assert_eq!(1, call_counts.get(FnIdx::CreateKey));

            // Check that we can sign with the SignerRouter using the Krill
            // key identifier. The SignerRouter should
            // discover from the SignerMapper that the key belongs to the mock
            // signer and so dispatch the signing request to the
            // mock signer.
            router.sign(&key_identifier, DEF_SIG_ALG, &out_buf).unwrap();
            assert_eq!(1, call_counts.get(FnIdx::Sign));

            // Throw the SignerRouter away and create a new one. This is like
            // restarting Krill. Keep the mock signer as otherwise
            // we will lose its in-memory private key store. Keep the
            // SignerMapper as the mock signer is using it, and
            // because destroying it and recreating it would just be like
            // forcing it to re-read it's saved state from disk
            // (and we're not trying to test the AggregateStore here anyway!).
            let router = create_signer_router(
                slice::from_ref(&mock_signer),
                signer_mapper.clone(),
            );

            // Try to use the SignerRouter to sign again. This time around the
            // SignerMapper should find the existing signer in its
            // records and only ask the signer to sign the registration
            // challenge, but not ask it to create a registration
            // key.
            router.sign(&key_identifier, DEF_SIG_ALG, &out_buf).unwrap();
            assert_eq!(1, call_counts.get(FnIdx::CreateRegistrationKey));
            assert_eq!(2, call_counts.get(FnIdx::SignRegistrationChallenge));
            assert_eq!(2, call_counts.get(FnIdx::GetInfo));
            assert_eq!(2, call_counts.get(FnIdx::SetHandle));
            assert_eq!(2, call_counts.get(FnIdx::Sign));

            // Now delete the key and verify that we can no longer sign with
            // it.
            router.destroy_key(&key_identifier).unwrap();
            assert_eq!(1, call_counts.get(FnIdx::DestroyKey));

            let err = router.sign(
                &key_identifier,
                RpkiSignatureAlgorithm::default(),
                &out_buf,
            );
            // TODO: Should this error from the SignerRouter actually be
            // SigningError::KeyNotFound instead of
            // SigningError::Signer(SignerError::KeyNotFound)?
            assert!(matches!(
                err,
                Err(SigningError::Signer(SignerError::KeyNotFound))
            ));

            // The Sign call count is still 2 because the SignerRouter fails
            // to determine which signer owns the key and fails.
            assert_eq!(2, call_counts.get(FnIdx::Sign));

            // Now ask the mock signer to forget its registration key. After
            // this the SignerRouter should fail to verify it and
            // require it to register anew.
            mock_signer.wipe_all_keys();

            // The mock signer still works for the moment because the
            // SignerRouter doesn't do registration again as
            // it thinks it still has an active signer.
            let key_identifier =
                router.create_key(PublicKeyFormat::Rsa).unwrap();
            router.sign(&key_identifier, DEF_SIG_ALG, &out_buf).unwrap();

            assert_eq!(1, call_counts.get(FnIdx::CreateRegistrationKey));
            assert_eq!(2, call_counts.get(FnIdx::SignRegistrationChallenge));
            assert_eq!(2, call_counts.get(FnIdx::CreateKey));
            assert_eq!(3, call_counts.get(FnIdx::Sign));

            // Throw away the SignerRouter again, thereby forcing the mock
            // signer to be in the pending set again instead of
            // the ready set. Now the SignerRouter should register the mock
            // signer again and we should end up with a second
            // signer in the SignerMapper as the ability to identify the first
            // one has been lost (because above we instructed the
            // mock signer to wipe all its keys). As the SignerMapper contains
            // an existing signer the call count to
            // sign_registration_challenge() in the mock signer will actually
            // increase twice because the SignerRouter will first challenge it
            // to prove that it is the already known signer.
            // Without the identity key however the mock signer fails this
            // identity check and is registered again (and then
            // sign challenged again, hence the double increment).
            let router =
                create_signer_router(&[mock_signer], signer_mapper.clone());

            let err = router.sign(&key_identifier, DEF_SIG_ALG, &out_buf);
            assert!(matches!(
                err,
                Err(SigningError::Signer(SignerError::KeyNotFound))
            ));

            assert_eq!(2, call_counts.get(FnIdx::CreateRegistrationKey));
            assert_eq!(4, call_counts.get(FnIdx::SignRegistrationChallenge));
            assert_eq!(3, call_counts.get(FnIdx::GetInfo));
            assert_eq!(3, call_counts.get(FnIdx::SetHandle));
            assert_eq!(3, call_counts.get(FnIdx::Sign));

            // Two signers have been registered with the SignerMapper by this
            // point, one of which is now orphaned as
            // the keys that it knows about refer to a signer backend that is
            // no longer able to prove that it is the
            // owner of these keys (because its identity key was deleted in
            // the signer backend). Thus the SignerRouter
            // doesn't know which signer to forward requests to in order to
            // work with the keys owned by the orphaned signer.
            assert_eq!(2, signer_mapper.get_signer_handles().unwrap().len());
        });
    }

    #[test]
    pub fn verify_that_unusable_signers_are_neither_registered_nor_retried() {
        fn perm_unusable(
            _: &MockSignerCallCounts,
        ) -> Result<(), SignerError> {
            Err(SignerError::PermanentlyUnusable)
        }

        fn internal_error(
            _: &MockSignerCallCounts,
        ) -> Result<(), SignerError> {
            Err(SignerError::Other("internal error".to_string()))
        }

        fn temp_unavail(_: &MockSignerCallCounts) -> Result<(), SignerError> {
            Err(SignerError::TemporarilyUnavailable)
        }

        fn create_broken_signer(
            signer_mapper: Arc<SignerMapper>,
            call_counts: Arc<MockSignerCallCounts>,
            create_registration_key_error_cb: Option<
                CreateRegistrationKeyErrorCb,
            >,
            sign_registration_challenge_error_cb: Option<
                SignRegistrationChallengeErrorCb,
            >,
        ) -> Arc<SignerProvider> {
            Arc::new(SignerProvider::Mock(
                SignerFlags::default(),
                MockSigner::new(
                    "broken mock signer",
                    signer_mapper,
                    call_counts,
                    create_registration_key_error_cb,
                    sign_registration_challenge_error_cb,
                ),
            ))
        }

        fn create_broken_signers(
            sm: Arc<SignerMapper>,
            cc: Arc<MockSignerCallCounts>,
        ) -> Vec<Arc<SignerProvider>> {
            vec![
                create_broken_signer(
                    sm.clone(),
                    cc.clone(),
                    Some(perm_unusable),
                    None,
                ),
                create_broken_signer(
                    sm.clone(),
                    cc.clone(),
                    Some(internal_error),
                    None,
                ),
                create_broken_signer(
                    sm.clone(),
                    cc.clone(),
                    Some(temp_unavail),
                    None,
                ),
                create_broken_signer(
                    sm.clone(),
                    cc.clone(),
                    None,
                    Some(perm_unusable),
                ),
                create_broken_signer(
                    sm.clone(),
                    cc.clone(),
                    None,
                    Some(internal_error),
                ),
                create_broken_signer(sm, cc, None, Some(temp_unavail)),
            ]
        }

        test::test_in_memory(|storage_uri| {
            let call_counts = Arc::new(MockSignerCallCounts::new());
            let signer_mapper =
                Arc::new(SignerMapper::build(storage_uri).unwrap());
            let broken_signers = create_broken_signers(
                signer_mapper.clone(),
                call_counts.clone(),
            );

            // Create a SignerRouter that has access to all of the broken
            // signers
            let router = create_signer_router(
                broken_signers.as_slice(),
                signer_mapper.clone(),
            );

            // No signers have been registered with the SignerMapper yet
            assert_eq!(0, signer_mapper.get_signer_handles().unwrap().len());

            let mut rand_out: [u8; 1] = [0; 1];

            // Try to use the SignerRouter to generate a random value. This
            // should cause the SignerRouter to contact all of the
            // mock signers, asking them to create a registration key, and if
            // that succeeds to then verify that the signer can
            // sign correctly with that key. None of the broken signers will
            // succeed at these steps and so the counter of
            // registered signers will remain at zero.
            router.rand(&mut rand_out).unwrap();

            // The number of attempts to register a signer should have
            // increased by the number of signers. Half of the
            // signers should fail at the registration step, the other half at
            // the challenge signing step. So the number of
            // signers that we succeeded in moving out of the pending set to
            // the active set and registering with the signer
            // mapper should be zero.
            assert_eq!(6, call_counts.get(FnIdx::CreateRegistrationKey));
            assert_eq!(3, call_counts.get(FnIdx::SignRegistrationChallenge));
            assert_eq!(0, signer_mapper.get_signer_handles().unwrap().len());

            //
            // Try again.
            //
            router.rand(&mut rand_out).unwrap();

            // The signers that were permanently unusable at registration
            // should not be tried again.
            assert_eq!(6 + 2, call_counts.get(FnIdx::CreateRegistrationKey));

            // The signers that were permanently unusable at challenge signing
            // should not be tried again.
            assert_eq!(
                3 + 1,
                call_counts.get(FnIdx::SignRegistrationChallenge)
            );

            // And the end result should be that no signers were registered
            // with the signer mapper.
            assert_eq!(0, signer_mapper.get_signer_handles().unwrap().len());
        });
    }

    #[test]
    pub fn verify_that_temporarily_unavailable_signers_are_registered_when_available(
    ) {
        fn temp_unavail(
            call_counts: &MockSignerCallCounts,
        ) -> Result<(), SignerError> {
            if call_counts.get(FnIdx::CreateRegistrationKey) == 1 {
                // Fail the first time registration is attempted
                Err(SignerError::TemporarilyUnavailable)
            } else {
                // Succeed on subsequent attempts
                Ok(())
            }
        }

        test::test_in_memory(|storage_uri| {
            let call_counts = Arc::new(MockSignerCallCounts::new());
            let signer_mapper =
                Arc::new(SignerMapper::build(storage_uri).unwrap());

            let temp_unavail_signer = Arc::new(SignerProvider::Mock(
                SignerFlags::default(),
                MockSigner::new(
                    "mock temporararily unavailable signer",
                    signer_mapper.clone(),
                    call_counts.clone(),
                    Some(temp_unavail),
                    None,
                ),
            ));

            // Create a SignerRouter that uses the mock signer with the mock
            // signer starting in the pending signer set.
            let router = create_signer_router(
                &[temp_unavail_signer],
                signer_mapper.clone(),
            );

            // No signers have been registered with the SignerMapper yet
            assert_eq!(0, signer_mapper.get_signer_handles().unwrap().len());

            let mut rand_out: [u8; 1] = [0; 1];

            // Try to use the SignerRouter to generate a random value. This
            // should cause the SignerRouter to contact
            // the mock signer, ask it to create a registration key, verify
            // that it can sign correctly with that key,
            // assign a signer mapper handle to the signer, then check for
            // random number generation support and finally
            // actually generate the random number. This should fail the first
            // time due to the logic imlpemented by the
            // temp_avail() function above.
            router.rand(&mut rand_out).unwrap();

            // The number of attempts to register a signer should have
            // increased by one.
            assert_eq!(1, call_counts.get(FnIdx::CreateRegistrationKey));
            assert_eq!(0, call_counts.get(FnIdx::SignRegistrationChallenge));
            assert_eq!(0, signer_mapper.get_signer_handles().unwrap().len());

            //
            // Try again. We should succeed the second time due to the logic
            // imlpemented by the temp_avail() function above.
            //
            router.rand(&mut rand_out).unwrap();

            // We should be all green now
            assert_eq!(2, call_counts.get(FnIdx::CreateRegistrationKey));
            assert_eq!(1, call_counts.get(FnIdx::SignRegistrationChallenge));
            assert_eq!(1, signer_mapper.get_signer_handles().unwrap().len());
        });
    }
}