geth/crates/geth-ssh-identity/src/lib.rs

use std::path::Path;
use std::process::Command;

use geth_types::{NodeId, SshCertId, SshCertRequestId, SshRevocationId, UnixMillis};
use serde::{Deserialize, Serialize};

pub const KEYCHAIN_NAMESPACE: &str = "geth.keychain.v1@geth.local";
pub const AUTH_OP_NAMESPACE: &str = "geth.auth-op.v1@geth.local";
pub const RESOURCE_GRANT_NAMESPACE: &str = "geth.resource-grant.v1@geth.local";
pub const RESOURCE_SECRET_NAMESPACE: &str = "geth.resource-secret.v1@geth.local";
pub const REVOCATION_NAMESPACE: &str = "geth.revocation.v1@geth.local";
pub const SSH_CERT_REQUEST_NAMESPACE: &str = "geth.ssh-cert-request.v1@geth.local";
pub const SSH_CERT_ISSUANCE_NAMESPACE: &str = "geth.ssh-cert-issuance.v1@geth.local";
pub const SSH_REVOCATION_LIST_NAMESPACE: &str = "geth.ssh-revocation-list.v1@geth.local";

pub fn ensure_ssh_keygen_available() -> Result<(), SshIdentityError> {
    let status = Command::new("ssh-keygen").arg("-?").status();
    match status {
        Ok(_) => Ok(()),
        Err(error) if error.kind() == std::io::ErrorKind::NotFound => {
            Err(SshIdentityError::SshKeygenUnavailable)
        }
        Err(error) => Err(SshIdentityError::Io(error)),
    }
}

pub fn sign_command(key_path: &Path, namespace: &str, input_path: &Path) -> Command {
    let mut command = Command::new("ssh-keygen");
    command
        .arg("-Y")
        .arg("sign")
        .arg("-f")
        .arg(key_path)
        .arg("-n")
        .arg(namespace)
        .arg(input_path);
    command
}

#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
#[serde(rename_all = "kebab-case")]
pub enum SshCertKind {
    User,
    Host,
}

impl SshCertKind {
    #[must_use]
    pub fn as_str(&self) -> &'static str {
        match self {
            Self::User => "user",
            Self::Host => "host",
        }
    }
}

impl std::fmt::Display for SshCertKind {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_str(self.as_str())
    }
}

impl std::str::FromStr for SshCertKind {
    type Err = SshIdentityError;

    fn from_str(value: &str) -> Result<Self, Self::Err> {
        match value {
            "user" => Ok(Self::User),
            "host" => Ok(Self::Host),
            _ => Err(SshIdentityError::InvalidCertKind(value.to_owned())),
        }
    }
}

#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
#[serde(rename_all = "kebab-case")]
pub enum SshCertRequestStatus {
    Pending,
    Approved,
    Signed,
    Rejected,
    Revoked,
}

impl SshCertRequestStatus {
    #[must_use]
    pub fn as_str(&self) -> &'static str {
        match self {
            Self::Pending => "pending",
            Self::Approved => "approved",
            Self::Signed => "signed",
            Self::Rejected => "rejected",
            Self::Revoked => "revoked",
        }
    }
}

impl std::fmt::Display for SshCertRequestStatus {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_str(self.as_str())
    }
}

impl std::str::FromStr for SshCertRequestStatus {
    type Err = SshIdentityError;

    fn from_str(value: &str) -> Result<Self, Self::Err> {
        match value {
            "pending" => Ok(Self::Pending),
            "approved" => Ok(Self::Approved),
            "signed" => Ok(Self::Signed),
            "rejected" => Ok(Self::Rejected),
            "revoked" => Ok(Self::Revoked),
            _ => Err(SshIdentityError::InvalidRequestStatus(value.to_owned())),
        }
    }
}

#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
pub struct SshCertRequest {
    pub id: SshCertRequestId,
    pub requester_node: NodeId,
    pub public_key: String,
    pub public_key_fingerprint: String,
    pub cert_kind: SshCertKind,
    pub principals: Vec<String>,
    pub requested_validity: Option<String>,
    pub renewal_of: Option<SshCertId>,
    pub reason: Option<String>,
    pub status: SshCertRequestStatus,
    pub created_at: UnixMillis,
}

#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
pub struct SshCertApproval {
    pub request_id: SshCertRequestId,
    pub approved_by_node: NodeId,
    pub ca_key_path: String,
    pub key_id: String,
    pub valid_for: String,
    pub serial: Option<u64>,
    pub output_path: Option<String>,
    pub signing_command: Vec<String>,
    pub note: String,
}

#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
pub struct SshCertificateRecord {
    pub id: SshCertId,
    pub request_id: SshCertRequestId,
    pub certificate: String,
    pub certificate_fingerprint: String,
    pub imported_at: UnixMillis,
}

#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
#[serde(rename_all = "kebab-case")]
pub enum SshRevocationKind {
    PublicKey,
    Certificate,
    Serial,
    KeyId,
}

impl SshRevocationKind {
    #[must_use]
    pub fn as_str(&self) -> &'static str {
        match self {
            Self::PublicKey => "public-key",
            Self::Certificate => "certificate",
            Self::Serial => "serial",
            Self::KeyId => "key-id",
        }
    }
}

impl std::fmt::Display for SshRevocationKind {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_str(self.as_str())
    }
}

impl std::str::FromStr for SshRevocationKind {
    type Err = SshIdentityError;

    fn from_str(value: &str) -> Result<Self, Self::Err> {
        match value {
            "public-key" | "key" => Ok(Self::PublicKey),
            "certificate" | "cert" => Ok(Self::Certificate),
            "serial" => Ok(Self::Serial),
            "key-id" | "keyid" => Ok(Self::KeyId),
            _ => Err(SshIdentityError::InvalidRevocationKind(value.to_owned())),
        }
    }
}

#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
pub struct SshRevocationEntry {
    pub id: SshRevocationId,
    pub kind: SshRevocationKind,
    pub target: String,
    pub reason: Option<String>,
    pub created_at: UnixMillis,
    pub published: bool,
}

#[derive(Debug, thiserror::Error)]
pub enum SshCertFlowError {
    #[error("certificate request has no principals")]
    MissingPrincipals,
}

#[must_use]
pub fn ssh_public_key_fingerprint(public_key: &str) -> String {
    format!("ssh:blake3:{}", blake3::hash(public_key.trim().as_bytes()))
}

pub fn cert_request_id(
    requester_node: &NodeId,
    public_key: &str,
    principals: &[String],
    created_at: UnixMillis,
) -> SshCertRequestId {
    let mut input = String::new();
    input.push_str(requester_node.as_str());
    input.push('\n');
    input.push_str(public_key.trim());
    input.push('\n');
    input.push_str(&principals.join(","));
    input.push('\n');
    input.push_str(&created_at.0.to_string());
    SshCertRequestId::new(format!(
        "ssh-cert-request:{}",
        blake3::hash(input.as_bytes())
    ))
}

pub fn certificate_id(certificate: &str) -> SshCertId {
    SshCertId::new(format!(
        "ssh-cert:{}",
        blake3::hash(certificate.trim().as_bytes())
    ))
}

pub fn revocation_id(
    kind: &SshRevocationKind,
    target: &str,
    created_at: UnixMillis,
) -> SshRevocationId {
    let input = format!("{}\n{}\n{}", kind, target.trim(), created_at.0);
    SshRevocationId::new(format!("ssh-revocation:{}", blake3::hash(input.as_bytes())))
}

pub fn build_ssh_cert_sign_command(
    request: &SshCertRequest,
    ca_key_path: &Path,
    public_key_path: &Path,
    valid_for: &str,
    serial: Option<u64>,
) -> Result<Vec<String>, SshCertFlowError> {
    if request.principals.is_empty() {
        return Err(SshCertFlowError::MissingPrincipals);
    }

    let mut command = vec![
        "ssh-keygen".to_owned(),
        "-s".to_owned(),
        ca_key_path.display().to_string(),
        "-I".to_owned(),
        request.id.to_string(),
        "-n".to_owned(),
        request.principals.join(","),
        "-V".to_owned(),
        valid_for.to_owned(),
    ];
    if let Some(serial) = serial {
        command.push("-z".to_owned());
        command.push(serial.to_string());
    }
    if request.cert_kind == SshCertKind::Host {
        command.push("-h".to_owned());
    }
    command.push(public_key_path.display().to_string());
    Ok(command)
}

#[derive(Debug, thiserror::Error)]
pub enum SshIdentityError {
    #[error("ssh-keygen failed or is unavailable")]
    SshKeygenUnavailable,
    #[error("invalid ssh certificate kind: {0}")]
    InvalidCertKind(String),
    #[error("invalid ssh certificate request status: {0}")]
    InvalidRequestStatus(String),
    #[error("invalid ssh revocation kind: {0}")]
    InvalidRevocationKind(String),
    #[error("io error: {0}")]
    Io(#[from] std::io::Error),
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn ssh_cert_request_roundtrips() {
        let request = SshCertRequest {
            id: "ssh-cert-request:1".into(),
            requester_node: "node:laptop".into(),
            public_key: "ssh-ed25519 AAAA test".to_owned(),
            public_key_fingerprint: ssh_public_key_fingerprint("ssh-ed25519 AAAA test"),
            cert_kind: SshCertKind::User,
            principals: vec!["eric".to_owned()],
            requested_validity: Some("+52w".to_owned()),
            renewal_of: None,
            reason: Some("bootstrap".to_owned()),
            status: SshCertRequestStatus::Pending,
            created_at: UnixMillis(1),
        };
        let json = serde_json::to_string(&request).expect("json");
        let decoded: SshCertRequest = serde_json::from_str(&json).expect("decode");
        assert_eq!(decoded, request);
    }

    #[test]
    fn sign_command_includes_host_flag_for_host_certs() {
        let request = SshCertRequest {
            id: "ssh-cert-request:1".into(),
            requester_node: "node:server".into(),
            public_key: "ssh-ed25519 AAAA host".to_owned(),
            public_key_fingerprint: ssh_public_key_fingerprint("ssh-ed25519 AAAA host"),
            cert_kind: SshCertKind::Host,
            principals: vec!["server.local".to_owned()],
            requested_validity: None,
            renewal_of: None,
            reason: None,
            status: SshCertRequestStatus::Pending,
            created_at: UnixMillis(1),
        };
        let command = build_ssh_cert_sign_command(
            &request,
            Path::new("/keys/ca_sk"),
            Path::new("/tmp/host.pub"),
            "+4w",
            Some(7),
        )
        .expect("command");
        assert!(command.contains(&"-h".to_owned()));
        assert!(command.contains(&"server.local".to_owned()));
    }
}