//! This crate implements a [libunftp](https://docs.rs/libunftp/latest/libunftp) `Authenticator`
//! that authenticates against credentials in a JSON format.
//!
//! It supports both plaintext as well as [PBKDF2](https://tools.ietf.org/html/rfc2898#section-5.2)
//! encoded passwords.
//!
//! # Plaintext example
//!
//! ```json
//! [
//!   {
//!     "username": "alice",
//!     "password": "I am in Wonderland!"
//!   }
//! ]
//! ```
//!
//! # PBKDF2 encoded Example
//!
//! Both the salt and key need to be base64 encoded.
//! Currently only HMAC_SHA256 is supported by libunftp (more will be supported later).
//!
//! There are various tools that can be used to generate the key.
//!
//! In this example we show two ways to generate the PBKDF2. First we show how to use the common tool [nettle-pbkdf2](http://www.lysator.liu.se/~nisse/nettle/) directly.
//!
//! Generate a secure salt:
//! ```sh
//! salt=$(dd if=/dev/random bs=1 count=8)
//! ```
//!
//! Generate the base64 encoded PBKDF2 key, to be copied into the `pbkdf2_key` field of the JSON structure.
//!
//! When using `nettle` directly, make sure not to exceed the output length of the digest algorithm (256 bit, 32 bytes in our case):
//! ```sh
//! echo -n "mypassword" | nettle-pbkdf2 -i 500000 -l 32 --hex-salt $(echo -n $salt | xxd -p -c 80) --raw |openssl base64 -A
//! ```
//!
//! Convert the salt into base64 to be copied into the `pbkdf2_salt` field of the JSON structure:
//! ```sh
//! echo -n $salt | openssl base64 -A
//! ```
//!
//! Alternatively to using `nettle` directly, you may use our convenient docker image: bolcom/unftp-key-generator
//!
//! ```sh
//! docker run -ti bolcom/unftp-key-generator -h
//! ```
//!
//! Running it without options, will generate a PBKDF2 key and a random salt from a given password.
//! If no password is entered, a secure password will be generated with default settings for the password complexity and number of iterations.
//!
//! Now write these to the JSON file, as seen below.
//! If you use our unftp-key-generator, you can use the `-u` switch, to generate the JSON output directly.
//! Otherwise, make sure that `pbkdf2_iter` in the example below, matches the iterations (`-i`) used with `nettle-pbkdf2`.
//!
//! ```json
//! [
//!   {
//!     "username": "bob",
//!     "pbkdf2_salt": "<<BASE_64_RANDOM_SALT>>",
//!     "pbkdf2_key": "<<BASE_64_KEY>>",
//!     "pbkdf2_iter": 500000
//!   },
//! ]
//! ```
//!
//! # Mixed example
//!
//! It is possible to mix plaintext and pbkdf2 encoded type passwords.
//!
//! ```json
//! [
//!   {
//!     "username": "alice",
//!     "pbkdf2_salt": "<<BASE_64_RANDOM_SALT>>",
//!     "pbkdf2_key": "<<BASE_64_KEY>>",
//!     "pbkdf2_iter": 500000
//!   },
//!   {
//!     "username": "bob",
//!     "password": "This password is a joke"
//!   }
//! ]
//! ```
//!
//! # Using it with libunftp
//!
//! Use [JsonFileAuthenticator::from_file](crate::JsonFileAuthenticator::from_file) to load the JSON structure directly from a file.
//! See the example `examples/jsonfile_auth.rs`.
//!
//! Alternatively use another source for your JSON credentials, and use [JsonFileAuthenticator::from_json](crate::JsonFileAuthenticator::from_json) instead.
//!
//! # Preventing unauthorized access with allow lists
//!
//! ```json
//! [
//!   {
//!     "username": "bob",
//!     "password": "it is me",
//!     "allowed_ip_ranges": ["192.168.178.0/24", "127.0.0.0/8"]
//!   },
//! ]
//! ```
//!
//! # Per user certificate validation
//!
//! The JSON authenticator can also check that the CN of a client certificate matches a certain
//! string or substring. Furthermore, password-less; certificate only; authentication can be configured
//! per user when libunftp is configured to use TLS and specifically also configured to request or
//! require a client certificate through the [Server.ftps_client_auth](https://docs.rs/libunftp/0.17.4/libunftp/struct.Server.html#method.ftps_client_auth)
//! method. For this to work correctly a trust store with the root certificate also needs to be configured
//! with [Server.ftps_trust_store](https://docs.rs/libunftp/0.17.4/libunftp/struct.Server.html#method.ftps_trust_store).
//!
//! Given this example configuration:
//!
//! ```json
//! [
//!   {
//!    "username": "eve",
//!    "pbkdf2_salt": "dGhpc2lzYWJhZHNhbHR0b28=",
//!    "pbkdf2_key": "C2kkRTybDzhkBGUkTn5Ys1LKPl8XINI46x74H4c9w8s=",
//!    "pbkdf2_iter": 500000,
//!    "client_cert": {
//!      "allowed_cn": "i.am.trusted"
//!    }
//!  },
//!  {
//!    "username": "freddie",
//!    "client_cert": {}
//!  },
//!  {
//!    "username": "santa",
//!    "password": "clara",
//!    "client_cert": {}
//!  }
//! ]
//! ```
//!
//! we can see that Eve needs to present a valid client certificate with a CN matching "i.am.trusted"
//! and then also needs to provide the correct password. Freddie just needs to present a valid
//! certificate that is signed by a certificate in the trust store. No password is required for
//! him when logging in. Santa needs to provide a valid certificate and password but the CN can
//! be anything.
//!

use async_trait::async_trait;
use bytes::Bytes;
use ipnet::Ipv4Net;
use iprange::IpRange;
use libunftp::auth::{AuthenticationError, Authenticator, DefaultUser};
use ring::{
    digest::SHA256_OUTPUT_LEN,
    pbkdf2::{verify, PBKDF2_HMAC_SHA256},
};
use serde::Deserialize;
use std::{collections::HashMap, convert::TryInto, fs, num::NonZeroU32, path::Path, time::Duration};
use tokio::time::sleep;
use valid::{constraint::Length, Validate};

#[derive(Deserialize, Clone, Debug)]
struct ClientCertCredential {
    allowed_cn: Option<String>,
}

#[derive(Deserialize, Clone, Debug)]
#[serde(untagged)]
enum Credentials {
    Pbkdf2 {
        username: String,
        pbkdf2_salt: String,
        pbkdf2_key: String,
        pbkdf2_iter: NonZeroU32,
        client_cert: Option<ClientCertCredential>,
        allowed_ip_ranges: Option<Vec<String>>,
    },
    Plaintext {
        username: String,
        password: Option<String>,
        client_cert: Option<ClientCertCredential>,
        allowed_ip_ranges: Option<Vec<String>>,
    },
}

/// This structure implements the libunftp `Authenticator` trait
#[derive(Clone, Debug)]
pub struct JsonFileAuthenticator {
    credentials_map: HashMap<String, UserCreds>,
}

#[derive(Clone, Debug)]
enum Password {
    PlainPassword {
        password: Option<String>,
    },
    Pbkdf2Password {
        pbkdf2_salt: Bytes,
        pbkdf2_key: Bytes,
        pbkdf2_iter: NonZeroU32,
    },
}

#[derive(Clone, Debug)]
struct UserCreds {
    pub password: Password,
    pub client_cert: Option<ClientCertCredential>,
    pub allowed_ip_ranges: Option<IpRange<Ipv4Net>>,
}

impl JsonFileAuthenticator {
    /// Initialize a new [`JsonFileAuthenticator`] from file.
    pub fn from_file<P: AsRef<Path>>(filename: P) -> Result<Self, Box<dyn std::error::Error>> {
        let json: String = fs::read_to_string(filename)?;
        Self::from_json(json)
    }

    /// Initialize a new [`JsonFileAuthenticator`] from json string.
    pub fn from_json<T: Into<String>>(json: T) -> Result<Self, Box<dyn std::error::Error>> {
        let credentials_list: Vec<Credentials> = serde_json::from_str::<Vec<Credentials>>(&json.into())?;
        let map: Result<HashMap<String, UserCreds>, _> = credentials_list.into_iter().map(Self::list_entry_to_map_entry).collect();
        Ok(JsonFileAuthenticator { credentials_map: map? })
    }

    fn list_entry_to_map_entry(user_info: Credentials) -> Result<(String, UserCreds), Box<dyn std::error::Error>> {
        let map_entry = match user_info {
            Credentials::Plaintext {
                username,
                password,
                client_cert,
                allowed_ip_ranges: ip_ranges,
            } => (
                username.clone(),
                UserCreds {
                    password: Password::PlainPassword { password },
                    client_cert,
                    allowed_ip_ranges: Self::parse_ip_range(username, ip_ranges)?,
                },
            ),
            Credentials::Pbkdf2 {
                username,
                pbkdf2_salt,
                pbkdf2_key,
                pbkdf2_iter,
                client_cert,
                allowed_ip_ranges: ip_ranges,
            } => (
                username.clone(),
                UserCreds {
                    password: Password::Pbkdf2Password {
                        pbkdf2_salt: base64::decode(pbkdf2_salt)
                            .map_err(|_| "Could not base64 decode the salt")?
                            .try_into()
                            .map_err(|_| "Could not convert String to Bytes")?,
                        pbkdf2_key: base64::decode(pbkdf2_key)
                            .map_err(|_| "Could not decode base64")?
                            .validate("pbkdf2_key", &Length::Max(SHA256_OUTPUT_LEN))
                            .result()
                            .map_err(|_| {
                                format!("Key of user \"{}\" is too long", username)
                            })?
                            .unwrap() // this unwrap is just giving the value within
                            .try_into()
                            .map_err(|_| "Could not convert to Bytes")?,
                        pbkdf2_iter,
                    },
                    client_cert,
                    allowed_ip_ranges: Self::parse_ip_range(username, ip_ranges)?,
                },
            ),
        };
        Ok(map_entry)
    }

    fn parse_ip_range(username: String, ip_ranges: Option<Vec<String>>) -> Result<Option<IpRange<Ipv4Net>>, String> {
        ip_ranges
            .map(|v| {
                let range: Result<IpRange<Ipv4Net>, _> = v
                    .iter()
                    .map(|s| s.parse::<Ipv4Net>().map_err(|_| format!("could not parse IP ranges for user {}", username)))
                    .collect();
                range
            })
            .transpose()
    }

    fn check_password(given_password: &str, actual_password: &Password) -> Result<(), ()> {
        match actual_password {
            Password::PlainPassword { password } => {
                if let Some(pwd) = password {
                    if pwd == given_password {
                        Ok(())
                    } else {
                        Err(())
                    }
                } else {
                    Err(())
                }
            }
            Password::Pbkdf2Password {
                pbkdf2_iter,
                pbkdf2_salt,
                pbkdf2_key,
            } => verify(PBKDF2_HMAC_SHA256, *pbkdf2_iter, pbkdf2_salt, given_password.as_bytes(), pbkdf2_key).map_err(|_| ()),
        }
    }

    fn ip_ok(creds: &libunftp::auth::Credentials, actual_creds: &UserCreds) -> bool {
        match &actual_creds.allowed_ip_ranges {
            Some(allowed) => match creds.source_ip {
                std::net::IpAddr::V4(ref ip) => allowed.contains(ip),
                _ => false,
            },
            None => true,
        }
    }
}

#[async_trait]
impl Authenticator<DefaultUser> for JsonFileAuthenticator {
    #[tracing_attributes::instrument]
    async fn authenticate(&self, username: &str, creds: &libunftp::auth::Credentials) -> Result<DefaultUser, AuthenticationError> {
        let res = if let Some(actual_creds) = self.credentials_map.get(username) {
            let client_cert = &actual_creds.client_cert;
            let certificate = &creds.certificate_chain.as_ref().and_then(|x| x.first());

            let ip_check_result = if !Self::ip_ok(creds, actual_creds) {
                Err(AuthenticationError::IpDisallowed)
            } else {
                Ok(DefaultUser {})
            };

            let cn_check_result = match (&client_cert, certificate) {
                // If client_cert is Some, it has an allowed_cn
                // Option, if it is set, the client cert is checked,
                // otherwise any trusted client cert will be accepted
                (Some(client_cert), Some(cert)) => match (&client_cert.allowed_cn, cert) {
                    (Some(cn), cert) => match cert.verify_cn(cn) {
                        Ok(is_authorized) => {
                            if is_authorized {
                                Some(Ok(DefaultUser {}))
                            } else {
                                Some(Err(AuthenticationError::CnDisallowed))
                            }
                        }
                        Err(e) => Some(Err(AuthenticationError::with_source("verify_cn", e))),
                    },
                    (None, _) => Some(Ok(DefaultUser {})),
                },
                (Some(_), None) => Some(Err(AuthenticationError::CnDisallowed)),
                _ => None,
            };

            let pass_check_result = match &creds.password {
                Some(ref given_password) => {
                    if Self::check_password(given_password, &actual_creds.password).is_ok() {
                        Some(Ok(DefaultUser {}))
                    } else {
                        Some(Err(AuthenticationError::BadPassword))
                    }
                }
                None => None,
            };

            // the ip_check_result is returned at the end if all the other credentials are good.
            // because from unauthorized sources, we want to know whether they posses valid credentials somehow
            // but for logging purposes it would be better if we simply logged all of the results instead
            match (pass_check_result, cn_check_result, ip_check_result) {
                (None, None, _) => Err(AuthenticationError::BadPassword), // At least a password or client cert check is required
                (Some(pass_res), None, ip_res) => {
                    if pass_res.is_ok() {
                        ip_res
                    } else {
                        pass_res
                    }
                }
                (None, Some(cn_res), ip_res) => {
                    if cn_res.is_ok() {
                        ip_res
                    } else {
                        cn_res
                    }
                }
                (Some(pass_res), Some(cn_res), ip_res) => match (pass_res, cn_res) {
                    (Ok(_), Ok(_)) => ip_res,
                    (Ok(_), Err(e)) => Err(e),
                    (Err(e), Ok(_)) => Err(e),
                    (Err(e), Err(_)) => Err(e), // AuthenticationError::BadPassword returned also if both password and CN are wrong
                },
            }
        } else {
            Err(AuthenticationError::BadUser)
        };

        if res.is_err() {
            sleep(Duration::from_millis(1500)).await;
        }

        res
    }

    /// Tells whether its OK to not ask for a password when a valid client cert
    /// was presented.
    ///
    /// For this JSON authenticator, if a certificate object is given
    /// (optionally matched against client certificate of a specific
    /// user during authentication), the user can omit the password as
    /// a way to indicate that the user + client cert is sufficient
    /// for authentication. If the password is given, then both are
    /// required.
    async fn cert_auth_sufficient(&self, username: &str) -> bool {
        if let Some(actual_creds) = self.credentials_map.get(username) {
            if let Password::PlainPassword { password: None } = &actual_creds.password {
                return actual_creds.client_cert.is_some();
            }
        }
        false
    }

    fn name(&self) -> &str {
        std::any::type_name::<Self>()
    }
}

mod test {
    #[allow(unused_imports)]
    use libunftp::auth::ClientCert;

    #[tokio::test]
    async fn test_json_auth() {
        use super::*;

        let json: &str = r#"[
  {
    "username": "alice",
    "pbkdf2_salt": "dGhpc2lzYWJhZHNhbHQ=",
    "pbkdf2_key": "jZZ20ehafJPQPhUKsAAMjXS4wx9FSbzUgMn7HJqx4Hg=",
    "pbkdf2_iter": 500000
  },
  {
    "username": "bella",
    "pbkdf2_salt": "dGhpc2lzYWJhZHNhbHR0b28=",
    "pbkdf2_key": "C2kkRTybDzhkBGUkTn5Ys1LKPl8XINI46x74H4c9w8s=",
    "pbkdf2_iter": 500000
  },
  {
    "username": "carol",
    "password": "not so secure"
  },
  {
    "username": "dan",
    "password": "",
    "allowed_ip_ranges": ["127.0.0.1/8"]
  }
]"#;
        let json_authenticator = JsonFileAuthenticator::from_json(json).unwrap();
        assert_eq!(
            json_authenticator
                .authenticate("alice", &"this is the correct password for alice".into())
                .await
                .unwrap(),
            DefaultUser
        );
        assert_eq!(
            json_authenticator
                .authenticate("bella", &"this is the correct password for bella".into())
                .await
                .unwrap(),
            DefaultUser
        );
        assert_eq!(json_authenticator.authenticate("carol", &"not so secure".into()).await.unwrap(), DefaultUser);
        assert_eq!(json_authenticator.authenticate("dan", &"".into()).await.unwrap(), DefaultUser);
        match json_authenticator.authenticate("carol", &"this is the wrong password".into()).await {
            Err(AuthenticationError::BadPassword) => assert!(true),
            _ => assert!(false),
        }
        match json_authenticator.authenticate("bella", &"this is the wrong password".into()).await {
            Err(AuthenticationError::BadPassword) => assert!(true),
            _ => assert!(false),
        }
        match json_authenticator.authenticate("chuck", &"12345678".into()).await {
            Err(AuthenticationError::BadUser) => assert!(true),
            _ => assert!(false),
        }

        assert_eq!(
            json_authenticator
                .authenticate(
                    "dan",
                    &libunftp::auth::Credentials {
                        certificate_chain: None,
                        password: Some("".into()),
                        source_ip: std::net::IpAddr::V4(std::net::Ipv4Addr::new(127, 0, 0, 1)),
                    },
                )
                .await
                .unwrap(),
            DefaultUser
        );

        match json_authenticator
            .authenticate(
                "dan",
                &libunftp::auth::Credentials {
                    certificate_chain: None,
                    password: Some("".into()),
                    source_ip: std::net::IpAddr::V4(std::net::Ipv4Addr::new(128, 0, 0, 1)),
                },
            )
            .await
        {
            Err(AuthenticationError::IpDisallowed) => assert!(true),
            _ => assert!(false),
        }
    }

    #[tokio::test]
    async fn test_json_cert_sufficient() {
        use super::*;

        let json: &str = r#"[
  {
    "username": "alice",
    "password": "has a password"
  },
  {
    "username": "bob",
    "client_cert": {
      "allowed_cn": "my.cert.is.everything"
    }
  },
  {
    "username": "carol",
    "password": "This is ultimate security.",
    "client_cert": {
      "allowed_cn": "i.am.trusted"
    }
  },
  {
    "username": "dan",
    "pbkdf2_salt": "dGhpc2lzYWJhZHNhbHQ=",
    "pbkdf2_key": "jZZ20ehafJPQPhUKsAAMjXS4wx9FSbzUgMn7HJqx4Hg=",
    "pbkdf2_iter": 500000
  },
  {
    "username": "eve",
    "pbkdf2_salt": "dGhpc2lzYWJhZHNhbHR0b28=",
    "pbkdf2_key": "C2kkRTybDzhkBGUkTn5Ys1LKPl8XINI46x74H4c9w8s=",
    "pbkdf2_iter": 500000,
    "client_cert": {
      "allowed_cn": "i.am.trusted"
    }
  },
  {
    "username": "freddie",
    "client_cert": {}
  },
  {
    "username": "santa",
    "password": "clara",
    "client_cert": {}
  }  
]"#;
        let json_authenticator = JsonFileAuthenticator::from_json(json).unwrap();
        assert!(!json_authenticator.cert_auth_sufficient("alice").await);
        assert!(json_authenticator.cert_auth_sufficient("bob").await);
        assert!(!json_authenticator.cert_auth_sufficient("carol").await);
        assert!(!json_authenticator.cert_auth_sufficient("dan").await);
        assert!(!json_authenticator.cert_auth_sufficient("eve").await);
        assert!(json_authenticator.cert_auth_sufficient("freddie").await);
        assert!(!json_authenticator.cert_auth_sufficient("santa").await);
    }

    #[tokio::test]
    async fn test_json_cert_authenticate() {
        use super::*;

        // DER formatted certificate: subject= /CN=unftp-client.mysite.com/O=mysite.com/C=NL
        let cert: &[u8] = &[
            0x30, 0x82, 0x03, 0x1f, 0x30, 0x82, 0x02, 0x07, 0xa0, 0x03, 0x02, 0x01, 0x02, 0x02, 0x09, 0x00, 0xc3, 0x3d, 0x48, 0x52, 0x68, 0x7e, 0x06, 0x83,
            0x30, 0x0d, 0x06, 0x09, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x01, 0x0b, 0x05, 0x00, 0x30, 0x40, 0x31, 0x1c, 0x30, 0x1a, 0x06, 0x03, 0x55,
            0x04, 0x03, 0x0c, 0x13, 0x75, 0x6e, 0x66, 0x74, 0x70, 0x2d, 0x63, 0x61, 0x2e, 0x6d, 0x79, 0x73, 0x69, 0x74, 0x65, 0x2e, 0x63, 0x6f, 0x6d, 0x31,
            0x13, 0x30, 0x11, 0x06, 0x03, 0x55, 0x04, 0x0a, 0x0c, 0x0a, 0x6d, 0x79, 0x73, 0x69, 0x74, 0x65, 0x2e, 0x63, 0x6f, 0x6d, 0x31, 0x0b, 0x30, 0x09,
            0x06, 0x03, 0x55, 0x04, 0x06, 0x13, 0x02, 0x4e, 0x4c, 0x30, 0x1e, 0x17, 0x0d, 0x32, 0x31, 0x30, 0x36, 0x32, 0x35, 0x31, 0x32, 0x30, 0x38, 0x30,
            0x38, 0x5a, 0x17, 0x0d, 0x32, 0x34, 0x30, 0x34, 0x31, 0x34, 0x31, 0x32, 0x30, 0x38, 0x30, 0x38, 0x5a, 0x30, 0x44, 0x31, 0x20, 0x30, 0x1e, 0x06,
            0x03, 0x55, 0x04, 0x03, 0x0c, 0x17, 0x75, 0x6e, 0x66, 0x74, 0x70, 0x2d, 0x63, 0x6c, 0x69, 0x65, 0x6e, 0x74, 0x2e, 0x6d, 0x79, 0x73, 0x69, 0x74,
            0x65, 0x2e, 0x63, 0x6f, 0x6d, 0x31, 0x13, 0x30, 0x11, 0x06, 0x03, 0x55, 0x04, 0x0a, 0x0c, 0x0a, 0x6d, 0x79, 0x73, 0x69, 0x74, 0x65, 0x2e, 0x63,
            0x6f, 0x6d, 0x31, 0x0b, 0x30, 0x09, 0x06, 0x03, 0x55, 0x04, 0x06, 0x13, 0x02, 0x4e, 0x4c, 0x30, 0x82, 0x01, 0x22, 0x30, 0x0d, 0x06, 0x09, 0x2a,
            0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x01, 0x01, 0x05, 0x00, 0x03, 0x82, 0x01, 0x0f, 0x00, 0x30, 0x82, 0x01, 0x0a, 0x02, 0x82, 0x01, 0x01, 0x00,
            0xec, 0xdf, 0x85, 0x48, 0xf4, 0x20, 0xdd, 0x52, 0x0b, 0x9c, 0x08, 0x6a, 0x78, 0x0f, 0x16, 0x16, 0x8b, 0x11, 0x79, 0xef, 0x32, 0xb6, 0x55, 0x90,
            0x50, 0x31, 0x09, 0xf6, 0x1a, 0x99, 0xff, 0xa2, 0x51, 0x0f, 0x74, 0x2b, 0x80, 0xeb, 0x69, 0x8e, 0x42, 0x53, 0x54, 0x7d, 0xf0, 0x13, 0x92, 0x2d,
            0x86, 0xda, 0x3b, 0x7d, 0x2b, 0x19, 0x15, 0x3a, 0xeb, 0xb0, 0xd8, 0x33, 0xb4, 0x4c, 0xb0, 0x4e, 0x63, 0x32, 0x35, 0x8e, 0x30, 0xc9, 0xfe, 0xaf,
            0xcc, 0xc7, 0xa6, 0xdc, 0xbf, 0x83, 0x16, 0x6f, 0xdc, 0xc5, 0xdf, 0x10, 0x24, 0x45, 0xb0, 0x7c, 0x5b, 0x36, 0xc7, 0xcd, 0xf7, 0x5b, 0x1e, 0x9f,
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        ];

        let json: &str = r#"[
  {
    "username": "alice",
    "password": "has a password",
    "client_cert": {
      "allowed_cn": "unftp-client.mysite.com"
    }
  },
  {
    "username": "bob",
    "client_cert": {
      "allowed_cn": "unftp-client.mysite.com"
    }
  },
  {
    "username": "carol",
    "client_cert": {
      "allowed_cn": "unftp-other-client.mysite.com"
    }
  },
  {
    "username": "dean",
    "client_cert": {}
  }
]"#;
        let json_authenticator = JsonFileAuthenticator::from_json(json).unwrap();
        let client_cert: Vec<u8> = cert.to_vec();

        // correct certificate and password combo authenticates successfully
        assert_eq!(
            json_authenticator
                .authenticate(
                    "alice",
                    &libunftp::auth::Credentials {
                        certificate_chain: Some(vec![ClientCert(client_cert.clone())]),
                        password: Some("has a password".into()),
                        source_ip: std::net::IpAddr::V4(std::net::Ipv4Addr::new(127, 0, 0, 1)),
                    },
                )
                .await
                .unwrap(),
            DefaultUser
        );

        // correct password but missing certificate fails
        match json_authenticator
            .authenticate(
                "alice",
                &libunftp::auth::Credentials {
                    certificate_chain: None,
                    password: Some("has a password".into()),
                    source_ip: std::net::IpAddr::V4(std::net::Ipv4Addr::new(127, 0, 0, 1)),
                },
            )
            .await
        {
            Err(AuthenticationError::CnDisallowed) => assert!(true),
            _ => assert!(false),
        }

        // correct certificate and no password needed according to json file authenticates successfully
        assert_eq!(
            json_authenticator
                .authenticate(
                    "bob",
                    &libunftp::auth::Credentials {
                        certificate_chain: Some(vec![ClientCert(client_cert.clone())]),
                        password: None,
                        source_ip: std::net::IpAddr::V4(std::net::Ipv4Addr::new(127, 0, 0, 1)),
                    },
                )
                .await
                .unwrap(),
            DefaultUser
        );

        // certificate with incorrect CN and no password needed according to json file fails to authenticate
        match json_authenticator
            .authenticate(
                "carol",
                &libunftp::auth::Credentials {
                    certificate_chain: Some(vec![ClientCert(client_cert.clone())]),
                    password: None,
                    source_ip: std::net::IpAddr::V4(std::net::Ipv4Addr::new(127, 0, 0, 1)),
                },
            )
            .await
        {
            Err(AuthenticationError::CnDisallowed) => assert!(true),
            _ => assert!(false),
        }

        // any trusted certificate without password according to json file authenticates successfully
        assert_eq!(
            json_authenticator
                .authenticate(
                    "dean",
                    &libunftp::auth::Credentials {
                        certificate_chain: Some(vec![ClientCert(client_cert.clone())]),
                        password: None,
                        source_ip: std::net::IpAddr::V4(std::net::Ipv4Addr::new(127, 0, 0, 1)),
                    },
                )
                .await
                .unwrap(),
            DefaultUser
        );
    }
}