yapi-core 0.4.0

//! What an extension may reach outside its sandbox.

use crate::tools::RegisteredTool;

/// The capabilities a manifest grants, in the order yapi lists them. Each
/// but `all` gives one grant, and `all` gives every grant, running
/// processes included. `none`, which grants nothing, stands alone.
pub const CAPABILITIES: [&str; 5] = ["fs", "net", "env", "session", "all"];

/// What an extension may reach. The default grants everything, as pi does.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub struct Grants {
    /// Read and write files.
    pub filesystem: bool,
    /// Run processes, which run as the user outside the sandbox.
    pub process: bool,
    /// Send HTTP requests and resolve host names.
    pub network: bool,
    /// Read environment variables.
    pub environment: bool,
    /// Start turns and change the session and its files.
    pub session: bool,
}

impl Default for Grants {
    fn default() -> Grants {
        Grants {
            filesystem: true,
            process: true,
            network: true,
            environment: true,
            session: true,
        }
    }
}

/// The manifest capabilities the grants amount to, as [`Grants::names`]
/// lists them, or `none`: such as `all`, or `fs, net`.
impl std::fmt::Display for Grants {
    fn fmt(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        let names = self.names();
        if names.is_empty() {
            return formatter.write_str("none");
        }
        formatter.write_str(&names.join(", "))
    }
}

impl Grants {
    /// Nothing outside the instance.
    pub fn none() -> Grants {
        Grants {
            filesystem: false,
            process: false,
            network: false,
            environment: false,
            session: false,
        }
    }

    /// Whether every grant is given, as only `all` gives it.
    pub fn is_all(&self) -> bool {
        *self == Grants::default()
    }

    /// The grants of `capability`, one of [`CAPABILITIES`], or `None`.
    fn of(capability: &str) -> Option<Grants> {
        let mut grants = Grants::none();
        match capability {
            "fs" => grants.filesystem = true,
            "net" => grants.network = true,
            "env" => grants.environment = true,
            "session" => grants.session = true,
            "all" => grants = Grants::default(),
            _ => return None,
        }
        Some(grants)
    }

    /// Whether these grants give all that `capability`, one of
    /// [`CAPABILITIES`], does. False for any other name.
    pub fn covers(&self, capability: &str) -> bool {
        Grants::of(capability).is_some_and(|needed| self.intersection(needed) == needed)
    }

    /// The capabilities the grants amount to, as a manifest names them:
    /// `all` alone when they give everything, else each other one of
    /// [`CAPABILITIES`] they cover, then `process` when they let processes
    /// run, which no manifest grants without `all`. Empty for none.
    pub fn names(&self) -> Vec<&'static str> {
        if self.is_all() {
            return vec!["all"];
        }
        let mut names: Vec<&'static str> = CAPABILITIES
            .into_iter()
            .filter(|capability| self.covers(capability))
            .collect();
        if self.process {
            names.push("process");
        }
        names
    }

    /// The grants of manifest capabilities `values`, each one of
    /// [`CAPABILITIES`] or `none`. An empty list grants nothing, and only
    /// `all` grants running processes. `Err` names an unknown value,
    /// `process`, or `none` combined with another value.
    pub fn parse(values: &[String]) -> Result<Grants, String> {
        let mut grants = Grants::none();
        for value in values {
            match value.as_str() {
                "none" if values.len() == 1 => {}
                "none" => return Err("\"none\" cannot be combined with other capabilities".into()),
                "process" => {
                    return Err(
                        "\"process\" is not a capability: a process runs as you, outside the sandbox, so only \"all\" allows it".into(),
                    );
                }
                other => match Grants::of(other) {
                    Some(granted) => grants = grants.union(granted),
                    None => return Err(format!("unknown capability \"{other}\"")),
                },
            }
        }
        Ok(grants)
    }

    /// What either `self` or `other` grants.
    pub fn union(self, other: Grants) -> Grants {
        Grants {
            filesystem: self.filesystem || other.filesystem,
            process: self.process || other.process,
            network: self.network || other.network,
            environment: self.environment || other.environment,
            session: self.session || other.session,
        }
    }

    /// What both `self` and `other` grant.
    pub fn intersection(self, other: Grants) -> Grants {
        Grants {
            filesystem: self.filesystem && other.filesystem,
            process: self.process && other.process,
            network: self.network && other.network,
            environment: self.environment && other.environment,
            session: self.session && other.session,
        }
    }
}

/// Whether `grants` allow running `tool`. The built-in `bash`, `grep` and
/// `find` run processes, and the other built-in tools need file access. Any
/// other tool, including one an extension registers under a built-in name,
/// may reach anything, so it needs every grant.
pub fn tool_granted(grants: &Grants, tool: &RegisteredTool) -> bool {
    let all = grants.is_all();
    match tool.name() {
        _ if tool.source.is_some() => all,
        "bash" => grants.process,
        // They run ripgrep and fd, which they download when missing.
        "grep" | "find" => grants.filesystem && grants.process && grants.network,
        "read" | "write" | "edit" | "ls" => grants.filesystem,
        _ => all,
    }
}

/// Whether an extension with `grants` hears pi event `kind`. The provider
/// request events carry the request's body and headers, credentials
/// included, which only the network grant may read.
pub fn receives(kind: &str, grants: &Grants) -> bool {
    match kind {
        "before_provider_request" | "before_provider_headers" => grants.network,
        _ => true,
    }
}

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

    #[test]
    fn capabilities_parse() {
        let fs = Grants {
            filesystem: true,
            ..Grants::none()
        };
        let all_but_process = Grants {
            process: false,
            ..Grants::default()
        };
        let process = "\"process\" is not a capability: a process runs as you, outside the sandbox, so only \"all\" allows it";
        let cases: &[(&[&str], Result<Grants, &str>)] = &[
            (&[], Ok(Grants::none())),
            (&["none"], Ok(Grants::none())),
            (&["all"], Ok(Grants::default())),
            (&["fs", "all"], Ok(Grants::default())),
            (&["fs"], Ok(fs)),
            (&["fs", "net", "env", "session"], Ok(all_but_process)),
            (&["process"], Err(process)),
            (
                &["none", "fs"],
                Err("\"none\" cannot be combined with other capabilities"),
            ),
            (&["exec"], Err("unknown capability \"exec\"")),
        ];
        for (values, expected) in cases {
            let values: Vec<String> = values.iter().map(|value| (*value).to_owned()).collect();
            let expected = expected.map_err(str::to_owned);
            assert_eq!(Grants::parse(&values), expected, "{values:?}");
        }
        // Grants name the capabilities they amount to, and cover those.
        let no_net = Grants {
            network: false,
            ..Grants::default()
        };
        for (grants, name) in [
            (Grants::default(), "all"),
            (Grants::none(), "none"),
            (fs, "fs"),
            (all_but_process, "fs, net, env, session"),
            (no_net, "fs, env, session, process"),
        ] {
            assert_eq!(grants.to_string(), name);
            for capability in CAPABILITIES {
                let named = grants.names().contains(&capability) || grants.is_all();
                assert_eq!(grants.covers(capability), named, "{name}: {capability}");
            }
        }
        // A name that is not a capability is never covered.
        assert!(!Grants::default().covers("process"));
        assert!(!Grants::default().covers("exec"));
        let net = Grants {
            network: true,
            ..Grants::none()
        };
        assert_eq!(
            fs.union(net),
            Grants {
                filesystem: true,
                network: true,
                ..Grants::none()
            }
        );
    }

    /// Built-in tools need the grants of what they reach, and any other
    /// tool, even one registered under a built-in name, needs every grant.
    #[test]
    fn grants_gate_tools() {
        let env = crate::tools::ToolEnv {
            cwd: std::path::PathBuf::new(),
            runtime: std::sync::Arc::default(),
            bin_dir: std::path::PathBuf::new(),
        };
        let fs = Grants {
            filesystem: true,
            ..Grants::none()
        };
        let all_but_process = Grants {
            process: false,
            ..Grants::default()
        };
        // Each tool, extension or built-in, and whether none, fs, all but
        // process, and all may run it.
        let cases = [
            ("read", false, [false, true, true, true]),
            ("write", false, [false, true, true, true]),
            ("edit", false, [false, true, true, true]),
            ("ls", false, [false, true, true, true]),
            ("bash", false, [false, false, false, true]),
            ("grep", false, [false, false, false, true]),
            ("find", false, [false, false, false, true]),
            ("read", true, [false, false, false, true]),
        ];
        for (name, extension, expected) in cases {
            let mut tool = crate::tools::builtin(name, &env).unwrap();
            if extension {
                tool.source = Some(yapi_types::rpc::SourceInfo::default());
            }
            let granted = [Grants::none(), fs, all_but_process, Grants::default()]
                .map(|grants| tool_granted(&grants, &tool));
            assert_eq!(granted, expected, "{name}, extension {extension}");
        }
    }

    #[test]
    fn provider_events_need_network() {
        let net = Grants {
            network: true,
            ..Grants::none()
        };
        let no_net = Grants {
            network: false,
            ..Grants::default()
        };
        for (kind, heard_without_network) in [
            ("before_provider_request", false),
            ("before_provider_headers", false),
            ("after_provider_response", true),
            ("provider_stream_event", true),
            ("tool_call", true),
        ] {
            assert!(receives(kind, &net), "{kind}");
            assert_eq!(receives(kind, &no_net), heard_without_network, "{kind}");
        }
    }
}