Access gates

Access ABI

The generic evaluator uses a dependency-free access ABI:

An access source must fail closed for unknown kinds and malformed scopes. NewAccessBindings rejects blank or whitespace-padded kinds, nil sources, duplicate kinds, and unsupported versions. AccessBindings.AccessFor(requirement tool.Requirement) returns only the three ABI values and wraps source failures in *gate.AccessError.

Bindings

package main

import (
    "github.com/looprig/harness/pkg/gate"
    "github.com/looprig/harness/pkg/tool"
)

type profile struct{}

func (profile) AccessVersion() uint16 { return gate.CurrentAccessVersion }
func (profile) AccessFor(kind, scope string) (uint8, error) {
    if kind == "filesystem.read" && scope != "" {
        return gate.AccessGated, nil
    }
    return gate.AccessDeny, nil
}

func route(req tool.Requirement) (uint8, error) {
    bindings, err := gate.NewAccessBindings([]gate.AccessBinding{{
        Kind: "filesystem.read", Source: profile{},
    }})
    if err != nil {
        return gate.AccessDeny, err
    }
    return bindings.AccessFor(req)
}

AccessError carries Kind AccessErrorKind, Requirement string, and Cause error. The closed kinds are AccessKindInvalid, AccessSourceMissing, AccessSourceDuplicate, AccessSourceNil, AccessVersionUnsupported, AccessValueInvalid, and AccessSourceFailed. Missing routes return AccessDeny plus an error, so callers cannot accidentally treat an unconfigured capability as allowed.

Evaluator contract

gate.Evaluator composes the bindings with these structural interfaces:

NewHeadlessEvaluator(bindings, matcher, issuer) never prompts and accepts no writer. NewInteractiveEvaluator(bindings, matcher, approver, writer, issuer) requires both an approver and writer so all three actions remain honest. CurrentGrantVersion is uint16 = 1; an issuer with another version is rejected at construction.

Decision order

For each prepared tool.Request, Evaluate applies this order:

1. Route every requirement through AccessBindings. Any AccessDeny is a structural denial and stops further rule evaluation.
2. For gated requirements, ask RuleMatcher.MatchesDeny for every requirement. Any match is a stored denial and stops before allow rules.
3. Ask MatchesAllow for every remaining gated requirement. Unmatched requirements are combined into one Evaluation.Unmet set, preserving request order, and their candidates are combined into one prompt.

An Evaluation has Denied []tool.Requirement, Unmet []tool.Requirement, and Candidates []tool.RuleCandidate. It retains private request and grant state for Resolve; grants and denial routing are not serialized.

Resolution

Authorize evaluates once and opens at most one prompt. A headless unmet request returns *gate.EvaluationError{Kind: EvaluationApprovalRequired}. An interactive approver must return exactly ApprovalApprove, ApprovalApproveAlwaysWorkspace, or ApprovalDeny.

Resolution has Approved bool, Grants []string with json:"-", Denial DenialReason with json:"-", and DenialDescription with json:"-". A configured or stored denial is a successful evaluation with Approved == false, not an exceptional process error. Dependency failures are *gate.EvaluationError with kinds EvaluationRuleMatchFailed, EvaluationDenied deprecated, EvaluationActionInvalid, EvaluationApproverMissing, EvaluationApprovalRequired, EvaluationApprovalFailed, EvaluationWriterMissing, EvaluationWriteFailed, EvaluationIssuerMissing, EvaluationGrantVersionUnsupported, or EvaluationGrantFailed.

The full decision implementation is pkg/gate/evaluator.go; access routing is pkg/gate/access.go. This package never imports an enforcing sandbox, stores a permission-file format, or accepts a grant token in a prompt or journal payload.

Source and proof

• gate.Evaluator
• access routing
• policy runnable fixture