Crate agent_uri_attestation 

PASETO v4.public attestation for agent-uri.

This crate provides cryptographic attestation of agent URIs using PASETO v4.public tokens (Ed25519 signatures). Attestations bind an agent URI to a set of capabilities, signed by a trust root.

Overview

Attestation tokens enable:

• Cryptographic binding of agent URIs to capabilities
• Prevention of spoofing and DHT poisoning
• Bearer token verification without callbacks

Example

use agent_uri_attestation::{Issuer, Verifier, SigningKey};
use agent_uri::AgentUri;
use std::time::Duration;

// Issuer side: create attestation
let signing_key = SigningKey::generate();
let issuer = Issuer::new("acme.com", signing_key.clone(), Duration::from_secs(86400));

let uri = AgentUri::parse(
    "agent://acme.com/workflow/approval/rule_01h455vb4pex5vsknk084sn02q"
).unwrap();
let token = issuer.issue(&uri, vec!["workflow.approval.read".into()]).unwrap();

// Verifier side: validate attestation
let mut verifier = Verifier::new();
verifier.add_trusted_root("acme.com", signing_key.verifying_key());

let claims = verifier.verify(&token).unwrap();
assert_eq!(claims.agent_uri, uri.to_string());
assert_eq!(claims.capabilities, vec!["workflow.approval.read"]);

Token Structure

Attestation tokens are PASETO v4.public tokens containing:

• agent_uri: The full agent URI being attested
• capabilities: Array of capability strings granted
• iss: Issuer (trust root) that created the attestation
• iat: Issued-at timestamp
• exp: Expiration timestamp
• aud: Optional audience restriction

Security Properties

Property	How Achieved
No algorithm confusion	PASETO v4 is Ed25519-only
Replay protection	exp claim validated automatically
Trust root binding	iss must match trusted roots
URI binding	agent_uri claim verified against expected
Tamper detection	Ed25519 signature verification

Grammar Specification

This crate includes a formal ABNF grammar specification in grammar.abnf that defines:

• PASETO v4.public token format (v4.public.<payload>[.<footer>])
• AttestationClaims JSON structure
• Field formats and constraints

The grammar follows RFC 5234 and references the agent-uri ABNF for the agent_uri field format.

Length Constraints

Component	Max Length
Total token	8192 chars
agent_uri	512 chars
capabilities	64 items
Each capability	128 chars
issuer	128 chars
audience	128 chars

Modules

prelude

A prelude module for convenient imports.

Structs

AttestationClaims

Claims embedded in an attestation token.

AttestationClaimsBuilder

Builder for constructing AttestationClaims.

Issuer

Creates attestation tokens for agent URIs.

SigningKey

A signing key for creating attestation tokens.

Verifier

Verifies attestation tokens for agent URIs.

VerifyingKey

A verifying key for validating attestation tokens.

Enums

AttestationError

Errors that can occur during attestation operations.

Functions

capability_covers

Pure function: checks if any attested capability covers the required path.

check_capability_coverage

Pure function: checks capability coverage and returns a structured error if insufficient.

check_expiration

Pure function: checks if a token has expired at a given time.

validate_issuer

Pure function: validates that the token issuer matches the URI trust root.

validate_subject

Pure function: validates that the token subject matches the presented URI.