feat: include trust anchors in found reports

- `report::Found` includes the DER representation of the trust anchor of
  the verified path. Applies some tweaks to extract the trust anchors
  from `rustls-webpki` or `openssl`.

src/api.rs

@@ -19,7 +19,9 @@ pub trait PathValidator {
 #[derive(Clone, PartialEq, Eq, Debug)]
 pub enum CertificatePathValidation {
     /// Valid path found
-    Found,
+    ///
+    /// The parameter is a DER representation of the trust anchor.
+    Found(Vec<u8>),
     /// Valid path not found
     NotFound(String),
 }

src/find.rs

@@ -98,9 +98,9 @@ where
                     .validator
                     .validate(path.iter().map(|c| c.as_ref()).collect())?
                 {
-                    CertificatePathValidation::Found => {
+                    CertificatePathValidation::Found(trust_anchor) => {
                         return Ok(Report {
-                            found: Some(Found { path, origin }),
+                            found: Some(Found { path, origin, trust_anchor }),
                             duration: Instant::now() - start,
                             failures,
                         });
@@ -150,9 +150,9 @@ where
                     .validator
                     .validate(path.iter().map(|c| c.as_ref()).collect())?
                 {
-                    CertificatePathValidation::Found => {
+                    CertificatePathValidation::Found(trust_anchor) => {
                         return Ok(Report {
-                            found: Some(Found { path, origin }),
+                            found: Some(Found { path, origin, trust_anchor }),
                             duration: Instant::now() - start,
                             failures,
                         });

src/provided/validator/default/mod.rs

@@ -86,7 +86,7 @@ impl<'a> PathValidator for DefaultPathValidator<'a> {
             self.usage,
             self.crls,
         ) {
-            Ok(_) => Ok(CertificatePathValidation::Found),
+            Ok(trust_anchor) => Ok(CertificatePathValidation::Found(trust_anchor.as_der().to_vec())),
 
             Err(f) => Ok(CertificatePathValidation::NotFound(f.to_string())),
         }

src/provided/validator/openssl/mod.rs

@@ -45,14 +45,30 @@ impl PathValidator for OpenSSLPathValidator {
             openssl_path.as_ref(),
             |context| {
                 Ok(match context.verify_cert()? {
-                    true => VerifyResult::Success,
+                    true => {
+                        let trust_anchor = context
+                            .chain()
+                            .and_then(|chain| {
+                                println!("chain.len(): {}", chain.len());
+                                let last = chain.len() - 1;
+                                chain.get(last)
+                            })
+                            .ok_or("no trust anchor in chain".to_string())
+                            .and_then(|trust_anchor| {
+                                trust_anchor
+                                    .to_der()
+                                    .map_err(|e| format!("failed to serialize trust anchor: {}", e))
+                            });
+                        VerifyResult::Success(trust_anchor)
+                    }
                     false => VerifyResult::Failure(context.error()),
                 })
             },
         )?;
 
         match verified {
-            VerifyResult::Success => Ok(CertificatePathValidation::Found),
+            VerifyResult::Success(Ok(trust_anchor)) => Ok(CertificatePathValidation::Found(trust_anchor)),
+            VerifyResult::Success(Err(e)) => Ok(CertificatePathValidation::NotFound(e)),
 
             VerifyResult::Failure(f) => Ok(CertificatePathValidation::NotFound(
                 f.error_string().to_string(),
@@ -64,6 +80,6 @@ impl PathValidator for OpenSSLPathValidator {
 impl PathValidatorError for OpenSSLPathValidatorError {}
 
 enum VerifyResult {
-    Success,
+    Success(Result<Vec<u8>, String>),
     Failure(X509VerifyResult),
 }

src/report.rs

@@ -40,6 +40,8 @@ pub struct Found {
     pub path: Vec<Arc<crate::Certificate>>,
     /// Certificate path origins
     pub origin: Vec<CertificateOrigin>,
+    /// DER representation of the trust anchor.
+    pub trust_anchor: Vec<u8>,
 }
 
 impl<'r> IntoIterator for &'r Found {

src/tests/test_validator.rs

@@ -1,6 +1,6 @@
 use crate::api::{CertificatePathValidation, PathValidator};
 use crate::provided::validator::default::result::DefaultPathValidatorError;
-use x509_cert::Certificate;
+use x509_cert::{Certificate, der::Encode as _};
 
 #[derive(Clone)]
 pub struct TestPathValidator {
@@ -29,7 +29,7 @@ impl PathValidator for TestPathValidator {
 
         for root in self.store.iter() {
             if root.tbs_certificate.subject == ic.tbs_certificate.issuer {
-                return Ok(CertificatePathValidation::Found);
+                return Ok(CertificatePathValidation::Found(root.to_der().unwrap()));
             }
         }
 

tests/default/validator.rs

@@ -7,13 +7,13 @@ use x509_path_finder_material::generate::CertificatePathGenerator;
 #[test]
 fn test_validator() {
     let mut certificates = CertificatePathGenerator::generate(8, "0").unwrap();
-    let root = certificates.pop().unwrap().to_der().unwrap();
-    let root = TrustAnchor::try_from_cert_der(root.as_slice()).unwrap();
+    let root_der = certificates.pop().unwrap().to_der().unwrap();
+    let root = TrustAnchor::try_from_cert_der(root_der.as_slice()).unwrap();
 
     let algorithms = &[&webpki::ECDSA_P256_SHA256];
 
     let validator =
         DefaultPathValidator::new(algorithms, vec![root], KeyUsage::client_auth(), &[], true);
     let validate = validator.validate(certificates.iter().collect()).unwrap();
-    assert_eq!(CertificatePathValidation::Found, validate);
+    assert_eq!(CertificatePathValidation::Found(root_der), validate);
 }

tests/openssl/validator.rs

@@ -10,13 +10,14 @@ use x509_path_finder_material::generate::CertificatePathGenerator;
 fn test_validator() {
     let mut certificates = CertificatePathGenerator::generate(8, "0").unwrap();
     let root = certificates.pop().unwrap();
-    let root = X509::from_der(root.to_der().unwrap().as_slice()).unwrap();
+    let root_der = root.to_der().unwrap();
+    let root = X509::from_der(root_der.as_slice()).unwrap();
 
     let mut builder = X509StoreBuilder::new().unwrap();
     builder.add_cert(root).unwrap();
     builder.set_flags(X509VerifyFlags::X509_STRICT).unwrap();
 
     let validator = OpenSSLPathValidator::new(builder.build());
     let validate = validator.validate(certificates.iter().collect()).unwrap();
-    assert_eq!(CertificatePathValidation::Found, validate);
+    assert_eq!(CertificatePathValidation::Found(root_der), validate);
 }