feat(nix-compat/narinfo): add PubKey::verify(fp, sig) r/7084

This makes it easy for each PubKey to check if a given Signature is
correct for a given fingerprint.

Change-Id: I56e6211d133f74f390fd1ae3ae799eef12221904
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10151
Reviewed-by: tazjin <tazjin@tvl.su>
Autosubmit: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI

1 files changed, 32 insertions, 0 deletions

diff --git a/tvix/nix-compat/src/narinfo/public_keys.rs b/tvix/nix-compat/src/narinfo/public_keys.rs
index 9075911082..dd82c8c22e 100644
--- a/tvix/nix-compat/src/narinfo/public_keys.rs
+++ b/tvix/nix-compat/src/narinfo/public_keys.rs
@@ -6,6 +6,8 @@ use std::fmt::Display;
 use data_encoding::BASE64;
 use ed25519_dalek::{VerifyingKey, PUBLIC_KEY_LENGTH};
 
+use super::Signature;
+
 /// This represents a ed25519 public key and "name".
 /// These are normally passed in the `trusted-public-keys` Nix config option,
 /// and consist of a name and base64-encoded ed25519 pubkey, separated by a `:`.
@@ -60,6 +62,19 @@ impl PubKey {
     pub fn name(&self) -> &str {
         &self.name
     }
+
+    /// Verify the passed in signature is a correct signature for the passed in fingerprint and is signed
+    /// by the key material referred to by [Self],
+    /// which means the name in the signature has to match,
+    /// and the signature bytes themselves need to be a valid signature made by
+    /// the signing key identified by [Self::verifying key].
+    pub fn verify(&self, fingerprint: &str, signature: &Signature) -> bool {
+        if self.name() != signature.name() {
+            return false;
+        }
+
+        return signature.verify(fingerprint.as_bytes(), &self.verifying_key);
+    }
 }
 
 #[derive(Debug, thiserror::Error)]
@@ -93,7 +108,10 @@ mod test {
     use ed25519_dalek::PUBLIC_KEY_LENGTH;
     use test_case::test_case;
 
+    use crate::narinfo::Signature;
+
     use super::PubKey;
+    const FINGERPRINT: &'static str = "1;/nix/store/syd87l2rxw8cbsxmxl853h0r6pdwhwjr-curl-7.82.0-bin;sha256:1b4sb93wp679q4zx9k1ignby1yna3z7c4c2ri3wphylbc2dwsys0;196040;/nix/store/0jqd0rlxzra1rs38rdxl43yh6rxchgc6-curl-7.82.0,/nix/store/6w8g7njm4mck5dmjxws0z1xnrxvl81xa-glibc-2.34-115,/nix/store/j5jxw3iy7bbz4a57fh9g2xm2gxmyal8h-zlib-1.2.12,/nix/store/yxvjs9drzsphm9pcf42a4byzj1kb9m7k-openssl-1.1.1n";
 
     #[test_case("cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=", "cache.nixos.org-1", BASE64.decode(b"6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=").unwrap()[..].try_into().unwrap(); "cache.nixos.org")]
     #[test_case("cheesecake:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=", "cheesecake", BASE64.decode(b"6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=").unwrap()[..].try_into().unwrap(); "cache.nixos.org different name")]
@@ -114,4 +132,18 @@ mod test {
     fn parse_fail(input: &'static str) {
         PubKey::parse(input).expect_err("must fail");
     }
+
+    #[test_case("cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=", FINGERPRINT, "cache.nixos.org-1:TsTTb3WGTZKphvYdBHXwo6weVILmTytUjLB+vcX89fOjjRicCHmKA4RCPMVLkj6TMJ4GMX3HPVWRdD1hkeKZBQ==", true; "correct cache.nixos.org")]
+    #[test_case("cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=", FINGERPRINT, "cache.nixos.org:TsTTb3WGTZKphvYdBHXwo6weVILmTytUjLB+vcX89fOjjRicCHmKA4RCPMVLkj6TMJ4GMX3HPVWRdD1hkeKZBQ==", false; "wrong name mismatch")]
+    fn verify(
+        pubkey_str: &'static str,
+        fingerprint: &'static str,
+        signature_str: &'static str,
+        expected: bool,
+    ) {
+        let pubkey = PubKey::parse(pubkey_str).expect("must parse");
+        let signature = Signature::parse(signature_str).expect("must parse");
+
+        assert_eq!(expected, pubkey.verify(fingerprint, &signature));
+    }
 }