apkverify: Rank based on v4 preferences
The signing algorithms were already ranked following the order of
preference used by the v4 signing scheme, so there's no functional
change. Documentation is added to make this connection explicit and a
functions for selecting the best signed is factored out.
Test: libapkverify.test
Bug: 234564414
Change-Id: I28e25ce744cbc5854d1cb2b73fee9f966d2f8eb6
diff --git a/libs/apkverify/src/sigutil.rs b/libs/apkverify/src/sigutil.rs
index 009154f..2b2f9da 100644
--- a/libs/apkverify/src/sigutil.rs
+++ b/libs/apkverify/src/sigutil.rs
@@ -282,6 +282,7 @@
}
}
+/// Rank the signature algorithm according to the preferences of the v4 signing scheme.
pub fn rank_signature_algorithm(algo: u32) -> Result<u32> {
rank_content_digest_algorithm(to_content_digest_algorithm(algo)?)
}
diff --git a/libs/apkverify/src/v3.rs b/libs/apkverify/src/v3.rs
index 16530be..710c9c3 100644
--- a/libs/apkverify/src/v3.rs
+++ b/libs/apkverify/src/v3.rs
@@ -129,15 +129,20 @@
}
impl Signer {
- fn verify<R: Read + Seek>(&self, sections: &mut ApkSections<R>) -> Result<Box<[u8]>> {
- // 1. Choose the strongest supported signature algorithm ID from signatures. The strength
- // ordering is up to each implementation/platform version.
- let strongest: &Signature = self
+ /// Select the signature that uses the strongest algorithm according to the preferences of the
+ /// v4 signing scheme.
+ fn strongest_signature(&self) -> Result<&Signature> {
+ Ok(self
.signatures
.iter()
.filter(|sig| is_supported_signature_algorithm(sig.signature_algorithm_id))
.max_by_key(|sig| rank_signature_algorithm(sig.signature_algorithm_id).unwrap())
- .ok_or_else(|| anyhow!("No supported signatures found"))?;
+ .ok_or_else(|| anyhow!("No supported signatures found"))?)
+ }
+
+ fn verify<R: Read + Seek>(&self, sections: &mut ApkSections<R>) -> Result<Box<[u8]>> {
+ // 1. Choose the strongest supported signature algorithm ID from signatures.
+ let strongest = self.strongest_signature()?;
// 2. Verify the corresponding signature from signatures against signed data using public key.
// (It is now safe to parse signed data.)