Use libhex to encode hex string in libs/apkverify/

Bug: 239413416
Test: libapkverify.test, libapkverify.integration_test
Change-Id: I21285b1528f6eb8806a594f53b7b1045255af3b5
Signed-off-by: Tanmoy Mollik <triploblastic@google.com>

libs/apkverify/Android.bp

@@ -12,6 +12,7 @@ rust_defaults {
         "libanyhow",
         "libbyteorder",
         "libbytes",
+        "libhex",
         "liblog_rust",
         "libnum_traits",
         "libopenssl",
@@ -33,7 +34,6 @@ rust_test {
     name: "libapkverify.test",
     defaults: ["libapkverify.defaults"],
     test_suites: ["general-tests"],
-    rustlibs: ["libhex"],
     data: ["tests/data/*"],
 }
 

libs/apkverify/src/sigutil.rs

@@ -235,7 +235,7 @@ mod tests {
     use std::fs::File;
     use std::mem::size_of_val;
 
-    use crate::v3::{to_hex_string, APK_SIGNATURE_SCHEME_V3_BLOCK_ID};
+    use crate::v3::APK_SIGNATURE_SCHEME_V3_BLOCK_ID;
 
     const CENTRAL_DIRECTORY_HEADER_SIGNATURE: u32 = 0x02014b50;
 
@@ -276,8 +276,8 @@ mod tests {
         let mut apk_sections = ApkSections::new(apk_file).unwrap();
         let digest = apk_sections.compute_digest(SignatureAlgorithmID::DsaWithSha256).unwrap();
         assert_eq!(
-            "0DF2426EA33AEDAF495D88E5BE0C6A1663FF0A81C5ED12D5B2929AE4B4300F2F",
-            to_hex_string(&digest[..])
+            "0df2426ea33aedaf495d88e5be0c6a1663ff0a81c5ed12d5b2929ae4b4300f2f",
+            hex::encode(&digest[..])
         );
     }
 

libs/apkverify/src/v3.rs

@@ -196,8 +196,8 @@ impl Signer {
         ensure!(
             computed == digest.digest.as_ref(),
             "Digest mismatch: computed={:?} vs expected={:?}",
-            to_hex_string(&computed),
-            to_hex_string(&digest.digest),
+            hex::encode(&computed),
+            hex::encode(digest.digest.as_ref()),
         );
 
         // 7. Verify that public key of the first certificate of certificates is identical
@@ -261,8 +261,3 @@ impl ReadFromBytes for PKey<pkey::Public> {
         Ok(PKey::public_key_from_der(raw_public_key.as_ref())?)
     }
 }
-
-#[inline]
-pub(crate) fn to_hex_string(buf: &[u8]) -> String {
-    buf.iter().map(|b| format!("{:02X}", b)).collect()
-}