Tag CMS signer identifier implicitly

apple · Jan 13, 2025 · e58b688 · e58b688
1 parent 274f866
commit e58b688
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Showing 2 changed files with 23 additions and 13 deletions.
diff --git a/Sources/X509/CryptographicMessageSyntax/CMSSignerIdentifier.swift b/Sources/X509/CryptographicMessageSyntax/CMSSignerIdentifier.swift
@@ -22,7 +22,6 @@ import SwiftASN1
 ///  ```
 @usableFromInline
 enum CMSSignerIdentifier: DERParseable, BERParseable, DERSerializable, BERSerializable, Hashable, Sendable {
-
     @usableFromInline
     static let skiIdentifier = ASN1Identifier(tagWithNumber: 0, tagClass: .contextSpecific)
 
@@ -36,13 +35,14 @@ enum CMSSignerIdentifier: DERParseable, BERParseable, DERSerializable, BERSerial
             self = try .issuerAndSerialNumber(.init(derEncoded: node))
 
         case Self.skiIdentifier:
-            self = try DER.explicitlyTagged(
-                node,
-                tagNumber: Self.skiIdentifier.tagNumber,
-                tagClass: Self.skiIdentifier.tagClass
-            ) { node in
-                .subjectKeyIdentifier(.init(keyIdentifier: try ASN1OctetString(derEncoded: node).bytes))
-            }
+            self = try .subjectKeyIdentifier(
+                .init(
+                    keyIdentifier: ASN1OctetString(
+                        derEncoded: node,
+                        withIdentifier: Self.skiIdentifier
+                    ).bytes
+                )
+            )
 
         default:
             throw ASN1Error.unexpectedFieldType(node.identifier)
@@ -56,11 +56,8 @@ enum CMSSignerIdentifier: DERParseable, BERParseable, DERSerializable, BERSerial
             try issuerAndSerialNumber.serialize(into: &coder)
 
         case .subjectKeyIdentifier(let subjectKeyIdentifier):
-            try coder.serialize(
-                ASN1OctetString(contentBytes: subjectKeyIdentifier.keyIdentifier),
-                explicitlyTaggedWithIdentifier: Self.skiIdentifier
-            )
-
+            try ASN1OctetString(contentBytes: subjectKeyIdentifier.keyIdentifier)
+                .serialize(into: &coder, withIdentifier: Self.skiIdentifier)
         }
     }
 

diff --git a/Tests/X509Tests/CMSTests.swift b/Tests/X509Tests/CMSTests.swift
@@ -1134,6 +1134,19 @@ final class CMSTests: XCTestCase {
         }
         XCTAssertInvalidCMSBlock(isValidSignature)
     }
+
+    func testSubjectKeyIdentifierIsCorrectlyImplicitylyTagged() throws {
+        let implicitlyTaggedSki: [UInt8] = [
+            0x80,  // Context-specific tag [0]
+            0x04,  // Length
+            0x0a, 0x14, 0x1e, 0x28
+        ]
+
+        XCTAssertEqual(
+            try CMSSignerIdentifier(derEncoded: implicitlyTaggedSki),
+            CMSSignerIdentifier.subjectKeyIdentifier(.init(keyIdentifier: [10, 20, 30, 40]))
+        )
+    }
 }
 
 extension DERSerializable {