Validate signatures without bouncycastle

app/build.gradle

@@ -214,7 +214,6 @@ dependencies {
     implementation 'org.apache.commons:commons-text:1.6'
 
     implementation 'org.whispersystems:curve25519-java:0.5.0'
-    implementation 'org.bouncycastle:bcutil-jdk15on:1.70'
 
     implementation 'com.google.zxing:core:3.3.3'
 

app/proguard-rules.pro

@@ -57,8 +57,4 @@
 -keep class org.whispersystems.curve25519.NativeCurve25519Provider {}
 -keep class org.whispersystems.curve25519.JavaCurve25519Provider {}
 -keep class org.whispersystems.curve25519.J2meCurve25519Provider {}
--keep class org.whispersystems.curve25519.OpportunisticCurve25519Provider {}
+-keep class org.whispersystems.curve25519.OpportunisticCurve25519Provider {}
-
-# bouncycastle
--keep class org.bouncycastle.jcajce.provider.** { *; }
--keep class org.bouncycastle.jce.provider.** { *; }

app/src/main/java/io/timelimit/android/u2f/U2FSignatureValidation.kt

@@ -16,26 +16,13 @@
 package io.timelimit.android.u2f
 
 import io.timelimit.android.u2f.protocol.U2FResponse
-import org.bouncycastle.asn1.sec.SECNamedCurves
-import org.bouncycastle.crypto.CryptoException
-import org.bouncycastle.jce.provider.BouncyCastleProvider
-import org.bouncycastle.jce.spec.ECParameterSpec
-import org.bouncycastle.jce.spec.ECPublicKeySpec
 import java.security.KeyFactory
-import java.security.Security
 import java.security.Signature
+import java.security.spec.InvalidKeySpecException
+import java.security.spec.X509EncodedKeySpec
 
 
 object U2FSignatureValidation {
-    init {
-        Security.removeProvider("BC")
-        Security.addProvider(BouncyCastleProvider())
-    }
-
-    private val curve = SECNamedCurves.getByName("secp256r1")
-    private val ecParamSpec = ECParameterSpec(curve.getCurve(), curve.getG(), curve.getN(),  curve.getH())
-
-    // based on https://github.com/Yubico/java-u2flib-server/blob/dd44d3cdce4eeaeb517f2acd1fd520d5a42ce752/u2flib-server-core/src/main/java/com/yubico/u2f/crypto/BouncyCastleCrypto.java
     fun validate(
         applicationId: ByteArray,
         challenge: ByteArray,
@@ -54,22 +41,22 @@ object U2FSignatureValidation {
 
             if (publicKey.size != 65 || publicKey[0] != 4.toByte()) return false
 
-            val point = curve.getCurve().decodePoint(publicKey)
+            val verifier = Signature.getInstance("SHA256withECDSA")
 
-            val decodedPublicKey = KeyFactory.getInstance("EC", "BC").generatePublic(
+            verifier.initVerify(
-                ECPublicKeySpec(point, ecParamSpec)
+                KeyFactory
+                    .getInstance("EC")
+                    .generatePublic(
+                        X509EncodedKeySpec(
+                            byteArrayOf(48, 89, 48, 19, 6, 7, 42, -122, 72, -50, 61, 2, 1, 6, 8, 42, -122, 72, -50, 61, 3, 1, 7, 3, 66, 0) + publicKey
+                        )
+                    )
             )
 
-            val verifier = Signature.getInstance("SHA256withECDSA", "BC")
-
-            verifier.initVerify(decodedPublicKey)
-
             verifier.update(signedData)
 
             return verifier.verify(response.signature)
-        } catch (ex: CryptoException) {
+        } catch (ex: InvalidKeySpecException) {
-            return false
-        } catch (ex: IllegalArgumentException) {
             return false
         }
     }

app/src/main/res/values/strings.xml

@@ -107,10 +107,6 @@
         (<a href="https://github.com/zxing/zxing/blob/master/LICENSE">Apache License 2.0</a>)
         \n<a href="https://github.com/square/wire/blob/master/README.md">Wire</a>
         (<a href="https://github.com/square/wire/blob/master/LICENSE.txt">Apache License 2.0</a>)
-        \n<a href="https://www.bouncycastle.org/">Bouncy Castle</a>
-        (<a href="https://www.bouncycastle.org/licence.html">MIT License</a>)
-        \n<a href="https://github.com/Yubico/java-u2flib-server">java-u2flib-server</a>
-        (<a href="https://github.com/Yubico/java-u2flib-server/blob/master/COPYING">BSD License</a>)
     </string>
 
     <string name="about_diagnose_title">Error diagnose</string>

contrib/publickeymetadata.js

@@ -0,0 +1,95 @@
+// https://www.rfc-editor.org/rfc/rfc5280.html#appendix-A.1
+// https://letsencrypt.org/docs/a-warm-welcome-to-asn1-and-der/
+// https://www.ietf.org/rfc/rfc5480.txt
+
+/*
+SubjectPublicKeyInfo  ::=  SEQUENCE  {
+     algorithm            AlgorithmIdentifier,
+     subjectPublicKey     BIT STRING  }
+
+
+AlgorithmIdentifier  ::=  SEQUENCE  {
+     algorithm               OBJECT IDENTIFIER,
+     parameters              ANY DEFINED BY algorithm OPTIONAL  }
+                                -- contains a value of the type
+                                -- registered for use with the
+                                -- algorithm object identifier value
+
+id-ecPublicKey OBJECT IDENTIFIER ::= {
+     iso(1) member-body(2) us(840) ansi-X9-62(10045) keyType(2) 1 }
+
+secp256r1 OBJECT IDENTIFIER ::= {
+     iso(1) member-body(2) us(840) ansi-X9-62(10045) curves(3)
+     prime(1) 7 }
+*/
+
+function encodeValue(type, valueBuffer) {
+  const length = valueBuffer.length
+
+  if (length >= 128) throw new Error('long encoding not supported')
+
+  const typeBuffer = Buffer.from([type])
+  const lengthBuffer = Buffer.from([length])
+
+  return Buffer.concat([typeBuffer, lengthBuffer, valueBuffer])
+}
+
+function encodeBitstring(valueBuffer) {
+  return encodeValue(3, Buffer.concat([Buffer.from([0 /* no unused bits */]), valueBuffer]))
+}
+
+function encodeOid(value) {
+  const numbers = [
+    value[0] * 40 + value[1],
+    ...value.slice(2)
+  ]
+
+  const result = []
+
+  for (let number of numbers) {
+    const tempResult = []
+    while (number) { tempResult.push(128 | (number % 128)); number = Math.floor(number / 128) }
+    tempResult.reverse()
+    tempResult[tempResult.length - 1] &= 127
+
+    for (const item of tempResult) result.push(item)
+  }
+
+  return encodeValue(6, Buffer.from(result))
+}
+
+function encodeSequence(itemBuffers) {
+  return encodeValue(0x30, Buffer.concat(itemBuffers))
+}
+
+function encodeAlogrithmIdentifier() {
+  return encodeSequence([
+    encodeOid([1, 2, 840, 10045, 2, 1]),
+    encodeOid([1, 2, 840, 10045, 3, 1, 7])
+  ])
+}
+
+function encodePublicKeyInfo() {
+  const dummyKey = Buffer.alloc(65)
+  for (let i = 0; i < dummyKey.length; i++) dummyKey.writeUInt8(255, i)
+
+  return encodeSequence([
+    encodeAlogrithmIdentifier(),
+    encodeBitstring(dummyKey)
+  ])
+}
+
+const result = encodePublicKeyInfo()
+
+// compare result with https://github.com/ashtuchkin/u2f/blob/2e45ea40acd8c3ad6c113cd1b4e0558acc4cda3a/index.js#L21
+if (result.toString('hex') !== '3059301306072a8648ce3d020106082a8648ce3d030107034200' + ('ff'.repeat(65))) throw new Error()
+
+const prefix = result.slice(0, result.length - 65)
+
+console.log(prefix.toString('hex'))
+console.log(prefix.toString('base64'))
+
+const prefixNumbers = []; for (let i = 0; i < prefix.length; i++) prefixNumbers.push(prefix.readInt8(i))
+const kotlinByteArray = 'byteArrayOf(' + prefixNumbers.join(', ') + ')'
+
+console.log(kotlinByteArray)