Give oracle ability to sign messages with private key (#3070)

app/cli/src/main/scala/org/bitcoins/cli/ConsoleCli.scala

@@ -1313,6 +1313,20 @@ object ConsoleCli {
                 case other => other
               }))
         ),
+      cmd("signmessage")
+        .action((_, conf) => conf.copy(command = SignMessage("")))
+        .text("Signs the SHA256 hash of the given string using the oracle's signing key")
+        .children(
+          arg[String]("message")
+            .text("Message to hash and sign")
+            .required()
+            .action((msg, conf) =>
+              conf.copy(command = conf.command match {
+                case signMessage: SignMessage =>
+                  signMessage.copy(message = msg)
+                case other => other
+              }))
+        ),
       note(sys.props("line.separator") + "=== Util ==="),
       cmd("createmultisig")
         .action((_, conf) =>
@@ -1628,6 +1642,9 @@ object ConsoleCli {
       case GetSignatures(eventName) =>
         RequestParam("getsignatures", Seq(up.writeJs(eventName)))
 
+      case SignMessage(message) =>
+        RequestParam("signmessage", Seq(up.writeJs(message)))
+
       case CreateMultisig(requiredKeys, keys, addressType) =>
         RequestParam("createmultisig",
                      Seq(up.writeJs(requiredKeys),
@@ -1997,4 +2014,6 @@ object CliCommand {
       extends OracleServerCliCommand
 
   case class GetSignatures(eventName: String) extends OracleServerCliCommand
+
+  case class SignMessage(message: String) extends OracleServerCliCommand
 }

app/oracle-server-test/src/test/scala/org/bitcoins/oracle/server/OracleRoutesSpec.scala

@@ -319,5 +319,22 @@ class OracleRoutesSpec
           String] == s"""{"result":"${dummyAttestmentTLV.hex}","error":null}""")
       }
     }
+
+    "sign message" in {
+      (mockOracleApi
+        .signMessage(_: String))
+        .expects("message")
+        .returning(sig)
+
+      val route =
+        oracleRoutes.handleCommand(
+          ServerCommand("signmessage", Arr(Str("message"))))
+
+      Post() ~> route ~> check {
+        assert(contentType == `application/json`)
+        assert(
+          responseAs[String] == s"""{"result":"${sig.hex}","error":null}""")
+      }
+    }
   }
 }

app/oracle-server/src/main/scala/org/bitcoins/oracle/server/OracleRoutes.scala

@@ -232,6 +232,17 @@ case class OracleRoutes(oracle: DLCOracleApi)(implicit
           }
       }
 
+    case ServerCommand("signmessage", arr) =>
+      SignMessage.fromJsArr(arr) match {
+        case Failure(exception) =>
+          reject(ValidationRejection("failure", Some(exception)))
+        case Success(SignMessage(message)) =>
+          complete {
+            val signature = oracle.signMessage(message)
+            Server.httpSuccess(signature.hex)
+          }
+      }
+
     case ServerCommand("keymanagerpassphrasechange", arr) =>
       KeyManagerPassphraseChange.fromJsArr(arr) match {
         case Failure(err) =>

app/oracle-server/src/main/scala/org/bitcoins/oracle/server/ServerJsonModels.scala

@@ -13,6 +13,28 @@ import java.time.Instant
 import scala.util.control.NonFatal
 import scala.util.{Failure, Try}
 
+case class SignMessage(message: String)
+
+object SignMessage extends ServerJsonModels {
+
+  def fromJsArr(jsArr: ujson.Arr): Try[SignMessage] = {
+    jsArr.arr.toList match {
+      case strJs :: Nil =>
+        Try {
+          val message = strJs.str
+
+          SignMessage(message)
+        }
+      case Nil =>
+        Failure(new IllegalArgumentException("Missing message argument"))
+      case other =>
+        Failure(
+          new IllegalArgumentException(
+            s"Bad number of arguments: ${other.length}. Expected: 1"))
+    }
+  }
+}
+
 case class CreateEvent(
     label: String,
     maturationTime: Instant,

core/src/main/scala/org/bitcoins/core/api/dlcoracle/DLCOracleApi.scala

@@ -6,7 +6,8 @@ import org.bitcoins.core.number._
 import org.bitcoins.core.protocol.Bech32Address
 import org.bitcoins.core.protocol.dlc.SigningVersion
 import org.bitcoins.core.protocol.tlv._
-import org.bitcoins.crypto.{SchnorrNonce, SchnorrPublicKey}
+import org.bitcoins.crypto._
+import scodec.bits.ByteVector
 
 import java.time.Instant
 import scala.concurrent.Future
@@ -76,4 +77,12 @@ trait DLCOracleApi {
     * the oracle private key will be revealed.
     */
   def deleteAttestations(oracleEventTLV: OracleEventTLV): Future[OracleEvent]
+
+  /** Signs the SHA256 hash of the given string using the oracle's signing key */
+  def signMessage(message: String): SchnorrDigitalSignature = {
+    signMessage(CryptoUtil.serializeForHash(message))
+  }
+
+  /** Signs the SHA256 hash of the given bytes using the oracle's signing key */
+  def signMessage(message: ByteVector): SchnorrDigitalSignature
 }

dlc-oracle-test/src/test/scala/org/bitcoins/dlc/oracle/DLCOracleTest.scala

@@ -60,6 +60,13 @@ class DLCOracleTest extends DLCOracleFixture {
     }
   }
 
+  it must "correctly sign a message" in { dlcOracle: DLCOracle =>
+    val message = "hello world"
+    val signature = dlcOracle.signMessage(message)
+    assert(
+      dlcOracle.publicKey.verify(CryptoUtil.sha256(message).bytes, signature))
+  }
+
   it must "get the correctly sorted nonces in an announcement " in {
     dlcOracle: DLCOracle =>
       val eventName = "test"

dlc-oracle/src/main/scala/org/bitcoins/dlc/oracle/DLCOracle.scala

@@ -18,6 +18,7 @@ import org.bitcoins.dlc.oracle.config.DLCOracleAppConfig
 import org.bitcoins.dlc.oracle.storage._
 import org.bitcoins.dlc.oracle.util.EventDbUtil
 import org.bitcoins.keymanager.{DecryptedMnemonic, WalletStorage}
+import scodec.bits.ByteVector
 
 import java.time.Instant
 import scala.concurrent.{ExecutionContext, Future}
@@ -373,6 +374,12 @@ class DLCOracle(private[this] val extPrivateKey: ExtPrivateKeyHardened)(implicit
     } yield OracleEvent.fromEventDbs(signSig ++ digitSigs)
   }
 
+  /** @inheritdoc */
+  def signMessage(message: ByteVector): SchnorrDigitalSignature = {
+    val hash = CryptoUtil.sha256(message)
+    signingKey.schnorrSign(hash.bytes)
+  }
+
   /** Deletes attestations for the given event
     *
     * WARNING: if previous signatures have been made public

docs/oracle/oracle-server.md

@@ -44,6 +44,8 @@ checkout [this page](build-oracle-server.md).
   - `outcome` - Number to sign for this event
 - `getsignatures` `event` - Get the signatures from a signed event
   - `eventName` - The event's name
+- `signmessage` `message` - Signs the SHA256 hash of the given string using the oracle's signing key
+  - `message` - Message to hash and sign
   
 ### Create Event Example