Implement BIP32Path.fromHardenedString(). (#2886)

* Implement BIP32Path.fromHardenedString(). This will throw exceptions a non hardened path in the string exists

* Do what ben says rather than re-implementing BIP32Path.fromString

core-test/src/test/scala/org/bitcoins/core/crypto/bip32/BIP32PathTest.scala

@@ -232,4 +232,34 @@ class BIP32PathTest extends BitcoinSUnitTest {
 
     }
   }
+
+  it must "ensure that all paths are hardened when using BIP32.fromHardenedString" in {
+    val string = "m/1'/2'/3'/4'/5'"
+    val bip32Path = BIP32Path.fromHardenedString(string)
+    assert(bip32Path.toString == string)
+
+    //bad paths
+    val badPath1 = "m/1/2'/3'/4'/5'"
+    assertThrows[IllegalArgumentException] {
+      BIP32Path.fromHardenedString(badPath1)
+    }
+
+    val badPath2 = "m/1'/2'/3'/4'/5"
+
+    assertThrows[IllegalArgumentException] {
+      BIP32Path.fromHardenedString(badPath2)
+    }
+
+    val badPath3 = "m/1'/2'/3/4'/5"
+
+    assertThrows[IllegalArgumentException] {
+      BIP32Path.fromHardenedString(badPath3)
+    }
+
+    val badPath4 = "m/1/2/3/4/5"
+
+    assertThrows[IllegalArgumentException] {
+      BIP32Path.fromHardenedString(badPath4)
+    }
+  }
 }

core/src/main/scala/org/bitcoins/core/hd/BIP32Path.scala

@@ -146,6 +146,16 @@ object BIP32Path extends Factory[BIP32Path] with StringFactory[BIP32Path] {
     BIP32PathImpl(path)
   }
 
+  /** Takes in a BIP32 Path and verifies all paths are hardened
+    * @throws RuntimeException is a non hardened path is found
+    */
+  def fromHardenedString(string: String): BIP32Path = {
+    val path = BIP32Path.fromString(string)
+    require(path.forall(_.hardened),
+            s"Found non hardened path in string=$string")
+    path
+  }
+
   private def fromBytes(bytes: ByteVector, littleEndian: Boolean): BIP32Path = {
     require(bytes.size % 4 == 0,
             s"ByteVector is not suited for KeyPath, got=${bytes.length}")

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

@@ -54,7 +54,7 @@ class DLCOracle(private[this] val extPrivateKey: ExtPrivateKeyHardened)(implicit
     val chain = HDChainType.External
     val index = 0
 
-    val path = BIP32Path.fromString(
+    val path = BIP32Path.fromHardenedString(
       s"m/${purpose.constant}'/${coin.coinType.toInt}'/${account.index}'/${chain.index}'/$index'")
 
     extPrivateKey.deriveChildPrivKey(path).key