Validate Crypto::Bcrypt::Password is a valid hash

Resolves #5357

Signed-off-by: Mike Fiedler <miketheman@gmail.com>

spec/std/crypto/bcrypt/password_spec.cr

@@ -20,6 +20,12 @@ describe "Crypto::Bcrypt::Password" do
     it "parses digest" do
       password.digest.should eq("weXJt7sno2HdPVrMvVf06kGgAZvPkga")
     end
+
+    it "validates the hash string has the required amount of parts" do
+      expect_raises(Crypto::Bcrypt::Error, /Invalid hash string/) do
+        Crypto::Bcrypt::Password.new("blarp")
+      end
+    end
   end
 
   describe "create" do

src/crypto/bcrypt/password.cr

@@ -40,6 +40,7 @@ class Crypto::Bcrypt::Password
   # ```
   def initialize(@raw_hash : String)
     parts = @raw_hash.split('$')
+    raise Error.new("Invalid hash string") unless parts.size == 4
 
     @version = parts[1]
     @cost = parts[2].to_i