Return clearer errors when splitting components and ensure there are …

…exactly three

src/error.rs

@@ -11,6 +11,10 @@ pub enum Error {
     AlgorithmMismatch(AlgorithmType, AlgorithmType),
     NoKeyId,
     NoKeyWithKeyId(String),
+    NoHeaderComponent,
+    NoClaimsComponent,
+    NoSignatureComponent,
+    TooManyComponents,
     Format,
     Base64(DecodeError),
     Json(JsonError),
@@ -29,6 +33,10 @@ impl fmt::Display for Error {
             }
             NoKeyId => write!(f, "No key id found"),
             NoKeyWithKeyId(ref kid) => write!(f, "Key with key id {} not found", kid),
+            NoHeaderComponent => write!(f, "No header component found in token string"),
+            NoClaimsComponent => write!(f, "No claims component found in token string"),
+            NoSignatureComponent => write!(f, "No signature component found in token string"),
+            TooManyComponents => write!(f, "Too many components found in token string"),
             Format => write!(f, "Format"),
             Base64(ref x) => write!(f, "{}", x),
             Json(ref x) => write!(f, "{}", x),

src/token/verified.rs

@@ -125,9 +125,13 @@ impl<'a, H: FromBase64, C: FromBase64> Token<H, C, Unverified<'a>> {
 
 pub(crate) fn split_components(token: &str) -> Result<[&str; 3], Error> {
     let mut components = token.split(SEPARATOR);
-    let header = components.next().ok_or(Error::Format)?;
-    let claims = components.next().ok_or(Error::Format)?;
-    let signature = components.next().ok_or(Error::Format)?;
+    let header = components.next().ok_or(Error::NoHeaderComponent)?;
+    let claims = components.next().ok_or(Error::NoClaimsComponent)?;
+    let signature = components.next().ok_or(Error::NoSignatureComponent)?;
+
+    if components.next().is_some() {
+        return Err(Error::TooManyComponents);
+    }
 
     Ok([header, claims, signature])
 }