Revert "fix(openssl): Update to 0.9.x"

The patch introduced an unwrap() failure in a test.

This reverts commit fe0a094.

src/service_account.rs

@@ -16,7 +16,6 @@ use std::default::Default;
 use std::error;
 use std::io::{Read, Write};
 use std::result;
-use std::str;
 
 use authenticator::GetToken;
 use types::{StringError, Token};
@@ -39,6 +38,33 @@ fn encode_base64<T: AsRef<[u8]>>(s: T) -> String {
     base64::encode_mode(s.as_ref(), base64::Base64Mode::UrlSafe)
 }
 
+// Calculates the SHA256 hash.
+fn hash_sha256(data: &[u8]) -> Vec<u8> {
+    let mut hasher = openssl::crypto::hash::Hasher::new(openssl::crypto::hash::Type::SHA256);
+    let _ = hasher.write(data);
+    hasher.finish()
+}
+
+// Signs the hash with key.
+fn sign_rsa(key: &openssl::crypto::rsa::RSA, hash: &[u8]) -> String {
+    let signature = key.sign(openssl::crypto::hash::Type::SHA256, hash).unwrap();
+    let b64_signature = encode_base64(signature);
+
+    b64_signature
+}
+
+// Reads an RSA key from pem_pkcs8 (the format of the 'private_key' field in the service account
+// key).
+fn decode_rsa_key(pem_pkcs8: &str) -> Result<openssl::crypto::rsa::RSA, Box<error::Error>> {
+    let private_key = pem_pkcs8.to_string().replace("\\n", "\n");
+    let privkey = openssl::crypto::rsa::RSA::private_key_from_pem(&mut private_key.as_bytes());
+
+    match privkey {
+        Err(e) => Err(Box::new(e)),
+        Ok(key) => Ok(key),
+    }
+}
+
 /// JSON schema of secret service account key. You can obtain the key from
 /// the Cloud Console at https://console.cloud.google.com/.
 ///
@@ -95,16 +121,12 @@ impl JWT {
     fn sign(&self, private_key: &str) -> Result<String, Box<error::Error>> {
         let mut jwt_head = self.encode_claims();
 
-        let key = openssl::pkey::PKey::hmac(private_key.as_bytes()).unwrap();
-
-        let mut signer =
-            try!(openssl::sign::Signer::new(
-                 openssl::hash::MessageDigest::sha256(), &key));
-        signer.update(&jwt_head.as_bytes()).unwrap();
-        let signature = signer.finish().unwrap();
+        let key = try!(decode_rsa_key(private_key));
+        let hash = hash_sha256(&jwt_head.as_bytes());
+        let signature = sign_rsa(&key, &hash);
 
         jwt_head.push_str(".");
-        jwt_head.push_str(str::from_utf8(&signature).unwrap());
+        jwt_head.push_str(&signature);
 
         Ok(jwt_head)
     }