Make libgmp dependency optional

Cargo.toml

@@ -14,4 +14,9 @@ dbus = "0.2.3"
 num = "0.1.30"
 rand = "0.3.13"
 rust-crypto = "0.2.34"
-rust-gmp = "0.2.10"
+rust-gmp = { version = "0.2.10", optional = true }
+
+[features]
+default = ["gmp"]
+
+gmp = ["rust-gmp"]

README.md

@@ -12,7 +12,7 @@ This library is feature complete but still in *experimental* stage.
 
 ### Basic Usage
 
-Requires dbus and gmp development libraries installed.
+Requires dbus and gmp development libraries installed (see [Advanced](#advanced) section if you need to disable gmp).
 
 On ubuntu, requires libdbus-1-dev and libgmp-dev.
 
@@ -75,6 +75,23 @@ fn main() {
 - Collections: create, delete, search.
 - Items: create, delete, search, get/set secret.
 
+### Advanced
+
+It is possible to disable the dependency on `libgmp` by disabling the default
+features in your `Cargo.toml` file:
+
+    [dependencies]
+    secret-service = { version = "^0.4", default-features = false }
+
+
+**Note**: this will build the library without support for creating encrypted connections 
+to `dbus`, `EncryptionType::Dh` will be unavailable. 
+
+In many cases this is OK, as `dbus` encryption is primarily intended to prevent secrets
+from being swapped to disk. 
+
+Use `EncryptionType::Plain` when `gmp` is disabled.
+
 ### Todo
 
 - use `map_err(|_| SsError::Parse)` for `inner()`? can't `try!` because `inner()` doesn't return an Error type in the Result. Or just `unwrap()`?

src/item.rs

@@ -481,6 +481,7 @@ mod test{
         assert_eq!(secret, b"new_test");
     }
 
+    #[cfg(feature = "gmp")]
     #[test]
     fn should_create_encrypted_item() {
         let ss = SecretService::new(EncryptionType::Dh).unwrap();
@@ -497,6 +498,8 @@ mod test{
         assert_eq!(secret, b"test_encrypted");
 
     }
+
+    #[cfg(feature = "gmp")]
     #[test]
     #[should_panic]
     fn should_not_create_encrypted_item_from_empty_secret() {
@@ -512,6 +515,7 @@ mod test{
         ).unwrap();
     }
 
+    #[cfg(feature = "gmp")]
     #[test]
     fn should_get_encrypted_secret_across_dbus_connections() {
         {

src/lib.rs

@@ -92,6 +92,12 @@
 //! SecretService::new(EncryptionType::Dh).unwrap();
 //! ```
 //!
+//! EncryptionType::Dh requires the `gmp` feature to be enabled in Cargo.toml, which is the default.
+//! This requires `libgmp` to be available.
+//!
+//! When the `gmp` feature is disabled by disabling the default features in Cargo.toml,
+//! EncryptionType::Plain will be the only one available.
+//!
 //! Once the SecretService struct is initialized, it can be used to navigate to a collection.
 //! Items can also be directly searched for without getting a collection first.
 //!
@@ -146,6 +152,7 @@
 
 extern crate crypto;
 extern crate dbus;
+#[cfg(feature = "gmp")]
 extern crate gmp;
 extern crate num;
 extern crate rand;
@@ -193,7 +200,7 @@ use std::rc::Rc;
 ///
 /// Creating a new SecretService will also initialize dbus
 /// and negotiate a new cryptographic session
-/// (`EncryptionType::Plain` or `EncryptionType::Dh`)
+/// (`EncryptionType::Plain` or `EncryptionType::Dh`, when the `gmp` feature is enabled)
 ///
 // Interfaces are the dbus namespace for methods
 #[derive(Debug)]

src/session.rs

@@ -38,9 +38,11 @@ use dbus::MessageItem::{
     Str,
     Variant,
 };
+#[cfg(feature = "gmp")]
 use gmp::mpz::Mpz;
 use num::bigint::BigUint;
 use rand::{Rng, OsRng};
+
 use std::rc::Rc;
 
 // for key exchange
@@ -58,6 +60,7 @@ const DH_PRIME_1024_BYTES: [u8; 128] = [
 #[derive(Debug, PartialEq)]
 pub enum EncryptionType {
     Plain,
+    #[cfg(feature = "gmp")]
     Dh,
 }
 
@@ -121,6 +124,7 @@ impl Session {
                     my_public_key: None,
                 })
             },
+            #[cfg(feature = "gmp")]
             EncryptionType::Dh => {
                 // crypto: create private and public key, send public key
                 // requires some finagling to get pow() for bigints
@@ -223,12 +227,14 @@ impl Session {
     }
 }
 
+#[cfg(feature = "gmp")]
 fn bytes_to_mpz(n: &[u8]) -> Result<Mpz, ()> {
     let bigint = BigUint::from_bytes_be(n);
     let bigint_str = bigint.to_str_radix(10);
     Mpz::from_str_radix(&bigint_str, 10)
 }
 
+#[cfg(feature = "gmp")]
 fn mpz_to_bytes(mpz: Mpz) -> Vec<u8> {
     let bigint_str = mpz.to_str_radix(10);
     let bigint = bigint_str.parse::<BigUint>().unwrap(); //TODO: turn this into a try or option?
@@ -239,6 +245,7 @@ fn mpz_to_bytes(mpz: Mpz) -> Vec<u8> {
 mod test {
     use std::rc::Rc;
     use super::*;
+    #[cfg(feature = "gmp")]
     use super::{bytes_to_mpz, mpz_to_bytes};
     use dbus::{Connection, BusType};
 
@@ -249,6 +256,7 @@ mod test {
         assert!(!session.is_encrypted());
     }
 
+    #[cfg(feature = "gmp")]
     #[test]
     fn should_create_encrypted_session() {
         let bus = Connection::get_private(BusType::Session).unwrap();
@@ -258,6 +266,7 @@ mod test {
         //assert!(false);
     }
 
+    #[cfg(feature = "gmp")]
     #[test]
     fn should_convert_bytes_to_mpz() {
         assert_eq!(bytes_to_mpz(&[1u8, 1]).unwrap(), From::<u32>::from(257));