Expose secp256k1 and keccak256 in the SDK (#1028)

### What

Expose `secp256k1` and `keccak256` in the SDK.

### Why

`secp256k1` is a widely used cryptographic signature algorithm and
`keccak256` is a widely used hashing algorithm. Exposing these functions
will allow smart contract developers to utilize these algorithms in
their applications without having to implement them themselves.

### Follow on work

* ~Pending [this
discussion](#1023 (comment))
on best practices I will call `check_env` where applicable.~


### Known limitations

N/A
------
**Github Issue**: [surface new crypto functions in
SDK](#970)

---------

Co-authored-by: Leigh McCulloch <351529+leighmcculloch@users.noreply.github.com>

soroban-sdk/src/crypto.rs

@@ -22,6 +22,13 @@ impl Crypto {
         unsafe { BytesN::unchecked_new(env.clone(), bin) }
     }
 
+    /// Returns the Keccak-256 hash of the data.
+    pub fn keccak256(&self, data: &Bytes) -> BytesN<32> {
+        let env = self.env();
+        let bin = internal::Env::compute_hash_keccak256(env, data.into()).unwrap_infallible();
+        unsafe { BytesN::unchecked_new(env.clone(), bin) }
+    }
+
     /// Verifies an ed25519 signature.
     ///
     /// The signature is verified as a valid signature of the message by the
@@ -39,4 +46,26 @@ impl Crypto {
             signature.to_object(),
         );
     }
+
+    /// Recovers the ECDSA secp256k1 public key.
+    ///
+    /// The public key returned is the SEC-1-encoded ECDSA secp256k1 public key
+    /// that produced the 64-byte signature over a given 32-byte message digest,
+    /// for a given recovery_id byte.
+    pub fn secp256k1_recover(
+        &self,
+        message_digest: &BytesN<32>,
+        signature: &BytesN<64>,
+        recorvery_id: u32,
+    ) -> BytesN<65> {
+        let env = self.env();
+        let bytes = internal::Env::recover_key_ecdsa_secp256k1(
+            env,
+            message_digest.to_object(),
+            signature.to_object(),
+            recorvery_id.into(),
+        )
+        .unwrap_infallible();
+        unsafe { BytesN::unchecked_new(env.clone(), bytes) }
+    }
 }

soroban-sdk/src/tests.rs

@@ -17,6 +17,8 @@ mod contract_udt_struct_tuple;
 mod contractimport;
 mod contractimport_with_error;
 mod crypto_ed25519;
+mod crypto_keccak256;
+mod crypto_secp256k1;
 mod crypto_sha256;
 mod env;
 mod prng;

soroban-sdk/src/tests/crypto_keccak256.rs

@@ -0,0 +1,13 @@
+use crate::{bytesn, Env, IntoVal};
+
+#[test]
+fn test_keccak256() {
+    let env = Env::default();
+
+    let bytes = b"test vector for soroban".into_val(&env);
+    let expect = bytesn!(
+        &env,
+        0x352fe2eaddf44eb02eb3eab1f8d6ff4ba426df4f1734b1e3f210d621ee8853d9
+    );
+    assert_eq!(env.crypto().keccak256(&bytes), expect);
+}

soroban-sdk/src/tests/crypto_secp256k1.rs

@@ -0,0 +1,26 @@
+use crate::{bytesn, Env};
+
+#[test]
+fn test_recover_key_ecdsa_secp256k1() {
+    let env = Env::default();
+
+    // From: https://github.com/ethereum/go-ethereum/blob/90d5bd85bcf2919ac2735a47fde675213348a0a6/crypto/secp256k1/secp256_test.go#L204-L217
+    let message_digest = bytesn!(
+        &env,
+        0xce0677bb30baa8cf067c88db9811f4333d131bf8bcf12fe7065d211dce971008
+    );
+    let signature = bytesn!(
+        &env,
+        0x90f27b8b488db00b00606796d2987f6a5f59ae62ea05effe84fef5b8b0e549984a691139ad57a3f0b906637673aa2f63d1f55cb1a69199d4009eea23ceaddc93
+    );
+    let recovery_id = 1;
+    let expected_public_key = bytesn!(
+        &env,
+        0x04e32df42865e97135acfb65f3bae71bdc86f4d49150ad6a440b6f15878109880a0a2b2667f7e725ceea70c673093bf67663e0312623c8e091b13cf2c0f11ef652
+    );
+    assert_eq!(
+        env.crypto()
+            .secp256k1_recover(&message_digest, &signature, recovery_id),
+        expected_public_key
+    );
+}