From 5a35ab9eee8d070cbc6a0f073e131cd6e567ed4d Mon Sep 17 00:00:00 2001
From: Jesse Luehrs <doy@tozt.net>
Date: Wed, 22 May 2019 02:08:01 -0400
Subject: problem 37

---
 src/crack.rs  | 30 ++++++++++++++++++++++++++++++
 src/lib.rs    |  1 +
 tests/set5.rs | 27 +++++++++++++++++++++++++++
 3 files changed, 58 insertions(+)

diff --git a/src/crack.rs b/src/crack.rs
index 731cfbd..535b12a 100644
--- a/src/crack.rs
+++ b/src/crack.rs
@@ -1016,6 +1016,36 @@ impl<'a> SRPClient for CorrectSRPClient<'a> {
     }
 }
 
+#[derive(Debug)]
+pub struct ZeroKeySRPClient<'a> {
+    server: &'a mut crate::dh::SRPServer,
+}
+
+impl<'a> ZeroKeySRPClient<'a> {
+    pub fn new(server: &'a mut crate::dh::SRPServer) -> ZeroKeySRPClient<'a> {
+        ZeroKeySRPClient { server }
+    }
+}
+
+impl<'a> SRPClient for ZeroKeySRPClient<'a> {
+    fn server(&mut self) -> &mut crate::dh::SRPServer {
+        self.server
+    }
+
+    fn key_exchange_impl(
+        &mut self,
+        user: &str,
+        _: &str,
+    ) -> (Vec<u8>, Vec<u8>, num_bigint::BigUint) {
+        let a_pub = num_bigint::BigUint::from(0 as u8);
+        let (session, salt, _b_pub) =
+            self.server.exchange_pubkeys(user, &a_pub);
+
+        let s = num_bigint::BigUint::from(0 as u8);
+        (session, salt, s)
+    }
+}
+
 fn crack_single_byte_xor_with_confidence(input: &[u8]) -> (u8, f64) {
     let mut min_diff = 100.0;
     let mut best_key = 0;
diff --git a/src/lib.rs b/src/lib.rs
index 97ce460..42e484d 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -42,6 +42,7 @@ pub use crack::DiffieHellmanMessageExchanger;
 pub use crack::NullDiffieHellmanMessageExchanger;
 pub use crack::ParameterInjectionDiffieHellmanMessageExchanger;
 pub use crack::SRPClient;
+pub use crack::ZeroKeySRPClient;
 pub use dh::DHKeyPair;
 pub use dh::SRPServer;
 pub use dh::SRPUser;
diff --git a/tests/set5.rs b/tests/set5.rs
index 66d2420..81030be 100644
--- a/tests/set5.rs
+++ b/tests/set5.rs
@@ -260,3 +260,30 @@ fn problem_36() {
 
     assert!(key.is_some());
 }
+
+#[test]
+fn problem_37() {
+    let n_hex = "ffffffffffffffffc90fdaa22168c234c4c6628b80dc1cd129024\
+                 e088a67cc74020bbea63b139b22514a08798e3404ddef9519b3cd\
+                 3a431b302b0a6df25f14374fe1356d6d51c245e485b576625e7ec\
+                 6f44c42e9a637ed6b0bff5cb6f406b7edee386bfb5a899fa5ae9f\
+                 24117c4b1fe649286651ece45b3dc2007cb8a163bf0598da48361\
+                 c55d39a69163fa8fd24cf5f83655d23dca3ad961c62f356208552\
+                 bb9ed529077096966d670c354e4abc9804f1746c08ca237327fff\
+                 fffffffffffff";
+    let n = num_bigint::BigUint::parse_bytes(n_hex.as_bytes(), 16).unwrap();
+    let g = num_bigint::BigUint::from(2 as u8);
+    let k = num_bigint::BigUint::from(3 as u8);
+
+    let user = "doy@tozt.net";
+    let pass = "supersecret";
+
+    let mut server = matasano::SRPServer::new(n, g, k);
+    let mut client = matasano::ZeroKeySRPClient::new(&mut server);
+
+    client.register(user, pass);
+
+    let key = client.key_exchange(user, pass);
+
+    assert!(key.is_some());
+}
-- 
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