From 7c28727f738f38ac69a8315ed95d99553f8d176c Mon Sep 17 00:00:00 2001
From: Adam Wick <awick@uhsure.com>
Date: Tue, 1 May 2018 22:30:07 -0700
Subject: [PATCH] RSA signature verification.

---
 src/rsa/gold_tests.rs | 33 +++++++++++++++++++++++++++------
 src/rsa/public.rs     | 16 ++++++++++++++--
 2 files changed, 41 insertions(+), 8 deletions(-)

diff --git a/src/rsa/gold_tests.rs b/src/rsa/gold_tests.rs
index f7d9b4b..ae40135 100644
--- a/src/rsa/gold_tests.rs
+++ b/src/rsa/gold_tests.rs
@@ -1,5 +1,5 @@
 use rsa::*;
-use testing::{make_unsigned,run_test};
+use testing::run_test;
 
 fn get_signing_hash(s: usize) -> &'static SigningHash {
     match s {
@@ -13,17 +13,17 @@ fn get_signing_hash(s: usize) -> &'static SigningHash {
 }
 
 #[test]
-fn rsa_signature_tests()
+fn rsa_signing_tests()
 {
     run_test("tests/rsa/signature.test", 7, |case| {
         let (neg0, dbytes) = case.get("d").unwrap();
         let (neg1, nbytes) = case.get("n").unwrap();
         let (neg2, hbytes) = case.get("h").unwrap();
-        let (neg2, kbytes) = case.get("k").unwrap();
-        let (neg3, msg)    = case.get("m").unwrap();
-        let (neg4, sig)    = case.get("s").unwrap();
+        let (neg3, kbytes) = case.get("k").unwrap();
+        let (neg4, msg)    = case.get("m").unwrap();
+        let (neg5, sig)    = case.get("s").unwrap();
 
-        assert!(!neg0 & !neg1 & !neg2 & !neg3 & !neg4);
+        assert!(!neg0 & !neg1 & !neg2 & !neg3 & !neg4 & !neg5);
         let hash = get_signing_hash(usize::from(UCN::from_bytes(hbytes)));
         let size = usize::from(UCN::from_bytes(kbytes));
         let key  = RSAPrivate::new(UCN::from_bytes(nbytes),
@@ -35,3 +35,24 @@ fn rsa_signature_tests()
         assert_eq!(*sig, sig2);
     });
 }
+
+#[test]
+fn rsa_verification_tests()
+{
+    run_test("tests/rsa/signature.test", 7, |case| {
+        let (neg1, nbytes) = case.get("n").unwrap();
+        let (neg2, hbytes) = case.get("h").unwrap();
+        let (neg3, kbytes) = case.get("k").unwrap();
+        let (neg4, msg)    = case.get("m").unwrap();
+        let (neg5, sig)    = case.get("s").unwrap();
+
+        assert!(!neg1 & !neg2 & !neg3 & !neg4 & !neg5);
+        let hash = get_signing_hash(usize::from(UCN::from_bytes(hbytes)));
+        let size = usize::from(UCN::from_bytes(kbytes));
+        let key  = RSAPublic::new(UCN::from_bytes(nbytes),
+                                  UCN::from(65537u64));
+
+        assert_eq!(key.byte_len * 8, size);
+        assert!(key.verify(hash, &msg, sig));
+    });
+}
diff --git a/src/rsa/public.rs b/src/rsa/public.rs
index 7599e15..1785387 100644
--- a/src/rsa/public.rs
+++ b/src/rsa/public.rs
@@ -1,5 +1,6 @@
 use cryptonum::{BarrettUCN,UCN};
-use rsa::core::ACCEPTABLE_KEY_SIZES;
+use rsa::core::{ACCEPTABLE_KEY_SIZES,pkcs1_pad,vp1};
+use rsa::signing_hashes::SigningHash;
 
 #[derive(Clone,Debug,PartialEq,Eq)]
 pub struct RSAPublic {
@@ -16,7 +17,7 @@ impl RSAPublic {
         let len = n.bits();
 
         for &(valid_bits, _) in ACCEPTABLE_KEY_SIZES.iter() {
-            if valid_bits > len {
+            if valid_bits >= len {
                 return RSAPublic{
                     byte_len: valid_bits / 8,
                     n: n.clone(),
@@ -27,4 +28,15 @@ impl RSAPublic {
         }
         panic!("Invalid RSA key size in new()")
     }
+
+    /// Verify the signature for a given message, using the given signing hash,
+    /// returning true iff the signature validates.
+    pub fn verify(&self, shash: &SigningHash, msg: &[u8], sig: &[u8]) -> bool {
+        let hash = (shash.run)(msg);
+        let s    = UCN::from_bytes(&sig);
+        let m    = vp1(&self.nu, &self.e, &s);
+        let em   = m.to_bytes(self.byte_len);
+        let em_  = pkcs1_pad(&shash.ident, &hash, self.byte_len);
+        (em == em_)
+    }
 }