Add tests for XOF-specific functions squeeze and update called on non…

… XOF digests to increase code coverage

crypto/fipsmodule/digest/internal.h

@@ -80,9 +80,9 @@ struct env_md_st {
 
   // update hashes |len| bytes of |data| into the state in |ctx->md_data|.
   // Digest update functions always return 1. update calls after |final| are 
-  // restricted via |ctx| check (|final| cleanses the |ctx|). Digest XOF update
-  // function propagates the return value from |SHAKE_Absorb|, that is 1 on
-  // success and 0 on failure, to restrict update calls after |squeezeXOF|.
+  // restricted via |ctx| check (|final| cleanses the |ctx|). Returns 1
+  // on success and 0 on failure. Failures can only occur on a
+  // digest XOF update if called after |squeezeXOF| or |finalXOF|.
   int (*update)(EVP_MD_CTX *ctx, const void *data, size_t count);
 
   // final completes the hash and writes |md_size| bytes of digest to |out|.

crypto/fipsmodule/sha/sha3_test.cc

@@ -74,6 +74,14 @@ class SHA3TestVector {
 
     ASSERT_EQ(Bytes(digest.get(), EVP_MD_size(algorithm)),
               Bytes(digest_.data(), EVP_MD_size(algorithm)));
+
+    // Test XOF-specific Digest functions with non XOF algorithms
+    // Assert failure when |EVP_DigestSqueeze| or |EVP_DigestFinalXOF|
+    // are called with digests different from XOF digests
+    ASSERT_TRUE(EVP_DigestInit(ctx.get(), algorithm));
+    ASSERT_TRUE(EVP_DigestUpdate(ctx.get(), msg_.data(), msg_.size()));
+    ASSERT_FALSE(EVP_DigestSqueeze(ctx.get(), digest.get(), digest_length));
+    ASSERT_FALSE(EVP_DigestFinalXOF(ctx.get(), digest.get(), digest_length));
   }
 
   void NISTTestVectors_SingleShot(const EVP_MD *algorithm) const {