From c8e347649e6323c3eae12b6d95fcc888ba73656f Mon Sep 17 00:00:00 2001
From: Benjamin Barenblat <bbaren@mit.edu>
Date: Mon, 15 Jun 2015 14:42:21 -0400
Subject: Abstract away OpenSSL API details

---
 src/hashFFI.cc | 52 +++++++++++++++++++++-------------------------------
 1 file changed, 21 insertions(+), 31 deletions(-)

diff --git a/src/hashFFI.cc b/src/hashFFI.cc
index f349ba4..dcc7375 100644
--- a/src/hashFFI.cc
+++ b/src/hashFFI.cc
@@ -16,6 +16,7 @@
 
 #include <array>
 #include <cstdio>
+#include <functional>
 
 #include <openssl/md5.h>
 #include <openssl/sha.h>
@@ -28,6 +29,10 @@ static_assert(sizeof(unsigned char) == 1, "unsigned char is not a single byte");
 
 namespace {
 
+using OpenSSLHashFunction =
+    std::function<unsigned char*(const unsigned char*, std::size_t,
+                                 unsigned char*)>;
+
 // Asserts a condition without crashing or releasing information about where the
 // error occurred.  This function is essential for web programming, where an
 // attacker should not be able to bring down the app by causing an assertion
@@ -44,15 +49,14 @@ void Assert(uw_context* const context,
   Assert(context, condition, FATAL, message);
 }
 
-}  // namespace
-
-uw_Basis_string uw_HashFFI_md5(uw_context* const context,
-                               const uw_Basis_blob input) {
-  using Digest = std::array<unsigned char, MD5_DIGEST_LENGTH>;
-  // Perform the MD5 operation.
+template<std::size_t digest_length>
+uw_Basis_string Hash(uw_context* const context, const uw_Basis_blob input,
+                     OpenSSLHashFunction hash) {
+  using Digest = std::array<unsigned char, digest_length>;
+  // Perform the hash operation.
   Digest raw_result;
-  MD5(reinterpret_cast<unsigned char*>(input.data), input.size,
-      raw_result.data());
+  hash(reinterpret_cast<unsigned char*>(input.data), input.size,
+       raw_result.data());
   // Convert it to a hex string.  This will be twice as large (two hex digits
   // per byte), plus an additional byte for the null terminator.
   const auto result_length = 2 * raw_result.size() + 1;
@@ -60,7 +64,7 @@ uw_Basis_string uw_HashFFI_md5(uw_context* const context,
       reinterpret_cast<uw_Basis_string>(uw_malloc(context, result_length));
   Assert(context, result, BOUNDED_RETRY,
          "unable to allocate memory for digest");
-  for (Digest::size_type i = 0; i < raw_result.size(); i++) {
+  for (typename Digest::size_type i = 0; i < raw_result.size(); i++) {
     sprintf(result + 2 * i, "%02x", raw_result[i]);
   }
   // Make sure the string is properly terminated.
@@ -72,28 +76,14 @@ uw_Basis_string uw_HashFFI_md5(uw_context* const context,
   return result;
 }
 
+}  // namespace
+
+uw_Basis_string uw_HashFFI_md5(uw_context* const context,
+                               const uw_Basis_blob input) {
+  return Hash<MD5_DIGEST_LENGTH>(context, input, MD5);
+}
+
 uw_Basis_string uw_HashFFI_sha1(uw_context* const context,
                                const uw_Basis_blob input) {
-  using Digest = std::array<unsigned char, SHA_DIGEST_LENGTH>;
-  // Perform the SHA-1 operation.
-  Digest raw_result;
-  SHA1(reinterpret_cast<unsigned char*>(input.data), input.size,
-      raw_result.data());
-  // Convert it to a hex string.  This will be twice as large (two hex digits
-  // per byte), plus an additional byte for the null terminator.
-  const auto result_length = 2 * raw_result.size() + 1;
-  uw_Basis_string result =
-      reinterpret_cast<uw_Basis_string>(uw_malloc(context, result_length));
-  Assert(context, result, BOUNDED_RETRY,
-         "unable to allocate memory for digest");
-  for (Digest::size_type i = 0; i < raw_result.size(); i++) {
-    sprintf(result + 2 * i, "%02x", raw_result[i]);
-  }
-  // Make sure the string is properly terminated.
-  for (std::size_t i = 0; i < result_length - 2; i++) {
-    Assert(context, result[i] != '\0', "null byte in digest");
-  }
-  Assert(context, result[result_length - 1] == '\0',
-         "failed to properly terminate digest");
-  return result;
+  return Hash<SHA_DIGEST_LENGTH>(context, input, SHA1);
 }
-- 
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