Add new constructor to HKDF that allows the client and server key/IV

crypto/hkdf.cc

Index: crypto/hkdf.cc
diff --git a/crypto/hkdf.cc b/crypto/hkdf.cc
index 2483e6029bc0454fcf6fe3aead6e3aaa83bb13b4..41e2d09bae2e8ff9822555c8604b4796fc19624d 100644
--- a/crypto/hkdf.cc
+++ b/crypto/hkdf.cc
@@ -21,6 +21,23 @@ HKDF::HKDF(const base::StringPiece& secret,
            const base::StringPiece& info,
            size_t key_bytes_to_generate,
            size_t iv_bytes_to_generate,
+           size_t subkey_secret_bytes_to_generate)
+    : HKDF(secret,
+           salt,
+           info,
+           key_bytes_to_generate,
+           key_bytes_to_generate,
+           iv_bytes_to_generate,
+           iv_bytes_to_generate,
+           subkey_secret_bytes_to_generate) {}
+
+HKDF::HKDF(const base::StringPiece& secret,
+           const base::StringPiece& salt,
+           const base::StringPiece& info,
+           size_t client_key_bytes_to_generate,
+           size_t server_key_bytes_to_generate,
+           size_t client_iv_bytes_to_generate,
+           size_t server_iv_bytes_to_generate,
            size_t subkey_secret_bytes_to_generate) {
   // https://tools.ietf.org/html/rfc5869#section-2.2
   base::StringPiece actual_salt = salt;
@@ -46,11 +63,12 @@ HKDF::HKDF(const base::StringPiece& secret,
   // https://tools.ietf.org/html/rfc5869#section-2.3
   // Perform the Expand phase to turn the pseudorandom key
   // and info into the output keying material.
-  const size_t material_length = 2 * key_bytes_to_generate +
-                                 2 * iv_bytes_to_generate +
-                                 subkey_secret_bytes_to_generate;
-  const size_t n = (material_length + kSHA256HashLength-1) /
-                   kSHA256HashLength;
+  const size_t material_length =
+      client_key_bytes_to_generate + client_iv_bytes_to_generate +
+      server_key_bytes_to_generate + server_iv_bytes_to_generate +
+      subkey_secret_bytes_to_generate;
+  const size_t n =
+      (material_length + kSHA256HashLength - 1) / kSHA256HashLength;
   DCHECK_LT(n, 256u);
 
   output_.resize(n * kSHA256HashLength);
@@ -82,23 +100,30 @@ HKDF::HKDF(const base::StringPiece& secret,
   // On Windows, when the size of output_ is zero, dereference of 0'th element
   // results in a crash. C++11 solves this problem by adding a data() getter
   // method to std::vector.
-  if (key_bytes_to_generate) {
+  if (client_key_bytes_to_generate) {
     client_write_key_ = base::StringPiece(reinterpret_cast<char*>(&output_[j]),
-                                          key_bytes_to_generate);
-    j += key_bytes_to_generate;
+                                          client_key_bytes_to_generate);
+    j += client_key_bytes_to_generate;
+  }
+
+  if (server_key_bytes_to_generate) {
     server_write_key_ = base::StringPiece(reinterpret_cast<char*>(&output_[j]),
-                                          key_bytes_to_generate);
-    j += key_bytes_to_generate;
+                                          server_key_bytes_to_generate);
+    j += server_key_bytes_to_generate;
   }
 
-  if (iv_bytes_to_generate) {
+  if (client_iv_bytes_to_generate) {
     client_write_iv_ = base::StringPiece(reinterpret_cast<char*>(&output_[j]),
-                                         iv_bytes_to_generate);
-    j += iv_bytes_to_generate;
+                                         client_iv_bytes_to_generate);
+    j += client_iv_bytes_to_generate;
+  }
+
+  if (server_iv_bytes_to_generate) {
     server_write_iv_ = base::StringPiece(reinterpret_cast<char*>(&output_[j]),
-                                         iv_bytes_to_generate);
-    j += iv_bytes_to_generate;
+                                         server_iv_bytes_to_generate);
+    j += server_iv_bytes_to_generate;
   }
+
   if (subkey_secret_bytes_to_generate) {
     subkey_secret_ = base::StringPiece(reinterpret_cast<char*>(&output_[j]),
                                        subkey_secret_bytes_to_generate);