ech: Remove fizz::ech::getRecordDigest

Summary:
Nothing uses this function, and this function puts a dependency on a concrete
backend (OpenSSL).

Reviewed By: zalecodez

Differential Revision: D62219043

fbshipit-source-id: 9f2fe44571e3e9ebcf586c0a1b69f52921cdb68d

Author: Mingtao Yang

fizz/protocol/ech/BUCK

@@ -26,7 +26,6 @@ cpp_library(
         "Encryption.h",
     ],
     deps = [
-        "//fizz/backend:openssl",
         "//fizz/crypto/hpke:utils",
         "//fizz/protocol:protocol",
         "//fizz/record:record",

fizz/protocol/ech/Encryption.cpp

@@ -9,7 +9,6 @@
 #include <fizz/protocol/ech/Encryption.h>
 #include "fizz/record/Types.h"
 
-#include <fizz/backend/openssl/OpenSSL.h>
 #include <fizz/crypto/hpke/Utils.h>
 #include <fizz/protocol/Protocol.h>
 #include <fizz/protocol/ech/ECHExtensions.h>
@@ -208,36 +207,6 @@ static hpke::SetupParam getSetupParam(
       0};
 }
 
-std::unique_ptr<folly::IOBuf> getRecordDigest(
-    const ECHConfig& echConfig,
-    hpke::KDFId id) {
-  switch (id) {
-    case hpke::KDFId::Sha256: {
-      std::array<uint8_t, fizz::Sha256::HashLen> recordDigest;
-      fizz::openssl::Hasher<Sha256>::hash(
-          *encode(echConfig),
-          folly::MutableByteRange(recordDigest.data(), recordDigest.size()));
-      return folly::IOBuf::copyBuffer(recordDigest);
-    }
-    case hpke::KDFId::Sha384: {
-      std::array<uint8_t, fizz::Sha384::HashLen> recordDigest;
-      fizz::openssl::Hasher<Sha384>::hash(
-          *encode(echConfig),
-          folly::MutableByteRange(recordDigest.data(), recordDigest.size()));
-      return folly::IOBuf::copyBuffer(recordDigest);
-    }
-    case hpke::KDFId::Sha512: {
-      std::array<uint8_t, fizz::Sha512::HashLen> recordDigest;
-      fizz::openssl::Hasher<Sha512>::hash(
-          *encode(echConfig),
-          folly::MutableByteRange(recordDigest.data(), recordDigest.size()));
-      return folly::IOBuf::copyBuffer(recordDigest);
-    }
-    default:
-      throw std::runtime_error("kdf: not implemented");
-  }
-}
-
 hpke::SetupResult constructHpkeSetupResult(
     std::unique_ptr<KeyExchange> kex,
     const SupportedECHConfig& supportedConfig) {

fizz/protocol/ech/Encryption.h

@@ -119,10 +119,6 @@ std::unique_ptr<hpke::HpkeContext> setupDecryptionContext(
     std::unique_ptr<KeyExchange> kex,
     uint64_t seqNum);
 
-std::unique_ptr<folly::IOBuf> getRecordDigest(
-    const ECHConfig& echConfig,
-    hpke::KDFId id);
-
 std::vector<Extension> substituteOuterExtensions(
     std::vector<Extension>&& innerExt,
     const std::vector<Extension>& outerExt);