Add AuthContext::CreateForTest for fuzzer

This change adds the ability for tests to create an AuthContext using a
fixed data string for the nonce.  This is to facilitate reproducibility
of fuzz tests and is a direct copy of the existing upstream version.

Bug: b/185815206
Change-Id: Ifef4e4cca641e6113356e5818bed2006e814a4de
Reviewed-on: https://chromium-review.googlesource.com/c/openscreen/+/3053623
Reviewed-by: Ryan Keane <rwkeane@google.com>
Commit-Queue: Brandon Tolsch <btolsch@chromium.org>

2 files changed, 18 insertions, 0 deletions

diff --git a/cast/sender/channel/cast_auth_util.cc b/cast/sender/channel/cast_auth_util.cc
index 6e9cf626..f0e1c36f 100644
--- a/cast/sender/channel/cast_auth_util.cc
+++ b/cast/sender/channel/cast_auth_util.cc
@@ -184,6 +184,21 @@ AuthContext AuthContext::Create() {
   return AuthContext(CastNonce::Get());
 }
 
+// static
+AuthContext AuthContext::CreateForTest(const std::string& nonce_data) {
+  std::string nonce;
+  if (nonce_data.empty()) {
+    nonce = std::string(kNonceSizeInBytes, '0');
+  } else {
+    while (nonce.size() < kNonceSizeInBytes) {
+      nonce += nonce_data;
+    }
+    nonce.erase(kNonceSizeInBytes);
+  }
+  OSP_DCHECK_EQ(nonce.size(), kNonceSizeInBytes);
+  return AuthContext(nonce);
+}
+
 AuthContext::AuthContext(const std::string& nonce) : nonce_(nonce) {}
 
 AuthContext::~AuthContext() {}
diff --git a/cast/sender/channel/cast_auth_util.h b/cast/sender/channel/cast_auth_util.h
index d23ebd7e..9c0646ec 100644
--- a/cast/sender/channel/cast_auth_util.h
+++ b/cast/sender/channel/cast_auth_util.h
@@ -36,6 +36,9 @@ class AuthContext {
   // The same context must be used in the challenge and reply.
   static AuthContext Create();
 
+  // Create a context with some seed nonce data for testing.
+  static AuthContext CreateForTest(const std::string& nonce_data);
+
   // Verifies the nonce received in the response is equivalent to the one sent.
   // Returns success if |nonce_response| matches nonce_
   Error VerifySenderNonce(const std::string& nonce_response,