boringssl/ssl/test

BoringSSL SSL Tests

This directory contains BoringSSL’s protocol-level test suite.

Testing a TLS implementation can be difficult. We need to produce invalid but sufficiently correct handshakes to get our implementation close to its edge cases. TLS’s cryptographic steps mean we cannot use a transcript and effectively need a TLS implementation on the other end. But we do not wish to litter BoringSSL with options for bugs to test against.

Instead, we use a fork of the Go crypto/tls package, heavily patched with configurable bugs. This code, along with a test suite and harness written in Go, lives in the runner directory. The harness runs BoringSSL via a C/C++ shim binary which lives in this directory. All communication with the shim binary occurs with command-line flags, sockets, and standard I/O.

This strategy also ensures we always test against a second implementation. All features should be implemented twice, once in C for BoringSSL and once in Go for testing. If possible, the Go code should be suitable for potentially upstreaming. However, sometimes test code has different needs. For example, our test DTLS code enforces strict ordering on sequence numbers and has controlled packet drop simulation.

To run the tests manually, run go test from the runner directory. It takes command-line flags found at the top of runner/runner.go. The -help option also works after using go test -c to make a runner.test binary first.

If adding a new test, these files may be a good starting point:

• runner/runner.go: the test harness and all the individual tests.
• runner/common.go: contains the Config and ProtocolBugs struct which control the Go TLS implementation’s behavior.
• test_config.h, test_config.cc: the command-line flags which control the shim’s behavior.
• bssl_shim.cc: the shim binary itself.