I'm updating an embedded TLS 1.0 implementation to TLS 1.2 (devices with 1MB of code space or less, and no OS). At this point, I have AES-128 and AES-256 CBC ciphers working with SHA-1 and SHA-256 digests for a minimal implementation. The library cannot negotiate an SSLv2, SSLv3, TLS 1.0 or TLS 1.1 connection.
I felt this would be sufficient, given that RFC 5246 states, "TLS_RSA_WITH_AES_128_CBC_SHA is now the mandatory to implement cipher suite."
Yet as I read various postings on security blogs, I'm seeing recommendations that would have users disable that suite, and (for example) only allow the ECDHE_RSA or DHE_RSA variants.
So my question is whether devices using our library will interoperate with modern web browsers (as a server) and modern https/smtps/pop servers (as a client). Are there TLS 1.2 clients/servers that fail to negotiate a TLS_RSA_WITH_AES_128_CBC_SHA connection?