CODEWITHSUNDEEP
csocketsssltcp
Marco
Marco

Reputation: 803

Detect SSL protocol in C

I'm writing a server which is accepting incoming TCP connections and I would like to implement a simple way in C to detect if connection is SSL just inspecting few received bytes. Any help?

Upvotes: 2

Views: 1295

Answers (1)

ldx
ldx

Reputation: 4074

It is possible since the first message after the connection is established should be a "hello" message from the client. The first field in the message is the SSL/TLS version, then a timestamp follows - depending on the application layer protocol a plain client uses, this may be enough to figure out if the client connecting uses SSL/TLS or not.

See https://www.rfc-editor.org/rfc/rfc5246#section-7.4 for more details on the message structure.

Edit: here's a very similar question with an excellent answer: https://security.stackexchange.com/questions/34780/checking-client-hello-for-https-classification

Upvotes: 2

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