How make signature in Amazon S3 in C

I'm writing in C, I'm using libcurl+openSSL to send POST request. In case of A开发者_如何学Gomazon S3, I have to make signature in my request, that is formed as RFC 2104 HMAC-SHA1 from AWS Secret Access Key. Advise, please, where can I get the implementation of that algorithm, that will suit Amazon? Is openSSL function SHA1 the one?

HMAC is a way to combine a message and a key securely using a hash function (in this case SHA1). Fortunately, OpenSSL includes an implementation of both, so you shouldn't need to touch the SHA1 function directly. See the documentation for HMAC in OpenSSL.