Module: Oximg::Server::Signer

Defined in:
lib/oximg/server/signer.rb

Overview

The imgproxy-style signing scheme, exactly as the server verifies it (+Signing::verify+ in src/main.rs): the signature is base64url(HMAC-SHA256(key, salt || path)) over the percent-DECODED path, so one signature covers every URL encoding of the same source.

test/server_signer_test.rb pins this against the vectors the Rust integration suite serves 200s for — a scheme with two implementations needs shared vectors, not two readings of the prose.

Class Method Summary collapse

Class Method Details

.sign(key, salt, path) ⇒ Object

path is the decoded path the server reconstructs before verifying: "/resize/w/h/file" on the positional route, "prefix/options/file" on the options route.



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# File 'lib/oximg/server/signer.rb', line 21

def sign(key, salt, path)
  # Force binary before concatenating: key material is arbitrary
  # bytes, and a non-ASCII filename in a UTF-8 path would otherwise
  # raise Encoding::CompatibilityError on the join.
  digest = OpenSSL::HMAC.digest("SHA256", key, salt + path.to_s.b)
  # Unpadded base64url. The server strips "=" before decoding, so
  # padding would verify too — but every vector it ships is
  # unpadded, and an unpadded signature is one path segment with no
  # escaping question.
  [digest].pack("m0").tr("+/", "-_").delete("=")
end