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HTTPSIG for Go

This library implements HTTP request signature generation and verification based on the RFC draft specification https://tools.ietf.org/html/draft-cavage-http-signatures-06.

The library strives be compatible with the popular python library of the same name: https://github.com/ahknight/httpsig

Installing

go get gopkg.in/spacemonkeygo/httpsig.v0

Signing Requests

Signing requests is done by constructing a new Signer. The key id, key, algorithm, and what headers to sign are required.

For example to construct a Signer with key id "foo", using an RSA private key, for the rsa-sha256 algorithm, with the default header set, you can do:

var key *rsa.PrivateKey = ...
signer := httpsig.NewSigner("foo", key, httpsig.RSASHA256, nil)

There are helper functions for specific algorithms that are less verbose and provide more type safety (the key paramater need not be of type interface{} because the type required for the algorithm is known).

var key *rsa.PrivateKey = ...
signer := httpsig.NewRSASHA256Signer("foo", key, nil)

By default, if no headers are passed to NewSigner (or the helpers), the (request-target) pseudo-header and Date header are signed.

To sign requests, call the Sign() method. The method signs the request and adds an Authorization header containing the signature parameters.

err = signer.Sign(req)
if err != nil {
    ...
}
fmt.Println("AUTHORIZATION:", req.Header.Get('Authorization'))

...

AUTHORIZATION: Signature: keyId="foo",algorithm="sha-256",signature="..."

Verifying Requests

Verifying requests is done by constructing a new Verifier. The verifier requires a KeyGetter implementation to look up keys based on keyId's retrieved from signature parameters.

var getter httpsig.KeyGetter = ....
verifier := httpsig.NewVerifier(getter)

A request can be verified by calling the Verify() method:

err = verifier.Verify(req)

By default, the verifier only requires the Date header to be included in the signature. The set of required headers be changed using the SetRequiredHeaders() method to enforce stricter requirements.

verifier.SetRequiredHeaders([]string{"(request-target)", "host", "date"})

Requests that don't include the full set of required headers in the headers signature parameter (either implicity or explicity) will fail verification.

Note that required headers are simply a specification for which headers must be included in the signature, and does not enforce header presence in requests. It is up to callers to validate header contents (or the lack thereof).

A simple in-memory key store is provided by the library and can be constructed with the NewMemoryKeyStore() function. Keys can be added using the SetKey method:

keystore := NewMemoryKeyStore()

var rsa_key *rsa.PublicKey = ...
keystore.SetKey("foo", rsa_key)

var hmac_key []byte = ...
keystore.SetKey("foo", hmac_key)

Handler

A convenience function is provided that wraps an http.Handler and verifies incoming request signatures before passing them down to the wrapped handler.

If requires a verifier and optionally a realm (for constructing the WWW-Authenticate header).

var handler http.Handler = ...
var verifier *httpsig.Verifier = ...
wrapped := httpsig.RequireSignature(handler, verifier, "example.com")

If signature validation fails, a 401 is returned along with a WWW-Authenticate header containing a Signature challenge with optional realm and headers parameters.

Supported algorithms

  • rsa-sha1 (using PKCS1v15)
  • rsa-sha256 (using PKCS1v15)
  • hmac-sha256

License

Copyright (C) 2017 Space Monkey, Inc.

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.