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95 lines
2.8 KiB
Markdown
95 lines
2.8 KiB
Markdown
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# httpsig
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`go get github.com/go-fed/httpsig`
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Implementation of [HTTP Signatures](https://tools.ietf.org/html/draft-cavage-http-signatures).
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Supports many different combinations of MAC, HMAC signing of hash, or RSA
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signing of hash schemes. Its goals are:
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* Have a very simple interface for signing and validating
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* Support a variety of signing algorithms and combinations
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* Support setting either headers (`Authorization` or `Signature`)
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* Remaining flexible with headers included in the signing string
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* Support both HTTP requests and responses
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* Explicitly not support known-cryptographically weak algorithms
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* Support automatic signing and validating Digest headers
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## How to use
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`import "github.com/go-fed/httpsig"`
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### Signing
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Signing a request or response requires creating a new `Signer` and using it:
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```
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func sign(privateKey crypto.PrivateKey, pubKeyId string, r *http.Request) error {
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prefs := []httpsig.Algorithm{httpsig.RSA_SHA512, httpsig.RSA_SHA256}
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digestAlgorithm := DigestSha256
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// The "Date" and "Digest" headers must already be set on r, as well as r.URL.
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headersToSign := []string{httpsig.RequestTarget, "date", "digest"}
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signer, chosenAlgo, err := httpsig.NewSigner(prefs, digestAlgorithm, headersToSign, httpsig.Signature)
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if err != nil {
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return err
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}
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// To sign the digest, we need to give the signer a copy of the body...
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// ...but it is optional, no digest will be signed if given "nil"
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body := ...
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// If r were a http.ResponseWriter, call SignResponse instead.
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return signer.SignRequest(privateKey, pubKeyId, r, body)
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}
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```
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`Signer`s are not safe for concurrent use by goroutines, so be sure to guard
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access:
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```
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type server struct {
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signer httpsig.Signer
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mu *sync.Mutex
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}
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func (s *server) handlerFunc(w http.ResponseWriter, r *http.Request) {
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privateKey := ...
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pubKeyId := ...
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// Set headers and such on w
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s.mu.Lock()
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defer s.mu.Unlock()
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// To sign the digest, we need to give the signer a copy of the response body...
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// ...but it is optional, no digest will be signed if given "nil"
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body := ...
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err := s.signer.SignResponse(privateKey, pubKeyId, w, body)
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if err != nil {
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...
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}
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...
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}
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```
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The `pubKeyId` will be used at verification time.
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### Verifying
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Verifying requires an application to use the `pubKeyId` to both retrieve the key
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needed for verification as well as determine the algorithm to use. Use a
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`Verifier`:
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```
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func verify(r *http.Request) error {
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verifier, err := httpsig.NewVerifier(r)
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if err != nil {
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return err
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}
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pubKeyId := verifier.KeyId()
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var algo httpsig.Algorithm = ...
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var pubKey crypto.PublicKey = ...
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// The verifier will verify the Digest in addition to the HTTP signature
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return verifier.Verify(pubKey, algo)
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}
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```
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`Verifier`s are not safe for concurrent use by goroutines, but since they are
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constructed on a per-request or per-response basis it should not be a common
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restriction.
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