evcc-io/util/transport/digest.go

63 lines
1.7 KiB
Go

package transport
import (
"errors"
"net/http"
"strings"
"github.com/icholy/digest"
)
// nonRfcSha256 is sent by some servers instead of the RFC 7616 compliant SHA-256
const nonRfcSha256 = "SHA256"
// Digest creates an http transport performing digest auth. The challenge is
// cached per host, so all requests after the first authenticate preemptively
// instead of paying a 401 challenge round trip each time (RFC 7616 §3.3).
func Digest(user, password string, base http.RoundTripper) http.RoundTripper {
return &digest.Transport{
Username: user,
Password: password,
Transport: base,
FindChallenge: digestChallenge,
Digest: digestCredentials,
}
}
// digestChallenge additionally accepts challenges announcing the non-RFC SHA256
func digestChallenge(h http.Header) (*digest.Challenge, error) {
chal, err := digest.FindChallenge(h)
if err == nil || !errors.Is(err, digest.ErrNoChallenge) {
return chal, err
}
for _, header := range h.Values("WWW-Authenticate") {
if !digest.IsDigest(header) {
continue
}
if chal, err := digest.ParseChallenge(header); err == nil && strings.EqualFold(chal.Algorithm, nonRfcSha256) {
return chal, nil
}
}
return nil, err
}
// digestCredentials hashes a non-RFC SHA256 challenge as SHA-256, echoing back
// the spelling the server used
func digestCredentials(_ *http.Request, chal *digest.Challenge, opt digest.Options) (*digest.Credentials, error) {
if !strings.EqualFold(chal.Algorithm, nonRfcSha256) {
return digest.Digest(chal, opt)
}
rfc := *chal
rfc.Algorithm = "SHA-256"
cred, err := digest.Digest(&rfc, opt)
if err != nil {
return nil, err
}
cred.Algorithm = chal.Algorithm
return cred, nil
}