cloudflared-mirror/ingress/middleware/jwtvalidator.go

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package middleware
import (
"context"
"fmt"
"net/http"
"github.com/coreos/go-oidc/v3/oidc"
)
const (
headerKeyAccessJWTAssertion = "Cf-Access-Jwt-Assertion"
)
var (
cloudflareAccessCertsURL = "https://%s.cloudflareaccess.com"
)
// JWTValidator is an implementation of Verifier that validates access based JWT tokens.
type JWTValidator struct {
*oidc.IDTokenVerifier
audTags []string
}
func NewJWTValidator(teamName string, certsURL string, audTags []string) *JWTValidator {
if certsURL == "" {
certsURL = fmt.Sprintf(cloudflareAccessCertsURL, teamName)
}
certsEndpoint := fmt.Sprintf("%s/cdn-cgi/access/certs", certsURL)
config := &oidc.Config{
SkipClientIDCheck: true,
}
ctx := context.Background()
keySet := oidc.NewRemoteKeySet(ctx, certsEndpoint)
verifier := oidc.NewVerifier(certsURL, keySet, config)
return &JWTValidator{
IDTokenVerifier: verifier,
audTags: audTags,
}
}
func (v *JWTValidator) Name() string {
return "AccessJWTValidator"
}
func (v *JWTValidator) Handle(ctx context.Context, r *http.Request) (*HandleResult, error) {
accessJWT := r.Header.Get(headerKeyAccessJWTAssertion)
if accessJWT == "" {
// log the exact error message here. the message is specific to the handler implementation logic, we don't gain anything
// in passing it upstream. and each handler impl know what logging level to use for each.
return &HandleResult{
ShouldFilterRequest: true,
StatusCode: http.StatusForbidden,
Reason: "no access token in request",
}, nil
}
token, err := v.IDTokenVerifier.Verify(ctx, accessJWT)
if err != nil {
return nil, err
}
// We want at least one audTag to match
for _, jwtAudTag := range token.Audience {
for _, acceptedAudTag := range v.audTags {
if acceptedAudTag == jwtAudTag {
return &HandleResult{ShouldFilterRequest: false}, nil
}
}
}
return &HandleResult{
ShouldFilterRequest: true,
StatusCode: http.StatusForbidden,
Reason: fmt.Sprintf("Invalid token in jwt: %v", token.Audience),
}, nil
}