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