profilefed/handler.go

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2024-03-09 04:56:26 +00:00
package profilefed
import (
"crypto/ed25519"
"encoding/base64"
"encoding/json"
"errors"
"net/http"
"slices"
"strings"
)
// ErrDescriptorNotFound should be returned
var ErrDescriptorNotFound = errors.New("descriptor not found")
// AddExtra is a convenience function that adds an extra data object to the descriptor.
// It defines any undefined namespaces and marshals the data parameter into JSON.
func (d *Descriptor) AddExtra(namespace, etype string, data any) error {
// Remove the fragment from the namespace URL if it exists
urlStr, _, _ := strings.Cut(namespace, "#")
if !slices.Contains(d.Namespaces, urlStr) {
d.Namespaces = append(d.Namespaces, urlStr)
}
msg, err := json.Marshal(data)
if err != nil {
return err
}
d.Extra = append(d.Extra, Extra{
Namespace: namespace,
Type: etype,
Data: msg,
})
return nil
}
type Handler struct {
// PrivateKey contains the server's Ed25519 private key for signing responses
PrivateKey ed25519.PrivateKey
// AllDescriptorsFunc should return all the profile descriptors known to the server.
// If no matching descriptors can be found, AllDescriptorsFunc should reutnr
// [ErrDescriptorNotFound].
AllDescriptorsFunc func(req *http.Request) (map[string]*Descriptor, error)
// DescriptorFunc should return a single descriptor. Make sure to check the `id`
// query parameter if your user has several descriptors available. If a matching
// descriptor cannot be found, DescriptorFunc should return [ErrDescriptorNotFound].
DescriptorFunc func(req *http.Request) (*Descriptor, error)
// ErrorHandler is called whenever an error is encountered.
ErrorHandler func(err error, res http.ResponseWriter)
}
// ServeHTTP implements the [http.Handler] interface
func (h Handler) ServeHTTP(res http.ResponseWriter, req *http.Request) {
var data []byte
if req.URL.Query().Get("all") == "1" {
descriptors, err := h.AllDescriptorsFunc(req)
if err != nil {
h.ErrorHandler(err, res)
return
}
data, err = json.Marshal(descriptors)
if err != nil {
h.ErrorHandler(err, res)
return
}
} else {
descriptor, err := h.DescriptorFunc(req)
if err != nil {
h.ErrorHandler(err, res)
return
}
data, err = json.Marshal(descriptor)
if err != nil {
h.ErrorHandler(err, res)
return
}
}
sig := ed25519.Sign(h.PrivateKey, data)
res.Header().Set("X-ProfileFed-Sig", base64.StdEncoding.EncodeToString(sig))
res.Header().Set("Content-Type", "application/x-pfd+json")
_, err := res.Write(data)
if err != nil {
h.ErrorHandler(err, res)
return
}
}