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extra.go
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extra.go
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package api
import (
"context"
"errors"
"fmt"
"io"
"log/slog"
"net"
"net/http"
"net/url"
"strings"
"sync"
"time"
"github.com/bluesky-social/indigo/did"
arc "github.com/hashicorp/golang-lru/arc/v2"
"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp"
otel "go.opentelemetry.io/otel"
)
func ResolveDidToHandle(ctx context.Context, res did.Resolver, hr HandleResolver, udid string) (string, string, error) {
ctx, span := otel.Tracer("gosky").Start(ctx, "resolveDidToHandle")
defer span.End()
doc, err := res.GetDocument(ctx, udid)
if err != nil {
return "", "", err
}
if len(doc.AlsoKnownAs) == 0 {
return "", "", fmt.Errorf("users did document does not specify a handle")
}
aka := doc.AlsoKnownAs[0]
u, err := url.Parse(aka)
if err != nil {
return "", "", fmt.Errorf("aka field in doc was not a valid url: %w", err)
}
handle := u.Host
var svc *did.Service
for _, s := range doc.Service {
if s.ID.String() == "#atproto_pds" && s.Type == "AtprotoPersonalDataServer" {
svc = &s
break
}
}
if svc == nil {
return "", "", fmt.Errorf("users did document has no pds service set")
}
verdid, err := hr.ResolveHandleToDid(ctx, handle)
if err != nil {
return "", "", err
}
if verdid != udid {
return "", "", fmt.Errorf("pds server reported different did for claimed handle")
}
return handle, svc.ServiceEndpoint, nil
}
type HandleResolver interface {
ResolveHandleToDid(ctx context.Context, handle string) (string, error)
}
type failCacheItem struct {
err error
count int
expiresAt time.Time
}
type ProdHandleResolver struct {
client *http.Client
resolver *net.Resolver
ReqMod func(*http.Request, string) error
FailCache *arc.ARCCache[string, *failCacheItem]
}
func NewProdHandleResolver(failureCacheSize int, resolveAddr string, forceUDP bool) (*ProdHandleResolver, error) {
failureCache, err := arc.NewARC[string, *failCacheItem](failureCacheSize)
if err != nil {
return nil, err
}
if resolveAddr == "" {
resolveAddr = "1.1.1.1:53"
}
c := http.Client{
Transport: otelhttp.NewTransport(http.DefaultTransport),
Timeout: time.Second * 10,
}
r := &net.Resolver{
PreferGo: true,
Dial: func(ctx context.Context, network, address string) (net.Conn, error) {
d := net.Dialer{
Timeout: time.Second * 10,
}
if forceUDP {
network = "udp"
}
return d.DialContext(ctx, network, resolveAddr)
},
}
return &ProdHandleResolver{
FailCache: failureCache,
client: &c,
resolver: r,
}, nil
}
func (dr *ProdHandleResolver) ResolveHandleToDid(ctx context.Context, handle string) (string, error) {
ctx, cancel := context.WithTimeout(ctx, time.Second*20)
defer cancel()
ctx, span := otel.Tracer("resolver").Start(ctx, "ResolveHandleToDid")
defer span.End()
var cachedFailureCount int
if dr.FailCache != nil {
if item, ok := dr.FailCache.Get(handle); ok {
cachedFailureCount = item.count
if item.expiresAt.After(time.Now()) {
return "", item.err
}
dr.FailCache.Remove(handle)
}
}
var wkres, dnsres string
var wkerr, dnserr error
var wg sync.WaitGroup
wg.Add(2)
go func() {
defer wg.Done()
wkres, wkerr = dr.resolveWellKnown(ctx, handle)
if wkerr == nil {
cancel()
}
}()
go func() {
defer wg.Done()
dnsres, dnserr = dr.resolveDNS(ctx, handle)
if dnserr == nil {
cancel()
}
}()
wg.Wait()
if dnserr == nil {
return dnsres, nil
}
if wkerr == nil {
return wkres, nil
}
err := errors.Join(fmt.Errorf("no did record found for handle %q", handle), dnserr, wkerr)
if dr.FailCache != nil {
cachedFailureCount++
expireAt := time.Now().Add(time.Millisecond * 100)
if cachedFailureCount > 1 {
// exponential backoff
expireAt = time.Now().Add(time.Millisecond * 100 * time.Duration(cachedFailureCount*cachedFailureCount))
// Clamp to one hour
if expireAt.After(time.Now().Add(time.Hour)) {
expireAt = time.Now().Add(time.Hour)
}
}
dr.FailCache.Add(handle, &failCacheItem{
err: err,
expiresAt: expireAt,
count: cachedFailureCount,
})
}
return "", err
}
func (dr *ProdHandleResolver) resolveWellKnown(ctx context.Context, handle string) (string, error) {
req, err := http.NewRequest("GET", fmt.Sprintf("https://%s/.well-known/atproto-did", handle), nil)
if err != nil {
return "", err
}
if dr.ReqMod != nil {
if err := dr.ReqMod(req, handle); err != nil {
return "", err
}
}
req = req.WithContext(ctx)
resp, err := dr.client.Do(req)
if err != nil {
return "", fmt.Errorf("failed to resolve handle (%s) through HTTP well-known route: %s", handle, err)
}
if resp.StatusCode != 200 {
return "", fmt.Errorf("failed to resolve handle (%s) through HTTP well-known route: status=%d", handle, resp.StatusCode)
}
if resp.ContentLength > 2048 {
return "", fmt.Errorf("http well-known route returned too much data")
}
b, err := io.ReadAll(io.LimitReader(resp.Body, 2048))
if err != nil {
return "", fmt.Errorf("failed to read resolved did: %w", err)
}
parsed, err := did.ParseDID(string(b))
if err != nil {
return "", err
}
return parsed.String(), nil
}
func (dr *ProdHandleResolver) resolveDNS(ctx context.Context, handle string) (string, error) {
res, err := dr.resolver.LookupTXT(ctx, "_atproto."+handle)
if err != nil {
return "", fmt.Errorf("handle lookup failed: %w", err)
}
for _, s := range res {
if strings.HasPrefix(s, "did=") {
parts := strings.Split(s, "=")
pdid, err := did.ParseDID(parts[1])
if err != nil {
return "", fmt.Errorf("invalid did in record: %w", err)
}
return pdid.String(), nil
}
}
return "", fmt.Errorf("no did record found")
}
type TestHandleResolver struct {
TrialHosts []string
}
func (tr *TestHandleResolver) ResolveHandleToDid(ctx context.Context, handle string) (string, error) {
c := http.DefaultClient
for _, h := range tr.TrialHosts {
req, err := http.NewRequest("GET", fmt.Sprintf("http://%s/.well-known/atproto-did", h), nil)
if err != nil {
return "", err
}
req.Host = handle
resp, err := c.Do(req)
if err != nil {
slog.Warn("failed to resolve handle to DID", "handle", handle, "err", err)
continue
}
if resp.StatusCode != 200 {
slog.Warn("got non-200 status code while resolving handle", "handle", handle, "statusCode", resp.StatusCode)
continue
}
b, err := io.ReadAll(resp.Body)
if err != nil {
return "", fmt.Errorf("failed to read resolved did: %w", err)
}
parsed, err := did.ParseDID(string(b))
if err != nil {
return "", err
}
return parsed.String(), nil
}
return "", fmt.Errorf("no did record found for handle %q", handle)
}