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hostname.go
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hostname.go
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package gateway
import (
"context"
"fmt"
"net"
"net/http"
"net/url"
"regexp"
"strings"
cid "github.com/ipfs/go-cid"
"github.com/libp2p/go-libp2p/core/peer"
dns "github.com/miekg/dns"
mbase "github.com/multiformats/go-multibase"
)
// NewHostnameHandler is a middleware that wraps an [http.Handler] in order to
// parse the Host header and translate it into the content path. This is useful
// for creating [Subdomain Gateways] or [DNSLink Gateways].
//
// [Subdomain Gateways]: https://specs.ipfs.tech/http-gateways/subdomain-gateway/
// [DNSLink Gateways]: https://specs.ipfs.tech/http-gateways/dnslink-gateway/
func NewHostnameHandler(c Config, backend IPFSBackend, next http.Handler) http.HandlerFunc {
gateways := prepareHostnameGateways(c.PublicGateways)
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
defer panicHandler(w)
ctx := context.WithValue(r.Context(), OriginalPathKey, r.URL.Path)
r = r.WithContext(ctx)
// First check for protocol handler redirects.
if handleProtocolHandlerRedirect(w, r, &c) {
return
}
// Unfortunately, many (well, ipfs.io) gateways use
// DNSLink so if we blindly rewrite with DNSLink, we'll
// break /ipfs links.
//
// We fix this by maintaining a list of known gateways
// and the paths that they serve "gateway" content on.
// That way, we can use DNSLink for everything else.
// Support X-Forwarded-Host if added by a reverse proxy
// https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Forwarded-Host
host := r.Host
if xHost := r.Header.Get("X-Forwarded-Host"); xHost != "" {
host = xHost
}
// HTTP Host & Path check: is this one of our "known gateways"?
if gw, ok := gateways.isKnownHostname(host); ok {
// This is a known gateway but request is not using
// the subdomain feature.
// Does this gateway _handle_ this path?
if hasPrefix(r.URL.Path, gw.Paths...) {
// It does.
// Should this gateway use subdomains instead of paths?
if gw.UseSubdomains {
// Yes, redirect if applicable
// Example: dweb.link/ipfs/{cid} → {cid}.ipfs.dweb.link
useInlinedDNSLink := gw.InlineDNSLink
newURL, err := toSubdomainURL(host, r.URL.Path, r, useInlinedDNSLink, backend)
if err != nil {
webError(w, r, &c, err, http.StatusBadRequest)
return
}
if newURL != "" {
http.Redirect(w, r, newURL, http.StatusMovedPermanently)
return
}
}
// Not a subdomain resource, continue with path processing
// Example: 127.0.0.1:8080/ipfs/{CID}, ipfs.io/ipfs/{CID} etc
next.ServeHTTP(w, withHostnameContext(r, host))
return
}
// Not a whitelisted path
// Try DNSLink, if it was not explicitly disabled for the hostname
if !gw.NoDNSLink && hasDNSLinkRecord(r.Context(), backend, host) {
// rewrite path and handle as DNSLink
r.URL.Path = "/ipns/" + stripPort(host) + r.URL.Path
next.ServeHTTP(w, withDNSLinkContext(r, host))
return
}
// If not, resource does not exist on the hostname, return 404
http.NotFound(w, r)
return
}
// HTTP Host check: is this one of our subdomain-based "known gateways"?
// IPFS details extracted from the host: {rootID}.{ns}.{gwHostname}
// /ipfs/ example: {cid}.ipfs.localhost:8080, {cid}.ipfs.dweb.link
// /ipns/ example: {libp2p-key}.ipns.localhost:8080, {inlined-dnslink-fqdn}.ipns.dweb.link
if gw, gwHostname, ns, rootID, ok := gateways.knownSubdomainDetails(host); ok {
// Looks like we're using a known gateway in subdomain mode.
// Assemble original path prefix.
pathPrefix := "/" + ns + "/" + rootID
// Retrieve whether or not we should inline DNSLink.
useInlinedDNSLink := gw.InlineDNSLink
// Does this gateway _handle_ subdomains AND this path?
if !(gw.UseSubdomains && hasPrefix(pathPrefix, gw.Paths...)) {
// If not, resource does not exist, return 404
http.NotFound(w, r)
return
}
// Check if rootID is a valid CID
if rootCID, err := cid.Decode(rootID); err == nil {
// Do we need to redirect root CID to a canonical DNS representation?
dnsCID, err := toDNSLabel(rootID, rootCID)
if err != nil {
webError(w, r, &c, err, http.StatusBadRequest)
return
}
if !strings.HasPrefix(r.Host, dnsCID) {
dnsPrefix := "/" + ns + "/" + dnsCID
newURL, err := toSubdomainURL(gwHostname, dnsPrefix+r.URL.Path, r, useInlinedDNSLink, backend)
if err != nil {
webError(w, r, &c, err, http.StatusBadRequest)
return
}
if newURL != "" {
// Redirect to deterministic CID to ensure CID
// always gets the same Origin on the web
http.Redirect(w, r, newURL, http.StatusMovedPermanently)
return
}
}
// Do we need to fix multicodec in PeerID represented as CIDv1?
if isPeerIDNamespace(ns) {
if rootCID.Type() != cid.Libp2pKey {
newURL, err := toSubdomainURL(gwHostname, pathPrefix+r.URL.Path, r, useInlinedDNSLink, backend)
if err != nil {
webError(w, r, &c, err, http.StatusBadRequest)
return
}
if newURL != "" {
// Redirect to CID fixed inside of toSubdomainURL()
http.Redirect(w, r, newURL, http.StatusMovedPermanently)
return
}
}
}
} else { // rootID is not a CID..
// Check if rootID is a single DNS label with an inlined
// DNSLink FQDN a single DNS label. We support this so
// loading DNSLink names over TLS "just works" on public
// HTTP gateways.
//
// Rationale for doing this can be found under "Option C"
// at: https://github.com/ipfs/in-web-browsers/issues/169
//
// TLDR is:
// https://dweb.link/ipns/my.v-long.example.com
// can be loaded from a subdomain gateway with a wildcard
// TLS cert if represented as a single DNS label:
// https://my-v--long-example-com.ipns.dweb.link
if ns == "ipns" && !strings.Contains(rootID, ".") && strings.Contains(rootID, "-") {
// If there are no '.' but '-' is present in rootID, we most
// likely have an inlined DNSLink (like my-v--long-example-com)
// We un-inline and check for DNSLink presence on domain with '.'
// first to minimize the amount of DNS lookups:
// my-v--long-example-com → my.v-long.example.com
dnslinkFQDN := UninlineDNSLink(rootID)
// Does _dnslink.my.v-long.example.com exist?
if hasDNSLinkRecord(r.Context(), backend, dnslinkFQDN) {
// Un-inlined DNS name has a valid DNSLink record.
// Update path prefix to use un-inlined FQDN in gateway processing.
pathPrefix = "/ipns/" + dnslinkFQDN // → /ipns/my.v-long.example.com
} else if !hasDNSLinkRecord(r.Context(), backend, rootID) {
// Inspected _dnslink.my-v--long-example-com as a
// fallback, but it had no DNSLink record either.
// At this point it is more likely the un-inlined
// dnslinkFQDN is what the end user wanted to load, so
// we switch to that. This ensures the error message
// about missing DNSLink will use the un-inlined FQDN,
// and not the inlined one.
pathPrefix = "/ipns/" + dnslinkFQDN
}
}
}
// Rewrite the path to not use subdomains
r.URL.Path = pathPrefix + r.URL.Path
// Serve path request
next.ServeHTTP(w, withSubdomainContext(r, gwHostname))
return
}
// We don't have a known gateway. Fallback on DNSLink lookup
// Wildcard HTTP Host check:
// 1. is wildcard DNSLink enabled (Gateway.NoDNSLink=false)?
// 2. does Host header include a fully qualified domain name (FQDN)?
// 3. does DNSLink record exist in DNS?
if !c.NoDNSLink && hasDNSLinkRecord(r.Context(), backend, host) {
// rewrite path and handle as DNSLink
r.URL.Path = "/ipns/" + stripPort(host) + r.URL.Path
next.ServeHTTP(w, withDNSLinkContext(r, host))
return
}
// else, treat it as an old school gateway, I guess.
next.ServeHTTP(w, r)
})
}
// withDNSLinkContext extends the context to include the hostname of the DNSLink
// Gateway (https://specs.ipfs.tech/http-gateways/dnslink-gateway/).
func withDNSLinkContext(r *http.Request, hostname string) *http.Request {
ctx := context.WithValue(r.Context(), DNSLinkHostnameKey, hostname)
return withHostnameContext(r.WithContext(ctx), hostname)
}
// withSubdomainContext extends the context to include the hostname of the
// Subdomain Gateway (https://specs.ipfs.tech/http-gateways/subdomain-gateway/).
func withSubdomainContext(r *http.Request, hostname string) *http.Request {
ctx := context.WithValue(r.Context(), SubdomainHostnameKey, hostname)
return withHostnameContext(r.WithContext(ctx), hostname)
}
// withHostnameContext extends the context to include the canonical gateway root,
// which can be a Subdomain Gateway, a DNSLink Gateway, or just a regular gateway.
func withHostnameContext(r *http.Request, hostname string) *http.Request {
ctx := context.WithValue(r.Context(), GatewayHostnameKey, hostname)
return r.WithContext(ctx)
}
// isDomainNameAndNotPeerID returns bool if string looks like a valid DNS name AND is not a PeerID
func isDomainNameAndNotPeerID(hostname string) bool {
if len(hostname) == 0 {
return false
}
if _, err := peer.Decode(hostname); err == nil {
return false
}
_, ok := dns.IsDomainName(hostname)
return ok
}
// hasDNSLinkRecord returns if a DNS TXT record exists for the provided host.
func hasDNSLinkRecord(ctx context.Context, backend IPFSBackend, host string) bool {
dnslinkName := stripPort(host)
if !isDomainNameAndNotPeerID(dnslinkName) {
return false
}
_, err := backend.GetDNSLinkRecord(ctx, dnslinkName)
return err == nil
}
func isSubdomainNamespace(ns string) bool {
switch ns {
case "ipfs", "ipns", "p2p", "ipld":
// Note: 'p2p' and 'ipld' is only kept here for compatibility with Kubo.
return true
default:
return false
}
}
func isPeerIDNamespace(ns string) bool {
switch ns {
case "ipns", "p2p":
// Note: 'p2p' and 'ipld' is only kept here for compatibility with Kubo.
return true
default:
return false
}
}
// Label's max length in DNS (https://tools.ietf.org/html/rfc1034#page-7)
const dnsLabelMaxLength int = 63
// Converts a CID to DNS-safe representation that fits in 63 characters
func toDNSLabel(rootID string, rootCID cid.Cid) (dnsCID string, err error) {
// Return as-is if things fit
if len(rootID) <= dnsLabelMaxLength {
return rootID, nil
}
// Convert to Base36 and see if that helped
rootID, err = cid.NewCidV1(rootCID.Type(), rootCID.Hash()).StringOfBase(mbase.Base36)
if err != nil {
return "", err
}
if len(rootID) <= dnsLabelMaxLength {
return rootID, nil
}
// Can't win with DNS at this point, return error
return "", fmt.Errorf("CID incompatible with DNS label length limit of 63: %s", rootID)
}
// Returns true if HTTP request involves TLS certificate.
// See https://github.com/ipfs/in-web-browsers/issues/169 to understand how it
// impacts DNSLink websites on public gateways.
func isHTTPSRequest(r *http.Request) bool {
// X-Forwarded-Proto if added by a reverse proxy
// https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Forwarded-Proto
xproto := r.Header.Get("X-Forwarded-Proto")
// Is request a native TLS (not used atm, but future-proofing)
// or a proxied HTTPS (eg. Kubo behind nginx at a public gw)?
return r.URL.Scheme == "https" || xproto == "https"
}
// Converts a FQDN to DNS-safe representation that fits in 63 characters:
// my.v-long.example.com → my-v--long-example-com
// InlineDNSLink implements specification from https://specs.ipfs.tech/http-gateways/subdomain-gateway/#host-request-header
func InlineDNSLink(fqdn string) (dnsLabel string, err error) {
/* What follows is an optimized version this three-liner:
dnsLabel = strings.ReplaceAll(fqdn, "-", "--")
dnsLabel = strings.ReplaceAll(dnsLabel, ".", "-")
if len(dnsLabel) > dnsLabelMaxLength {
return "", fmt.Errorf("DNSLink representation incompatible with DNS label length limit of 63: %s", dnsLabel)
}
return dnsLabel, nil
*/
result := make([]byte, 0, len(fqdn))
for i := 0; i < len(fqdn); i++ {
char := fqdn[i]
if char == '-' {
result = append(result, '-', '-')
} else if char == '.' {
result = append(result, '-')
} else {
result = append(result, char)
}
}
if len(result) > dnsLabelMaxLength {
return "", fmt.Errorf("inlined DNSLink incompatible with DNS label length limit of 63: %q", result)
}
return string(result), nil
}
// Converts a DNS-safe representation of DNSLink FQDN to real FQDN:
// my-v--long-example-com → my.v-long.example.com
// UninlineDNSLink implements specification from https://specs.ipfs.tech/http-gateways/subdomain-gateway/#host-request-header
func UninlineDNSLink(dnsLabel string) (fqdn string) {
/* What follows is an optimized version this three-liner:
fqdn = strings.ReplaceAll(dnsLabel, "--", "@") // @ placeholder is unused in DNS labels
fqdn = strings.ReplaceAll(fqdn, "-", ".")
fqdn = strings.ReplaceAll(fqdn, "@", "-")
return fqdn
*/
result := make([]byte, 0, len(dnsLabel))
for i := 0; i < len(dnsLabel); i++ {
if dnsLabel[i] == '-' {
if i+1 < len(dnsLabel) && dnsLabel[i+1] == '-' {
// Handle '--' by appending a single '-'
result = append(result, '-')
i++
} else {
// Handle single '-' by appending '.'
result = append(result, '.')
}
} else {
result = append(result, dnsLabel[i])
}
}
return string(result)
}
// Converts a hostname/path to a subdomain-based URL, if applicable.
func toSubdomainURL(hostname, path string, r *http.Request, inlineDNSLink bool, backend IPFSBackend) (redirURL string, err error) {
var ns, rootID, rest string
parts := strings.SplitN(path, "/", 4)
isHTTPS := isHTTPSRequest(r)
switch len(parts) {
case 4:
rest = parts[3]
fallthrough
case 3:
ns = parts[1]
rootID = parts[2]
default:
return "", nil
}
if !isSubdomainNamespace(ns) {
return "", nil
}
// Normalize problematic PeerIDs (eg. ed25519+identity) to CID representation
if isPeerIDNamespace(ns) && !isDomainNameAndNotPeerID(rootID) {
peerID, err := peer.Decode(rootID)
// Note: PeerID CIDv1 with protobuf multicodec will fail, but we fix it
// in the next block
if err == nil {
rootID = peer.ToCid(peerID).String()
}
}
// If rootID is a CID, ensure it uses DNS-friendly text representation
if rootCID, err := cid.Decode(rootID); err == nil {
multicodec := rootCID.Type()
var base mbase.Encoding = mbase.Base32
// Normalizations specific to /ipns/{libp2p-key}
if isPeerIDNamespace(ns) {
// Using Base36 for /ipns/ for consistency
// Context: https://github.com/ipfs/kubo/pull/7441#discussion_r452372828
base = mbase.Base36
// PeerIDs represented as CIDv1 are expected to have libp2p-key
// multicodec (https://github.com/libp2p/specs/pull/209).
// We ease the transition by fixing multicodec on the fly:
// https://github.com/ipfs/kubo/issues/5287#issuecomment-492163929
if multicodec != cid.Libp2pKey {
multicodec = cid.Libp2pKey
}
}
// Ensure CID text representation used in subdomain is compatible
// with the way DNS and URIs are implemented in user agents.
//
// 1. Switch to CIDv1 and enable case-insensitive Base encoding
// to avoid issues when user agent force-lowercases the hostname
// before making the request
// (https://github.com/ipfs/in-web-browsers/issues/89)
rootCID = cid.NewCidV1(multicodec, rootCID.Hash())
rootID, err = rootCID.StringOfBase(base)
if err != nil {
return "", err
}
// 2. Make sure CID fits in a DNS label, adjust encoding if needed
// (https://github.com/ipfs/kubo/issues/7318)
rootID, err = toDNSLabel(rootID, rootCID)
if err != nil {
return "", err
}
} else { // rootID is not a CID
// If rootID is an inlined notation of a FQDN with DNSLink we need to
// un-inline it first, to make it work in contexts where subdomain
// identifier is used on a path (/ipns/my-v--long-example-com)
// e.g. when ipfs-companion extension passes value from subdomain gateway
// for further normalization: https://github.com/ipfs/ipfs-companion/issues/1278#issuecomment-1724550623
if ns == "ipns" && !strings.Contains(rootID, ".") && strings.Contains(rootID, "-") {
dnsLinkFqdn := UninlineDNSLink(rootID) // my-v--long-example-com → my.v-long.example.com
if hasDNSLinkRecord(r.Context(), backend, dnsLinkFqdn) {
// update path prefix to use real FQDN with DNSLink
rootID = dnsLinkFqdn
}
}
if (inlineDNSLink || isHTTPS) && ns == "ipns" && strings.Contains(rootID, ".") {
// If rootID is a FQDN with DNSLink we need to inline it to make it TLS-safe
// representation that fits in a single DNS label. We support this so
// loading DNSLink names over TLS "just works" on public HTTP gateways
// that pass 'https' in X-Forwarded-Proto to Kubo.
//
// Rationale can be found under "Option C"
// at: https://github.com/ipfs/in-web-browsers/issues/169
//
// TLDR is:
// /ipns/my.v-long.example.com
// can be loaded from a subdomain gateway with a wildcard TLS cert if
// represented as a single DNS label:
// https://my-v--long-example-com.ipns.dweb.link
if hasDNSLinkRecord(r.Context(), backend, rootID) {
// my.v-long.example.com → my-v--long-example-com
dnsLabel, err := InlineDNSLink(rootID)
if err != nil {
return "", err
}
// update path prefix to use inlined FQDN with DNSLink as a single DNS label
rootID = dnsLabel
}
} else if ns == "ipfs" {
// If rootID is not a CID, but it's within the IPFS namespace, let it
// be handled by the regular handler.
return "", nil
}
}
if rootID == "" {
// If the rootID is empty, then we cannot produce a redirect URL.
return "", nil
}
// Produce subdomain redirect URL in a way that preserves any
// percent-encoded paths and query parameters
u, err := url.Parse(fmt.Sprintf("http://%s.%s.%s/", rootID, ns, hostname))
if err != nil {
return "", err
}
u.RawFragment = r.URL.RawFragment
u.RawQuery = r.URL.RawQuery
if rest != "" {
u.Path = rest
}
if isHTTPS {
u.Scheme = "https"
}
return u.String(), nil
}
func hasPrefix(path string, prefixes ...string) bool {
for _, prefix := range prefixes {
// Assume people are creative with trailing slashes in Gateway config
p := strings.TrimSuffix(prefix, "/")
// Support for both /version and /ipfs/$cid
if p == path || strings.HasPrefix(path, p+"/") {
return true
}
}
return false
}
func stripPort(hostname string) string {
host, _, err := net.SplitHostPort(hostname)
if err == nil {
return host
}
return hostname
}
type hostnameGateways struct {
exact map[string]*PublicGateway
wildcard map[*regexp.Regexp]*PublicGateway
}
// prepareHostnameGateways converts the user given gateways into an internal format
// split between exact and wildcard-based gateway hostnames.
func prepareHostnameGateways(gateways map[string]*PublicGateway) *hostnameGateways {
h := &hostnameGateways{
exact: map[string]*PublicGateway{},
wildcard: map[*regexp.Regexp]*PublicGateway{},
}
for hostname, gw := range gateways {
if strings.Contains(hostname, "*") {
// from *.domain.tld, construct a regexp that match any direct subdomain
// of .domain.tld.
//
// Regexp will be in the form of ^[^.]+\.domain.tld(?::\d+)?$
escaped := strings.ReplaceAll(hostname, ".", `\.`)
regexed := strings.ReplaceAll(escaped, "*", "[^.]+")
re, err := regexp.Compile(fmt.Sprintf(`^%s(?::\d+)?$`, regexed))
if err != nil {
log.Warn("invalid wildcard gateway hostname \"%s\"", hostname)
}
h.wildcard[re] = gw
} else {
h.exact[hostname] = gw
}
}
return h
}
// isKnownHostname checks the given hostname gateways and returns a matching
// specification with graceful fallback to version without port.
func (gws *hostnameGateways) isKnownHostname(hostname string) (gw *PublicGateway, ok bool) {
// Try hostname (host+optional port - value from Host header as-is)
if gw, ok := gws.exact[hostname]; ok {
return gw, ok
}
// Also test without port
if gw, ok = gws.exact[stripPort(hostname)]; ok {
return gw, ok
}
// Wildcard support. Test both with and without port.
for re, spec := range gws.wildcard {
if re.MatchString(hostname) {
return spec, true
}
}
return nil, false
}
// knownSubdomainDetails parses the Host header and looks for a known gateway matching
// the subdomain host. If found, returns a Specification and the subdomain components
// extracted from Host header: {rootID}.{ns}.{gwHostname}.
// Note: hostname is host + optional port
func (gws *hostnameGateways) knownSubdomainDetails(hostname string) (gw *PublicGateway, gwHostname, ns, rootID string, ok bool) {
labels := strings.Split(hostname, ".")
// Look for FQDN of a known gateway hostname.
// Example: given "dist.ipfs.tech.ipns.dweb.link":
// 1. Lookup "link" TLD in knownGateways: negative
// 2. Lookup "dweb.link" in knownGateways: positive
//
// Stops when we have 2 or fewer labels left as we need at least a
// rootId and a namespace.
for i := len(labels) - 1; i >= 2; i-- {
fqdn := strings.Join(labels[i:], ".")
gw, ok := gws.isKnownHostname(fqdn)
if !ok {
continue
}
ns := labels[i-1]
if !isSubdomainNamespace(ns) {
continue
}
// Merge remaining labels (could be a FQDN with DNSLink)
rootID := strings.Join(labels[:i-1], ".")
return gw, fqdn, ns, rootID, true
}
// no match
return nil, "", "", "", false
}