/
hostname.go
594 lines (523 loc) · 19.3 KB
/
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"
)
// Specification is the specification of an IPFS Public Gateway.
type Specification struct {
// Paths is explicit list of path prefixes that should be handled by
// this gateway. Example: `["/ipfs", "/ipns"]`
// Useful if you only want to support immutable `/ipfs`.
Paths []string
// UseSubdomains indicates whether or not this gateway uses subdomains
// for IPFS resources instead of paths. That is: http://CID.ipfs.GATEWAY/...
//
// If this flag is set, any /ipns/$id and/or /ipfs/$id paths in Paths
// will be permanently redirected to http://$id.[ipns|ipfs].$gateway/.
//
// We do not support using both paths and subdomains for a single domain
// for security reasons (Origin isolation).
UseSubdomains bool
// NoDNSLink configures this gateway to _not_ resolve DNSLink for the
// specific FQDN provided in `Host` HTTP header. Useful when you want to
// explicitly allow or refuse hosting a single hostname. To refuse all
// DNSLinks in `Host` processing, pass noDNSLink to `WithHostname` instead.
// This flag overrides the global one.
NoDNSLink bool
// InlineDNSLink configures this gateway to always inline DNSLink names
// (FQDN) into a single DNS label in order to interop with wildcard TLS certs
// and Origin per CID isolation provided by rules like https://publicsuffix.org
// This should be set to true if you use HTTPS.
InlineDNSLink bool
}
// WithHostname is a middleware that can wrap an http.Handler in order to parse the
// Host header and translating it to the content path. This is useful for Subdomain
// and DNSLink gateways.
//
// publicGateways configures the behavior of known public gateways. Each key is a
// fully qualified domain name (FQDN).
//
// noDNSLink configures the gateway to _not_ perform DNS TXT record lookups in
// response to requests with values in `Host` HTTP header. This flag can be overridden
// per FQDN in publicGateways.
func WithHostname(next http.Handler, api IPFSBackend, publicGateways map[string]*Specification, noDNSLink bool) http.HandlerFunc {
gateways := prepareHostnameGateways(publicGateways)
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
defer panicHandler(w)
// 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, api)
if err != nil {
http.Error(w, err.Error(), http.StatusBadRequest)
return
}
if newURL != "" {
// Set "Location" header with redirect destination.
// It is ignored by curl in default mode, but will
// be respected by user agents that follow
// redirects by default, namely web browsers
w.Header().Set("Location", newURL)
// Note: we continue regular gateway processing:
// HTTP Status Code http.StatusMovedPermanently
// will be set later, in statusResponseWriter
}
}
// Not a subdomain resource, continue with path processing
// Example: 127.0.0.1:8080/ipfs/{CID}, ipfs.io/ipfs/{CID} etc
next.ServeHTTP(w, r)
return
}
// Not a whitelisted path
// Try DNSLink, if it was not explicitly disabled for the hostname
if !gw.NoDNSLink && hasDNSLinkRecord(r.Context(), api, host) {
// rewrite path and handle as DNSLink
r.URL.Path = "/ipns/" + stripPort(host) + r.URL.Path
next.ServeHTTP(w, withHostnameContext(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 {
http.Error(w, err.Error(), http.StatusBadRequest)
return
}
if !strings.HasPrefix(r.Host, dnsCID) {
dnsPrefix := "/" + ns + "/" + dnsCID
newURL, err := toSubdomainURL(gwHostname, dnsPrefix+r.URL.Path, r, useInlinedDNSLink, api)
if err != nil {
http.Error(w, err.Error(), 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, api)
if err != nil {
http.Error(w, err.Error(), 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, ".") {
// if there is no TXT recordfor rootID
if !hasDNSLinkRecord(r.Context(), api, rootID) {
// my-v--long-example-com → my.v-long.example.com
dnslinkFQDN := toDNSLinkFQDN(rootID)
if hasDNSLinkRecord(r.Context(), api, dnslinkFQDN) {
// update path prefix to use real FQDN with DNSLink
pathPrefix = "/ipns/" + dnslinkFQDN
}
}
}
}
// Rewrite the path to not use subdomains
r.URL.Path = pathPrefix + r.URL.Path
// Serve path request
next.ServeHTTP(w, withHostnameContext(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 !noDNSLink && hasDNSLinkRecord(r.Context(), api, host) {
// rewrite path and handle as DNSLink
r.URL.Path = "/ipns/" + stripPort(host) + r.URL.Path
ctx := context.WithValue(r.Context(), DNSLinkHostnameKey, host)
next.ServeHTTP(w, withHostnameContext(r.WithContext(ctx), host))
return
}
// else, treat it as an old school gateway, I guess.
next.ServeHTTP(w, r)
})
}
// Extends request context to include hostname of a canonical gateway root
// (subdomain root or dnslink fqdn)
func withHostnameContext(r *http.Request, hostname string) *http.Request {
// This is required for links on directory listing pages to work correctly
// on subdomain and dnslink gateways. While DNSlink could read value from
// Host header, subdomain gateways have more comples rules (knownSubdomainDetails)
// More: https://github.com/ipfs/dir-index-html/issues/42
// nolint: staticcheck // non-backward compatible change
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, api IPFSBackend, host string) bool {
dnslinkName := stripPort(host)
if !isDomainNameAndNotPeerID(dnslinkName) {
return false
}
_, err := api.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. go-ipfs 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
func toDNSLinkDNSLabel(fqdn string) (dnsLabel string, err error) {
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
}
// Converts a DNS-safe representation of DNSLink FQDN to real FQDN:
// my-v--long-example-com → my.v-long.example.com
func toDNSLinkFQDN(dnsLabel string) (fqdn string) {
fqdn = strings.ReplaceAll(dnsLabel, "--", "@") // @ placeholder is unused in DNS labels
fqdn = strings.ReplaceAll(fqdn, "-", ".")
fqdn = strings.ReplaceAll(fqdn, "@", "-")
return fqdn
}
// Converts a hostname/path to a subdomain-based URL, if applicable.
func toSubdomainURL(hostname, path string, r *http.Request, inlineDNSLink bool, api IPFSBackend) (redirURL string, err error) {
var scheme, ns, rootID, rest string
query := r.URL.RawQuery
parts := strings.SplitN(path, "/", 4)
isHTTPS := isHTTPSRequest(r)
safeRedirectURL := func(in string) (out string, err error) {
safeURI, err := url.ParseRequestURI(in)
if err != nil {
return "", err
}
return safeURI.String(), nil
}
if isHTTPS {
scheme = "https:"
} else {
scheme = "http:"
}
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
}
// add prefix if query is present
if query != "" {
query = "?" + query
}
// 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
// Check if rootID is a FQDN with DNSLink and convert it to 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 go-ipfs.
//
// 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 (inlineDNSLink || isHTTPS) && ns == "ipns" && strings.Contains(rootID, ".") {
if hasDNSLinkRecord(r.Context(), api, rootID) {
// my.v-long.example.com → my-v--long-example-com
dnsLabel, err := toDNSLinkDNSLabel(rootID)
if err != nil {
return "", err
}
// update path prefix to use real FQDN with DNSLink
rootID = dnsLabel
}
}
}
return safeRedirectURL(fmt.Sprintf(
"%s//%s.%s.%s/%s%s",
scheme,
rootID,
ns,
hostname,
rest,
query,
))
}
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/$cid
if p == path || strings.HasPrefix(path, p+"/") {
return true
}
}
return false
}
func stripPort(hostname string) string {
host, _, err := net.SplitHostPort(hostname)
if err == nil {
return host
}
return hostname
}
type hostnameGateways struct {
exact map[string]*Specification
wildcard map[*regexp.Regexp]*Specification
}
// prepareHostnameGateways converts the user given gateways into an internal format
// split between exact and wildcard-based gateway hostnames.
func prepareHostnameGateways(gateways map[string]*Specification) *hostnameGateways {
h := &hostnameGateways{
exact: map[string]*Specification{},
wildcard: map[*regexp.Regexp]*Specification{},
}
for hostname, gw := range gateways {
if strings.Contains(hostname, "*") {
// from *.domain.tld, construct a regexp that match any direct subdomain
// of .domain.tld.
//
// Regexp will be in the form of ^[^.]+\.domain.tld(?::\d+)?$
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 *Specification, 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 *Specification, 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
}