From 5b92a7ba5a18d6371e52a9e6dd3858b33a9f4e01 Mon Sep 17 00:00:00 2001 From: Bryan Frimin Date: Tue, 30 Jun 2026 18:27:39 +0200 Subject: [PATCH] Allow ephemeral ports for loopback redirect URIs Native OAuth clients such as Claude Code publish loopback redirect URIs without a port (http://localhost/callback) and pick an ephemeral port at request time, as described in RFC 8252 section 7.3. The authorize flow matched the requested redirect URI against the registered set with an exact string comparison, so http://localhost:3118/callback was rejected with invalid_redirect_uri even for a trusted, allow-listed client. Make OAuth2Client.IsRedirectURIAllowed the single source of truth for redirect matching: it keeps exact matching and adds loopback-aware matching that ignores the port when scheme, host, path, and query agree. The redundant document-level check and its duplicate loopback helper in the CIMD resolver are removed, so both the registered-client and CIMD paths now rely on one matcher. Also add a pkg/netx package for the loopback helper. Signed-off-by: Bryan Frimin --- pkg/coredata/oauth2_client.go | 39 ++++++++- pkg/coredata/oauth2_client_test.go | 96 ++++++++++++++++++++++ pkg/iam/oauth2/cimd.go | 50 +---------- pkg/iam/oauth2/cimd_test.go | 24 ------ pkg/iam/oauth2/service.go | 10 +-- pkg/{net/net.go => netx/netx.go} | 2 +- pkg/{net/net_test.go => netx/netx_test.go} | 6 +- 7 files changed, 144 insertions(+), 83 deletions(-) create mode 100644 pkg/coredata/oauth2_client_test.go rename pkg/{net/net.go => netx/netx.go} (98%) rename pkg/{net/net_test.go => netx/netx_test.go} (96%) diff --git a/pkg/coredata/oauth2_client.go b/pkg/coredata/oauth2_client.go index f0bcae8cb..0bf40d374 100644 --- a/pkg/coredata/oauth2_client.go +++ b/pkg/coredata/oauth2_client.go @@ -19,6 +19,7 @@ import ( "errors" "fmt" "maps" + "net/url" "slices" "time" @@ -26,6 +27,7 @@ import ( "go.gearno.de/kit/pg" "go.probo.inc/probo/pkg/gid" "go.probo.inc/probo/pkg/iam/policy" + "go.probo.inc/probo/pkg/netx" "go.probo.inc/probo/pkg/page" "go.probo.inc/probo/pkg/uri" ) @@ -54,7 +56,42 @@ type ( ) func (c *OAuth2Client) IsRedirectURIAllowed(rawURI string) bool { - return slices.Contains(c.RedirectURIs, uri.URI(rawURI)) + if slices.Contains(c.RedirectURIs, uri.URI(rawURI)) { + return true + } + + // RFC 8252 ยง7.3: native apps using a loopback redirect URI choose an + // ephemeral port at request time, so the port must be ignored when + // matching against the registered loopback redirect URIs. + requested, err := url.Parse(rawURI) + if err != nil || !netx.IsLoopback(requested.Hostname()) { + return false + } + + for _, registered := range c.RedirectURIs { + candidate, err := url.Parse(registered.String()) + if err != nil { + continue + } + + if candidate.Scheme != requested.Scheme { + continue + } + + if !netx.IsLoopback(candidate.Hostname()) { + continue + } + + if candidate.Hostname() != requested.Hostname() { + continue + } + + if candidate.Path == requested.Path && candidate.RawQuery == requested.RawQuery { + return true + } + } + + return false } func (c *OAuth2Client) HasGrantType(grantType OAuth2GrantType) bool { diff --git a/pkg/coredata/oauth2_client_test.go b/pkg/coredata/oauth2_client_test.go new file mode 100644 index 000000000..303a0d632 --- /dev/null +++ b/pkg/coredata/oauth2_client_test.go @@ -0,0 +1,96 @@ +// Copyright (c) 2026 Probo Inc . +// +// Permission to use, copy, modify, and/or distribute this software for any +// purpose with or without fee is hereby granted, provided that the above +// copyright notice and this permission notice appear in all copies. +// +// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH +// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY +// AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, +// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM +// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR +// OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR +// PERFORMANCE OF THIS SOFTWARE. + +package coredata_test + +import ( + "testing" + + "github.com/stretchr/testify/assert" + "go.probo.inc/probo/pkg/coredata" + "go.probo.inc/probo/pkg/uri" +) + +func TestOAuth2Client_IsRedirectURIAllowed(t *testing.T) { + t.Parallel() + + tests := []struct { + name string + registered []uri.URI + requested string + want bool + }{ + { + name: "exact https match", + registered: []uri.URI{"https://chatgpt.com/connector/oauth/callback"}, + requested: "https://chatgpt.com/connector/oauth/callback", + want: true, + }, + { + name: "https mismatch", + registered: []uri.URI{"https://chatgpt.com/connector/oauth/callback"}, + requested: "https://evil.example/callback", + want: false, + }, + { + name: "loopback ignores port when registered without port", + registered: []uri.URI{"http://localhost/callback"}, + requested: "http://localhost:3118/callback", + want: true, + }, + { + name: "loopback ignores port when registered with a different port", + registered: []uri.URI{"http://127.0.0.1:53682/callback"}, + requested: "http://127.0.0.1:8080/callback", + want: true, + }, + { + name: "loopback host must match (localhost vs 127.0.0.1)", + registered: []uri.URI{"http://127.0.0.1/callback"}, + requested: "http://localhost:3118/callback", + want: false, + }, + { + name: "loopback path must match", + registered: []uri.URI{"http://localhost/callback"}, + requested: "http://localhost:3118/other", + want: false, + }, + { + name: "loopback scheme must match", + registered: []uri.URI{"http://localhost/callback"}, + requested: "https://localhost:3118/callback", + want: false, + }, + { + name: "non-loopback host does not get port flexibility", + registered: []uri.URI{"https://app.example.com/callback"}, + requested: "https://app.example.com:8443/callback", + want: false, + }, + } + + for _, tt := range tests { + t.Run( + tt.name, + func(t *testing.T) { + t.Parallel() + + client := &coredata.OAuth2Client{RedirectURIs: tt.registered} + + assert.Equal(t, tt.want, client.IsRedirectURIAllowed(tt.requested)) + }, + ) + } +} diff --git a/pkg/iam/oauth2/cimd.go b/pkg/iam/oauth2/cimd.go index 4b2dd673b..9868d675a 100644 --- a/pkg/iam/oauth2/cimd.go +++ b/pkg/iam/oauth2/cimd.go @@ -33,7 +33,7 @@ import ( "go.probo.inc/probo/pkg/cachecontrol" "go.probo.inc/probo/pkg/coredata" "go.probo.inc/probo/pkg/gid" - "go.probo.inc/probo/pkg/net" + "go.probo.inc/probo/pkg/netx" ) const ( @@ -239,7 +239,7 @@ func validateCIMDRedirectURI(redirectURI string) error { switch parsed.Scheme { case "https": case "http": - if !net.IsLoopback(parsed.Hostname()) { + if !netx.IsLoopback(parsed.Hostname()) { return NewError( ErrInvalidClient, WithDescription("client metadata document contains invalid redirect_uri"), @@ -255,47 +255,6 @@ func validateCIMDRedirectURI(redirectURI string) error { return nil } -func cimdRedirectURIAllowed(doc *ClientMetadataDocument, redirectURI string) bool { - for _, allowed := range doc.RedirectURIs { - if redirectURI == allowed { - return true - } - - if cimdLoopbackRedirectMatches(allowed, redirectURI) { - return true - } - } - - return false -} - -func cimdLoopbackRedirectMatches(registered, requested string) bool { - registeredURL, err := url.Parse(registered) - if err != nil { - return false - } - - requestedURL, err := url.Parse(requested) - if err != nil { - return false - } - - if registeredURL.Scheme != requestedURL.Scheme { - return false - } - - if !net.IsLoopback(registeredURL.Hostname()) || !net.IsLoopback(requestedURL.Hostname()) { - return false - } - - if registeredURL.Hostname() != requestedURL.Hostname() { - return false - } - - return registeredURL.Path == requestedURL.Path && - registeredURL.RawQuery == requestedURL.RawQuery -} - func (f *cimdFetcher) loadCache(clientIDURL string) (*ClientMetadataDocument, bool) { raw, ok := f.cache.Load(clientIDURL) if !ok { @@ -338,7 +297,6 @@ func (s *Service) resolveClient( ctx context.Context, tx pg.Tx, clientIDRaw string, - redirectURI string, ) (*coredata.OAuth2Client, error) { if clientID, err := gid.ParseGID(clientIDRaw); err == nil { if tx != nil { @@ -373,10 +331,6 @@ func (s *Service) resolveClient( return nil, err } - if redirectURI != "" && !cimdRedirectURIAllowed(doc, redirectURI) { - return nil, ErrInvalidRedirectURI - } - client, err := s.upsertCIMDClient(ctx, tx, clientIDRaw, doc) if err != nil { return nil, err diff --git a/pkg/iam/oauth2/cimd_test.go b/pkg/iam/oauth2/cimd_test.go index 3b8ba1a07..3847d6d60 100644 --- a/pkg/iam/oauth2/cimd_test.go +++ b/pkg/iam/oauth2/cimd_test.go @@ -141,30 +141,6 @@ func TestValidateClientMetadataDocument(t *testing.T) { ) } -func TestCIMDRedirectURIAllowed(t *testing.T) { - t.Parallel() - - doc := &ClientMetadataDocument{ - RedirectURIs: []string{ - "https://chatgpt.com/connector/oauth/callback", - "http://127.0.0.1:53682/callback", - }, - } - - assert.True( - t, - cimdRedirectURIAllowed(doc, "https://chatgpt.com/connector/oauth/callback"), - ) - assert.True( - t, - cimdRedirectURIAllowed(doc, "http://127.0.0.1:8080/callback"), - ) - assert.False( - t, - cimdRedirectURIAllowed(doc, "https://evil.example/callback"), - ) -} - func TestCIMDFetcherFetch(t *testing.T) { t.Parallel() diff --git a/pkg/iam/oauth2/service.go b/pkg/iam/oauth2/service.go index d7262d254..77ee03662 100644 --- a/pkg/iam/oauth2/service.go +++ b/pkg/iam/oauth2/service.go @@ -32,7 +32,7 @@ import ( "go.probo.inc/probo/pkg/crypto/rand" "go.probo.inc/probo/pkg/gid" "go.probo.inc/probo/pkg/iam/oauth2scope" - "go.probo.inc/probo/pkg/net" + "go.probo.inc/probo/pkg/netx" "go.probo.inc/probo/pkg/page" "go.probo.inc/probo/pkg/uri" ) @@ -1060,7 +1060,7 @@ func (s *Service) RegisterClient( } case coredata.OAuth2ClientVisibilityPrivate: if parsed.Scheme == "http" { - if !net.IsLoopback(parsed.Hostname()) { + if !netx.IsLoopback(parsed.Hostname()) { return gid.Nil, "", NewError( @@ -1433,13 +1433,11 @@ func (s *Service) Authorize( if err := s.pg.WithTx( ctx, func(ctx context.Context, tx pg.Tx) error { - client, err := s.resolveClient(ctx, tx, req.ClientIDRaw, req.RedirectURI) + client, err := s.resolveClient(ctx, tx, req.ClientIDRaw) if err != nil { return err } - fmt.Printf("X: %+v\n", client) - if !client.IsRedirectURIAllowed(req.RedirectURI) { return ErrInvalidRedirectURI } @@ -1738,7 +1736,7 @@ func (s *Service) AuthenticateClient( clientIDRaw string, clientSecret string, ) (*coredata.OAuth2Client, error) { - client, err := s.resolveClient(ctx, nil, clientIDRaw, "") + client, err := s.resolveClient(ctx, nil, clientIDRaw) if err != nil { return nil, err } diff --git a/pkg/net/net.go b/pkg/netx/netx.go similarity index 98% rename from pkg/net/net.go rename to pkg/netx/netx.go index 20524d0b7..7e7539c53 100644 --- a/pkg/net/net.go +++ b/pkg/netx/netx.go @@ -12,7 +12,7 @@ // OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR // PERFORMANCE OF THIS SOFTWARE. -package net +package netx import "net" diff --git a/pkg/net/net_test.go b/pkg/netx/netx_test.go similarity index 96% rename from pkg/net/net_test.go rename to pkg/netx/netx_test.go index 5f0850e9f..28d5fd9eb 100644 --- a/pkg/net/net_test.go +++ b/pkg/netx/netx_test.go @@ -12,13 +12,13 @@ // OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR // PERFORMANCE OF THIS SOFTWARE. -package net_test +package netx_test import ( "testing" "github.com/stretchr/testify/assert" - "go.probo.inc/probo/pkg/net" + "go.probo.inc/probo/pkg/netx" ) func TestIsLoopback(t *testing.T) { @@ -77,7 +77,7 @@ func TestIsLoopback(t *testing.T) { func(t *testing.T) { t.Parallel() - assert.Equal(t, tt.want, net.IsLoopback(tt.host)) + assert.Equal(t, tt.want, netx.IsLoopback(tt.host)) }, ) }