style(sidecar): gofmt hmac_test.go

Align comment spacing flagged by the fast-gate gofmt check.

extension/transport/sidecar/interceptor.go

@@ -4,11 +4,12 @@
 //go:build authsidecar
 
 // Package sidecar provides a transport interceptor for the auth sidecar
-// proxy mode. When LARKSUITE_CLI_AUTH_PROXY is set (an HTTP URL), all
-// outgoing requests are rewritten to the sidecar address. The interceptor
-// strips placeholder credentials, injects proxy headers, and signs each
-// request with HMAC-SHA256. No custom DialContext is needed — Go's
-// standard http.Transport connects to the sidecar via plain HTTP.
+// proxy mode. When LARKSUITE_CLI_AUTH_PROXY is set (an http:// or https://
+// URL), all outgoing requests are rewritten to the sidecar address. The
+// interceptor strips placeholder credentials, injects proxy headers, and
+// signs each request with HMAC-SHA256. No custom DialContext is needed —
+// Go's standard http.Transport connects to the sidecar via HTTP, or via
+// HTTPS (TLS) when the sidecar address is an https:// URL.
 package sidecar
 
 import (
@@ -46,15 +47,17 @@ func (p *Provider) ResolveInterceptor(ctx context.Context) transport.Interceptor
 	}
 	key := os.Getenv(envvars.CliProxyKey)
 	return &Interceptor{
-		key:         []byte(key),
-		sidecarHost: sidecar.ProxyHost(proxyAddr),
+		key:           []byte(key),
+		sidecarHost:   sidecar.ProxyHost(proxyAddr),
+		sidecarScheme: sidecar.ProxyScheme(proxyAddr),
 	}
 }
 
 // Interceptor rewrites requests for the sidecar proxy.
 type Interceptor struct {
-	key         []byte // HMAC signing key
-	sidecarHost string // sidecar host:port for URL rewriting
+	key           []byte // HMAC signing key
+	sidecarHost   string // sidecar host[:port] for URL rewriting
+	sidecarScheme string // "http" (same-host) or "https" (remote TLS sidecar)
 }
 
 // PreRoundTrip rewrites the request for sidecar routing when it carries a
@@ -130,8 +133,13 @@ func (i *Interceptor) PreRoundTrip(req *http.Request) func(resp *http.Response,
 	req.Header.Set(sidecar.HeaderProxyTimestamp, ts)
 	req.Header.Set(sidecar.HeaderProxySignature, sig)
 
-	// 5. Rewrite URL to route through sidecar
-	req.URL.Scheme = "http"
+	// 5. Rewrite URL to route through sidecar. Scheme follows the configured
+	// proxy address: https for a remote (TLS) sidecar, http for a same-host one.
+	scheme := i.sidecarScheme
+	if scheme == "" {
+		scheme = "http"
+	}
+	req.URL.Scheme = scheme
 	req.URL.Host = i.sidecarHost
 
 	return nil // no post-hook needed

extension/transport/sidecar/interceptor_test.go

@@ -7,11 +7,13 @@ package sidecar
 
 import (
 	"bytes"
+	"context"
 	"errors"
 	"io"
 	"net/http"
 	"testing"
 
+	"github.com/larksuite/cli/internal/envvars"
 	"github.com/larksuite/cli/sidecar"
 )
 
@@ -97,6 +99,54 @@ func TestInterceptor_PreRoundTrip(t *testing.T) {
 	}
 }
 
+// TestInterceptor_PreRoundTrip_HTTPS verifies that a remote (TLS) sidecar
+// rewrites the request to https://<remote-host>, while still preserving the
+// original target and signing the request.
+func TestInterceptor_PreRoundTrip_HTTPS(t *testing.T) {
+	key := []byte("test-key-for-hmac-signing-32byte!")
+	interceptor := &Interceptor{key: key, sidecarHost: "sidecar.mycorp.com", sidecarScheme: "https"}
+
+	req, _ := http.NewRequest("GET", "https://open.feishu.cn/open-apis/im/v1/chats", nil)
+	req.Header.Set("Authorization", "Bearer "+sidecar.SentinelUAT)
+
+	interceptor.PreRoundTrip(req)
+
+	if req.URL.Scheme != "https" {
+		t.Errorf("scheme = %q, want %q", req.URL.Scheme, "https")
+	}
+	if req.URL.Host != "sidecar.mycorp.com" {
+		t.Errorf("host = %q, want %q", req.URL.Host, "sidecar.mycorp.com")
+	}
+	// Original target still preserved for the sidecar to forward upstream.
+	if target := req.Header.Get(sidecar.HeaderProxyTarget); target != "https://open.feishu.cn" {
+		t.Errorf("target = %q, want %q", target, "https://open.feishu.cn")
+	}
+	// Request is still signed.
+	if sig := req.Header.Get(sidecar.HeaderProxySignature); sig == "" {
+		t.Error("signature header should be set")
+	}
+}
+
+// TestResolveInterceptor_HTTPSScheme pins the end-to-end env→scheme path: a
+// (mixed-case) https proxy address must produce an interceptor that rewrites to
+// https, never silently downgrading a remote sidecar to plaintext http.
+func TestResolveInterceptor_HTTPSScheme(t *testing.T) {
+	t.Setenv(envvars.CliAuthProxy, "HTTPS://sidecar.mycorp.com") // uppercase on purpose
+	t.Setenv(envvars.CliProxyKey, "key")
+
+	ic := (&Provider{}).ResolveInterceptor(context.Background())
+	si, ok := ic.(*Interceptor)
+	if !ok || si == nil {
+		t.Fatalf("expected *Interceptor, got %T", ic)
+	}
+	if si.sidecarScheme != "https" {
+		t.Errorf("sidecarScheme = %q, want %q (uppercase HTTPS must not downgrade)", si.sidecarScheme, "https")
+	}
+	if si.sidecarHost != "sidecar.mycorp.com" {
+		t.Errorf("sidecarHost = %q, want %q", si.sidecarHost, "sidecar.mycorp.com")
+	}
+}
+
 func TestInterceptor_BotIdentity(t *testing.T) {
 	interceptor := &Interceptor{key: []byte("key"), sidecarHost: "127.0.0.1:16384"}
 

internal/envvars/envvars.go

@@ -13,7 +13,7 @@ const (
 	CliStrictMode        = "LARKSUITE_CLI_STRICT_MODE"
 
 	// Sidecar proxy (auth proxy mode)
-	CliAuthProxy = "LARKSUITE_CLI_AUTH_PROXY" // sidecar HTTP address, e.g. "http://127.0.0.1:16384"
+	CliAuthProxy = "LARKSUITE_CLI_AUTH_PROXY" // sidecar address http(s)://host[:port]; plaintext http is same-host only, a remote sidecar must use https. e.g. "http://127.0.0.1:16384" or "https://sidecar.mycorp.com"
 	CliProxyKey  = "LARKSUITE_CLI_PROXY_KEY"  // HMAC signing key shared with sidecar
 
 	// Content safety scanning mode

sidecar/hmac_test.go

@@ -161,6 +161,11 @@ func TestValidateProxyAddr(t *testing.T) {
 		"http://gateway.docker.internal:16384",
 		// trailing slash is tolerated
 		"http://127.0.0.1:8080/",
+		// https: any valid host (including remote, cross-machine) is allowed
+		"https://127.0.0.1:16384",
+		"https://sidecar.mycorp.com",
+		"https://sidecar.mycorp.com:8443",
+		"https://sidecar.corp.internal:443/",
 	}
 	for _, addr := range valid {
 		if err := ValidateProxyAddr(addr); err != nil {
@@ -242,6 +247,8 @@ func TestValidateProxyAddr_RejectsUserinfo(t *testing.T) {
 		"http://user@127.0.0.1:16384",
 		"http://user:pass@127.0.0.1:16384",
 		"http://127.0.0.1@attacker.com:16384",
+		"https://x@evil.com",
+		"https://user:pass@sidecar.mycorp.com",
 	} {
 		err := ValidateProxyAddr(addr)
 		if err == nil {
@@ -259,23 +266,99 @@ func TestValidateProxyAddr_RejectsUserinfo(t *testing.T) {
 	}
 }
 
-// TestValidateProxyAddr_HTTPSRejected pins the current contract: https is
-// rejected explicitly (not lumped into a generic "bad scheme" error) because
-// the interceptor hardcodes http and would silently downgrade an https URL
-// otherwise. The message must mention https so users understand why their
-// perfectly-looking config is refused.
-func TestValidateProxyAddr_HTTPSRejected(t *testing.T) {
+// TestValidateProxyAddr_HTTPSAllowed pins the contract: https addresses are
+// accepted, including a remote sidecar on another machine. TLS provides
+// confidentiality over the network and the HMAC signature provides
+// integrity/auth, so cross-machine https is supported.
+func TestValidateProxyAddr_HTTPSAllowed(t *testing.T) {
 	for _, addr := range []string{
-		"https://127.0.0.1:16384",
+		"https://127.0.0.1:16384", // same-host over TLS
 		"https://sidecar.corp.internal:443",
+		"https://sidecar.mycorp.com", // remote, no explicit port
+		"https://sidecar.mycorp.com:8443",
+	} {
+		if err := ValidateProxyAddr(addr); err != nil {
+			t.Errorf("ValidateProxyAddr(%q): expected accepted, got: %v", addr, err)
+		}
+	}
+}
+
+// TestValidateProxyAddr_HTTPRemoteRejected: plaintext http to a non-same-host
+// address stays rejected — a remote sidecar must use https.
+func TestValidateProxyAddr_HTTPRemoteRejected(t *testing.T) {
+	for _, addr := range []string{
+		"http://sidecar.mycorp.com",
+		"http://sidecar.mycorp.com:8080",
+		"http://10.0.0.1:16384",
 	} {
 		err := ValidateProxyAddr(addr)
 		if err == nil {
-			t.Errorf("ValidateProxyAddr(%q): expected error, got nil", addr)
+			t.Errorf("ValidateProxyAddr(%q): expected rejection (http remote), got nil", addr)
 			continue
 		}
-		if !strings.Contains(err.Error(), "https") {
-			t.Errorf("ValidateProxyAddr(%q): error should mention https, got: %v", addr, err)
+		msg := err.Error()
+		if !strings.Contains(msg, "https") && !strings.Contains(msg, "same-host") && !strings.Contains(msg, "loopback") {
+			t.Errorf("ValidateProxyAddr(%q): error should point to https/same-host, got: %v", addr, err)
+		}
+	}
+}
+
+// TestProxyScheme: scheme is https only for https:// addresses, http otherwise.
+// Case-insensitive: HTTPS:// must resolve to https, otherwise a remote sidecar
+// would silently downgrade to plaintext http (see ProxyScheme doc).
+func TestProxyScheme(t *testing.T) {
+	tests := map[string]string{
+		"https://sidecar.mycorp.com": "https",
+		"https://127.0.0.1:16384":    "https",
+		"http://127.0.0.1:16384":     "http",
+		"127.0.0.1:16384":            "http",
+		// case-insensitive scheme
+		"HTTPS://sidecar.mycorp.com": "https",
+		"Https://sidecar.mycorp.com": "https",
+		"HtTp://127.0.0.1:16384":     "http",
+	}
+	for in, want := range tests {
+		if got := ProxyScheme(in); got != want {
+			t.Errorf("ProxyScheme(%q) = %q, want %q", in, got, want)
+		}
+	}
+}
+
+// TestValidateProxyAddr_SchemeCaseInsensitive: mixed-case scheme must follow the
+// same policy as lower-case — HTTPS accepted (remote allowed), HTTP remote
+// rejected — so case can't be used to bypass the plaintext same-host rule.
+func TestValidateProxyAddr_SchemeCaseInsensitive(t *testing.T) {
+	for _, addr := range []string{"HTTPS://sidecar.mycorp.com", "Https://sidecar.corp.internal:443"} {
+		if err := ValidateProxyAddr(addr); err != nil {
+			t.Errorf("ValidateProxyAddr(%q): expected accepted, got: %v", addr, err)
+		}
+	}
+	for _, addr := range []string{"HtTp://sidecar.mycorp.com", "HTTP://10.0.0.1:16384"} {
+		if err := ValidateProxyAddr(addr); err == nil {
+			t.Errorf("ValidateProxyAddr(%q): expected rejection (http remote), got nil", addr)
+		}
+	}
+}
+
+// TestValidateProxyAddr_IPv6HTTPS pins IPv6 https forms.
+func TestValidateProxyAddr_IPv6HTTPS(t *testing.T) {
+	for _, addr := range []string{"https://[::1]:443", "https://[::1]"} {
+		if err := ValidateProxyAddr(addr); err != nil {
+			t.Errorf("ValidateProxyAddr(%q): expected accepted, got: %v", addr, err)
+		}
+	}
+}
+
+// TestValidateProxyAddr_RejectsQueryFragment: a proxy address must not carry a
+// query or fragment, for either scheme.
+func TestValidateProxyAddr_RejectsQueryFragment(t *testing.T) {
+	for _, addr := range []string{
+		"https://sidecar.mycorp.com?x=1",
+		"https://sidecar.mycorp.com#frag",
+		"http://127.0.0.1:16384?x=1",
+	} {
+		if err := ValidateProxyAddr(addr); err == nil {
+			t.Errorf("ValidateProxyAddr(%q): expected rejection, got nil", addr)
 		}
 	}
 }
@@ -289,6 +372,10 @@ func TestProxyHost(t *testing.T) {
 		{"http://0.0.0.0:8080", "0.0.0.0:8080"},
 		{"http://host.docker.internal:16384/", "host.docker.internal:16384"},
 		{"127.0.0.1:16384", "127.0.0.1:16384"}, // no scheme
+		// https forms (remote sidecar)
+		{"https://sidecar.mycorp.com", "sidecar.mycorp.com"},
+		{"https://sidecar.mycorp.com:8443/", "sidecar.mycorp.com:8443"},
+		{"HTTPS://sidecar.mycorp.com", "sidecar.mycorp.com"},
 	}
 	for _, tt := range tests {
 		t.Run(tt.input, func(t *testing.T) {

sidecar/protocol.go

@@ -3,7 +3,8 @@
 
 // Package sidecar defines the wire protocol shared between the CLI client
 // (running inside a sandbox) and the auth sidecar proxy (running in a
-// trusted environment). Communication uses plain HTTP.
+// trusted environment). Communication uses HTTP for a same-host sidecar, or
+// HTTPS (TLS) for a remote sidecar.
 package sidecar
 
 import (
@@ -103,32 +104,31 @@ func isSameHost(host string) bool {
 	return false
 }
 
-// errNotSameHost is the shared error returned when the sidecar address does
-// not resolve to the same physical host as the sandbox. Kept in one place so
-// tests can look for a stable marker.
+// errNotSameHost is the shared error returned when a plaintext (http) sidecar
+// address does not resolve to the same physical host as the sandbox. Kept in
+// one place so tests can look for a stable marker.
 func errNotSameHost(addr string) error {
-	return fmt.Errorf("invalid proxy address %q: host must be loopback "+
-		"(127.0.0.1 / ::1) or a recognized same-host alias "+
+	return fmt.Errorf("invalid proxy address %q: a plaintext (http) sidecar must be "+
+		"loopback (127.0.0.1 / ::1) or a recognized same-host alias "+
 		"(localhost, host.docker.internal, host.containers.internal, "+
 		"host.lima.internal, gateway.docker.internal). "+
-		"The sidecar must run on the same physical machine as the sandbox — "+
-		"cross-machine deployment is not a sidecar and is not supported", addr)
+		"For a remote sidecar on another machine, use an https:// address instead", addr)
 }
 
 // ValidateProxyAddr validates the LARKSUITE_CLI_AUTH_PROXY value.
 // Accepted formats:
-//   - http://host:port
-//   - host:port         (bare address, treated as http)
+//   - https://host[:port]  (remote sidecar; cross-machine allowed)
+//   - http://host:port     (plaintext; same-host only)
+//   - host:port            (bare address, treated as plaintext http; same-host only)
 //
-// Host must be loopback or in sameHostAliases. The sidecar pattern is
-// inherently same-machine; cross-machine deployment is a different product
-// and is not supported by this feature.
-//
-// https:// is rejected because sidecar is a same-host pattern: loopback
-// and virtual same-host bridges don't traverse any untrusted medium, so
-// TLS adds no security. Cross-machine deployment is out of scope (see the
-// host constraint above), so there is no scenario today where https
-// provides a real benefit over http on loopback.
+// Scheme policy:
+//   - https:// — any valid host is allowed, including a remote central sidecar
+//     on another machine. TLS provides confidentiality over the untrusted
+//     network; the per-request HMAC signature provides integrity/auth.
+//   - http:// (or bare host:port) — plaintext, allowed only when the host is
+//     loopback (127.0.0.1 / ::1) or a recognized same-host alias (a virtual
+//     same-host bridge that stays on the physical machine). For a remote
+//     sidecar, use an https:// address instead.
 //
 // userinfo (user:pass@) is rejected unconditionally — the sidecar protocol
 // does not use basic auth, and the syntactic slot exists only as a phishing
@@ -140,11 +140,11 @@ func ValidateProxyAddr(addr string) error {
 		return fmt.Errorf("proxy address is empty")
 	}
 
-	// Bare host:port (no scheme) — validate as a net address.
+	// Bare host:port (no scheme) — treated as plaintext http, so same-host only.
 	if !strings.Contains(addr, "://") {
 		host, port, err := net.SplitHostPort(addr)
 		if err != nil {
-			return fmt.Errorf("invalid proxy address %q: expected host:port or http://host:port", addr)
+			return fmt.Errorf("invalid proxy address %q: expected host:port or http(s)://host[:port]", addr)
 		}
 		if host == "" || port == "" {
 			return fmt.Errorf("invalid proxy address %q: host and port must not be empty", addr)
@@ -159,33 +159,47 @@ func ValidateProxyAddr(addr string) error {
 	if err != nil {
 		return fmt.Errorf("invalid proxy address %q: %w", addr, err)
 	}
+	// userinfo (user:pass@) is rejected unconditionally (phishing vector).
 	if u.User != nil {
 		return fmt.Errorf("invalid proxy address %q: userinfo is not allowed", addr)
 	}
-	if u.Scheme == "https" {
-		return fmt.Errorf("invalid proxy address %q: use http:// — sidecar is "+
-			"same-host only (loopback or virtual same-host bridge), so TLS adds "+
-			"no security; cross-machine deployment is out of scope", addr)
-	}
-	if u.Scheme != "http" {
-		return fmt.Errorf("invalid proxy address %q: scheme must be http", addr)
-	}
 	if u.Host == "" {
 		return fmt.Errorf("invalid proxy address %q: missing host", addr)
 	}
 	if u.Path != "" && u.Path != "/" {
 		return fmt.Errorf("invalid proxy address %q: path is not allowed", addr)
 	}
-	// u.Hostname() strips the port and unwraps IPv6 brackets.
-	if !isSameHost(u.Hostname()) {
-		return errNotSameHost(addr)
+	if u.RawQuery != "" {
+		return fmt.Errorf("invalid proxy address %q: query is not allowed", addr)
+	}
+	if u.Fragment != "" {
+		return fmt.Errorf("invalid proxy address %q: fragment is not allowed", addr)
+	}
+
+	switch u.Scheme {
+	case "https":
+		// Remote sidecar over TLS. Cross-machine is allowed: https provides
+		// confidentiality over the network and the per-request HMAC signature
+		// provides integrity/authentication, so a remote central sidecar is
+		// supported without exposing credentials or signing material in clear.
+		return nil
+	case "http":
+		// Plaintext: only safe on the same physical host (loopback or a virtual
+		// same-host bridge). For a remote sidecar use an https:// address.
+		// u.Hostname() strips the port and unwraps IPv6 brackets.
+		if !isSameHost(u.Hostname()) {
+			return errNotSameHost(addr)
+		}
+		return nil
+	default:
+		return fmt.Errorf("invalid proxy address %q: scheme must be http or https", addr)
 	}
-	return nil
 }
 
 // ProxyHost extracts the host:port from an AUTH_PROXY URL.
-// Input is expected to be an HTTP URL like "http://127.0.0.1:16384".
-// Returns the host:port portion for URL rewriting.
+// Input is expected to be an http:// or https:// URL like
+// "http://127.0.0.1:16384" or "https://sidecar.mycorp.com".
+// Returns the host[:port] portion for URL rewriting.
 func ProxyHost(authProxy string) string {
 	// Strip scheme
 	host := authProxy
@@ -196,3 +210,19 @@ func ProxyHost(authProxy string) string {
 	host = strings.TrimRight(host, "/")
 	return host
 }
+
+// ProxyScheme returns the URL scheme the CLI must use when routing to the
+// sidecar: "https" for a TLS (remote) sidecar, otherwise "http" (same-host
+// plaintext). Input is a value already accepted by ValidateProxyAddr.
+//
+// It parses the address (rather than a case-sensitive prefix check) so the
+// result stays consistent with ValidateProxyAddr, which relies on url.Parse
+// normalizing the scheme. Otherwise "HTTPS://host" — accepted as https by
+// ValidateProxyAddr — would silently downgrade to plaintext http here,
+// breaking the "remote must use TLS" boundary.
+func ProxyScheme(authProxy string) string {
+	if u, err := url.Parse(authProxy); err == nil && strings.EqualFold(u.Scheme, "https") {
+		return "https"
+	}
+	return "http"
+}

sidecar/server-demo/README.md

@@ -114,18 +114,23 @@ export LARKSUITE_CLI_STRICT_MODE="user"            # optional: lock sandbox to o
 
 **`LARKSUITE_CLI_AUTH_PROXY` constraints** — validated by the CLI on startup:
 
-- Scheme must be `http://` (or bare `host:port`). `https://` is rejected
-  today because the interceptor does not yet perform TLS; a future PR that
-  wires up real TLS will relax this.
-- Host must be loopback (`127.0.0.1`, `::1`) or one of the recognized
-  same-host aliases: `localhost`, `host.docker.internal`,
-  `host.containers.internal`, `host.lima.internal`, `gateway.docker.internal`.
-  The sidecar pattern is inherently same-machine; cross-machine deployment
-  is a different product (auth broker / STS) with different security
-  requirements (mTLS, cert rotation, per-client keys) and is not supported
-  by this feature.
+- Scheme must be `http://` / `https://` (or bare `host:port`, treated as
+  plaintext http).
+  - `https://<any-host>` is allowed, **including a remote sidecar on another
+    machine**: TLS provides confidentiality over the network and the
+    per-request HMAC signature provides integrity/authentication.
+  - Plaintext `http://` (and bare `host:port`) is allowed **only same-host**:
+    loopback (`127.0.0.1`, `::1`) or a recognized same-host alias
+    (`localhost`, `host.docker.internal`, `host.containers.internal`,
+    `host.lima.internal`, `gateway.docker.internal`). For a remote sidecar,
+    use an `https://` address.
 - No path, query, fragment, or `user:pass@` in the URL.
 
+> Note: this demo server itself terminates plain HTTP and is meant to run
+> locally. A production **remote** sidecar must terminate TLS (its own
+> `https://` endpoint, e.g. behind a load balancer or with a real
+> certificate); the CLI-side policy above is what enables pointing at it.
+
 **How auto identity detection works in sidecar mode**: on every invocation the
 CLI asks the sidecar to look up the logged-in user's `open_id` via
 `/open-apis/authen/v1/user_info`. If that succeeds, `--as` defaults to `user`;