[feature/bugfix] Probe S3 storage for CSP uri, add config flag for extra URIs (#2134)

* [feature/bugfix] Probe S3 storage for CSP uri, add config flag for extra URIs

* env parsing tests, my coy mistress

3 files changed, 170 insertions, 108 deletions

diff --git a/internal/middleware/contentsecuritypolicy.go b/internal/middleware/contentsecuritypolicy.go
new file mode 100644
index 000000000..5984a75c3
--- /dev/null
+++ b/internal/middleware/contentsecuritypolicy.go
@@ -0,0 +1,144 @@
+// GoToSocial
+// Copyright (C) GoToSocial Authors admin@gotosocial.org
+// SPDX-License-Identifier: AGPL-3.0-or-later
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package middleware
+
+import (
+	"strings"
+
+	"codeberg.org/gruf/go-debug"
+	"github.com/gin-gonic/gin"
+)
+
+func ContentSecurityPolicy(extraURIs ...string) gin.HandlerFunc {
+	csp := BuildContentSecurityPolicy(extraURIs...)
+
+	return func(c *gin.Context) {
+		// Inform the browser we only load
+		// CSS/JS/media using the given policy.
+		c.Header("Content-Security-Policy", csp)
+	}
+}
+
+func BuildContentSecurityPolicy(extraURIs ...string) string {
+	const (
+		defaultSrc = "default-src"
+		objectSrc  = "object-src"
+		imgSrc     = "img-src"
+		mediaSrc   = "media-src"
+
+		self = "'self'"
+		none = "'none'"
+		blob = "blob:"
+	)
+
+	// CSP values keyed by directive.
+	values := make(map[string][]string, 4)
+
+	/*
+		default-src
+		https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/default-src
+	*/
+
+	if !debug.DEBUG {
+		// Restrictive 'self' policy
+		values[defaultSrc] = []string{self}
+	} else {
+		// If debug is enabled, allow
+		// serving things from localhost
+		// as well (regardless of port).
+		values[defaultSrc] = []string{
+			self,
+			"localhost:*",
+			"ws://localhost:*",
+		}
+	}
+
+	/*
+		object-src
+		https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/object-src
+	*/
+
+	// Disallow object-src as recommended.
+	values[objectSrc] = []string{none}
+
+	/*
+		img-src
+		https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/img-src
+	*/
+
+	// Restrictive 'self' policy,
+	// include extraURIs, and 'blob:'
+	// for previewing uploaded images
+	// (header, avi, emojis) in settings.
+	values[imgSrc] = append(
+		[]string{self, blob},
+		extraURIs...,
+	)
+
+	/*
+		media-src
+		https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/media-src
+	*/
+
+	// Restrictive 'self' policy,
+	// include extraURIs.
+	values[mediaSrc] = append(
+		[]string{self},
+		extraURIs...,
+	)
+
+	/*
+		Assemble policy directives.
+	*/
+
+	// Iterate through an ordered slice rather than
+	// iterating through the map, since we want these
+	// policyDirectives in a determinate order.
+	policyDirectives := make([]string, 4)
+	for i, directive := range []string{
+		defaultSrc,
+		objectSrc,
+		imgSrc,
+		mediaSrc,
+	} {
+		// Each policy directive should look like:
+		// `[directive] [value1] [value2] [etc]`
+
+		// Get assembled values
+		// for this directive.
+		values := values[directive]
+
+		// Prepend values with
+		// the directive name.
+		directiveValues := append(
+			[]string{directive},
+			values...,
+		)
+
+		// Space-separate them.
+		policyDirective := strings.Join(directiveValues, " ")
+
+		// Done.
+		policyDirectives[i] = policyDirective
+	}
+
+	// Content-security-policy looks like this:
+	// `Content-Security-Policy: <policy-directive>; <policy-directive>`
+	// So join each policy directive appropriately.
+	return strings.Join(policyDirectives, "; ")
+}
diff --git a/internal/middleware/extraheaders.go b/internal/middleware/extraheaders.go
index 064e85cca..1a3f1d522 100644
--- a/internal/middleware/extraheaders.go
+++ b/internal/middleware/extraheaders.go
@@ -18,15 +18,11 @@
 package middleware
 
 import (
-	"codeberg.org/gruf/go-debug"
 	"github.com/gin-gonic/gin"
-	"github.com/superseriousbusiness/gotosocial/internal/config"
 )
 
 // ExtraHeaders returns a new gin middleware which adds various extra headers to the response.
 func ExtraHeaders() gin.HandlerFunc {
-	csp := BuildContentSecurityPolicy()
-
 	return func(c *gin.Context) {
 		// Inform all callers which server implementation this is.
 		c.Header("Server", "gotosocial")
@@ -39,56 +35,5 @@ func ExtraHeaders() gin.HandlerFunc {
 		//
 		// See: https://github.com/patcg-individual-drafts/topics
 		c.Header("Permissions-Policy", "browsing-topics=()")
-
-		// Inform the browser we only load
-		// CSS/JS/media using the given policy.
-		c.Header("Content-Security-Policy", csp)
-	}
-}
-
-func BuildContentSecurityPolicy() string {
-	// Start with restrictive policy.
-	policy := "default-src 'self'"
-
-	if debug.DEBUG {
-		// Debug is enabled, allow
-		// serving things from localhost
-		// as well (regardless of port).
-		policy += " localhost:* ws://localhost:*"
-	}
-
-	// Disallow object-src as recommended https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/object-src
-	policy += "; object-src 'none'"
-
-	s3Endpoint := config.GetStorageS3Endpoint()
-	if s3Endpoint == "" || config.GetStorageS3Proxy() {
-		// S3 not configured or in proxy mode, just allow images from self and blob:
-		policy += "; img-src 'self' blob:"
-		return policy
 	}
-
-	// S3 is on and in non-proxy mode, so we need to add the S3 host to
-	// the policy to allow images and video to be pulled from there too.
-
-	// If secure is false,
-	// use 'http' scheme.
-	scheme := "https"
-	if !config.GetStorageS3UseSSL() {
-		scheme = "http"
-	}
-
-	// Construct endpoint URL.
-	s3EndpointURLStr := scheme + "://" + s3Endpoint
-
-	// When object storage is in use in non-proxied mode, GtS still serves some
-	// assets itself like the logo, so keep 'self' in there. That should also
-	// handle any redirects from the fileserver to object storage.
-
-	// https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/img-src
-	policy += "; img-src 'self' blob: " + s3EndpointURLStr
-
-	// https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/media-src
-	policy += "; media-src 'self' " + s3EndpointURLStr
-
-	return policy
 }
diff --git a/internal/middleware/middleware_test.go b/internal/middleware/middleware_test.go
index 29376304e..fad05931b 100644
--- a/internal/middleware/middleware_test.go
+++ b/internal/middleware/middleware_test.go
@@ -20,80 +20,53 @@ package middleware_test
 import (
 	"testing"
 
-	"github.com/superseriousbusiness/gotosocial/internal/config"
 	"github.com/superseriousbusiness/gotosocial/internal/middleware"
 )
 
 func TestBuildContentSecurityPolicy(t *testing.T) {
 	type cspTest struct {
-		s3Endpoint string
-		s3Proxy    bool
-		s3Secure   bool
-		expected   string
-		actual     string
+		extraURLs []string
+		expected  string
 	}
 
 	for _, test := range []cspTest{
 		{
-			s3Endpoint: "",
-			s3Proxy:    false,
-			s3Secure:   false,
-			expected:   "default-src 'self'; object-src 'none'; img-src 'self' blob:",
+			extraURLs: nil,
+			expected:  "default-src 'self'; object-src 'none'; img-src 'self' blob:; media-src 'self'",
 		},
 		{
-			s3Endpoint: "some-bucket-provider.com",
-			s3Proxy:    false,
-			s3Secure:   true,
-			expected:   "default-src 'self'; object-src 'none'; img-src 'self' blob: https://some-bucket-provider.com; media-src 'self' https://some-bucket-provider.com",
+			extraURLs: []string{
+				"https://some-bucket-provider.com",
+			},
+			expected: "default-src 'self'; object-src 'none'; img-src 'self' blob: https://some-bucket-provider.com; media-src 'self' https://some-bucket-provider.com",
 		},
 		{
-			s3Endpoint: "some-bucket-provider.com:6969",
-			s3Proxy:    false,
-			s3Secure:   true,
-			expected:   "default-src 'self'; object-src 'none'; img-src 'self' blob: https://some-bucket-provider.com:6969; media-src 'self' https://some-bucket-provider.com:6969",
+			extraURLs: []string{
+				"https://some-bucket-provider.com:6969",
+			},
+			expected: "default-src 'self'; object-src 'none'; img-src 'self' blob: https://some-bucket-provider.com:6969; media-src 'self' https://some-bucket-provider.com:6969",
 		},
 		{
-			s3Endpoint: "some-bucket-provider.com:6969",
-			s3Proxy:    false,
-			s3Secure:   false,
-			expected:   "default-src 'self'; object-src 'none'; img-src 'self' blob: http://some-bucket-provider.com:6969; media-src 'self' http://some-bucket-provider.com:6969",
+			extraURLs: []string{
+				"http://some-bucket-provider.com:6969",
+			},
+			expected: "default-src 'self'; object-src 'none'; img-src 'self' blob: http://some-bucket-provider.com:6969; media-src 'self' http://some-bucket-provider.com:6969",
 		},
 		{
-			s3Endpoint: "s3.nl-ams.scw.cloud",
-			s3Proxy:    false,
-			s3Secure:   true,
-			expected:   "default-src 'self'; object-src 'none'; img-src 'self' blob: https://s3.nl-ams.scw.cloud; media-src 'self' https://s3.nl-ams.scw.cloud",
+			extraURLs: []string{
+				"https://s3.nl-ams.scw.cloud",
+			},
+			expected: "default-src 'self'; object-src 'none'; img-src 'self' blob: https://s3.nl-ams.scw.cloud; media-src 'self' https://s3.nl-ams.scw.cloud",
 		},
 		{
-			s3Endpoint: "some-bucket-provider.com",
-			s3Proxy:    true,
-			s3Secure:   true,
-			expected:   "default-src 'self'; object-src 'none'; img-src 'self' blob:",
-		},
-		{
-			s3Endpoint: "some-bucket-provider.com:6969",
-			s3Proxy:    true,
-			s3Secure:   true,
-			expected:   "default-src 'self'; object-src 'none'; img-src 'self' blob:",
-		},
-		{
-			s3Endpoint: "some-bucket-provider.com:6969",
-			s3Proxy:    true,
-			s3Secure:   true,
-			expected:   "default-src 'self'; object-src 'none'; img-src 'self' blob:",
-		},
-		{
-			s3Endpoint: "s3.nl-ams.scw.cloud",
-			s3Proxy:    true,
-			s3Secure:   true,
-			expected:   "default-src 'self'; object-src 'none'; img-src 'self' blob:",
+			extraURLs: []string{
+				"https://s3.nl-ams.scw.cloud",
+				"https://s3.somewhere.else.example.org",
+			},
+			expected: "default-src 'self'; object-src 'none'; img-src 'self' blob: https://s3.nl-ams.scw.cloud https://s3.somewhere.else.example.org; media-src 'self' https://s3.nl-ams.scw.cloud https://s3.somewhere.else.example.org",
 		},
 	} {
-		config.SetStorageS3Endpoint(test.s3Endpoint)
-		config.SetStorageS3Proxy(test.s3Proxy)
-		config.SetStorageS3UseSSL(test.s3Secure)
-
-		csp := middleware.BuildContentSecurityPolicy()
+		csp := middleware.BuildContentSecurityPolicy(test.extraURLs...)
 		if csp != test.expected {
 			t.Logf("expected '%s', got '%s'", test.expected, csp)
 			t.Fail()