crypto/x509: honor SSL_CERT_{FILE,DIR} on windows/darwin

When these env vars are set, load roots from on-disk, and don't use the
platform verifier.

Fixes #77865

Change-Id: I3183d1636238bed924252fe1288cfa263d17f61d
Reviewed-on: https://go-review.googlesource.com/c/go/+/776940
Reviewed-by: Neal Patel <nealpatel@google.com>
Auto-Submit: Roland Shoemaker <roland@golang.org>
Reviewed-by: Filippo Valsorda <filippo@golang.org>
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: David Chase <drchase@google.com>

doc/godebug.md

@@ -170,6 +170,14 @@ to `1`. This opt-out is expected to be kept indefinitely in case goroutine
 labels acquire sensitive information that shouldn't be made available in
 tracebacks.
 
+Go 1.27 added a new `x509sslcertoverrideplatform` setting that controls whether
+crypto/x509 will load roots from disk on Windows and Darwin when `SSL_CERT_FILE`
+or `SSL_CERT_DIR` are set. The default value `x509sslcertoverrideplatform=1` will
+cause roots to be loaded from disk when these environment variables are set.
+Setting `x509sslcertoverrideplatform=0` disables this behavior in favor of using
+the platform certificate store instead of honoring the environment variables. We
+plan to remove this setting in Go 1.31.
+
 ### Go 1.26
 
 Go 1.26 added a new `httpcookiemaxnum` setting that controls the maximum number

doc/next/6-stdlib/99-minor/crypto/x509/77865.md

@@ -0,0 +1,5 @@
+[SystemCertPool] now respects SSL_CERT_FILE and SSL_CERT_DIR on Windows and
+Darwin. When these environment variables are set, roots are loaded from disk and
+instead of using the platform certificate verification APIs, the native Go
+verifier is used. This behavior can be disabled with
+`GODEBUG=x509sslcertoverrideplatform=0`.

src/crypto/x509/cert_pool.go

@@ -105,10 +105,14 @@ func (s *CertPool) Clone() *CertPool {
 
 // SystemCertPool returns a copy of the system cert pool.
 //
-// On Unix systems other than macOS the environment variables SSL_CERT_FILE and
-// SSL_CERT_DIR can be used to override the system default locations for the SSL
-// certificate file and SSL certificate files directory, respectively. The
-// latter can be a colon-separated list.
+// The environment variables SSL_CERT_FILE and SSL_CERT_DIR can be used to
+// override the system default locations for the SSL certificate file and SSL
+// certificate files directory, respectively. The latter can be a
+// colon-separated list, or a semicolon-separated list on Windows. On platforms
+// which have system APIs for certificate verification (macOS and Windows),
+// setting SSL_CERT_FILE or SSL_CERT_DIR will prevent those APIs from being
+// used, unless the x509sslcertoverrideplatform=0 GODEBUG setting is used. (This
+// changed in Go 1.27.)
 //
 // Any mutations to the returned pool are not written to disk and do not affect
 // any other pool returned by SystemCertPool.

src/crypto/x509/root.go

@@ -6,6 +6,11 @@ package x509
 
 import (
 	"internal/godebug"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"runtime"
+	"strings"
 	"sync"
 	_ "unsafe" // for linkname
 )
@@ -115,3 +120,111 @@ func SetFallbackRoots(roots *CertPool) {
 
 	systemRoots, systemRootsErr = roots, nil
 }
+
+const (
+	// certFileEnv is the environment variable which identifies where to locate
+	// the SSL certificate file. If set this overrides the system default.
+	certFileEnv = "SSL_CERT_FILE"
+
+	// certDirEnv is the environment variable which identifies which directory
+	// to check for SSL certificate files. If set this overrides the system default.
+	// See https://docs.openssl.org/4.0/man1/openssl-rehash/#environment.
+	certDirEnv = "SSL_CERT_DIR"
+)
+
+var x509sslcertoverrideplatform = godebug.New("x509sslcertoverrideplatform")
+
+func loadSystemRoots() (*CertPool, error) {
+	certFilePath, certDirPath := os.Getenv(certFileEnv), os.Getenv(certDirEnv)
+
+	if runtime.GOOS == "windows" || runtime.GOOS == "darwin" || runtime.GOOS == "ios" {
+		if certFilePath == "" && certDirPath == "" {
+			return &CertPool{systemPool: true}, nil
+		}
+		if x509sslcertoverrideplatform.Value() == "0" {
+			x509sslcertoverrideplatform.IncNonDefault()
+			return &CertPool{systemPool: true}, nil
+		}
+	}
+
+	return loadOnDiskRoots(certFilePath, certDirPath)
+}
+
+func loadOnDiskRoots(certFilePath, certDirPath string) (*CertPool, error) {
+	roots := NewCertPool()
+
+	files := certFiles
+	if certFilePath != "" {
+		files = []string{certFilePath}
+	}
+
+	var firstErr error
+	for _, file := range files {
+		data, err := os.ReadFile(file)
+		if err == nil {
+			roots.AppendCertsFromPEM(data)
+			break
+		}
+		if firstErr == nil && !os.IsNotExist(err) {
+			firstErr = err
+		}
+	}
+
+	dirs := certDirectories
+	if certDirPath != "" {
+		// OpenSSL and BoringSSL both use ":" as the SSL_CERT_DIR separator on
+		// Unix-like systems, and ";" on Windows.
+		// See:
+		//  * https://golang.org/issue/35325
+		//  * https://docs.openssl.org/4.0/man1/openssl-rehash/#environment
+		dirs = filepath.SplitList(certDirPath)
+	}
+
+	for _, directory := range dirs {
+		fis, err := readUniqueDirectoryEntries(directory)
+		if err != nil {
+			if firstErr == nil && !os.IsNotExist(err) {
+				firstErr = err
+			}
+			continue
+		}
+		for _, fi := range fis {
+			data, err := os.ReadFile(filepath.Join(directory, fi.Name()))
+			if err == nil {
+				roots.AppendCertsFromPEM(data)
+			}
+		}
+	}
+
+	if roots.len() > 0 || firstErr == nil {
+		return roots, nil
+	}
+
+	return nil, firstErr
+}
+
+// readUniqueDirectoryEntries is like os.ReadDir but omits
+// symlinks that point within the directory.
+func readUniqueDirectoryEntries(dir string) ([]fs.DirEntry, error) {
+	files, err := os.ReadDir(dir)
+	if err != nil {
+		return nil, err
+	}
+	uniq := files[:0]
+	for _, f := range files {
+		if !isSameDirSymlink(f, dir) {
+			uniq = append(uniq, f)
+		}
+	}
+	return uniq, nil
+}
+
+// isSameDirSymlink reports whether f in dir is a symlink with a
+// target not containing a slash.
+func isSameDirSymlink(f fs.DirEntry, dir string) bool {
+	if f.Type()&fs.ModeSymlink == 0 {
+		return false
+	}
+	target, err := os.Readlink(filepath.Join(dir, f.Name()))
+	return err == nil && !strings.ContainsRune(target, filepath.Separator)
+}

src/crypto/x509/root_darwin.go

@@ -10,6 +10,9 @@ import (
 	"fmt"
 )
 
+// macOS has no default SSL_CERT_{FILE,DIR} paths.
+var certFiles, certDirectories []string
+
 func (c *Certificate) systemVerify(opts *VerifyOptions) (chains [][]*Certificate, err error) {
 	certs := macos.CFArrayCreateMutable()
 	defer macos.ReleaseCFArray(certs)
@@ -125,7 +128,3 @@ func exportCertificate(cert macos.CFRef) (*Certificate, error) {
 	}
 	return ParseCertificate(data)
 }
-
-func loadSystemRoots() (*CertPool, error) {
-	return &CertPool{systemPool: true}, nil
-}

src/crypto/x509/root_plan9.go

@@ -6,34 +6,13 @@
 
 package x509
 
-import (
-	"os"
-)
-
 // Possible certificate files; stop after finding one.
 var certFiles = []string{
 	"/sys/lib/tls/ca.pem",
 }
 
+var certDirectories = []string{}
+
 func (c *Certificate) systemVerify(opts *VerifyOptions) (chains [][]*Certificate, err error) {
 	return nil, nil
 }
-
-func loadSystemRoots() (*CertPool, error) {
-	roots := NewCertPool()
-	var bestErr error
-	for _, file := range certFiles {
-		data, err := os.ReadFile(file)
-		if err == nil {
-			roots.AppendCertsFromPEM(data)
-			return roots, nil
-		}
-		if bestErr == nil || (os.IsNotExist(bestErr) && !os.IsNotExist(err)) {
-			bestErr = err
-		}
-	}
-	if bestErr == nil {
-		return roots, nil
-	}
-	return nil, bestErr
-}

src/crypto/x509/root_test.go

@@ -5,6 +5,14 @@
 package x509
 
 import (
+	"bytes"
+	"fmt"
+	"internal/testenv"
+	"os"
+	"path/filepath"
+	"runtime"
+	"slices"
+	"strings"
 	"testing"
 )
 
@@ -108,3 +116,252 @@ func TestFallback(t *testing.T) {
 		})
 	}
 }
+
+const (
+	testDirCN   = "test-dir"
+	testFile    = "test-file.crt"
+	testFileCN  = "test-file"
+	testMissing = "missing"
+)
+
+func TestEnvVars(t *testing.T) {
+	tmpDir := t.TempDir()
+	testCert, err := os.ReadFile("testdata/test-dir.crt")
+	if err != nil {
+		t.Fatalf("failed to read test cert: %s", err)
+	}
+	if err := os.WriteFile(filepath.Join(tmpDir, testFile), testCert, 0644); err != nil {
+		t.Fatalf("failed to write test cert: %s", err)
+	}
+
+	testCases := []struct {
+		name    string
+		fileEnv string
+		dirEnv  string
+		files   []string
+		dirs    []string
+		cns     []string
+	}{
+		{
+			// Environment variables override the default locations preventing fall through.
+			name:    "override-defaults",
+			fileEnv: testMissing,
+			dirEnv:  testMissing,
+			files:   []string{testFile},
+			dirs:    []string{tmpDir},
+			cns:     nil,
+		},
+		{
+			// File environment overrides default file locations.
+			name:    "file",
+			fileEnv: testFile,
+			dirEnv:  "",
+			files:   nil,
+			dirs:    nil,
+			cns:     []string{testFileCN},
+		},
+		{
+			// Directory environment overrides default directory locations.
+			name:    "dir",
+			fileEnv: "",
+			dirEnv:  tmpDir,
+			files:   nil,
+			dirs:    nil,
+			cns:     []string{testDirCN},
+		},
+		{
+			// File & directory environment overrides both default locations.
+			name:    "file+dir",
+			fileEnv: testFile,
+			dirEnv:  tmpDir,
+			files:   nil,
+			dirs:    nil,
+			cns:     []string{testFileCN, testDirCN},
+		},
+		{
+			// Environment variable empty / unset uses default locations.
+			name:    "empty-fall-through",
+			fileEnv: "",
+			dirEnv:  "",
+			files:   []string{testFile},
+			dirs:    []string{tmpDir},
+			cns:     []string{testFileCN, testDirCN},
+		},
+	}
+
+	// Save old settings so we can restore before the test ends.
+	origCertFiles, origCertDirectories := certFiles, certDirectories
+	origFile, origDir := os.Getenv(certFileEnv), os.Getenv(certDirEnv)
+	defer func() {
+		certFiles = origCertFiles
+		certDirectories = origCertDirectories
+		os.Setenv(certFileEnv, origFile)
+		os.Setenv(certDirEnv, origDir)
+	}()
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			if err := os.Setenv(certFileEnv, tc.fileEnv); err != nil {
+				t.Fatalf("setenv %q failed: %v", certFileEnv, err)
+			}
+			if err := os.Setenv(certDirEnv, tc.dirEnv); err != nil {
+				t.Fatalf("setenv %q failed: %v", certDirEnv, err)
+			}
+
+			certFiles, certDirectories = tc.files, tc.dirs
+
+			r, err := loadSystemRoots()
+			if err != nil {
+				t.Fatal("unexpected failure:", err)
+			}
+
+			if r == nil {
+				t.Fatal("nil roots")
+			}
+
+			wantSystemPool := (runtime.GOOS == "darwin" || runtime.GOOS == "windows") && tc.dirEnv == "" && tc.fileEnv == ""
+
+			if wantSystemPool {
+				if !r.systemPool {
+					t.Fatal("expected returned cert pool to be a system pool")
+				}
+				if r.len() != 0 {
+					t.Fatalf("expected empty system pool, pool has %d roots", r.len())
+				}
+				return
+			}
+
+			// Verify that the returned certs match, otherwise report where the mismatch is.
+			for i, cn := range tc.cns {
+				if i >= r.len() {
+					t.Errorf("missing cert %v @ %v", cn, i)
+				} else if r.mustCert(t, i).Subject.CommonName != cn {
+					fmt.Printf("%#v\n", r.mustCert(t, 0).Subject)
+					t.Errorf("unexpected cert common name %q, want %q", r.mustCert(t, i).Subject.CommonName, cn)
+				}
+			}
+			if r.len() > len(tc.cns) {
+				t.Errorf("got %v certs, which is more than %v wanted", r.len(), len(tc.cns))
+			}
+		})
+	}
+}
+
+// Ensure that "SSL_CERT_DIR" when used as the environment variable delimited by
+// colons on Unix-like systems, and semicolons on Windows, allows
+// loadSystemRoots to load all the roots from the respective directories.
+// See https://golang.org/issue/35325.
+func TestLoadSystemCertsLoadColonSeparatedDirs(t *testing.T) {
+	origFile, origDir := os.Getenv(certFileEnv), os.Getenv(certDirEnv)
+	origCertFiles := certFiles[:]
+
+	// To prevent any other certs from being loaded in
+	// through "SSL_CERT_FILE" or from known "certFiles",
+	// clear them all, and they'll be reverted on defer.
+	certFiles = certFiles[:0]
+	os.Setenv(certFileEnv, "")
+
+	defer func() {
+		certFiles = origCertFiles[:]
+		os.Setenv(certDirEnv, origDir)
+		os.Setenv(certFileEnv, origFile)
+	}()
+
+	tmpDir := t.TempDir()
+
+	rootPEMs := []string{
+		gtsRoot,
+		googleLeaf,
+	}
+
+	var certDirs []string
+	for i, certPEM := range rootPEMs {
+		certDir := filepath.Join(tmpDir, fmt.Sprintf("cert-%d", i))
+		if err := os.MkdirAll(certDir, 0755); err != nil {
+			t.Fatalf("failed to create certificate dir: %v", err)
+		}
+		certOutFile := filepath.Join(certDir, "cert.crt")
+		if err := os.WriteFile(certOutFile, []byte(certPEM), 0655); err != nil {
+			t.Fatalf("failed to write certificate to file: %v", err)
+		}
+		certDirs = append(certDirs, certDir)
+	}
+
+	// Sanity check: the number of certDirs should be equal to the number of roots.
+	if g, w := len(certDirs), len(rootPEMs); g != w {
+		t.Fatalf("failed sanity check: len(certsDir)=%d is not equal to len(rootsPEMS)=%d", g, w)
+	}
+
+	// Now finally concatenate them with a colon/semicolon.
+	concatCertDirs := strings.Join(certDirs, string(filepath.ListSeparator))
+	os.Setenv(certDirEnv, concatCertDirs)
+	gotPool, err := loadSystemRoots()
+	if err != nil {
+		t.Fatalf("failed to load system roots: %v", err)
+	}
+	subjects := gotPool.Subjects()
+	// We expect exactly len(rootPEMs) subjects back.
+	if g, w := len(subjects), len(rootPEMs); g != w {
+		t.Fatalf("invalid number of subjects: got %d want %d", g, w)
+	}
+
+	wantPool := NewCertPool()
+	for _, certPEM := range rootPEMs {
+		wantPool.AppendCertsFromPEM([]byte(certPEM))
+	}
+	strCertPool := func(p *CertPool) string {
+		return string(bytes.Join(p.Subjects(), []byte("\n")))
+	}
+
+	if !certPoolEqual(gotPool, wantPool) {
+		got, want := strCertPool(gotPool), strCertPool(wantPool)
+		t.Fatalf("mismatched certPools\nGot:\n%s\n\nWant:\n%s", got, want)
+	}
+}
+
+func TestReadUniqueDirectoryEntries(t *testing.T) {
+	baseTmpDir := t.TempDir()
+	path := func(base string) string { return filepath.Join(baseTmpDir, base) }
+	if f, err := os.Create(path("file")); err != nil {
+		t.Fatal(err)
+	} else {
+		f.Close()
+	}
+	if err := os.Symlink("target-in", path("link-in")); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.Symlink("../target-out", path("link-out")); err != nil {
+		t.Fatal(err)
+	}
+	got, err := readUniqueDirectoryEntries(baseTmpDir)
+	if err != nil {
+		t.Fatal(err)
+	}
+	gotNames := []string{}
+	for _, fi := range got {
+		gotNames = append(gotNames, fi.Name())
+	}
+	wantNames := []string{"file", "link-out"}
+	if !slices.Equal(gotNames, wantNames) {
+		t.Errorf("got %q; want %q", gotNames, wantNames)
+	}
+}
+
+func TestSSLCertEnvOverride(t *testing.T) {
+	testenv.SetGODEBUG(t, "x509sslcertoverrideplatform=0")
+	t.Setenv(certFileEnv, "/tmp/nope")
+	t.Setenv(certDirEnv, "/tmp/nope")
+
+	p, err := loadSystemRoots()
+	if err != nil {
+		t.Fatalf("unexpected failure: %s", err)
+	}
+
+	if runtime.GOOS == "windows" || runtime.GOOS == "darwin" || runtime.GOOS == "ios" {
+		if !p.systemPool {
+			t.Fatal("x509sslcertoverrideplatform did not override SSL_CERT_{FILE,DIR}")
+		}
+	} else if p.systemPool {
+		t.Fatal("x509sslcertoverrideplatform caused a systemPool to be returned on OS other than windows or darwin")
+	}
+}

src/crypto/x509/root_unix.go

@@ -6,103 +6,6 @@
 
 package x509
 
-import (
-	"io/fs"
-	"os"
-	"path/filepath"
-	"strings"
-)
-
-const (
-	// certFileEnv is the environment variable which identifies where to locate
-	// the SSL certificate file. If set this overrides the system default.
-	certFileEnv = "SSL_CERT_FILE"
-
-	// certDirEnv is the environment variable which identifies which directory
-	// to check for SSL certificate files. If set this overrides the system default.
-	// It is a colon separated list of directories.
-	// See https://www.openssl.org/docs/man1.0.2/man1/c_rehash.html.
-	certDirEnv = "SSL_CERT_DIR"
-)
-
 func (c *Certificate) systemVerify(opts *VerifyOptions) (chains [][]*Certificate, err error) {
 	return nil, nil
 }
-
-func loadSystemRoots() (*CertPool, error) {
-	roots := NewCertPool()
-
-	files := certFiles
-	if f := os.Getenv(certFileEnv); f != "" {
-		files = []string{f}
-	}
-
-	var firstErr error
-	for _, file := range files {
-		data, err := os.ReadFile(file)
-		if err == nil {
-			roots.AppendCertsFromPEM(data)
-			break
-		}
-		if firstErr == nil && !os.IsNotExist(err) {
-			firstErr = err
-		}
-	}
-
-	dirs := certDirectories
-	if d := os.Getenv(certDirEnv); d != "" {
-		// OpenSSL and BoringSSL both use ":" as the SSL_CERT_DIR separator.
-		// See:
-		//  * https://golang.org/issue/35325
-		//  * https://www.openssl.org/docs/man1.0.2/man1/c_rehash.html
-		dirs = strings.Split(d, ":")
-	}
-
-	for _, directory := range dirs {
-		fis, err := readUniqueDirectoryEntries(directory)
-		if err != nil {
-			if firstErr == nil && !os.IsNotExist(err) {
-				firstErr = err
-			}
-			continue
-		}
-		for _, fi := range fis {
-			data, err := os.ReadFile(directory + "/" + fi.Name())
-			if err == nil {
-				roots.AppendCertsFromPEM(data)
-			}
-		}
-	}
-
-	if roots.len() > 0 || firstErr == nil {
-		return roots, nil
-	}
-
-	return nil, firstErr
-}
-
-// readUniqueDirectoryEntries is like os.ReadDir but omits
-// symlinks that point within the directory.
-func readUniqueDirectoryEntries(dir string) ([]fs.DirEntry, error) {
-	files, err := os.ReadDir(dir)
-	if err != nil {
-		return nil, err
-	}
-	uniq := files[:0]
-	for _, f := range files {
-		if !isSameDirSymlink(f, dir) {
-			uniq = append(uniq, f)
-		}
-	}
-	return uniq, nil
-}
-
-// isSameDirSymlink reports whether fi in dir is a symlink with a
-// target not containing a slash.
-func isSameDirSymlink(f fs.DirEntry, dir string) bool {
-	if f.Type()&fs.ModeSymlink == 0 {
-		return false
-	}
-	target, err := os.Readlink(filepath.Join(dir, f.Name()))
-	return err == nil && !strings.Contains(target, "/")
-}

src/crypto/x509/root_unix_test.go

@@ -1,235 +0,0 @@
-// Copyright 2017 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build dragonfly || freebsd || linux || netbsd || openbsd || solaris
-
-package x509
-
-import (
-	"bytes"
-	"fmt"
-	"os"
-	"path/filepath"
-	"slices"
-	"strings"
-	"testing"
-)
-
-const (
-	testDirCN   = "test-dir"
-	testFile    = "test-file.crt"
-	testFileCN  = "test-file"
-	testMissing = "missing"
-)
-
-func TestEnvVars(t *testing.T) {
-	tmpDir := t.TempDir()
-	testCert, err := os.ReadFile("testdata/test-dir.crt")
-	if err != nil {
-		t.Fatalf("failed to read test cert: %s", err)
-	}
-	if err := os.WriteFile(filepath.Join(tmpDir, testFile), testCert, 0644); err != nil {
-		t.Fatalf("failed to write test cert: %s", err)
-	}
-
-	testCases := []struct {
-		name    string
-		fileEnv string
-		dirEnv  string
-		files   []string
-		dirs    []string
-		cns     []string
-	}{
-		{
-			// Environment variables override the default locations preventing fall through.
-			name:    "override-defaults",
-			fileEnv: testMissing,
-			dirEnv:  testMissing,
-			files:   []string{testFile},
-			dirs:    []string{tmpDir},
-			cns:     nil,
-		},
-		{
-			// File environment overrides default file locations.
-			name:    "file",
-			fileEnv: testFile,
-			dirEnv:  "",
-			files:   nil,
-			dirs:    nil,
-			cns:     []string{testFileCN},
-		},
-		{
-			// Directory environment overrides default directory locations.
-			name:    "dir",
-			fileEnv: "",
-			dirEnv:  tmpDir,
-			files:   nil,
-			dirs:    nil,
-			cns:     []string{testDirCN},
-		},
-		{
-			// File & directory environment overrides both default locations.
-			name:    "file+dir",
-			fileEnv: testFile,
-			dirEnv:  tmpDir,
-			files:   nil,
-			dirs:    nil,
-			cns:     []string{testFileCN, testDirCN},
-		},
-		{
-			// Environment variable empty / unset uses default locations.
-			name:    "empty-fall-through",
-			fileEnv: "",
-			dirEnv:  "",
-			files:   []string{testFile},
-			dirs:    []string{tmpDir},
-			cns:     []string{testFileCN, testDirCN},
-		},
-	}
-
-	// Save old settings so we can restore before the test ends.
-	origCertFiles, origCertDirectories := certFiles, certDirectories
-	origFile, origDir := os.Getenv(certFileEnv), os.Getenv(certDirEnv)
-	defer func() {
-		certFiles = origCertFiles
-		certDirectories = origCertDirectories
-		os.Setenv(certFileEnv, origFile)
-		os.Setenv(certDirEnv, origDir)
-	}()
-
-	for _, tc := range testCases {
-		t.Run(tc.name, func(t *testing.T) {
-			if err := os.Setenv(certFileEnv, tc.fileEnv); err != nil {
-				t.Fatalf("setenv %q failed: %v", certFileEnv, err)
-			}
-			if err := os.Setenv(certDirEnv, tc.dirEnv); err != nil {
-				t.Fatalf("setenv %q failed: %v", certDirEnv, err)
-			}
-
-			certFiles, certDirectories = tc.files, tc.dirs
-
-			r, err := loadSystemRoots()
-			if err != nil {
-				t.Fatal("unexpected failure:", err)
-			}
-
-			if r == nil {
-				t.Fatal("nil roots")
-			}
-
-			// Verify that the returned certs match, otherwise report where the mismatch is.
-			for i, cn := range tc.cns {
-				if i >= r.len() {
-					t.Errorf("missing cert %v @ %v", cn, i)
-				} else if r.mustCert(t, i).Subject.CommonName != cn {
-					fmt.Printf("%#v\n", r.mustCert(t, 0).Subject)
-					t.Errorf("unexpected cert common name %q, want %q", r.mustCert(t, i).Subject.CommonName, cn)
-				}
-			}
-			if r.len() > len(tc.cns) {
-				t.Errorf("got %v certs, which is more than %v wanted", r.len(), len(tc.cns))
-			}
-		})
-	}
-}
-
-// Ensure that "SSL_CERT_DIR" when used as the environment
-// variable delimited by colons, allows loadSystemRoots to
-// load all the roots from the respective directories.
-// See https://golang.org/issue/35325.
-func TestLoadSystemCertsLoadColonSeparatedDirs(t *testing.T) {
-	origFile, origDir := os.Getenv(certFileEnv), os.Getenv(certDirEnv)
-	origCertFiles := certFiles[:]
-
-	// To prevent any other certs from being loaded in
-	// through "SSL_CERT_FILE" or from known "certFiles",
-	// clear them all, and they'll be reverting on defer.
-	certFiles = certFiles[:0]
-	os.Setenv(certFileEnv, "")
-
-	defer func() {
-		certFiles = origCertFiles[:]
-		os.Setenv(certDirEnv, origDir)
-		os.Setenv(certFileEnv, origFile)
-	}()
-
-	tmpDir := t.TempDir()
-
-	rootPEMs := []string{
-		gtsRoot,
-		googleLeaf,
-	}
-
-	var certDirs []string
-	for i, certPEM := range rootPEMs {
-		certDir := filepath.Join(tmpDir, fmt.Sprintf("cert-%d", i))
-		if err := os.MkdirAll(certDir, 0755); err != nil {
-			t.Fatalf("Failed to create certificate dir: %v", err)
-		}
-		certOutFile := filepath.Join(certDir, "cert.crt")
-		if err := os.WriteFile(certOutFile, []byte(certPEM), 0655); err != nil {
-			t.Fatalf("Failed to write certificate to file: %v", err)
-		}
-		certDirs = append(certDirs, certDir)
-	}
-
-	// Sanity check: the number of certDirs should be equal to the number of roots.
-	if g, w := len(certDirs), len(rootPEMs); g != w {
-		t.Fatalf("Failed sanity check: len(certsDir)=%d is not equal to len(rootsPEMS)=%d", g, w)
-	}
-
-	// Now finally concatenate them with a colon.
-	colonConcatCertDirs := strings.Join(certDirs, ":")
-	os.Setenv(certDirEnv, colonConcatCertDirs)
-	gotPool, err := loadSystemRoots()
-	if err != nil {
-		t.Fatalf("Failed to load system roots: %v", err)
-	}
-	subjects := gotPool.Subjects()
-	// We expect exactly len(rootPEMs) subjects back.
-	if g, w := len(subjects), len(rootPEMs); g != w {
-		t.Fatalf("Invalid number of subjects: got %d want %d", g, w)
-	}
-
-	wantPool := NewCertPool()
-	for _, certPEM := range rootPEMs {
-		wantPool.AppendCertsFromPEM([]byte(certPEM))
-	}
-	strCertPool := func(p *CertPool) string {
-		return string(bytes.Join(p.Subjects(), []byte("\n")))
-	}
-
-	if !certPoolEqual(gotPool, wantPool) {
-		g, w := strCertPool(gotPool), strCertPool(wantPool)
-		t.Fatalf("Mismatched certPools\nGot:\n%s\n\nWant:\n%s", g, w)
-	}
-}
-
-func TestReadUniqueDirectoryEntries(t *testing.T) {
-	tmp := t.TempDir()
-	temp := func(base string) string { return filepath.Join(tmp, base) }
-	if f, err := os.Create(temp("file")); err != nil {
-		t.Fatal(err)
-	} else {
-		f.Close()
-	}
-	if err := os.Symlink("target-in", temp("link-in")); err != nil {
-		t.Fatal(err)
-	}
-	if err := os.Symlink("../target-out", temp("link-out")); err != nil {
-		t.Fatal(err)
-	}
-	got, err := readUniqueDirectoryEntries(tmp)
-	if err != nil {
-		t.Fatal(err)
-	}
-	gotNames := []string{}
-	for _, fi := range got {
-		gotNames = append(gotNames, fi.Name())
-	}
-	wantNames := []string{"file", "link-out"}
-	if !slices.Equal(gotNames, wantNames) {
-		t.Errorf("got %q; want %q", gotNames, wantNames)
-	}
-}

src/crypto/x509/root_windows.go

@@ -12,9 +12,8 @@ import (
 	"unsafe"
 )
 
-func loadSystemRoots() (*CertPool, error) {
-	return &CertPool{systemPool: true}, nil
-}
+// Windows has no default SSL_CERT_{FILE,DIR} paths.
+var certFiles, certDirectories []string
 
 // Creates a new *syscall.CertContext representing the leaf certificate in an in-memory
 // certificate store containing itself and all of the intermediate certificates specified

src/internal/godebugs/table.go

@@ -81,6 +81,7 @@ var All = []Info{
 	{Name: "x509negativeserial", Package: "crypto/x509", Changed: 23, Old: "1"},
 	{Name: "x509rsacrt", Package: "crypto/x509", Changed: 24, Old: "0"},
 	{Name: "x509sha256skid", Package: "crypto/x509", Changed: 25, Old: "0"},
+	{Name: "x509sslcertoverrideplatform", Package: "crypto/x509", Changed: 27, Old: "0"},
 	{Name: "x509usefallbackroots", Package: "crypto/x509"},
 	{Name: "x509usepolicies", Package: "crypto/x509", Changed: 24, Old: "0"},
 	{Name: "zipinsecurepath", Package: "archive/zip"},

src/runtime/metrics/doc.go

@@ -441,6 +441,11 @@ Below is the full list of supported metrics, ordered lexicographically.
 		The number of non-default behaviors executed by the crypto/x509
 		package due to a non-default GODEBUG=x509sha256skid=... setting.
 
+	/godebug/non-default-behavior/x509sslcertoverrideplatform:events
+		The number of non-default behaviors executed by
+		the crypto/x509 package due to a non-default
+		GODEBUG=x509sslcertoverrideplatform=... setting.
+
 	/godebug/non-default-behavior/x509usefallbackroots:events
 		The number of non-default behaviors executed by the crypto/x509
 		package due to a non-default GODEBUG=x509usefallbackroots=...