1 files changed, 243 insertions, 0 deletions
diff --git a/src/crypto/x509/root_darwin.go b/src/crypto/x509/root_darwin.go
new file mode 100644
index 0000000000..ce88de025e
--- /dev/null
+++ b/src/crypto/x509/root_darwin.go
@@ -0,0 +1,243 @@
+// Copyright 2020 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.
+
+// +build !ios
+
+package x509
+
+import (
+	"bytes"
+	macOS "crypto/x509/internal/macos"
+	"fmt"
+	"os"
+	"strings"
+)
+
+var debugDarwinRoots = strings.Contains(os.Getenv("GODEBUG"), "x509roots=1")
+
+func (c *Certificate) systemVerify(opts *VerifyOptions) (chains [][]*Certificate, err error) {
+	return nil, nil
+}
+
+// loadSystemRootsWithCgo is set in root_cgo_darwin_amd64.go when cgo is
+// available, and is only used for testing.
+var loadSystemRootsWithCgo func() (*CertPool, error)
+
+func loadSystemRoots() (*CertPool, error) {
+	var trustedRoots []*Certificate
+	untrustedRoots := make(map[string]bool)
+
+	// macOS has three trust domains: one for CAs added by users to their
+	// "login" keychain, one for CAs added by Admins to the "System" keychain,
+	// and one for the CAs that ship with the OS.
+	for _, domain := range []macOS.SecTrustSettingsDomain{
+		macOS.SecTrustSettingsDomainUser,
+		macOS.SecTrustSettingsDomainAdmin,
+		macOS.SecTrustSettingsDomainSystem,
+	} {
+		certs, err := macOS.SecTrustSettingsCopyCertificates(domain)
+		if err == macOS.ErrNoTrustSettings {
+			continue
+		} else if err != nil {
+			return nil, err
+		}
+		defer macOS.CFRelease(certs)
+
+		for i := 0; i < macOS.CFArrayGetCount(certs); i++ {
+			c := macOS.CFArrayGetValueAtIndex(certs, i)
+			cert, err := exportCertificate(c)
+			if err != nil {
+				if debugDarwinRoots {
+					fmt.Fprintf(os.Stderr, "crypto/x509: domain %d, certificate #%d: %v\n", domain, i, err)
+				}
+				continue
+			}
+
+			var result macOS.SecTrustSettingsResult
+			if domain == macOS.SecTrustSettingsDomainSystem {
+				// Certs found in the system domain are always trusted. If the user
+				// configures "Never Trust" on such a cert, it will also be found in the
+				// admin or user domain, causing it to be added to untrustedRoots.
+				result = macOS.SecTrustSettingsResultTrustRoot
+			} else {
+				result, err = sslTrustSettingsResult(c)
+				if err != nil {
+					if debugDarwinRoots {
+						fmt.Fprintf(os.Stderr, "crypto/x509: trust settings for %v: %v\n", cert.Subject, err)
+					}
+					continue
+				}
+				if debugDarwinRoots {
+					fmt.Fprintf(os.Stderr, "crypto/x509: trust settings for %v: %d\n", cert.Subject, result)
+				}
+			}
+
+			switch result {
+			// "Note the distinction between the results kSecTrustSettingsResultTrustRoot
+			// and kSecTrustSettingsResultTrustAsRoot: The former can only be applied to
+			// root (self-signed) certificates; the latter can only be applied to
+			// non-root certificates."
+			case macOS.SecTrustSettingsResultTrustRoot:
+				if isRootCertificate(cert) {
+					trustedRoots = append(trustedRoots, cert)
+				}
+			case macOS.SecTrustSettingsResultTrustAsRoot:
+				if !isRootCertificate(cert) {
+					trustedRoots = append(trustedRoots, cert)
+				}
+
+			case macOS.SecTrustSettingsResultDeny:
+				// Add this certificate to untrustedRoots, which are subtracted
+				// from trustedRoots, so that we don't have to evaluate policies
+				// for every root in the system domain, but still apply user and
+				// admin policies that override system roots.
+				untrustedRoots[string(cert.Raw)] = true
+
+			case macOS.SecTrustSettingsResultUnspecified:
+				// Certificates with unspecified trust should be added to a pool
+				// of intermediates for chain building, but we don't support it
+				// at the moment. This is Issue 35631.
+
+			default:
+				if debugDarwinRoots {
+					fmt.Fprintf(os.Stderr, "crypto/x509: unknown trust setting for %v: %d\n", cert.Subject, result)
+				}
+			}
+		}
+	}
+
+	pool := NewCertPool()
+	for _, cert := range trustedRoots {
+		if !untrustedRoots[string(cert.Raw)] {
+			pool.AddCert(cert)
+		}
+	}
+	return pool, nil
+}
+
+// exportCertificate returns a *Certificate for a SecCertificateRef.
+func exportCertificate(cert macOS.CFRef) (*Certificate, error) {
+	data, err := macOS.SecItemExport(cert)
+	if err != nil {
+		return nil, err
+	}
+	defer macOS.CFRelease(data)
+	der := macOS.CFDataToSlice(data)
+
+	return ParseCertificate(der)
+}
+
+// isRootCertificate reports whether Subject and Issuer match.
+func isRootCertificate(cert *Certificate) bool {
+	return bytes.Equal(cert.RawSubject, cert.RawIssuer)
+}
+
+// sslTrustSettingsResult obtains the final kSecTrustSettingsResult value for a
+// certificate in the user or admin domain, combining usage constraints for the
+// SSL SecTrustSettingsPolicy,
+//
+// It ignores SecTrustSettingsKeyUsage and kSecTrustSettingsAllowedError, and
+// doesn't support kSecTrustSettingsDefaultRootCertSetting.
+//
+// https://developer.apple.com/documentation/security/1400261-sectrustsettingscopytrustsetting
+func sslTrustSettingsResult(cert macOS.CFRef) (macOS.SecTrustSettingsResult, error) {
+	// In Apple's implementation user trust settings override admin trust settings
+	// (which themselves override system trust settings). If SecTrustSettingsCopyTrustSettings
+	// fails, or returns a NULL trust settings, when looking for the user trust
+	// settings then fallback to checking the admin trust settings.
+	//
+	// See Security-59306.41.2/trust/headers/SecTrustSettings.h for a description of
+	// the trust settings overrides, and SecLegacyAnchorSourceCopyUsageConstraints in
+	// Security-59306.41.2/trust/trustd/SecCertificateSource.c for a concrete example
+	// of how Apple applies the override in the case of NULL trust settings, or non
+	// success errors.
+	trustSettings, err := macOS.SecTrustSettingsCopyTrustSettings(cert, macOS.SecTrustSettingsDomainUser)
+	if err != nil || trustSettings == 0 {
+		if debugDarwinRoots && err != macOS.ErrNoTrustSettings {
+			fmt.Fprintf(os.Stderr, "crypto/x509: SecTrustSettingsCopyTrustSettings for SecTrustSettingsDomainUser failed: %s\n", err)
+		}
+		trustSettings, err = macOS.SecTrustSettingsCopyTrustSettings(cert, macOS.SecTrustSettingsDomainAdmin)
+	}
+	if err != nil || trustSettings == 0 {
+		// If there are neither user nor admin trust settings for a certificate returned
+		// from SecTrustSettingsCopyCertificates Apple returns kSecTrustSettingsResultInvalid,
+		// as this method is intended to return certificates _which have trust settings_.
+		// The most likely case for this being triggered is that the existing trust settings
+		// are invalid and cannot be properly parsed. In this case SecTrustSettingsCopyTrustSettings
+		// returns errSecInvalidTrustSettings. The existing cgo implementation returns
+		// kSecTrustSettingsResultUnspecified in this case, which mostly matches the Apple
+		// implementation because we don't do anything with certificates marked with this
+		// result.
+		//
+		// See SecPVCGetTrustSettingsResult in Security-59306.41.2/trust/trustd/SecPolicyServer.c
+		if debugDarwinRoots && err != macOS.ErrNoTrustSettings {
+			fmt.Fprintf(os.Stderr, "crypto/x509: SecTrustSettingsCopyTrustSettings for SecTrustSettingsDomainAdmin failed: %s\n", err)
+		}
+		return macOS.SecTrustSettingsResultUnspecified, nil
+	}
+	defer macOS.CFRelease(trustSettings)
+
+	// "An empty trust settings array means 'always trust this certificate' with an
+	// overall trust setting for the certificate of kSecTrustSettingsResultTrustRoot."
+	if macOS.CFArrayGetCount(trustSettings) == 0 {
+		return macOS.SecTrustSettingsResultTrustRoot, nil
+	}
+
+	isSSLPolicy := func(policyRef macOS.CFRef) bool {
+		properties := macOS.SecPolicyCopyProperties(policyRef)
+		defer macOS.CFRelease(properties)
+		if v, ok := macOS.CFDictionaryGetValueIfPresent(properties, macOS.SecPolicyOid); ok {
+			return macOS.CFEqual(v, macOS.CFRef(macOS.SecPolicyAppleSSL))
+		}
+		return false
+	}
+
+	for i := 0; i < macOS.CFArrayGetCount(trustSettings); i++ {
+		tSetting := macOS.CFArrayGetValueAtIndex(trustSettings, i)
+
+		// First, check if this trust setting is constrained to a non-SSL policy.
+		if policyRef, ok := macOS.CFDictionaryGetValueIfPresent(tSetting, macOS.SecTrustSettingsPolicy); ok {
+			if !isSSLPolicy(policyRef) {
+				continue
+			}
+		}
+
+		// Then check if it is restricted to a hostname, so not a root.
+		if _, ok := macOS.CFDictionaryGetValueIfPresent(tSetting, macOS.SecTrustSettingsPolicyString); ok {
+			continue
+		}
+
+		cfNum, ok := macOS.CFDictionaryGetValueIfPresent(tSetting, macOS.SecTrustSettingsResultKey)
+		// "If this key is not present, a default value of kSecTrustSettingsResultTrustRoot is assumed."
+		if !ok {
+			return macOS.SecTrustSettingsResultTrustRoot, nil
+		}
+		result, err := macOS.CFNumberGetValue(cfNum)
+		if err != nil {
+			return 0, err
+		}
+
+		// If multiple dictionaries match, we are supposed to "OR" them,
+		// the semantics of which are not clear. Since TrustRoot and TrustAsRoot
+		// are mutually exclusive, Deny should probably override, and Invalid and
+		// Unspecified be overridden, approximate this by stopping at the first
+		// TrustRoot, TrustAsRoot or Deny.
+		switch r := macOS.SecTrustSettingsResult(result); r {
+		case macOS.SecTrustSettingsResultTrustRoot,
+			macOS.SecTrustSettingsResultTrustAsRoot,
+			macOS.SecTrustSettingsResultDeny:
+			return r, nil
+		}
+	}
+
+	// If trust settings are present, but none of them match the policy...
+	// the docs don't tell us what to do.
+	//
+	// "Trust settings for a given use apply if any of the dictionaries in the
+	// certificate’s trust settings array satisfies the specified use." suggests
+	// that it's as if there were no trust settings at all, so we should maybe
+	// fallback to the admin trust settings? TODO(golang.org/issue/38888).
+
+	return macOS.SecTrustSettingsResultUnspecified, nil
+}