crypto/x509/internal/macos: return errors when CFRef might be NULL

Updates #51759

Change-Id: Ib73fa5ec62d90c7e595150217b048158789f1afd
Reviewed-on: https://go-review.googlesource.com/c/go/+/394674
Run-TryBot: Filippo Valsorda <filippo@golang.org>
Trust: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Roland Shoemaker <roland@golang.org>

src/crypto/x509/internal/macos/corefoundation.go

@@ -37,9 +37,12 @@ func CFDataToSlice(data CFRef) []byte {
 }
 
 // CFStringToString returns a Go string representation of the passed
-// in CFString.
+// in CFString, or an empty string if it's invalid.
 func CFStringToString(ref CFRef) string {
-	data := CFStringCreateExternalRepresentation(ref)
+	data, err := CFStringCreateExternalRepresentation(ref)
+	if err != nil {
+		return ""
+	}
 	b := CFDataToSlice(data)
 	CFRelease(data)
 	return string(b)
@@ -186,9 +189,12 @@ func x509_CFErrorCopyDescription_trampoline()
 
 //go:cgo_import_dynamic x509_CFStringCreateExternalRepresentation CFStringCreateExternalRepresentation "/System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation"
 
-func CFStringCreateExternalRepresentation(strRef CFRef) CFRef {
+func CFStringCreateExternalRepresentation(strRef CFRef) (CFRef, error) {
 	ret := syscall(abi.FuncPCABI0(x509_CFStringCreateExternalRepresentation_trampoline), kCFAllocatorDefault, uintptr(strRef), kCFStringEncodingUTF8, 0, 0, 0)
-	return CFRef(ret)
+	if ret == 0 {
+		return 0, errors.New("string can't be represented as UTF-8")
+	}
+	return CFRef(ret), nil
 }
 func x509_CFStringCreateExternalRepresentation_trampoline()
 

src/crypto/x509/internal/macos/security.go

@@ -131,11 +131,16 @@ func x509_SecTrustCreateWithCertificates_trampoline()
 
 //go:cgo_import_dynamic x509_SecCertificateCreateWithData SecCertificateCreateWithData "/System/Library/Frameworks/Security.framework/Versions/A/Security"
 
-func SecCertificateCreateWithData(b []byte) CFRef {
+func SecCertificateCreateWithData(b []byte) (CFRef, error) {
 	data := BytesToCFData(b)
+	defer CFRelease(data)
 	ret := syscall(abi.FuncPCABI0(x509_SecCertificateCreateWithData_trampoline), kCFAllocatorDefault, uintptr(data), 0, 0, 0, 0)
-	CFRelease(data)
-	return CFRef(ret)
+	// Returns NULL if the data passed in the data parameter is not a valid
+	// DER-encoded X.509 certificate.
+	if ret == 0 {
+		return 0, errors.New("SecCertificateCreateWithData: invalid certificate")
+	}
+	return CFRef(ret), nil
 }
 func x509_SecCertificateCreateWithData_trampoline()
 

src/crypto/x509/root_darwin.go

@@ -12,8 +12,8 @@ import (
 func (c *Certificate) systemVerify(opts *VerifyOptions) (chains [][]*Certificate, err error) {
 	certs := macOS.CFArrayCreateMutable()
 	defer macOS.ReleaseCFArray(certs)
-	leaf := macOS.SecCertificateCreateWithData(c.Raw)
-	if leaf == 0 {
+	leaf, err := macOS.SecCertificateCreateWithData(c.Raw)
+	if err != nil {
 		return nil, errors.New("invalid leaf certificate")
 	}
 	macOS.CFArrayAppendValue(certs, leaf)
@@ -23,8 +23,8 @@ func (c *Certificate) systemVerify(opts *VerifyOptions) (chains [][]*Certificate
 			if err != nil {
 				return nil, err
 			}
-			sc := macOS.SecCertificateCreateWithData(c.Raw)
-			if sc != 0 {
+			sc, err := macOS.SecCertificateCreateWithData(c.Raw)
+			if err == nil {
 				macOS.CFArrayAppendValue(certs, sc)
 			}
 		}