crypto/x509: use the platform verifier on iOS

Use the same certificate verification APIs on iOS as on macOS (they
share the same APIs, so we should be able to transparently use them
on both.)

Updates #46287
Fixes #38843

Change-Id: If70f99b0823dd5fa747c42ff4f20c3b625605327
Reviewed-on: https://go-review.googlesource.com/c/go/+/353403
Trust: Roland Shoemaker <roland@golang.org>
Reviewed-by: Filippo Valsorda <filippo@golang.org>
Run-TryBot: Roland Shoemaker <roland@golang.org>

Author: rolandshoemaker

src/cmd/dist/test.go

@@ -499,17 +499,6 @@ func (t *tester) registerTests() {
 		})
 	}
 
-	if t.iOS() && !t.compileOnly {
-		t.tests = append(t.tests, distTest{
-			name:    "x509omitbundledroots",
-			heading: "crypto/x509 without bundled roots",
-			fn: func(dt *distTest) error {
-				t.addCmd(dt, "src", t.goTest(), t.timeout(300), "-tags=x509omitbundledroots", "-run=OmitBundledRoots", "crypto/x509")
-				return nil
-			},
-		})
-	}
-
 	// Test ios/amd64 for the iOS simulator.
 	if goos == "darwin" && goarch == "amd64" && t.cgoEnabled {
 		t.tests = append(t.tests, distTest{

src/crypto/x509/cert_pool.go

@@ -108,6 +108,8 @@ func SystemCertPool() (*CertPool, error) {
 		return nil, errors.New("crypto/x509: system root pool is not available on Windows")
 	} else if runtime.GOOS == "darwin" {
 		return nil, errors.New("crypto/x509: system root pool is not available on macOS")
+	} else if runtime.GOOS == "ios" {
+		return nil, errors.New("crypto/x509: system root pool is not available on iOS")
 	}
 
 	if sysRoots := systemRootsPool(); sysRoots != nil {

src/crypto/x509/root_darwin.go

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build !ios
-
 package x509
 
 import (

src/crypto/x509/root_ios.go

@@ -742,7 +742,7 @@ func (c *Certificate) Verify(opts VerifyOptions) (chains [][]*Certificate, err e
 	}
 
 	// Use platform verifiers, where available
-	if opts.Roots == nil && (runtime.GOOS == "windows" || runtime.GOOS == "darwin") {
+	if opts.Roots == nil && (runtime.GOOS == "windows" || runtime.GOOS == "darwin" || runtime.GOOS == "ios") {
 		return c.systemVerify(&opts)
 	}
 

src/crypto/x509/root_ios_gen.go

@@ -1836,7 +1836,7 @@ func TestLongChain(t *testing.T) {
 }
 
 func TestSystemRootsError(t *testing.T) {
-	if runtime.GOOS == "windows" || runtime.GOOS == "darwin" {
+	if runtime.GOOS == "windows" || runtime.GOOS == "darwin" || runtime.GOOS == "ios" {
 		t.Skip("Windows and darwin do not use (or support) systemRoots")
 	}
 

src/crypto/x509/root_omit.go

@@ -1975,7 +1975,7 @@ func TestMultipleRDN(t *testing.T) {
 }
 
 func TestSystemCertPool(t *testing.T) {
-	if runtime.GOOS == "windows" || runtime.GOOS == "darwin" {
+	if runtime.GOOS == "windows" || runtime.GOOS == "darwin" || runtime.GOOS == "ios" {
 		t.Skip("not implemented on Windows (Issue 16736, 18609) or darwin (Issue 46287)")
 	}
 	a, err := SystemCertPool()