Regres: Add llvm.Version.Download() to download and verify a LLVM toolchain

tests/regres/llvm/10.0.0.pub.key

+-----BEGIN PGP PUBLIC KEY BLOCK-----
+
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+67H2IH//2sf8dw==
+=ADVe
+-----END PGP PUBLIC KEY BLOCK-----

tests/regres/llvm/llvm.go

@@ -17,7 +17,11 @@
 package llvm
 
 import (
+	"bytes"
 	"fmt"
+	"io/ioutil"
+	"net/http"
+	"os"
 	"os/exec"
 	"path/filepath"
 	"regexp"
@@ -52,6 +56,79 @@ func (v Version) GreaterEqual(rhs Version) bool {
 	return v.Point >= rhs.Point
 }
 
+// Download downloads and verifies the LLVM toolchain for the current OS.
+func (v Version) Download() ([]byte, error) {
+	return v.DownloadForOS(runtime.GOOS)
+}
+
+// DownloadForOS downloads and verifies the LLVM toolchain for the given OS.
+func (v Version) DownloadForOS(osName string) ([]byte, error) {
+	url, sig, key, err := v.DownloadInfoForOS(osName)
+	if err != nil {
+		return nil, err
+	}
+
+	resp, err := http.Get(url)
+	if err != nil {
+		return nil, fmt.Errorf("Could not download LLVM from %v: %v", url, err)
+	}
+	defer resp.Body.Close()
+
+	content, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return nil, fmt.Errorf("Could not download LLVM from %v: %v", url, err)
+	}
+
+	sigfile, err := os.Open(sig)
+	if err != nil {
+		return nil, fmt.Errorf("Couldn't open file '%s': %v", sig, err)
+	}
+	defer sigfile.Close()
+
+	keyfile, err := os.Open(key)
+	if err != nil {
+		return nil, fmt.Errorf("Couldn't open file '%s': %v", key, err)
+	}
+	defer keyfile.Close()
+
+	if err := util.CheckPGP(bytes.NewReader(content), sigfile, keyfile); err != nil {
+		return nil, err
+	}
+	return content, nil
+}
+
+// DownloadInfoForOS returns the download url, signature and key for the given
+// LLVM version for the given OS.
+func (v Version) DownloadInfoForOS(os string) (url, sig, key string, err error) {
+	switch v {
+	case Version{10, 0, 0}:
+		key = relfile("10.0.0.pub.key")
+		switch os {
+		case "linux":
+			url = "https://github.com/llvm/llvm-project/releases/download/llvmorg-10.0.0/clang+llvm-10.0.0-x86_64-linux-gnu-ubuntu-18.04.tar.xz"
+			sig = relfile("10.0.0-ubuntu.sig")
+			return
+		case "darwin":
+			url = "https://github.com/llvm/llvm-project/releases/download/llvmorg-10.0.0/clang+llvm-10.0.0-x86_64-apple-darwin.tar.xz"
+			sig = relfile("10.0.0-darwin.sig")
+			return
+		case "windows":
+			url = "https://github.com/llvm/llvm-project/releases/download/llvmorg-10.0.0/LLVM-10.0.0-win64.exe"
+			sig = relfile("10.0.0-win64.sig")
+			return
+		default:
+			return "", "", "", fmt.Errorf("Unsupported OS: %v", os)
+		}
+	default:
+		return "", "", "", fmt.Errorf("Unknown download for LLVM %v", v)
+	}
+}
+func relfile(path string) string {
+	_, thisFile, _, _ := runtime.Caller(1)
+	thisDir := filepath.Dir(thisFile)
+	return filepath.Join(thisDir, path)
+}
+
 // Toolchain holds the paths and version information about an LLVM toolchain.
 type Toolchain struct {
 	Version Version

tests/regres/llvm/llvm_test.go

+// Copyright 2020 The SwiftShader Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package llvm_test
+
+import (
+	"testing"
+
+	llvm "."
+)
+
+func TestLLVMDownloads(t *testing.T) {
+	for _, version := range []llvm.Version{
+		llvm.Version{Major: 10, Minor: 0, Point: 0},
+	} {
+		t.Logf("Downloading %v...", version)
+		for _, os := range []string{"linux", "darwin", "windows"} {
+			data, err := version.DownloadForOS(os)
+			switch {
+			case err != nil:
+				t.Errorf("Download of LLVM %v failed with: %v", version, err)
+			case len(data) == 0:
+				t.Errorf("Download of LLVM %v resulted in no data", version)
+			default:
+				t.Logf("done\n")
+			}
+		}
+	}
+}

tests/regres/util/pgp.go

+// Copyright 2020 The SwiftShader Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package util
+
+import (
+	"fmt"
+	"io"
+
+	"golang.org/x/crypto/openpgp"
+)
+
+// CheckPGP verifies that data has the PGP signature sig and was signed with the
+// PGP key key.
+func CheckPGP(data, sig, key io.Reader) error {
+	keyring, err := openpgp.ReadArmoredKeyRing(key)
+	if err != nil {
+		return fmt.Errorf("Failed to read pgp key: %v", err)
+	}
+
+	if _, err := openpgp.CheckDetachedSignature(keyring, data, sig); err != nil {
+		return fmt.Errorf("Failed to verify pgp: %v", err)
+	}
+
+	return nil
+}