Authenticate releases using the embedded verification key.

Fixes #15.

Signed-off-by: Piotr Sikora <piotrsikora@google.com>

Author: PiotrSikora

WORKSPACE

@@ -34,6 +34,34 @@ go_repository(
     version = "v0.24.3",
 )
 
+go_repository(
+    name = "org_golang_x_crypto",
+    importpath = "golang.org/x/crypto",
+    sum = "h1:pLI5jrR7OSLijeIDcmRxNmw2api+jEfxLoykJVice/E=",
+    version = "v0.0.0-20201016220609-9e8e0b390897",
+)
+
+go_repository(
+    name = "org_golang_x_net",
+    importpath = "golang.org/x/net",
+    sum = "h1:0GoQqolDA55aaLxZyTzK/Y2ePZzZTUrRacwib7cNsYQ=",
+    version = "v0.0.0-20190404232315-eb5bcb51f2a3",
+)
+
+go_repository(
+    name = "org_golang_x_sys",
+    importpath = "golang.org/x/sys",
+    sum = "h1:+R4KGOnez64A81RvjARKc4UT5/tI9ujCIVX+P5KiHuI=",
+    version = "v0.0.0-20190412213103-97732733099d",
+)
+
+go_repository(
+    name = "org_golang_x_text",
+    importpath = "golang.org/x/text",
+    sum = "h1:g61tztE5qeGQ89tm6NTjjM9VPIm088od1l6aSorWRWg=",
+    version = "v0.3.0",
+)
+
 gazelle_dependencies()
 
 go_repository(

core/repositories.go

@@ -175,7 +175,7 @@ func (r *Repositories) DownloadFromBaseURL(baseURL, version, destDir, destFile s
 	}
 
 	url := fmt.Sprintf("%s/%s/%s", baseURL, version, srcFile)
-	return httputil.DownloadBinary(url, destDir, destFile)
+	return httputil.DownloadBinary(url, "", "", destDir, destFile)
 }
 
 // CreateRepositories creates a new Repositories instance with the given repositories. Any nil repository will be replaced by a dummy repository that raises an error whenever a download is attempted.

go.mod

@@ -6,4 +6,5 @@ require (
 	github.com/bazelbuild/rules_go v0.24.3
 	github.com/hashicorp/go-version v1.2.1
 	github.com/mitchellh/go-homedir v1.1.0
+	golang.org/x/crypto v0.0.0-20201016220609-9e8e0b390897
 )

go.sum

@@ -4,3 +4,10 @@ github.com/hashicorp/go-version v1.2.1 h1:zEfKbn2+PDgroKdiOzqiE8rsmLqU2uwi5PB5pB
 github.com/hashicorp/go-version v1.2.1/go.mod h1:fltr4n8CU8Ke44wwGCBoEymUuxUHl09ZGVZPK5anwXA=
 github.com/mitchellh/go-homedir v1.1.0 h1:lukF9ziXFxDFPkA1vsr5zpc1XuPDn/wFntq5mG+4E0Y=
 github.com/mitchellh/go-homedir v1.1.0/go.mod h1:SfyaCUpYCn1Vlf4IUYiD9fPX4A5wJrkLzIz1N1q0pr0=
+golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
+golang.org/x/crypto v0.0.0-20201016220609-9e8e0b390897 h1:pLI5jrR7OSLijeIDcmRxNmw2api+jEfxLoykJVice/E=
+golang.org/x/crypto v0.0.0-20201016220609-9e8e0b390897/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
+golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
+golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
+golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=

httputil/BUILD

@@ -5,4 +5,5 @@ go_library(
     srcs = ["httputil.go"],
     importpath = "github.com/bazelbuild/bazelisk/httputil",
     visibility = ["//visibility:public"],
+    deps = ["@org_golang_x_crypto//openpgp:go_default_library"],
 )

httputil/httputil.go

@@ -3,12 +3,14 @@ package httputil
 
 import (
 	"fmt"
+	"golang.org/x/crypto/openpgp"
 	"io"
 	"io/ioutil"
 	"log"
 	"net/http"
 	"os"
 	"path/filepath"
+	"strings"
 	"time"
 )
 
@@ -51,7 +53,7 @@ func ReadRemoteFile(url string, token string) ([]byte, error) {
 }
 
 // DownloadBinary downloads a file from the given URL into the specified location, marks it executable and returns its full path.
-func DownloadBinary(originURL, destDir, destFile string) (string, error) {
+func DownloadBinary(originURL, signatureURL, verificationKey, destDir, destFile string) (string, error) {
 	err := os.MkdirAll(destDir, 0755)
 	if err != nil {
 		return "", fmt.Errorf("could not create directory %s: %v", destDir, err)
@@ -91,6 +93,38 @@ func DownloadBinary(originURL, destDir, destFile string) (string, error) {
 			return "", fmt.Errorf("could not chmod file %s: %v", tmpfile.Name(), err)
 		}
 
+		if signatureURL != "" && verificationKey != "" {
+			tmpfile.Seek(0, io.SeekStart)
+
+			signature, err := getClient().Get(signatureURL)
+			if err != nil {
+				return "", fmt.Errorf("HTTP GET %s failed: %v", signatureURL, err)
+			}
+			defer signature.Body.Close()
+
+			if signature.StatusCode != 200 {
+				return "", fmt.Errorf("HTTP GET %s failed with error %v", signatureURL, signature.StatusCode)
+			}
+
+			keys, err := openpgp.ReadArmoredKeyRing(strings.NewReader(verificationKey))
+			if err != nil {
+				return "", fmt.Errorf("failed to load the embedded Verification Key")
+			}
+
+			if len(keys) != 1 {
+				return "", fmt.Errorf("failed to load the embedded Verification Key")
+			}
+
+			entity, err := openpgp.CheckDetachedSignature(keys, tmpfile, signature.Body)
+			if err != nil {
+				return "", fmt.Errorf("failed to verify the downloaded file using signature from %s", signatureURL)
+			}
+
+			for _, identity := range entity.Identities {
+				log.Printf("Signed by %s", identity.Name)
+			}
+		}
+
 		tmpfile.Close()
 		err = os.Rename(tmpfile.Name(), destinationPath)
 		if err != nil {

repositories/gcs.go

@@ -19,6 +19,60 @@ const (
 	candidateBaseURL    = "https://releases.bazel.build"
 	nonCandidateBaseURL = "https://storage.googleapis.com/bazel-builds/artifacts"
 	lastGreenBaseURL    = "https://storage.googleapis.com/bazel-untrusted-builds/last_green_commit/"
+	verificationKey     = `
+-----BEGIN PGP PUBLIC KEY BLOCK-----
+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+TVbJSpwNiLlPIcGVaCjXp8Ow3SzOGTRKIjFTO/I6FiSJOpgfri07clXmnb4ETjou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+Zk8xeE5UUIxFMdOxF8B7Itb6rbFWv+tzWdX/0/M8/b0ZJhVvngWzuh/agdS4E5an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Embu
+-----END PGP PUBLIC KEY BLOCK-----
+`
 )
 
 var (
@@ -106,7 +160,7 @@ func (gcs *GCSRepo) DownloadRelease(version, destDir, destFile string) (string,
 	}
 
 	url := fmt.Sprintf("%s/%s/release/%s", candidateBaseURL, version, srcFile)
-	return httputil.DownloadBinary(url, destDir, destFile)
+	return httputil.DownloadBinary(url, url+".sig", verificationKey, destDir, destFile)
 }
 
 func (gcs *GCSRepo) removeCandidates(history []string, lastN int) ([]string, error) {
@@ -189,7 +243,7 @@ func (gcs *GCSRepo) DownloadCandidate(version, destDir, destFile string) (string
 	baseVersion := versionComponents[0]
 	rcVersion := "rc" + versionComponents[1]
 	url := fmt.Sprintf("%s/%s/%s/%s", candidateBaseURL, baseVersion, rcVersion, srcFile)
-	return httputil.DownloadBinary(url, destDir, destFile)
+	return httputil.DownloadBinary(url, url+".sig", verificationKey, destDir, destFile)
 }
 
 // CommitRepo
@@ -210,5 +264,5 @@ func (gcs *GCSRepo) GetLastGreenCommit(bazeliskHome string, downstreamGreen bool
 func (gcs *GCSRepo) DownloadAtCommit(commit, destDir, destFile string) (string, error) {
 	log.Printf("Using unreleased version at commit %s", commit)
 	url := fmt.Sprintf("%s/%s/%s/bazel", nonCandidateBaseURL, platforms.GetPlatform(), commit)
-	return httputil.DownloadBinary(url, destDir, destFile)
+	return httputil.DownloadBinary(url, "", "", destDir, destFile)
 }

repositories/github.go

@@ -59,5 +59,5 @@ func (gh *GitHubRepo) DownloadVersion(fork, version, destDir, destFile string) (
 		return "", err
 	}
 	url := fmt.Sprintf(urlPattern, fork, version, filename)
-	return httputil.DownloadBinary(url, destDir, destFile)
+	return httputil.DownloadBinary(url, "", "", destDir, destFile)
 }