Add support for custom platform

cmd/kaniko-docker/main.go

@@ -12,7 +12,7 @@ import (
 	"github.com/urfave/cli"
 
 	kaniko "github.com/drone/drone-kaniko"
-	"github.com/drone/drone-kaniko/cmd/artifact"
+	"github.com/drone/drone-kaniko/pkg/artifact"
 )
 
 const (
@@ -145,6 +145,11 @@ func main() {
 			Usage:  "Set this flag with value as oneof <panic|fatal|error|warn|info|debug|trace> to set the logging level for kaniko. Defaults to info.",
 			EnvVar: "PLUGIN_VERBOSITY",
 		},
+		cli.StringFlag{
+			Name:   "platform",
+			Usage:  "Allows to build with another default platform than the host, similarly to docker build --platform",
+			EnvVar: "PLUGIN_PLATFORM",
+		},
 	}
 
 	if err := app.Run(os.Args); err != nil {
@@ -181,6 +186,7 @@ func run(c *cli.Context) error {
 			DigestFile:    defaultDigestFile,
 			NoPush:        noPush,
 			Verbosity:     c.String("verbosity"),
+			Platform:      c.String("platform"),
 		},
 		Artifact: kaniko.Artifact{
 			Tags:         c.StringSlice("tags"),

cmd/kaniko-ecr/main.go

@@ -14,7 +14,7 @@ import (
 	"github.com/aws/aws-sdk-go-v2/service/ecrpublic"
 	"github.com/aws/smithy-go"
 	kaniko "github.com/drone/drone-kaniko"
-	"github.com/drone/drone-kaniko/cmd/artifact"
+	"github.com/drone/drone-kaniko/pkg/artifact"
 	"github.com/drone/drone-kaniko/pkg/docker"
 	"github.com/joho/godotenv"
 	"github.com/pkg/errors"
@@ -174,6 +174,11 @@ func main() {
 			Usage:  "Set this flag with value as oneof <panic|fatal|error|warn|info|debug|trace> to set the logging level for kaniko. Defaults to info.",
 			EnvVar: "PLUGIN_VERBOSITY",
 		},
+		cli.StringFlag{
+			Name:   "platform",
+			Usage:  "Allows to build with another default platform than the host, similarly to docker build --platform",
+			EnvVar: "PLUGIN_PLATFORM",
+		},
 	}
 
 	if err := app.Run(os.Args); err != nil {
@@ -252,6 +257,7 @@ func run(c *cli.Context) error {
 			DigestFile:   defaultDigestFile,
 			NoPush:       noPush,
 			Verbosity:    c.String("verbosity"),
+			Platform:     c.String("platform"),
 		},
 		Artifact: kaniko.Artifact{
 			Tags:         c.StringSlice("tags"),

cmd/kaniko-gcr/main.go

@@ -11,7 +11,7 @@ import (
 	"github.com/urfave/cli"
 
 	kaniko "github.com/drone/drone-kaniko"
-	"github.com/drone/drone-kaniko/cmd/artifact"
+	"github.com/drone/drone-kaniko/pkg/artifact"
 )
 
 const (
@@ -130,6 +130,11 @@ func main() {
 			Usage:  "Set this flag as --verbosity=<panic|fatal|error|warn|info|debug|trace> to set the logging level for kaniko. Defaults to info.",
 			EnvVar: "PLUGIN_VERBOSITY",
 		},
+		cli.StringFlag{
+			Name:   "platform",
+			Usage:  "Allows to build with another default platform than the host, similarly to docker build --platform",
+			EnvVar: "PLUGIN_PLATFORM",
+		},
 	}
 
 	if err := app.Run(os.Args); err != nil {
@@ -141,8 +146,10 @@ func run(c *cli.Context) error {
 	noPush := c.Bool("no-push")
 	jsonKey := c.String("json-key")
 
-	// only setup auth when pushing or credentials are defined
-	if !noPush || jsonKey != "" {
+	// JSON key may not be set in the following cases:
+	// 1. Image does not need to be pushed to GCR.
+	// 2. Workload identity is set on GKE in which pod will inherit the credentials via service account.
+	if jsonKey != "" {
 		if err := setupGCRAuth(jsonKey); err != nil {
 			return err
 		}
@@ -165,6 +172,7 @@ func run(c *cli.Context) error {
 			DigestFile:   defaultDigestFile,
 			NoPush:       noPush,
 			Verbosity:    c.String("verbosity"),
+			Platform:     c.String("platform"),
 		},
 		Artifact: kaniko.Artifact{
 			Tags:         c.StringSlice("tags"),
@@ -178,10 +186,6 @@ func run(c *cli.Context) error {
 }
 
 func setupGCRAuth(jsonKey string) error {
-	if jsonKey == "" {
-		return fmt.Errorf("GCR JSON key must be specified")
-	}
-
 	err := ioutil.WriteFile(gcrKeyPath, []byte(jsonKey), 0644)
 	if err != nil {
 		return errors.Wrap(err, "failed to write GCR JSON key")

kaniko.go

@@ -7,7 +7,7 @@ import (
 	"os/exec"
 	"strings"
 
-	"github.com/drone/drone-kaniko/cmd/artifact"
+	"github.com/drone/drone-kaniko/pkg/artifact"
 	"golang.org/x/mod/semver"
 )
 
@@ -30,6 +30,7 @@ type (
 		DigestFile    string   // Digest file location
 		NoPush        bool     // Set this flag if you only want to build the image, without pushing to a registry
 		Verbosity     string   // Log level
+		Platform      string   // Allows to build with another default platform than the host, similarly to docker build --platform
 	}
 
 	// Artifact defines content of artifact file
@@ -157,6 +158,10 @@ func (p Plugin) Exec() error {
 		cmdArgs = append(cmdArgs, fmt.Sprintf("--verbosity=%s", p.Build.Verbosity))
 	}
 
+	if p.Build.Platform != "" {
+		cmdArgs = append(cmdArgs, fmt.Sprintf("--customPlatform=%s", p.Build.Platform))
+	}
+
 	cmd := exec.Command("/kaniko/executor", cmdArgs...)
 	cmd.Stdout = os.Stdout
 	cmd.Stderr = os.Stderr