dex/cmd/docker-entrypoint/main.go

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// Package main provides a utility program to launch the Dex container process with an optional
// templating step (provided by gomplate).
//
// This was originally written as a shell script, but we rewrote it as a Go program so that it could
// run as a raw binary in a distroless container.
package main
import (
"fmt"
"os"
"os/exec"
"strings"
"syscall"
)
func main() {
// Note that this docker-entrypoint program is args[0], and it is provided with the true process
// args.
args := os.Args[1:]
if err := run(args, realExec, realWhich); err != nil {
fmt.Println("error:", err.Error())
os.Exit(1)
}
}
func realExec(fork bool, args ...string) error {
if fork {
if output, err := exec.Command(args[0], args[1:]...).CombinedOutput(); err != nil {
return fmt.Errorf("cannot fork/exec command %s: %w (output: %q)", args, err, string(output))
}
return nil
}
argv0, err := exec.LookPath(args[0])
if err != nil {
return fmt.Errorf("cannot lookup path for command %s: %w", args[0], err)
}
if err := syscall.Exec(argv0, args, os.Environ()); err != nil {
return fmt.Errorf("cannot exec command %s (%q): %w", args, argv0, err)
}
return nil
}
func realWhich(path string) string {
fullPath, err := exec.LookPath(path)
if err != nil {
return ""
}
return fullPath
}
func run(args []string, execFunc func(bool, ...string) error, whichFunc func(string) string) error {
if args[0] != "dex" && args[0] != whichFunc("dex") {
return execFunc(false, args...)
}
if args[1] != "serve" {
return execFunc(false, args...)
}
newArgs := []string{}
for _, tplCandidate := range args {
if hasSuffixes(tplCandidate, ".tpl", ".tmpl", ".yaml") {
tmpFile, err := os.CreateTemp("/tmp", "dex.config.yaml-*")
if err != nil {
return fmt.Errorf("cannot create temp file: %w", err)
}
if err := execFunc(true, "gomplate", "-f", tplCandidate, "-o", tmpFile.Name()); err != nil {
return err
}
newArgs = append(newArgs, tmpFile.Name())
} else {
newArgs = append(newArgs, tplCandidate)
}
}
return execFunc(false, newArgs...)
}
func hasSuffixes(s string, suffixes ...string) bool {
for _, suffix := range suffixes {
if strings.HasSuffix(s, suffix) {
return true
}
}
return false
}