feat(cnbBuild): support builders with different CNB user ids (#4625)

Co-authored-by: Ralf Pannemans <ralf.pannemans@sap.com>

pkg/cnbutils/user.go

@@ -0,0 +1,32 @@
+package cnbutils
+
+import (
+	"os"
+	"strconv"
+
+	"github.com/pkg/errors"
+)
+
+func CnbUserInfo() (int, int, error) {
+	uidStr, ok := os.LookupEnv("CNB_USER_ID")
+	if !ok {
+		return 0, 0, errors.New("environment variable CNB_USER_ID not found")
+	}
+
+	gidStr, ok := os.LookupEnv("CNB_GROUP_ID")
+	if !ok {
+		return 0, 0, errors.New("environment variable CNB_GROUP_ID not found")
+	}
+
+	uid, err := strconv.Atoi(uidStr)
+	if err != nil {
+		return 0, 0, err
+	}
+
+	gid, err := strconv.Atoi(gidStr)
+	if err != nil {
+		return 0, 0, err
+	}
+
+	return uid, gid, nil
+}

pkg/command/command.go

@@ -42,6 +42,7 @@ type runner interface {
 type ExecRunner interface {
 	runner
 	RunExecutable(executable string, params ...string) error
+	RunExecutableWithAttrs(executable string, sysProcAttr *syscall.SysProcAttr, params ...string) error
 	RunExecutableInBackground(executable string, params ...string) (Execution, error)
 }
 
@@ -127,9 +128,18 @@ func (c *Command) RunShell(shell, script string) error {
 //
 //	Thus the executable needs to be on the PATH of the current process and it is not sufficient to alter the PATH on cmd.Env.
 func (c *Command) RunExecutable(executable string, params ...string) error {
+	return c.RunExecutableWithAttrs(executable, nil, params...)
+}
+
+// RunExecutableWithAttrs runs the specified executable with parameters and as a specified UID and GID
+// !! While the cmd.Env is applied during command execution, it is NOT involved when the actual executable is resolved.
+//
+//	Thus the executable needs to be on the PATH of the current process and it is not sufficient to alter the PATH on cmd.Env.
+func (c *Command) RunExecutableWithAttrs(executable string, sysProcAttr *syscall.SysProcAttr, params ...string) error {
 	c.prepareOut()
 
 	cmd := ExecCommand(executable, params...)
+	cmd.SysProcAttr = sysProcAttr
 
 	if len(c.dir) > 0 {
 		cmd.Dir = c.dir

pkg/mock/fileUtils.go

@@ -511,6 +511,10 @@ func (f *FilesMock) Chmod(path string, mode os.FileMode) error {
 	return nil
 }
 
+func (f *FilesMock) Chown(path string, uid, gid int) error {
+	return nil
+}
+
 func (f *FilesMock) Abs(path string) (string, error) {
 	f.init()
 	return f.toAbsPath(path), nil

pkg/mock/runner.go

@@ -7,6 +7,7 @@ import (
 	"io"
 	"regexp"
 	"strings"
+	"syscall"
 
 	"github.com/SAP/jenkins-library/pkg/command"
 )
@@ -25,10 +26,11 @@ type ExecMockRunner struct {
 }
 
 type ExecCall struct {
-	Execution *Execution
-	Async     bool
-	Exec      string
-	Params    []string
+	Execution    *Execution
+	SysProcAttrs *syscall.SysProcAttr
+	Async        bool
+	Exec         string
+	Params       []string
 }
 
 type Execution struct {
@@ -61,8 +63,11 @@ func (m *ExecMockRunner) AppendEnv(e []string) {
 }
 
 func (m *ExecMockRunner) RunExecutable(e string, p ...string) error {
+	return m.RunExecutableWithAttrs(e, nil, p...)
+}
 
-	exec := ExecCall{Exec: e, Params: p}
+func (m *ExecMockRunner) RunExecutableWithAttrs(e string, attrs *syscall.SysProcAttr, p ...string) error {
+	exec := ExecCall{Exec: e, SysProcAttrs: attrs, Params: p}
 	m.Calls = append(m.Calls, exec)
 
 	c := strings.Join(append([]string{e}, p...), " ")

pkg/piperutils/fileUtils.go

@@ -31,6 +31,7 @@ type FileUtils interface {
 	FileRemove(path string) error
 	MkdirAll(path string, perm os.FileMode) error
 	Chmod(path string, mode os.FileMode) error
+	Chown(path string, uid, gid int) error
 	Glob(pattern string) (matches []string, err error)
 	Chdir(path string) error
 	TempDir(string, string) (string, error)
@@ -144,6 +145,17 @@ func (f Files) Chmod(path string, mode os.FileMode) error {
 	return os.Chmod(path, mode)
 }
 
+// Chown is a recursive wrapper for os.Chown().
+func (f Files) Chown(path string, uid, gid int) error {
+	return filepath.WalkDir(path, func(name string, d fs.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+
+		return os.Chown(name, uid, gid)
+	})
+}
+
 // Unzip will decompress a zip archive, moving all files and folders
 // within the zip file (parameter 1) to an output directory (parameter 2).
 // from https://golangcode.com/unzip-files-in-go/ with the following license: