Enhance subid check by using library function

Fix tab

Declare structs

Error correctly if no ranges found

Signed-off-by: Martin Jackson <[email protected]>

src/cmd/root.go

@@ -16,8 +16,26 @@
 
 package cmd
 
+/*
+#cgo LDFLAGS: -l subid
+#include <shadow/subid.h>
+#include <stdlib.h>
+#include <stdio.h>
+const char *Prog = "storage";
+FILE *shadow_logfd = NULL;
+struct subid_range get_range(struct subid_range *ranges, int i)
+{
+	shadow_logfd = stderr;
+	return ranges[i];
+}
+#if !defined(SUBID_ABI_MAJOR) || (SUBID_ABI_MAJOR < 4)
+# define subid_get_uid_ranges get_subuid_ranges
+# define subid_get_gid_ranges get_subgid_ranges
+#endif
+*/
+import "C"
+
 import (
-	"bufio"
 	"errors"
 	"fmt"
 	"io/ioutil"
@@ -26,6 +44,7 @@ import (
 	"path/filepath"
 	"strings"
 	"syscall"
+	"unsafe"
 
 	"github.com/containers/toolbox/pkg/podman"
 	"github.com/containers/toolbox/pkg/utils"
@@ -66,6 +85,13 @@ type exitError struct {
 	err  error
 }
 
+type subIDRange struct {
+	Start  int
+	Length int
+}
+
+type ranges []subIDRange
+
 func (e *exitError) Error() string {
 	if e.err != nil {
 		return e.err.Error()
@@ -141,15 +167,15 @@ func preRun(cmd *cobra.Command, args []string) error {
 		logrus.Debugf("Running on a cgroups v%d host", cgroupsVersion)
 
 		if currentUser.Uid != "0" {
-			logrus.Debugf("Checking if /etc/subgid and /etc/subuid have entries for user %s",
+			logrus.Debugf("Checking for subuid and subgid have entries for user %s",
 				currentUser.Username)
 
-			if _, err := validateSubIDFile("/etc/subuid"); err != nil {
-				return newSubIDFileError()
+			if _, err := validateSubIDRange(currentUser.Username, true); err != nil {
+				return newSubIDError()
 			}
 
-			if _, err := validateSubIDFile("/etc/subgid"); err != nil {
-				return newSubIDFileError()
+			if _, err := validateSubIDRange(currentUser.Username, false); err != nil {
+				return newSubIDError()
 			}
 		}
 	}
@@ -319,9 +345,9 @@ func migrate() error {
 	return nil
 }
 
-func newSubIDFileError() error {
+func newSubIDError() error {
 	var builder strings.Builder
-	fmt.Fprintf(&builder, "/etc/subgid and /etc/subuid don't have entries for user %s\n", currentUser.Username)
+	fmt.Fprintf(&builder, "Missing subuid and/or subgid entries for user %s\n", currentUser.Username)
 	fmt.Fprintf(&builder, "See the podman(1), subgid(5), subuid(5) and usermod(8) manuals for more\n")
 	fmt.Fprintf(&builder, "information.")
 
@@ -392,28 +418,65 @@ func setUpLoggers() error {
 	return nil
 }
 
-func validateSubIDFile(path string) (bool, error) {
-	logrus.Debugf("Validating sub-ID file %s", path)
+func validateSubIDRange(username string, isUser bool) (ranges, error) {
+	var ret ranges
 
-	file, err := os.Open(path)
-	if err != nil {
-		logrus.Debugf("Validating sub-ID file: failed to open %s: %s", path, err)
-		return false, fmt.Errorf("failed to open %s", path)
+	queryType := ""
+
+	if isUser {
+		queryType = "subuid"
+	} else {
+		queryType = "subgid"
 	}
 
-	scanner := bufio.NewScanner(file)
-	scanner.Split(bufio.ScanLines)
+	uidstr := ""
 
-	prefixes := []string{currentUser.Username + ":", currentUser.Uid + ":"}
+	if username == "ALL" {
+		return nil, errors.New("username ALL not supported")
+	}
 
-	for scanner.Scan() {
-		line := scanner.Text()
-		for _, prefix := range prefixes {
-			if strings.HasPrefix(line, prefix) {
-				return true, nil
-			}
+	if u, err := user.Lookup(username); err == nil {
+		uidstr = u.Uid
+	}
+
+	cUsername := C.CString(username)
+	defer C.free(unsafe.Pointer(cUsername))
+
+	cuidstr := C.CString(uidstr)
+	defer C.free(unsafe.Pointer(cuidstr))
+
+	var nRanges C.int
+	var cRanges *C.struct_subid_range
+	if isUser {
+		nRanges = C.subid_get_uid_ranges(cUsername, &cRanges)
+		if nRanges <= 0 {
+			nRanges = C.subid_get_uid_ranges(cuidstr, &cRanges)
+		}
+	} else {
+		nRanges = C.subid_get_gid_ranges(cUsername, &cRanges)
+		if nRanges <= 0 {
+			nRanges = C.subid_get_gid_ranges(cuidstr, &cRanges)
 		}
 	}
+	if nRanges <= 0 {
+		return nil, errors.New("cannot read subids")
+	}
+	defer C.free(unsafe.Pointer(cRanges))
 
-	return false, fmt.Errorf("failed to find an entry for user %s in %s", currentUser.Username, path)
+	for i := 0; i < int(nRanges); i++ {
+		r := C.get_range(cRanges, C.int(i))
+		newRange := subIDRange{
+			Start:  int(r.start),
+			Length: int(r.count),
+		}
+		ret = append(ret, newRange)
+
+		logrus.Debugf("Found %s range %d for %s: start [%d] length [%d]",
+			queryType,
+			i,
+			username,
+			r.start,
+			r.count)
+	}
+	return ret, nil
 }