Modify --user flag for podman create and run

If an integer is passed into the --user flag, i.e --user=1234
don't look up the user in /etc/passwd, just assign the integer as the uid.

Signed-off-by: umohnani8 <umohnani@redhat.com>

Closes: #652
Approved by: mheon

4 files changed, 46 insertions, 7 deletions

diff --git a/libpod/container_internal.go b/libpod/container_internal.go
index 62960fa0f..561b8853d 100644
--- a/libpod/container_internal.go
+++ b/libpod/container_internal.go
@@ -9,7 +9,6 @@ import (
 	"os"
 	"path/filepath"
 	"regexp"
-	"strconv"
 	"strings"
 	"syscall"
 	"time"
@@ -956,17 +955,17 @@ func (c *Container) generateSpec(ctx context.Context) (*spec.Spec, error) {
 			return nil, errors.Wrapf(ErrCtrStateInvalid, "container %s must be mounted in order to add additional groups", c.ID())
 		}
 		for _, group := range c.config.Groups {
-			_, gid, err := chrootuser.GetUser(c.state.Mountpoint, strconv.Itoa(int(g.Spec().Process.User.UID))+":"+group)
+			gid, err := chrootuser.GetGroup(c.state.Mountpoint, group)
 			if err != nil {
 				return nil, err
 			}
-			g.AddProcessAdditionalGid(uint32(gid))
+			g.AddProcessAdditionalGid(gid)
 		}
 	}
 
 	// Look up and add groups the user belongs to
 	groups, err := chrootuser.GetAdditionalGroupsForUser(c.state.Mountpoint, uint64(g.Spec().Process.User.UID))
-	if err != nil {
+	if err != nil && err != chrootuser.ErrNoSuchUser {
 		return nil, err
 	}
 	for _, gid := range groups {
diff --git a/pkg/chrootuser/user.go b/pkg/chrootuser/user.go
index 22ba5ff8a..54917b843 100644
--- a/pkg/chrootuser/user.go
+++ b/pkg/chrootuser/user.go
@@ -37,8 +37,8 @@ func GetUser(rootdir, userspec string) (uint32, uint32, error) {
 			userspec = name
 		} else {
 			// Leave userspec alone, but swallow the error and just
-			// use GID 0.
-			gid64 = 0
+			// use GID == UID.
+			gid64 = uid64
 			gerr = nil
 		}
 	}
@@ -70,6 +70,21 @@ func GetUser(rootdir, userspec string) (uint32, uint32, error) {
 	return 0, 0, err
 }
 
+// GetGroup returns the gid by looking it up in the /etc/passwd file
+// groupspec format [ group | gid ]
+func GetGroup(rootdir, groupspec string) (uint32, error) {
+	gid64, gerr := strconv.ParseUint(groupspec, 10, 32)
+	if gerr != nil {
+		// The group couldn't be parsed as a number, so look up
+		// the group's GID.
+		gid64, gerr = lookupGroupInContainer(rootdir, groupspec)
+	}
+	if gerr != nil {
+		return 0, errors.Wrapf(gerr, "error looking up group for gid %q", groupspec)
+	}
+	return uint32(gid64), nil
+}
+
 // GetAdditionalGroupsForUser returns a list of gids that userid is associated with
 func GetAdditionalGroupsForUser(rootdir string, userid uint64) ([]uint32, error) {
 	return lookupAdditionalGroupsForUIDInContainer(rootdir, userid)
diff --git a/pkg/chrootuser/user_linux.go b/pkg/chrootuser/user_linux.go
index 64ff7cef6..d48a1c7c2 100644
--- a/pkg/chrootuser/user_linux.go
+++ b/pkg/chrootuser/user_linux.go
@@ -4,6 +4,7 @@ package chrootuser
 
 import (
 	"bufio"
+	"errors"
 	"flag"
 	"fmt"
 	"io"
@@ -78,6 +79,9 @@ func openChrootedFile(rootdir, filename string) (*exec.Cmd, io.ReadCloser, error
 
 var (
 	lookupUser, lookupGroup sync.Mutex
+	// ErrNoSuchUser indicates that the user provided by the caller does not
+	// exist in /etc/passws
+	ErrNoSuchUser = errors.New("user does not exist in /etc/passwd")
 )
 
 type lookupPasswdEntry struct {
@@ -207,7 +211,7 @@ func lookupGroupForUIDInContainer(rootdir string, userid uint64) (username strin
 		return pwd.name, pwd.gid, nil
 	}
 
-	return "", 0, user.UnknownUserError(fmt.Sprintf("error looking up user with UID %d", userid))
+	return "", 0, ErrNoSuchUser
 }
 
 func lookupAdditionalGroupsForUIDInContainer(rootdir string, userid uint64) (gid []uint32, err error) {
diff --git a/test/e2e/run_test.go b/test/e2e/run_test.go
index 501434852..cfeabe6a0 100644
--- a/test/e2e/run_test.go
+++ b/test/e2e/run_test.go
@@ -330,6 +330,27 @@ var _ = Describe("Podman run", func() {
 		Expect(session.OutputToString()).To(Equal("uid=0(root) gid=0(root) groups=0(root),1(bin),2(daemon),3(sys),4(adm),6(disk),10(wheel),11(floppy),18(audio),20(dialout),26(tape),27(video),777,65533(nogroup)"))
 	})
 
+	It("podman run with user (default)", func() {
+		session := podmanTest.Podman([]string{"run", "--rm", ALPINE, "id"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+		Expect(session.OutputToString()).To(Equal("uid=0(root) gid=0(root) groups=0(root),1(bin),2(daemon),3(sys),4(adm),6(disk),10(wheel),11(floppy),20(dialout),26(tape),27(video)"))
+	})
+
+	It("podman run with user (integer)", func() {
+		session := podmanTest.Podman([]string{"run", "--rm", "--user=1234", ALPINE, "id"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+		Expect(session.OutputToString()).To(Equal("uid=1234 gid=1234"))
+	})
+
+	It("podman run with user (username)", func() {
+		session := podmanTest.Podman([]string{"run", "--rm", "--user=mail", ALPINE, "id"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+		Expect(session.OutputToString()).To(Equal("uid=8(mail) gid=12(mail) groups=12(mail)"))
+	})
+
 	It("podman run with attach stdin outputs container ID", func() {
 		session := podmanTest.Podman([]string{"run", "--attach", "stdin", ALPINE, "printenv"})
 		session.WaitWithDefaultTimeout()