os/user: make Lookup* functions properly handle ENOENT

The libc docs say that these functions can return ENOENT, and
per issue #67912, this does happen in practice sometimes. Handle
both the ENOENT and !found cases the same way, for Lookup,
LookupId, LookupGroup, LookupGroupId.

Fixes #67912

Change-Id: I993935af44c83ad785b6cd735fc313a3647daa19
Reviewed-on: https://go-review.googlesource.com/c/go/+/591555
Reviewed-by: Ian Lance Taylor <iant@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>

diff --git a/src/os/user/cgo_lookup_unix.go b/src/os/user/cgo_lookup_unix.go
index 402429ba4ac5427bb10ea3788ec31f9cda35c5b7..458d8cd453ac3a2ed2e4c1606d6f47fc09b9a647 100644 (file)
--- a/src/os/user/cgo_lookup_unix.go
+++ b/src/os/user/cgo_lookup_unix.go
@@ -31,12 +31,12 @@ func lookupUser(username string) (*User, error) {
                        (*_C_char)(unsafe.Pointer(&buf[0])), _C_size_t(len(buf)))
                return errno
        })
+       if err == syscall.ENOENT || (err == nil && !found) {
+               return nil, UnknownUserError(username)
+       }
        if err != nil {
                return nil, fmt.Errorf("user: lookup username %s: %v", username, err)
        }
-       if !found {
-               return nil, UnknownUserError(username)
-       }
        return buildUser(&pwd), err
 }
 
@@ -58,12 +58,12 @@ func lookupUnixUid(uid int) (*User, error) {
                        (*_C_char)(unsafe.Pointer(&buf[0])), _C_size_t(len(buf)))
                return errno
        })
+       if err == syscall.ENOENT || (err == nil && !found) {
+               return nil, UnknownUserIdError(uid)
+       }
        if err != nil {
                return nil, fmt.Errorf("user: lookup userid %d: %v", uid, err)
        }
-       if !found {
-               return nil, UnknownUserIdError(uid)
-       }
        return buildUser(&pwd), nil
 }
 
@@ -96,12 +96,12 @@ func lookupGroup(groupname string) (*Group, error) {
                        (*_C_char)(unsafe.Pointer(&buf[0])), _C_size_t(len(buf)))
                return errno
        })
+       if err == syscall.ENOENT || (err == nil && !found) {
+               return nil, UnknownGroupError(groupname)
+       }
        if err != nil {
                return nil, fmt.Errorf("user: lookup groupname %s: %v", groupname, err)
        }
-       if !found {
-               return nil, UnknownGroupError(groupname)
-       }
        return buildGroup(&grp), nil
 }
 
@@ -123,12 +123,12 @@ func lookupUnixGid(gid int) (*Group, error) {
                        (*_C_char)(unsafe.Pointer(&buf[0])), _C_size_t(len(buf)))
                return syscall.Errno(errno)
        })
+       if err == syscall.ENOENT || (err == nil && !found) {
+               return nil, UnknownGroupIdError(strconv.Itoa(gid))
+       }
        if err != nil {
                return nil, fmt.Errorf("user: lookup groupid %d: %v", gid, err)
        }
-       if !found {
-               return nil, UnknownGroupIdError(strconv.Itoa(gid))
-       }
        return buildGroup(&grp), nil
 }