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// Copyright 2016 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//go:build (cgo || darwin) && !osusergo && (darwin || dragonfly || freebsd || (linux && !android) || netbsd || openbsd || (solaris && !illumos))
package user
import (
"fmt"
"strconv"
"unsafe"
)
const maxGroups = 2048
func listGroups(u *User) ([]string, error) {
ug, err := strconv.Atoi(u.Gid)
if err != nil {
return nil, fmt.Errorf("user: list groups for %s: invalid gid %q", u.Username, u.Gid)
}
userGID := _C_gid_t(ug)
nameC := make([]byte, len(u.Username)+1)
copy(nameC, u.Username)
n := _C_int(256)
gidsC := make([]_C_gid_t, n)
rv := getGroupList((*_C_char)(unsafe.Pointer(&nameC[0])), userGID, &gidsC[0], &n)
if rv == -1 {
// Mac is the only Unix that does not set n properly when rv == -1, so
// we need to use different logic for Mac vs. the other OS's.
if err := groupRetry(u.Username, nameC, userGID, &gidsC, &n); err != nil {
return nil, err
}
}
gidsC = gidsC[:n]
gids := make([]string, 0, n)
for _, g := range gidsC[:n] {
gids = append(gids, strconv.Itoa(int(g)))
}
return gids, nil
}
// groupRetry retries getGroupList with much larger size for n. The result is
// stored in gids.
func groupRetry(username string, name []byte, userGID _C_gid_t, gids *[]_C_gid_t, n *_C_int) error {
// More than initial buffer, but now n contains the correct size.
if *n > maxGroups {
return fmt.Errorf("user: %q is a member of more than %d groups", username, maxGroups)
}
*gids = make([]_C_gid_t, *n)
rv := getGroupList((*_C_char)(unsafe.Pointer(&name[0])), userGID, &(*gids)[0], n)
if rv == -1 {
return fmt.Errorf("user: list groups for %s failed", username)
}
return nil
}
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