1 files changed, 270 insertions, 0 deletions
diff --git a/src/os/user/cgo_lookup_unix.go b/src/os/user/cgo_lookup_unix.go
new file mode 100644
index 0000000..4f8577b
--- /dev/null
+++ b/src/os/user/cgo_lookup_unix.go
@@ -0,0 +1,270 @@
+// Copyright 2011 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 unix && !android && cgo && !osusergo
+
+package user
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+	"syscall"
+	"unsafe"
+)
+
+/*
+#cgo solaris CFLAGS: -D_POSIX_PTHREAD_SEMANTICS
+#include <unistd.h>
+#include <sys/types.h>
+#include <pwd.h>
+#include <grp.h>
+#include <stdlib.h>
+
+static int mygetpwuid_r(int uid, struct passwd *pwd,
+	char *buf, size_t buflen, struct passwd **result) {
+	return getpwuid_r(uid, pwd, buf, buflen, result);
+}
+
+static int mygetpwnam_r(const char *name, struct passwd *pwd,
+	char *buf, size_t buflen, struct passwd **result) {
+	return getpwnam_r(name, pwd, buf, buflen, result);
+}
+
+static int mygetgrgid_r(int gid, struct group *grp,
+	char *buf, size_t buflen, struct group **result) {
+ return getgrgid_r(gid, grp, buf, buflen, result);
+}
+
+static int mygetgrnam_r(const char *name, struct group *grp,
+	char *buf, size_t buflen, struct group **result) {
+ return getgrnam_r(name, grp, buf, buflen, result);
+}
+*/
+import "C"
+
+func current() (*User, error) {
+	return lookupUnixUid(syscall.Getuid())
+}
+
+func lookupUser(username string) (*User, error) {
+	var pwd C.struct_passwd
+	var result *C.struct_passwd
+	nameC := make([]byte, len(username)+1)
+	copy(nameC, username)
+
+	buf := alloc(userBuffer)
+	defer buf.free()
+
+	err := retryWithBuffer(buf, func() syscall.Errno {
+		// mygetpwnam_r is a wrapper around getpwnam_r to avoid
+		// passing a size_t to getpwnam_r, because for unknown
+		// reasons passing a size_t to getpwnam_r doesn't work on
+		// Solaris.
+		return syscall.Errno(C.mygetpwnam_r((*C.char)(unsafe.Pointer(&nameC[0])),
+			&pwd,
+			(*C.char)(buf.ptr),
+			C.size_t(buf.size),
+			&result))
+	})
+	if err != nil {
+		return nil, fmt.Errorf("user: lookup username %s: %v", username, err)
+	}
+	if result == nil {
+		return nil, UnknownUserError(username)
+	}
+	return buildUser(&pwd), err
+}
+
+func lookupUserId(uid string) (*User, error) {
+	i, e := strconv.Atoi(uid)
+	if e != nil {
+		return nil, e
+	}
+	return lookupUnixUid(i)
+}
+
+func lookupUnixUid(uid int) (*User, error) {
+	var pwd C.struct_passwd
+	var result *C.struct_passwd
+
+	buf := alloc(userBuffer)
+	defer buf.free()
+
+	err := retryWithBuffer(buf, func() syscall.Errno {
+		// mygetpwuid_r is a wrapper around getpwuid_r to avoid using uid_t
+		// because C.uid_t(uid) for unknown reasons doesn't work on linux.
+		return syscall.Errno(C.mygetpwuid_r(C.int(uid),
+			&pwd,
+			(*C.char)(buf.ptr),
+			C.size_t(buf.size),
+			&result))
+	})
+	if err != nil {
+		return nil, fmt.Errorf("user: lookup userid %d: %v", uid, err)
+	}
+	if result == nil {
+		return nil, UnknownUserIdError(uid)
+	}
+	return buildUser(&pwd), nil
+}
+
+func buildUser(pwd *C.struct_passwd) *User {
+	u := &User{
+		Uid:      strconv.FormatUint(uint64(pwd.pw_uid), 10),
+		Gid:      strconv.FormatUint(uint64(pwd.pw_gid), 10),
+		Username: C.GoString(pwd.pw_name),
+		Name:     C.GoString(pwd.pw_gecos),
+		HomeDir:  C.GoString(pwd.pw_dir),
+	}
+	// The pw_gecos field isn't quite standardized. Some docs
+	// say: "It is expected to be a comma separated list of
+	// personal data where the first item is the full name of the
+	// user."
+	u.Name, _, _ = strings.Cut(u.Name, ",")
+	return u
+}
+
+func lookupGroup(groupname string) (*Group, error) {
+	var grp C.struct_group
+	var result *C.struct_group
+
+	buf := alloc(groupBuffer)
+	defer buf.free()
+	cname := make([]byte, len(groupname)+1)
+	copy(cname, groupname)
+
+	err := retryWithBuffer(buf, func() syscall.Errno {
+		return syscall.Errno(C.mygetgrnam_r((*C.char)(unsafe.Pointer(&cname[0])),
+			&grp,
+			(*C.char)(buf.ptr),
+			C.size_t(buf.size),
+			&result))
+	})
+	if err != nil {
+		return nil, fmt.Errorf("user: lookup groupname %s: %v", groupname, err)
+	}
+	if result == nil {
+		return nil, UnknownGroupError(groupname)
+	}
+	return buildGroup(&grp), nil
+}
+
+func lookupGroupId(gid string) (*Group, error) {
+	i, e := strconv.Atoi(gid)
+	if e != nil {
+		return nil, e
+	}
+	return lookupUnixGid(i)
+}
+
+func lookupUnixGid(gid int) (*Group, error) {
+	var grp C.struct_group
+	var result *C.struct_group
+
+	buf := alloc(groupBuffer)
+	defer buf.free()
+
+	err := retryWithBuffer(buf, func() syscall.Errno {
+		// mygetgrgid_r is a wrapper around getgrgid_r to avoid using gid_t
+		// because C.gid_t(gid) for unknown reasons doesn't work on linux.
+		return syscall.Errno(C.mygetgrgid_r(C.int(gid),
+			&grp,
+			(*C.char)(buf.ptr),
+			C.size_t(buf.size),
+			&result))
+	})
+	if err != nil {
+		return nil, fmt.Errorf("user: lookup groupid %d: %v", gid, err)
+	}
+	if result == nil {
+		return nil, UnknownGroupIdError(strconv.Itoa(gid))
+	}
+	return buildGroup(&grp), nil
+}
+
+func buildGroup(grp *C.struct_group) *Group {
+	g := &Group{
+		Gid:  strconv.Itoa(int(grp.gr_gid)),
+		Name: C.GoString(grp.gr_name),
+	}
+	return g
+}
+
+type bufferKind C.int
+
+const (
+	userBuffer  = bufferKind(C._SC_GETPW_R_SIZE_MAX)
+	groupBuffer = bufferKind(C._SC_GETGR_R_SIZE_MAX)
+)
+
+func (k bufferKind) initialSize() C.size_t {
+	sz := C.sysconf(C.int(k))
+	if sz == -1 {
+		// DragonFly and FreeBSD do not have _SC_GETPW_R_SIZE_MAX.
+		// Additionally, not all Linux systems have it, either. For
+		// example, the musl libc returns -1.
+		return 1024
+	}
+	if !isSizeReasonable(int64(sz)) {
+		// Truncate.  If this truly isn't enough, retryWithBuffer will error on the first run.
+		return maxBufferSize
+	}
+	return C.size_t(sz)
+}
+
+type memBuffer struct {
+	ptr  unsafe.Pointer
+	size C.size_t
+}
+
+func alloc(kind bufferKind) *memBuffer {
+	sz := kind.initialSize()
+	return &memBuffer{
+		ptr:  C.malloc(sz),
+		size: sz,
+	}
+}
+
+func (mb *memBuffer) resize(newSize C.size_t) {
+	mb.ptr = C.realloc(mb.ptr, newSize)
+	mb.size = newSize
+}
+
+func (mb *memBuffer) free() {
+	C.free(mb.ptr)
+}
+
+// retryWithBuffer repeatedly calls f(), increasing the size of the
+// buffer each time, until f succeeds, fails with a non-ERANGE error,
+// or the buffer exceeds a reasonable limit.
+func retryWithBuffer(buf *memBuffer, f func() syscall.Errno) error {
+	for {
+		errno := f()
+		if errno == 0 {
+			return nil
+		} else if errno != syscall.ERANGE {
+			return errno
+		}
+		newSize := buf.size * 2
+		if !isSizeReasonable(int64(newSize)) {
+			return fmt.Errorf("internal buffer exceeds %d bytes", maxBufferSize)
+		}
+		buf.resize(newSize)
+	}
+}
+
+const maxBufferSize = 1 << 20
+
+func isSizeReasonable(sz int64) bool {
+	return sz > 0 && sz <= maxBufferSize
+}
+
+// Because we can't use cgo in tests:
+func structPasswdForNegativeTest() C.struct_passwd {
+	sp := C.struct_passwd{}
+	sp.pw_uid = 1<<32 - 2
+	sp.pw_gid = 1<<32 - 3
+	return sp
+}