Simplify our trivial initgroups(), and add a test.
initgroups() is just a call to getgrouplist() followed by a call to
setgroups(). The tricky part is memory allocation. OpenBSD allocates an
NGROUPS_MAX-sized array of gid_t on the stack. FreeBSD allocates a
sysconf(_SC_NGROUPS_MAX)-sized array of gid_t on the heap. bionic had a
mix where it would try a 2-element stack array but fall back to a heap
allocation, which sounds reasonable if you want to avoid a 256KiB
(64Ki*4 bytes) allocation on either stack or heap. But that constant 2?
That's weird in two ways... It's really small (musl has an NGROUPS_MAX
of 32 unlike the Linux kernel's 64Ki, but 32 is still a lot larger than
2), but at the same time it's too big --- bionic's getgrouplist() always
returns a single element.
So although the FreeBSD "what the hell, let's just allocate 256KiB on
the heap" implementation would have been fine, there's really no point,
and anyone who's trying to understand initgroups() on Android really
needs to read getgroupslist() anyway, so let's just have the most
trivial implementation -- a single-element array -- and let's have it
right next to getgroupslist() in the same file as all the other <grp.h>
functions.
Also add a trivial smoke test. You mostly won't have permission to do
anything interesting with initgroups(), and it's basically unused save
for privilege dropping tcpdump and strace, but we may as well make an
effort. (I tested tcpdump before and after too.)
Test: treehugger
Change-Id: I67fe02e309ed1dbefc490c01733738363ca606be
diff --git a/libc/Android.bp b/libc/Android.bp
index 048cd73..071f309 100644
--- a/libc/Android.bp
+++ b/libc/Android.bp
@@ -857,7 +857,6 @@
"bionic/iconv.cpp",
"bionic/icu_wrappers.cpp",
"bionic/ifaddrs.cpp",
- "bionic/initgroups.c",
"bionic/inotify_init.cpp",
"bionic/ioctl.cpp",
"bionic/isatty.cpp",
diff --git a/libc/bionic/grp_pwd.cpp b/libc/bionic/grp_pwd.cpp
index 600693c..82ee7ba 100644
--- a/libc/bionic/grp_pwd.cpp
+++ b/libc/bionic/grp_pwd.cpp
@@ -609,6 +609,8 @@
}
// All users are in just one group, the one passed in.
+// In practice, id(1) will show you in a lot more groups, because adbd
+// adds you to a lot of supplementary groups when dropping privileges.
int getgrouplist(const char* /*user*/, gid_t group, gid_t* groups, int* ngroups) {
if (*ngroups < 1) {
*ngroups = 1;
@@ -618,6 +620,12 @@
return (*ngroups = 1);
}
+// See getgrouplist() to understand why we don't call it.
+int initgroups(const char* /*user*/, gid_t group) {
+ gid_t groups[] = {group};
+ return setgroups(1, groups);
+}
+
char* getlogin() { // NOLINT: implementing bad function.
passwd *pw = getpwuid(getuid()); // NOLINT: implementing bad function in terms of bad function.
return pw ? pw->pw_name : nullptr;
diff --git a/libc/bionic/initgroups.c b/libc/bionic/initgroups.c
deleted file mode 100644
index dea6d96..0000000
--- a/libc/bionic/initgroups.c
+++ /dev/null
@@ -1,58 +0,0 @@
-/*
- * Copyright (C) 2008 The Android Open Source Project
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- * * Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- * * Redistributions in binary form must reproduce the above copyright
- * notice, this list of conditions and the following disclaimer in
- * the documentation and/or other materials provided with the
- * distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
- * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
- * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
- * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
- * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
- * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
- * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
- * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
- * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
- * SUCH DAMAGE.
- */
-#include <grp.h>
-#include <unistd.h>
-#include <stdlib.h>
-
-#define INIT_GROUPS 2
-
-int
-initgroups (const char *user, gid_t group)
-{
- gid_t groups0[ INIT_GROUPS ];
- gid_t* groups = groups0;
- int ret = -1;
- int numgroups = INIT_GROUPS;
-
- if (getgrouplist(user, group, groups, &numgroups) < 0) {
- groups = malloc(numgroups*sizeof(groups[0]));
- if (groups == NULL)
- return -1;
- if (getgrouplist(user,group,groups,&numgroups) < 0) {
- goto EXIT;
- }
- }
-
- ret = setgroups(numgroups, groups);
-
-EXIT:
- if (groups != groups0)
- free(groups);
-
- return ret;
-}