hush/libbb/appletlib.c
Denis Vlasenko 15ca51e3e2 appletlib.c: make it actally follow _BB_SUID_ALWAYS rules
adduser: implement -S and code shrink / fix uid selection
*: sanitize getspnam_r use

   text    data     bss     dec     hex filename
 777042     974    9676  787692   c04ec busybox_old
 776883     974    9676  787533   c044d busybox_unstripped
2007-10-29 19:25:45 +00:00

686 lines
18 KiB
C

/* vi: set sw=4 ts=4: */
/*
* Utility routines.
*
* Copyright (C) tons of folks. Tracking down who wrote what
* isn't something I'm going to worry about... If you wrote something
* here, please feel free to acknowledge your work.
*
* Based in part on code from sash, Copyright (c) 1999 by David I. Bell
* Permission has been granted to redistribute this code under the GPL.
*
* Licensed under GPLv2 or later, see file License in this tarball for details.
*/
#include <assert.h>
#include "busybox.h"
/* Declare <applet>_main() */
#define PROTOTYPES
#include "applets.h"
#undef PROTOTYPES
#if ENABLE_SHOW_USAGE && !ENABLE_FEATURE_COMPRESS_USAGE
/* Define usage_messages[] */
static const char usage_messages[] ALIGN1 = ""
#define MAKE_USAGE
#include "usage.h"
#include "applets.h"
;
#undef MAKE_USAGE
#else
#define usage_messages 0
#endif /* SHOW_USAGE */
/* Define struct bb_applet applets[] */
#include "applets.h"
#if ENABLE_FEATURE_SH_STANDALONE
/* -1 because last entry is NULL */
const unsigned short NUM_APPLETS = ARRAY_SIZE(applets) - 1;
#endif
#if ENABLE_FEATURE_COMPRESS_USAGE
#include "usage_compressed.h"
#include "unarchive.h"
static const char *unpack_usage_messages(void)
{
char *outbuf = NULL;
bunzip_data *bd;
int i;
i = start_bunzip(&bd,
/* src_fd: */ -1,
/* inbuf: */ packed_usage,
/* len: */ sizeof(packed_usage));
/* read_bunzip can longjmp to start_bunzip, and ultimately
* end up here with i != 0 on read data errors! Not trivial */
if (!i) {
/* Cannot use xmalloc: will leak bd in NOFORK case! */
outbuf = malloc_or_warn(SIZEOF_usage_messages);
if (outbuf)
read_bunzip(bd, outbuf, SIZEOF_usage_messages);
}
dealloc_bunzip(bd);
return outbuf;
}
#define dealloc_usage_messages(s) free(s)
#else
#define unpack_usage_messages() usage_messages
#define dealloc_usage_messages(s) ((void)(s))
#endif /* FEATURE_COMPRESS_USAGE */
void bb_show_usage(void)
{
if (ENABLE_SHOW_USAGE) {
const char *format_string;
const char *p;
const char *usage_string = p = unpack_usage_messages();
const struct bb_applet *ap = find_applet_by_name(applet_name);
int i;
if (!ap) /* never happens, paranoia */
xfunc_die();
i = ap - applets;
while (i) {
while (*p++) continue;
i--;
}
fprintf(stderr, "%s multi-call binary\n", bb_banner);
format_string = "\nUsage: %s %s\n\n";
if (*p == '\b')
format_string = "\nNo help available.\n\n";
fprintf(stderr, format_string, applet_name, p);
dealloc_usage_messages((char*)usage_string);
}
xfunc_die();
}
static int applet_name_compare(const void *name, const void *vapplet)
{
const struct bb_applet *applet = vapplet;
return strcmp(name, applet->name);
}
const struct bb_applet *find_applet_by_name(const char *name)
{
/* Do a binary search to find the applet entry given the name. */
return bsearch(name, applets, ARRAY_SIZE(applets)-1, sizeof(applets[0]),
applet_name_compare);
}
#ifdef __GLIBC__
/* Make it reside in R/W memory: */
int *const bb_errno __attribute__ ((section (".data")));
#endif
void lbb_prepare(const char *applet, char **argv)
{
#ifdef __GLIBC__
(*(int **)&bb_errno) = __errno_location();
#endif
applet_name = applet;
/* Set locale for everybody except 'init' */
if (ENABLE_LOCALE_SUPPORT && getpid() != 1)
setlocale(LC_ALL, "");
#if ENABLE_FEATURE_INDIVIDUAL
/* Redundant for busybox (run_applet_and_exit covers that case)
* but needed for "individual applet" mode */
if (argv[1] && strcmp(argv[1], "--help") == 0)
bb_show_usage();
#endif
}
/* The code below can well be in applets/applets.c, as it is used only
* for busybox binary, not "individual" binaries.
* However, keeping it here and linking it into libbusybox.so
* (together with remaining tiny applets/applets.o)
* makes it possible to avoid --whole-archive at link time.
* This makes (shared busybox) + libbusybox smaller.
* (--gc-sections would be even better....)
*/
const char *applet_name;
#if !BB_MMU
bool re_execed;
#endif
USE_FEATURE_SUID(static uid_t ruid;) /* real uid */
#if ENABLE_FEATURE_SUID_CONFIG
/* applets[] is const, so we have to define this "override" structure */
static struct BB_suid_config {
const struct bb_applet *m_applet;
uid_t m_uid;
gid_t m_gid;
mode_t m_mode;
struct BB_suid_config *m_next;
} *suid_config;
static bool suid_cfg_readable;
/* check if u is member of group g */
static int ingroup(uid_t u, gid_t g)
{
struct group *grp = getgrgid(g);
if (grp) {
char **mem;
for (mem = grp->gr_mem; *mem; mem++) {
struct passwd *pwd = getpwnam(*mem);
if (pwd && (pwd->pw_uid == u))
return 1;
}
}
return 0;
}
/* This should probably be a libbb routine. In that case,
* I'd probably rename it to something like bb_trimmed_slice.
*/
static char *get_trimmed_slice(char *s, char *e)
{
/* First, consider the value at e to be nul and back up until we
* reach a non-space char. Set the char after that (possibly at
* the original e) to nul. */
while (e-- > s) {
if (!isspace(*e)) {
break;
}
}
e[1] = '\0';
/* Next, advance past all leading space and return a ptr to the
* first non-space char; possibly the terminating nul. */
return skip_whitespace(s);
}
/* Don't depend on the tools to combine strings. */
static const char config_file[] ALIGN1 = "/etc/busybox.conf";
/* We don't supply a value for the nul, so an index adjustment is
* necessary below. Also, we use unsigned short here to save some
* space even though these are really mode_t values. */
static const unsigned short mode_mask[] ALIGN2 = {
/* SST sst xxx --- */
S_ISUID, S_ISUID|S_IXUSR, S_IXUSR, 0, /* user */
S_ISGID, S_ISGID|S_IXGRP, S_IXGRP, 0, /* group */
0, S_IXOTH, S_IXOTH, 0 /* other */
};
#define parse_error(x) do { errmsg = x; goto pe_label; } while (0)
static void parse_config_file(void)
{
struct BB_suid_config *sct_head;
struct BB_suid_config *sct;
const struct bb_applet *applet;
FILE *f;
const char *errmsg;
char *s;
char *e;
int i;
unsigned lc;
smallint section;
char buffer[256];
struct stat st;
assert(!suid_config); /* Should be set to NULL by bss init. */
ruid = getuid();
if (ruid == 0) /* run by root - don't need to even read config file */
return;
if ((stat(config_file, &st) != 0) /* No config file? */
|| !S_ISREG(st.st_mode) /* Not a regular file? */
|| (st.st_uid != 0) /* Not owned by root? */
|| (st.st_mode & (S_IWGRP | S_IWOTH)) /* Writable by non-root? */
|| !(f = fopen(config_file, "r")) /* Cannot open? */
) {
return;
}
suid_cfg_readable = 1;
sct_head = NULL;
section = lc = 0;
while (1) {
s = buffer;
if (!fgets(s, sizeof(buffer), f)) { /* Are we done? */
if (ferror(f)) { /* Make sure it wasn't a read error. */
parse_error("reading");
}
fclose(f);
suid_config = sct_head; /* Success, so set the pointer. */
return;
}
lc++; /* Got a (partial) line. */
/* If a line is too long for our buffer, we consider it an error.
* The following test does mistreat one corner case though.
* If the final line of the file does not end with a newline and
* yet exactly fills the buffer, it will be treated as too long
* even though there isn't really a problem. But it isn't really
* worth adding code to deal with such an unlikely situation, and
* we do err on the side of caution. Besides, the line would be
* too long if it did end with a newline. */
if (!strchr(s, '\n') && !feof(f)) {
parse_error("line too long");
}
/* Trim leading and trailing whitespace, ignoring comments, and
* check if the resulting string is empty. */
s = get_trimmed_slice(s, strchrnul(s, '#'));
if (!*s) {
continue;
}
/* Check for a section header. */
if (*s == '[') {
/* Unlike the old code, we ignore leading and trailing
* whitespace for the section name. We also require that
* there are no stray characters after the closing bracket. */
e = strchr(s, ']');
if (!e /* Missing right bracket? */
|| e[1] /* Trailing characters? */
|| !*(s = get_trimmed_slice(s+1, e)) /* Missing name? */
) {
parse_error("section header");
}
/* Right now we only have one section so just check it.
* If more sections are added in the future, please don't
* resort to cascading ifs with multiple strcasecmp calls.
* That kind of bloated code is all too common. A loop
* and a string table would be a better choice unless the
* number of sections is very small. */
if (strcasecmp(s, "SUID") == 0) {
section = 1;
continue;
}
section = -1; /* Unknown section so set to skip. */
continue;
}
/* Process sections. */
if (section == 1) { /* SUID */
/* Since we trimmed leading and trailing space above, we're
* now looking for strings of the form
* <key>[::space::]*=[::space::]*<value>
* where both key and value could contain inner whitespace. */
/* First get the key (an applet name in our case). */
e = strchr(s, '=');
if (e) {
s = get_trimmed_slice(s, e);
}
if (!e || !*s) { /* Missing '=' or empty key. */
parse_error("keyword");
}
/* Ok, we have an applet name. Process the rhs if this
* applet is currently built in and ignore it otherwise.
* Note: this can hide config file bugs which only pop
* up when the busybox configuration is changed. */
applet = find_applet_by_name(s);
if (applet) {
/* Note: We currently don't check for duplicates!
* The last config line for each applet will be the
* one used since we insert at the head of the list.
* I suppose this could be considered a feature. */
sct = xmalloc(sizeof(struct BB_suid_config));
sct->m_applet = applet;
sct->m_mode = 0;
sct->m_next = sct_head;
sct_head = sct;
/* Get the specified mode. */
e = skip_whitespace(e+1);
for (i = 0; i < 3; i++) {
/* There are 4 chars + 1 nul for each of user/group/other. */
static const char mode_chars[] ALIGN1 = "Ssx-\0" "Ssx-\0" "Ttx-";
const char *q;
q = strchrnul(mode_chars + 5*i, *e++);
if (!*q) {
parse_error("mode");
}
/* Adjust by -i to account for nul. */
sct->m_mode |= mode_mask[(q - mode_chars) - i];
}
/* Now get the the user/group info. */
s = skip_whitespace(e);
/* Note: we require whitespace between the mode and the
* user/group info. */
if ((s == e) || !(e = strchr(s, '.'))) {
parse_error("<uid>.<gid>");
}
*e++ = '\0';
/* We can't use get_ug_id here since it would exit()
* if a uid or gid was not found. Oh well... */
sct->m_uid = bb_strtoul(s, NULL, 10);
if (errno) {
struct passwd *pwd = getpwnam(s);
if (!pwd) {
parse_error("user");
}
sct->m_uid = pwd->pw_uid;
}
sct->m_gid = bb_strtoul(e, NULL, 10);
if (errno) {
struct group *grp;
grp = getgrnam(e);
if (!grp) {
parse_error("group");
}
sct->m_gid = grp->gr_gid;
}
}
continue;
}
/* Unknown sections are ignored. */
/* Encountering configuration lines prior to seeing a
* section header is treated as an error. This is how
* the old code worked, but it may not be desirable.
* We may want to simply ignore such lines in case they
* are used in some future version of busybox. */
if (!section) {
parse_error("keyword outside section");
}
} /* while (1) */
pe_label:
fprintf(stderr, "Parse error in %s, line %d: %s\n",
config_file, lc, errmsg);
fclose(f);
/* Release any allocated memory before returning. */
while (sct_head) {
sct = sct_head->m_next;
free(sct_head);
sct_head = sct;
}
}
#else
static inline void parse_config_file(void)
{
USE_FEATURE_SUID(ruid = getuid();)
}
#endif /* FEATURE_SUID_CONFIG */
#if ENABLE_FEATURE_SUID
static void check_suid(const struct bb_applet *applet)
{
gid_t rgid; /* real gid */
if (ruid == 0) /* set by parse_config_file() */
return; /* run by root - no need to check more */
rgid = getgid();
#if ENABLE_FEATURE_SUID_CONFIG
if (suid_cfg_readable) {
uid_t uid;
struct BB_suid_config *sct;
mode_t m;
for (sct = suid_config; sct; sct = sct->m_next) {
if (sct->m_applet == applet)
goto found;
}
goto check_need_suid;
found:
m = sct->m_mode;
if (sct->m_uid == ruid)
/* same uid */
m >>= 6;
else if ((sct->m_gid == rgid) || ingroup(ruid, sct->m_gid))
/* same group / in group */
m >>= 3;
if (!(m & S_IXOTH)) /* is x bit not set ? */
bb_error_msg_and_die("you have no permission to run this applet!");
/* _both_ sgid and group_exec have to be set for setegid */
if ((sct->m_mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP))
rgid = sct->m_gid;
/* else (no setegid) we will set egid = rgid */
/* We set effective AND saved ids. If saved-id is not set
* like we do below, seteiud(0) can still later succeed! */
if (setresgid(-1, rgid, rgid))
bb_perror_msg_and_die("setresgid");
/* do we have to set effective uid? */
uid = ruid;
if (sct->m_mode & S_ISUID)
uid = sct->m_uid;
/* else (no seteuid) we will set euid = ruid */
if (setresuid(-1, uid, uid))
bb_perror_msg_and_die("setresuid");
return;
}
#if !ENABLE_FEATURE_SUID_CONFIG_QUIET
{
static bool onetime = 0;
if (!onetime) {
onetime = 1;
fprintf(stderr, "Using fallback suid method\n");
}
}
#endif
check_need_suid:
#endif
if (applet->need_suid == _BB_SUID_ALWAYS) {
/* Real uid is not 0. If euid isn't 0 too, suid bit
* is most probably not set on our executable */
if (geteuid())
bb_error_msg_and_die("must be suid to work properly");
} else if (applet->need_suid == _BB_SUID_NEVER) {
xsetgid(rgid); /* drop all privileges */
xsetuid(ruid);
}
}
#else
#define check_suid(x) ((void)0)
#endif /* FEATURE_SUID */
#if ENABLE_FEATURE_INSTALLER
/* create (sym)links for each applet */
static void install_links(const char *busybox, int use_symbolic_links)
{
/* directory table
* this should be consistent w/ the enum,
* busybox.h::bb_install_loc_t, or else... */
static const char usr_bin [] ALIGN1 = "/usr/bin";
static const char usr_sbin[] ALIGN1 = "/usr/sbin";
static const char *const install_dir[] = {
&usr_bin [8], /* "", equivalent to "/" for concat_path_file() */
&usr_bin [4], /* "/bin" */
&usr_sbin[4], /* "/sbin" */
usr_bin,
usr_sbin
};
int (*lf)(const char *, const char *) = link;
char *fpc;
int i;
int rc;
if (use_symbolic_links)
lf = symlink;
for (i = 0; applets[i].name != NULL; i++) {
fpc = concat_path_file(
install_dir[applets[i].install_loc],
applets[i].name);
rc = lf(busybox, fpc);
if (rc != 0 && errno != EEXIST) {
bb_simple_perror_msg(fpc);
}
free(fpc);
}
}
#else
#define install_links(x,y) ((void)0)
#endif /* FEATURE_INSTALLER */
/* If we were called as "busybox..." */
static int busybox_main(char **argv)
{
if (!argv[1]) {
/* Called without arguments */
const struct bb_applet *a;
int col, output_width;
help:
output_width = 80;
if (ENABLE_FEATURE_AUTOWIDTH) {
/* Obtain the terminal width */
get_terminal_width_height(0, &output_width, NULL);
}
/* leading tab and room to wrap */
output_width -= sizeof("start-stop-daemon, ") + 8;
printf("%s multi-call binary\n", bb_banner); /* reuse const string... */
printf("Copyright (C) 1998-2006 Erik Andersen, Rob Landley, and others.\n"
"Licensed under GPLv2. See source distribution for full notice.\n"
"\n"
"Usage: busybox [function] [arguments]...\n"
" or: [function] [arguments]...\n"
"\n"
"\tBusyBox is a multi-call binary that combines many common Unix\n"
"\tutilities into a single executable. Most people will create a\n"
"\tlink to busybox for each function they wish to use and BusyBox\n"
"\twill act like whatever it was invoked as!\n"
"\nCurrently defined functions:\n");
col = 0;
a = applets;
while (a->name) {
if (col > output_width) {
puts(",");
col = 0;
}
col += printf("%s%s", (col ? ", " : "\t"), a->name);
a++;
}
puts("\n");
return 0;
}
if (ENABLE_FEATURE_INSTALLER && strcmp(argv[1], "--install") == 0) {
const char *busybox;
busybox = xmalloc_readlink(bb_busybox_exec_path);
if (!busybox)
busybox = bb_busybox_exec_path;
/* -s makes symlinks */
install_links(busybox, argv[2] && strcmp(argv[2], "-s") == 0);
return 0;
}
if (strcmp(argv[1], "--help") == 0) {
/* "busybox --help [<applet>]" */
if (!argv[2])
goto help;
/* convert to "<applet> --help" */
argv[0] = argv[2];
argv[2] = NULL;
} else {
/* "busybox <applet> arg1 arg2 ..." */
argv++;
}
/* We support "busybox /a/path/to/applet args..." too. Allows for
* "#!/bin/busybox"-style wrappers */
applet_name = bb_get_last_path_component_nostrip(argv[0]);
run_applet_and_exit(applet_name, argv);
bb_error_msg_and_die("applet not found");
}
void run_appletstruct_and_exit(const struct bb_applet *applet, char **argv)
{
int argc = 1;
while (argv[argc])
argc++;
/* Reinit some shared global data */
optind = 1;
xfunc_error_retval = EXIT_FAILURE;
applet_name = applet->name;
if (argc == 2 && !strcmp(argv[1], "--help"))
bb_show_usage();
if (ENABLE_FEATURE_SUID)
check_suid(applet);
exit(applet->main(argc, argv));
}
void run_applet_and_exit(const char *name, char **argv)
{
const struct bb_applet *applet = find_applet_by_name(name);
if (applet)
run_appletstruct_and_exit(applet, argv);
if (!strncmp(name, "busybox", 7))
exit(busybox_main(argv));
}
#if ENABLE_BUILD_LIBBUSYBOX
int lbb_main(int argc, char **argv)
#else
int main(int argc, char **argv)
#endif
{
lbb_prepare("busybox", argv);
#if !BB_MMU
/* NOMMU re-exec trick sets high-order bit in first byte of name */
if (argv[0][0] & 0x80) {
re_execed = 1;
argv[0][0] &= 0x7f;
}
#endif
applet_name = argv[0];
if (applet_name[0] == '-')
applet_name++;
applet_name = bb_basename(applet_name);
parse_config_file(); /* ...maybe, if FEATURE_SUID_CONFIG */
run_applet_and_exit(applet_name, argv);
bb_error_msg_and_die("applet not found");
}