busybox/libpwdgrp/pwd_grp.c
Denys Vlasenko b5dabd9078 libpwdgrp: fix comment discrepancies
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2015-10-13 00:31:02 +02:00

561 lines
14 KiB
C

/* vi: set sw=4 ts=4: */
/* Copyright (C) 2014 Tito Ragusa <farmatito@tiscali.it>
*
* Licensed under GPLv2 or later, see file LICENSE in this source tree.
*/
/* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY!!
*
* Rewrite of some parts. Main differences are:
*
* 1) the buffer for getpwuid, getgrgid, getpwnam, getgrnam is dynamically
* allocated.
* If ENABLE_FEATURE_CLEAN_UP is set the buffers are freed at program
* exit using the atexit function to make valgrind happy.
* 2) the passwd/group files:
* a) must contain the expected number of fields (as per count of field
* delimeters ":") or we will complain with a error message.
* b) leading and trailing whitespace in fields is stripped.
* c) some fields are not allowed to be empty (e.g. username, uid/gid),
* and in this case NULL is returned and errno is set to EINVAL.
* This behaviour could be easily changed by modifying PW_DEF, GR_DEF,
* SP_DEF strings (uppercase makes a field mandatory).
* d) the string representing uid/gid must be convertible by strtoXX
* functions, or errno is set to EINVAL.
* e) leading and trailing whitespace in group member names is stripped.
* 3) the internal function for getgrouplist uses dynamically allocated buffer.
* 4) at the moment only the functions really used by busybox code are
* implemented, if you need a particular missing function it should be
* easy to write it by using the internal common code.
*/
#include "libbb.h"
struct const_passdb {
const char *filename;
char def[7 + 2*ENABLE_USE_BB_SHADOW];
uint8_t off[7 + 2*ENABLE_USE_BB_SHADOW];
uint8_t numfields;
uint8_t size_of;
};
struct passdb {
const char *filename;
char def[7 + 2*ENABLE_USE_BB_SHADOW];
uint8_t off[7 + 2*ENABLE_USE_BB_SHADOW];
uint8_t numfields;
uint8_t size_of;
FILE *fp;
char *malloced;
};
/* Note: for shadow db, def[] will not contain terminating NUL,
* but convert_to_struct() logic detects def[] end by "less than SP?",
* not by "is it NUL?" condition; and off[0] happens to be zero
* for every db anyway, so there _is_ in fact a terminating NUL there.
*/
/* S = string not empty, s = string maybe empty,
* I = uid,gid, l = long maybe empty, m = members,
* r = reserved
*/
#define PW_DEF "SsIIsss"
#define GR_DEF "SsIm"
#define SP_DEF "Ssllllllr"
static const struct const_passdb const_pw_db = {
_PATH_PASSWD, PW_DEF,
{
offsetof(struct passwd, pw_name), /* 0 S */
offsetof(struct passwd, pw_passwd), /* 1 s */
offsetof(struct passwd, pw_uid), /* 2 I */
offsetof(struct passwd, pw_gid), /* 3 I */
offsetof(struct passwd, pw_gecos), /* 4 s */
offsetof(struct passwd, pw_dir), /* 5 s */
offsetof(struct passwd, pw_shell) /* 6 s */
},
sizeof(PW_DEF)-1, sizeof(struct passwd)
};
static const struct const_passdb const_gr_db = {
_PATH_GROUP, GR_DEF,
{
offsetof(struct group, gr_name), /* 0 S */
offsetof(struct group, gr_passwd), /* 1 s */
offsetof(struct group, gr_gid), /* 2 I */
offsetof(struct group, gr_mem) /* 3 m (char **) */
},
sizeof(GR_DEF)-1, sizeof(struct group)
};
#if ENABLE_USE_BB_SHADOW
static const struct const_passdb const_sp_db = {
_PATH_SHADOW, SP_DEF,
{
offsetof(struct spwd, sp_namp), /* 0 S Login name */
offsetof(struct spwd, sp_pwdp), /* 1 s Encrypted password */
offsetof(struct spwd, sp_lstchg), /* 2 l */
offsetof(struct spwd, sp_min), /* 3 l */
offsetof(struct spwd, sp_max), /* 4 l */
offsetof(struct spwd, sp_warn), /* 5 l */
offsetof(struct spwd, sp_inact), /* 6 l */
offsetof(struct spwd, sp_expire), /* 7 l */
offsetof(struct spwd, sp_flag) /* 8 r Reserved */
},
sizeof(SP_DEF)-1, sizeof(struct spwd)
};
#endif
/* We avoid having big global data. */
struct statics {
/* We use same buffer (db[0].malloced) for getpwuid and getpwnam.
* Manpage says:
* "The return value may point to a static area, and may be overwritten
* by subsequent calls to getpwent(), getpwnam(), or getpwuid()."
*/
struct passdb db[2 + ENABLE_USE_BB_SHADOW];
char *tokenize_end;
unsigned string_size;
};
static struct statics *ptr_to_statics;
#define S (*ptr_to_statics)
#define has_S (ptr_to_statics)
#if ENABLE_FEATURE_CLEAN_UP
static void free_static(void)
{
free(S.db[0].malloced);
free(S.db[1].malloced);
# if ENABLE_USE_BB_SHADOW
free(S.db[2].malloced);
# endif
free(ptr_to_statics);
}
#endif
static struct statics *get_S(void)
{
if (!ptr_to_statics) {
ptr_to_statics = xzalloc(sizeof(S));
memcpy(&S.db[0], &const_pw_db, sizeof(const_pw_db));
memcpy(&S.db[1], &const_gr_db, sizeof(const_gr_db));
#if ENABLE_USE_BB_SHADOW
memcpy(&S.db[2], &const_sp_db, sizeof(const_sp_db));
#endif
#if ENABLE_FEATURE_CLEAN_UP
atexit(free_static);
#endif
}
return ptr_to_statics;
}
/* Internal functions */
/* Divide the passwd/group/shadow record in fields
* by substituting the given delimeter
* e.g. ':' or ',' with '\0'.
* Returns the number of fields found.
* Strips leading and trailing whitespace in fields.
*/
static int tokenize(char *buffer, int ch)
{
char *p = buffer;
char *s = p;
int num_fields = 0;
for (;;) {
if (isblank(*s)) {
overlapping_strcpy(s, skip_whitespace(s));
}
if (*p == ch || *p == '\0') {
char *end = p;
while (p != s && isblank(p[-1]))
p--;
if (p != end)
overlapping_strcpy(p, end);
num_fields++;
if (*end == '\0') {
S.tokenize_end = p + 1;
return num_fields;
}
*p = '\0';
s = p + 1;
}
p++;
}
}
/* Returns !NULL on success and matching line broken up in fields by '\0' in buf.
* We require the expected number of fields to be found.
*/
static char *parse_common(FILE *fp, struct passdb *db,
const char *key, int field_pos)
{
char *buf;
while ((buf = xmalloc_fgetline(fp)) != NULL) {
/* Skip empty lines, comment lines */
if (buf[0] == '\0' || buf[0] == '#')
goto free_and_next;
if (tokenize(buf, ':') != db->numfields) {
/* number of fields is wrong */
bb_error_msg("%s: bad record", db->filename);
goto free_and_next;
}
if (field_pos == -1) {
/* no key specified: sequential read, return a record */
break;
}
if (strcmp(key, nth_string(buf, field_pos)) == 0) {
/* record found */
break;
}
free_and_next:
free(buf);
}
S.string_size = S.tokenize_end - buf;
/*
* Ugly hack: group db requires additional buffer space
* for members[] array. If there is only one group, we need space
* for 3 pointers: alignment padding, group name, NULL.
* +1 for every additional group.
*/
if (buf && db->numfields == sizeof(GR_DEF)-1) { /* if we read group file... */
int cnt = 3;
char *p = buf;
while (p < S.tokenize_end)
if (*p++ == ',')
cnt++;
S.string_size += cnt * sizeof(char*);
//bb_error_msg("+%d words = %u key:%s buf:'%s'", cnt, S.string_size, key, buf);
buf = xrealloc(buf, S.string_size);
}
return buf;
}
static char *parse_file(struct passdb *db,
const char *key, int field_pos)
{
char *buf = NULL;
FILE *fp = fopen_for_read(db->filename);
if (fp) {
buf = parse_common(fp, db, key, field_pos);
fclose(fp);
}
return buf;
}
/* Convert passwd/group/shadow file record in buffer to a struct */
static void *convert_to_struct(struct passdb *db,
char *buffer, void *result)
{
const char *def = db->def;
const uint8_t *off = db->off;
/* For consistency, zero out all fields */
memset(result, 0, db->size_of);
for (;;) {
void *member = (char*)result + (*off++);
if ((*def | 0x20) == 's') { /* s or S */
*(char **)member = (char*)buffer;
if (!buffer[0] && (*def == 'S')) {
errno = EINVAL;
}
}
if (*def == 'I') {
*(int *)member = bb_strtou(buffer, NULL, 10);
}
#if ENABLE_USE_BB_SHADOW
if (*def == 'l') {
long n = -1;
if (buffer[0])
n = bb_strtol(buffer, NULL, 10);
*(long *)member = n;
}
#endif
if (*def == 'm') {
char **members;
int i = tokenize(buffer, ',');
/* Store members[] after buffer's end.
* This is safe ONLY because there is a hack
* in parse_common() which allocates additional space
* at the end of malloced buffer!
*/
members = (char **)
( ((intptr_t)S.tokenize_end + sizeof(members[0]))
& -(intptr_t)sizeof(members[0])
);
((struct group *)result)->gr_mem = members;
while (--i >= 0) {
if (buffer[0]) {
*members++ = buffer;
// bb_error_msg("member[]='%s'", buffer);
}
buffer += strlen(buffer) + 1;
}
*members = NULL;
}
/* def "r" does nothing */
def++;
if ((unsigned char)*def <= (unsigned char)' ')
break;
buffer += strlen(buffer) + 1;
}
if (errno)
result = NULL;
return result;
}
static int massage_data_for_r_func(struct passdb *db,
char *buffer, size_t buflen,
void **result,
char *buf)
{
void *result_buf = *result;
*result = NULL;
if (buf) {
if (S.string_size > buflen) {
errno = ERANGE;
} else {
memcpy(buffer, buf, S.string_size);
*result = convert_to_struct(db, buffer, result_buf);
}
free(buf);
}
/* "The reentrant functions return zero on success.
* In case of error, an error number is returned."
* NB: not finding the record is also a "success" here:
*/
return errno;
}
static void* massage_data_for_non_r_func(struct passdb *db, char *buf)
{
if (!buf)
return NULL;
free(db->malloced);
/* We enlarge buf and move string data up, freeing space
* for struct passwd/group/spwd at the beginning. This way,
* entire result of getXXnam is in a single malloced block.
* This enables easy creation of xmalloc_getpwnam() API.
*/
db->malloced = buf = xrealloc(buf, db->size_of + S.string_size);
memmove(buf + db->size_of, buf, S.string_size);
return convert_to_struct(db, buf + db->size_of, buf);
}
/****** getXXnam/id_r */
static int FAST_FUNC getXXnam_r(const char *name, uintptr_t db_and_field_pos,
char *buffer, size_t buflen,
void *result)
{
char *buf;
struct passdb *db = &get_S()->db[db_and_field_pos >> 2];
buf = parse_file(db, name, 0 /*db_and_field_pos & 3*/);
/* "db_and_field_pos & 3" is commented out since so far we don't implement
* getXXXid_r() functions which would use that to pass 2 here */
return massage_data_for_r_func(db, buffer, buflen, result, buf);
}
int FAST_FUNC getpwnam_r(const char *name, struct passwd *struct_buf,
char *buffer, size_t buflen,
struct passwd **result)
{
/* Why the "store buffer address in result" trick?
* This way, getXXnam_r has the same ABI signature as getpwnam_r,
* hopefully compiler can optimize tail call better in this case.
*/
*result = struct_buf;
return getXXnam_r(name, (0 << 2) + 0, buffer, buflen, result);
}
#if ENABLE_USE_BB_SHADOW
int FAST_FUNC getspnam_r(const char *name, struct spwd *struct_buf, char *buffer, size_t buflen,
struct spwd **result)
{
*result = struct_buf;
return getXXnam_r(name, (2 << 2) + 0, buffer, buflen, result);
}
#endif
#ifdef UNUSED
/****** getXXent_r */
static int FAST_FUNC getXXent_r(uintptr_t db_idx, char *buffer, size_t buflen,
void *result)
{
char *buf;
struct passdb *db = &get_S()->db[db_idx];
if (!db->fp) {
db->fp = fopen_for_read(db->filename);
if (!db->fp) {
return errno;
}
close_on_exec_on(fileno(db->fp));
}
buf = parse_common(db->fp, db, /*no search key:*/ NULL, -1);
if (!buf && !errno)
errno = ENOENT;
return massage_data_for_r_func(db, buffer, buflen, result, buf);
}
int FAST_FUNC getpwent_r(struct passwd *struct_buf, char *buffer, size_t buflen,
struct passwd **result)
{
*result = struct_buf;
return getXXent_r(0, buffer, buflen, result);
}
#endif
/****** getXXent */
static void* FAST_FUNC getXXent(uintptr_t db_idx)
{
char *buf;
struct passdb *db = &get_S()->db[db_idx];
if (!db->fp) {
db->fp = fopen_for_read(db->filename);
if (!db->fp) {
return NULL;
}
close_on_exec_on(fileno(db->fp));
}
buf = parse_common(db->fp, db, /*no search key:*/ NULL, -1);
return massage_data_for_non_r_func(db, buf);
}
struct passwd* FAST_FUNC getpwent(void)
{
return getXXent(0);
}
/****** getXXnam/id */
static void* FAST_FUNC getXXnam(const char *name, unsigned db_and_field_pos)
{
char *buf;
struct passdb *db = &get_S()->db[db_and_field_pos >> 2];
buf = parse_file(db, name, db_and_field_pos & 3);
return massage_data_for_non_r_func(db, buf);
}
struct passwd* FAST_FUNC getpwnam(const char *name)
{
return getXXnam(name, (0 << 2) + 0);
}
struct group* FAST_FUNC getgrnam(const char *name)
{
return getXXnam(name, (1 << 2) + 0);
}
struct passwd* FAST_FUNC getpwuid(uid_t id)
{
return getXXnam(utoa(id), (0 << 2) + 2);
}
struct group* FAST_FUNC getgrgid(gid_t id)
{
return getXXnam(utoa(id), (1 << 2) + 2);
}
/****** end/setXXend */
void FAST_FUNC endpwent(void)
{
if (has_S && S.db[0].fp) {
fclose(S.db[0].fp);
S.db[0].fp = NULL;
}
}
void FAST_FUNC setpwent(void)
{
if (has_S && S.db[0].fp) {
rewind(S.db[0].fp);
}
}
void FAST_FUNC endgrent(void)
{
if (has_S && S.db[1].fp) {
fclose(S.db[1].fp);
S.db[1].fp = NULL;
}
}
/****** initgroups and getgrouplist */
static gid_t* FAST_FUNC getgrouplist_internal(int *ngroups_ptr,
const char *user, gid_t gid)
{
FILE *fp;
gid_t *group_list;
int ngroups;
/* We alloc space for 8 gids at a time. */
group_list = xzalloc(8 * sizeof(group_list[0]));
group_list[0] = gid;
ngroups = 1;
fp = fopen_for_read(_PATH_GROUP);
if (fp) {
struct passdb *db = &get_S()->db[1];
char *buf;
while ((buf = parse_common(fp, db, NULL, -1)) != NULL) {
char **m;
struct group group;
if (!convert_to_struct(db, buf, &group))
goto next;
if (group.gr_gid == gid)
goto next;
for (m = group.gr_mem; *m; m++) {
if (strcmp(*m, user) != 0)
continue;
group_list = xrealloc_vector(group_list, /*8=2^3:*/ 3, ngroups);
group_list[ngroups++] = group.gr_gid;
goto next;
}
next:
free(buf);
}
fclose(fp);
}
*ngroups_ptr = ngroups;
return group_list;
}
int FAST_FUNC initgroups(const char *user, gid_t gid)
{
int ngroups;
gid_t *group_list = getgrouplist_internal(&ngroups, user, gid);
ngroups = setgroups(ngroups, group_list);
free(group_list);
return ngroups;
}
int FAST_FUNC getgrouplist(const char *user, gid_t gid, gid_t *groups, int *ngroups)
{
int ngroups_old = *ngroups;
gid_t *group_list = getgrouplist_internal(ngroups, user, gid);
if (*ngroups <= ngroups_old) {
ngroups_old = *ngroups;
memcpy(groups, group_list, ngroups_old * sizeof(groups[0]));
} else {
ngroups_old = -1;
}
free(group_list);
return ngroups_old;
}