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#include <grp.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/mman.h>
#include <AK/AKString.h>
extern "C" {
#define GRDB_STR_MAX_LEN 256
struct group_with_strings : public group {
char name_buffer[GRDB_STR_MAX_LEN];
char passwd_buffer[GRDB_STR_MAX_LEN];
char* members[32];
char members_buffer[32][32];
};
static FILE* __grdb_stream = nullptr;
static unsigned __grdb_line_number = 0;
static struct group_with_strings* __grdb_entry = nullptr;
void setgrent()
{
__grdb_line_number = 0;
if (__grdb_stream) {
rewind(__grdb_stream);
} else {
__grdb_stream = fopen("/etc/group", "r");
if (!__grdb_stream) {
perror("open /etc/group");
}
assert(__grdb_stream);
__grdb_entry = (struct group_with_strings*)mmap(nullptr, getpagesize(), PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, 0, 0);
set_mmap_name(__grdb_entry, getpagesize(), "setgrent");
}
}
void endgrent()
{
__grdb_line_number = 0;
if (__grdb_stream) {
fclose(__grdb_stream);
__grdb_stream = nullptr;
}
if (__grdb_entry) {
munmap(__grdb_entry, getpagesize());
__grdb_entry = nullptr;
}
}
struct group* getgrgid(gid_t gid)
{
setgrent();
while (auto* gr = getgrent()) {
if (gr->gr_gid == gid)
return gr;
}
return nullptr;
}
struct group* getgrnam(const char* name)
{
setgrent();
while (auto* gr = getgrent()) {
if (!strcmp(gr->gr_name, name))
return gr;
}
return nullptr;
}
struct group* getgrent()
{
if (!__grdb_stream)
setgrent();
assert(__grdb_stream);
if (feof(__grdb_stream))
return nullptr;
next_entry:
char buffer[1024];
++__grdb_line_number;
char* s = fgets(buffer, sizeof(buffer), __grdb_stream);
if (!s)
return nullptr;
assert(__grdb_stream);
if (feof(__grdb_stream))
return nullptr;
String line(s, Chomp);
auto parts = line.split(':');
if (parts.size() != 4) {
fprintf(stderr, "getgrent(): Malformed entry on line %u: '%s' has %u parts\n", __grdb_line_number, line.characters(), parts.size());
goto next_entry;
}
auto& e_name = parts[0];
auto& e_passwd = parts[1];
auto& e_gid_string = parts[2];
auto& e_members_string = parts[3];
bool ok;
gid_t e_gid = e_gid_string.to_uint(ok);
if (!ok) {
fprintf(stderr, "getgrent(): Malformed GID on line %u\n", __grdb_line_number);
goto next_entry;
}
auto members = e_members_string.split(',');
__grdb_entry->gr_gid = e_gid;
__grdb_entry->gr_name = __grdb_entry->name_buffer;
__grdb_entry->gr_passwd = __grdb_entry->passwd_buffer;
for (ssize_t i = 0; i < members.size(); ++i) {
__grdb_entry->members[i] = __grdb_entry->members_buffer[i];
strcpy(__grdb_entry->members_buffer[i], members[i].characters());
}
__grdb_entry->members[members.size()] = nullptr;
__grdb_entry->gr_mem = __grdb_entry->members;
strncpy(__grdb_entry->name_buffer, e_name.characters(), GRDB_STR_MAX_LEN);
strncpy(__grdb_entry->passwd_buffer, e_passwd.characters(), GRDB_STR_MAX_LEN);
return __grdb_entry;
}
int initgroups(const char* user, gid_t extra_gid)
{
size_t count = 0;
gid_t gids[32];
bool extra_gid_added = false;
setgrent();
while (auto* gr = getgrent()) {
for (auto* mem = gr->gr_mem; *mem; ++mem) {
if (!strcmp(*mem, user)) {
gids[count++] = gr->gr_gid;
if (gr->gr_gid == extra_gid)
extra_gid_added = true;
break;
}
}
}
endgrent();
if (!extra_gid_added)
gids[count++] = extra_gid;
return setgroups(count, gids);
}
}
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