utils

id.c (6050B)

// Collection of Unix tools, comparable to coreutils
// SPDX-FileCopyrightText: 2017-2022 Haelwenn (lanodan) Monnier <contact+utils@hacktivis.me>
// SPDX-License-Identifier: GPL-2.0-only OR GPL-3.0-only
#define _POSIX_C_SOURCE 200809L
#include <grp.h>       // getgrgid, getgroups
#include <pwd.h>       // getpwuid
#include <stdbool.h>   // bool
#include <stdio.h>     // printf, perror
#include <stdlib.h>    // malloc, free
#include <sys/types.h> // uid_t
#include <unistd.h>    // getuid, getgid, getopt, opt*
bool name_flag = false;
static int
simple_list_groups(struct passwd *pw)
{
	int ngroups_max = (int)sysconf(_SC_NGROUPS_MAX) + 1;
	gid_t *groups   = malloc(sizeof(gid_t) * ngroups_max);
	if(groups == NULL)
	{
		perror("groups malloc");
		return 1;
	}
	int ngroups = getgroups(ngroups_max, groups);
	if(ngroups < 0)
	{
		perror("getgroups");
		goto failure;
	}
	for(int i = 0; i < ngroups; i++)
	{
		if(name_flag)
		{
			struct group *lgr = getgrgid(groups[i]);
			if(lgr == NULL)
			{
				goto failure;
			}
			int sep = ' ';
			if(i == ngroups - 1)
			{
				sep = '\n';
			}
			int ret = printf("%s%c", lgr->gr_name, sep);
			if(ret < 0)
			{
				goto failure;
			}
		}
		else
		{
			int sep = ' ';
			if(i == ngroups - 1)
			{
				sep = '\n';
			}
			int ret = printf("%u%c", groups[i], sep);
			if(ret < 0)
			{
				goto failure;
			}
		}
	}
	free(groups);
	return 0;
failure:
	free(groups);
	return 1;
}
static int
list_groups(struct passwd *pw)
{
	int ngroups_max = (int)sysconf(_SC_NGROUPS_MAX) + 1;
	gid_t *groups   = malloc(sizeof(gid_t) * ngroups_max);
	if(groups == NULL)
	{
		perror("groups malloc");
		return 1;
	}
	int ngroups = getgroups(ngroups_max, groups);
	if(ngroups < 0)
	{
		perror("getgroups");
		goto failure;
	}
	else
	{
		printf(" groups=");
		for(int i = 0; i < ngroups; i++)
		{
			struct group *lgr = getgrgid(groups[i]);
			if(name_flag)
			{
				if(lgr == NULL)
				{
					goto failure;
				}
				int sep = ' ';
				if(i == ngroups - 1)
				{
					sep = '\0';
				}
				int ret = printf("%s%c", lgr->gr_name, sep);
				if(ret < 0)
				{
					goto failure;
				}
			}
			else
			{
				int ret = printf("%u", groups[i]);
				if(ret < 0)
				{
					goto failure;
				}
				if(lgr != NULL)
				{
					int ret = printf("(%s)", lgr->gr_name);
					if(ret < 0)
					{
						goto failure;
					}
				}
				if(i != ngroups - 1)
				{
					printf(",");
				}
			}
		}
	}
	free(groups);
	return 0;
failure:
	free(groups);
	return 1;
}
int
print_gid(char *field, struct group *gr, gid_t gid)
{
	if(gr && gr->gr_name)
	{
		if(name_flag)
		{
			return printf("%s=%s", field, gr->gr_name);
		}
		return printf("%s=%u(%s)", field, gid, gr->gr_name);
	}
	else
	{
		if(name_flag)
		{
			return -1;
		}
		return printf("%s=%u", field, gid);
	}
}
int
print_uid(char *field, struct passwd *pw, uid_t uid)
{
	if(pw && pw->pw_name)
	{
		if(name_flag)
		{
			return printf("%s=%s", field, pw->pw_name);
		}
		return printf("%s=%u(%s)", field, uid, pw->pw_name);
	}
	else
	{
		if(name_flag)
		{
			return -1;
		}
		return printf("%s=%u", field, uid);
	}
}
void
safe_getpwuid(uid_t uid, struct passwd *res)
{
	struct passwd *pw = getpwuid(uid);
	if(pw != NULL)
	{
		*res = *pw;
	}
}
enum id_modes
{
	ID_NORMAL,
	ID_GROUPS,
	ID_GID,
	ID_UID,
};
void
usage()
{
	fprintf(stderr, "Usage: id [-Ggu] [-nr] [user]\n");
}
int
main(int argc, char *argv[])
{
	int ret, c;
	enum id_modes mode = ID_NORMAL;
	bool real_flag     = false;
	// geteuid, getuid, getegid, getgid shall always be successful
	uid_t uid  = getuid();
	uid_t euid = geteuid();
	gid_t gid  = getgid();
	gid_t egid = getegid();
	struct passwd pw  = {.pw_uid = uid, .pw_gid = gid};
	struct passwd epw = {.pw_uid = euid, .pw_gid = egid};
	/* flawfinder: ignore. Old implementations of getopt should fix themselves */
	while((c = getopt(argc, argv, ":Ggunr")) != EOF)
	{
		switch(c)
		{
		case 'G':
			mode = ID_GROUPS;
			break;
		case 'u':
			mode = ID_UID;
			break;
		case 'g':
			mode = ID_GID;
			break;
		case 'n':
			name_flag = true;
			break;
		case 'r':
			real_flag = true;
			break;
		default:
			usage();
			return 1;
		}
	}
	argc -= optind;
	argv += optind;
	if(argc == 0)
	{
		safe_getpwuid(uid, &pw);
		safe_getpwuid(euid, &epw);
	}
	else if(argc == 1)
	{
		struct passwd *pw_n = getpwnam(argv[0]);
		if(pw_n == NULL)
		{
			return 1;
		}
		pw  = *pw_n;
		epw = *pw_n;
		uid  = pw.pw_uid;
		euid = epw.pw_uid;
		gid  = pw.pw_gid;
		egid = epw.pw_gid;
	}
	else
	{
		usage();
	}
	struct group *gr  = getgrgid(gid);
	struct group *egr = getgrgid(egid);
	if(mode == ID_GID)
	{
		if(!real_flag)
		{
			gid = egid;
		}
		if(!name_flag)
		{
			ret = printf("%u\n", gid);
		}
		else
		{
			if(gr == NULL || gr->gr_name == NULL)
			{
				ret--;
				fprintf(stderr, "id: cannot find name for group ID %u\n", gid);
				printf("%u\n", gid);
			}
			else
			{
				ret = printf("%s\n", gr->gr_name);
			}
		}
		if(ret < 0)
		{
			return 1;
		}
		return 0;
	}
	if(mode == ID_UID)
	{
		if(!real_flag)
		{
			uid = euid;
		}
		if(!name_flag)
		{
			ret = printf("%u\n", uid);
		}
		else
		{
			if(pw.pw_name == NULL)
			{
				ret--;
				fprintf(stderr, "id: cannot find name for user ID %u\n", uid);
				printf("%u\n", uid);
			}
			else
			{
				ret = printf("%s\n", pw.pw_name);
			}
		}
		if(ret < 0)
		{
			return 1;
		}
		return 0;
	}
	if(mode == ID_GROUPS)
	{
		if(real_flag)
		{
			ret = simple_list_groups(&pw);
		}
		else
		{
			ret = simple_list_groups(&epw);
		}
		if(ret != 0)
		{
			goto failure;
		}
		return 0;
	}
	ret = print_uid("uid", &pw, uid);
	if(ret < 0)
	{
		return 1;
	}
	if(euid != uid)
	{
		ret = print_uid(" euid", &epw, euid);
		if(ret < 0)
		{
			goto failure;
		}
	}
	ret = print_gid(" gid", gr, gid);
	if(ret < 0)
	{
		goto failure;
	}
	if(egid != gid)
	{
		ret = print_gid(" egid", egr, egid);
		if(ret < 0)
		{
			goto failure;
		}
	}
	if(list_groups(&pw) != 0)
	{
		goto failure;
	}
	ret = printf("\n");
	if(ret < 0)
	{
		return 1;
	}
	return 0;
failure:
	printf("\n");
	return 1;
}