101 lines
2.2 KiB
C
101 lines
2.2 KiB
C
/**
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* chkgrp-min-native-extended is a program that checks if a user is a member
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* of a group.
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*
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* Author: Johannes Findeisen <you@hanez.org> - 2025
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* Homepage: https://git.xw3.org/hanez/chkusr
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* License: Apache-2.0 (see LICENSE)
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*/
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#include "config.h"
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <ctype.h>
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int main(int argc, char *argv[])
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{
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if (argc != 3)
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return 2;
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const char *username = argv[1];
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const char *groupname = argv[2];
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if (strlen(username) > MAX_NAME || strlen(groupname) > MAX_NAME)
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return 2;
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// Step 1: Find user in /etc/passwd to get their primary GID
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FILE *passwd = fopen("/etc/passwd", "r");
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if (!passwd)
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return 2;
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char line[MAX_LINE];
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int user_gid = -1;
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while (fgets(line, sizeof(line), passwd)) {
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char *u = strtok(line, ":");
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if (!u || strcmp(u, username) != 0)
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continue;
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strtok(NULL, ":"); // skip password
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strtok(NULL, ":"); // skip UID
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char *gid_str = strtok(NULL, ":");
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if (!gid_str)
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break;
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user_gid = atoi(gid_str);
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break;
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}
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fclose(passwd);
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if (user_gid < 0)
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return 2;
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// Step 2: Find group in /etc/group and check membership or GID match
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FILE *group = fopen("/etc/group", "r");
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if (!group)
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return 2;
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int found = 0;
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while (fgets(line, sizeof(line), group)) {
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char *grp = strtok(line, ":");
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if (!grp || strcmp(grp, groupname) != 0)
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continue;
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strtok(NULL, ":"); // skip password
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char *gid_str = strtok(NULL, ":");
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if (!gid_str)
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break;
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int group_gid = atoi(gid_str);
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if (group_gid == user_gid) {
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puts("Yes");
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fclose(group);
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return 0;
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}
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char *members = strtok(NULL, ":\n");
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if (!members)
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break;
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char *m = strtok(members, ",");
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while (m) {
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if (!strcmp(m, username)) {
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puts("Yes");
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fclose(group);
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return 0;
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}
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m = strtok(NULL, ",");
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}
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found = 1;
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break;
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}
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fclose(group);
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if (!found)
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return 2;
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puts("No");
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return 1;
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}
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