README update.

.gitignore

@@ -1,2 +1,13 @@
-checkpw
-checkpw.o
+*.o
+*.so
+chkgrp
+chkgrp-min
+chkgrp-native
+chkgrp-native-min
+chkgrp-native-min-extended
+chkgrp-ng
+chkpwd
+chkpwd.1.gz
+chkpwr
+test
+test.c

Makefile

@@ -1,17 +1,52 @@
 all:
-	$(CC) -Wall -o checkpw checkpw.c -lpam -lpam_misc
+	$(CC) -Wall -o ./chkgrp ./chkgrp.c
+	$(CC) -Wall -o ./chkgrp-min ./chkgrp-min.c
+	$(CC) -Wall -o ./chkgrp-native ./chkgrp-native.c
+	$(CC) -Wall -o ./chkgrp-native-min ./chkgrp-native-min.c
+	$(CC) -Wall -o ./chkgrp-native-min-extended ./chkgrp-native-min-extended.c
+	$(CC) -Wall -o ./chkgrp-ng ./chkgrp-ng.c
+	$(CC) -Wall -o ./chkpwd ./chkpwd.c -lpam
+	gzip -fk ./chkpwd.1
+	$(CC) -Wall -o ./chkpwr ./chkpwr.c
 
 clean:
-	rm -f ./checkpw
+	rm -f ./chkgrp
+	rm -f ./chkgrp-min
+	rm -f ./chkgrp-native
+	rm -f ./chkgrp-native-min
+	rm -f ./chkgrp-native-min-extended
+	rm -f ./chkgrp-ng
+	rm -f ./chkpwd
+	rm -f ./chkpwd.1.gz
+	rm -f ./chkpwr
+	rm -f ./test
 
 install:
-	cp ./checkpw /usr/bin/
-	cp ./checkpw.1 /usr/share/man/man1/
-	gzip -f /usr/share/man/man1/checkpw.1
-	cp ./checkpw.h /usr/include/
+	install -g 0 -o 0 -m 0655 ./chkgrp /usr/bin/
+	install -g 0 -o 0 -m 0655 ./chkgrp-min /usr/bin/
+	install -g 0 -o 0 -m 0655 ./chkgrp-native /usr/bin/
+	install -g 0 -o 0 -m 0655 ./chkgrp-native-min /usr/bin/
+	install -g 0 -o 0 -m 0655 ./chkgrp-native-min-extended /usr/bin/
+	install -g 0 -o 0 -m 0655 ./chkgrp-ng /usr/bin/
+	install -g 0 -o 0 -m 0655 ./chkpwd /usr/bin/
+	install -g 0 -o 0 -m 0644 ./chkpwd.h /usr/include/
+	install -g 0 -o 0 -m 0644 ./chkpwd.1.gz /usr/share/man/man1/
+	install -g 0 -o 0 -m 0655 ./chkpwr /usr/bin/
+	install -g 0 -o 0 -m 0655 ./lua/chkgrp-native-min-extended.lua /usr/bin/
 
 uninstall:
-	rm -f /usr/bin/checkpw
-	rm -f /usr/share/man/man1/checkpw.1.gz
-	rm -f /usr/include/checkpw.h
+	rm -f /usr/bin/chkgrp
+	rm -f /usr/bin/chkgrp-min
+	rm -f /usr/bin/chkgrp-native
+	rm -f /usr/bin/chkgrp-native-min
+	rm -f /usr/bin/chkgrp-native-min-extended
+	rm -f /usr/bin/chkgrp-native-min-extended.lua
+	rm -f /usr/bin/chkgrp-ng
+	rm -f /usr/bin/chkpwd
+	rm -f /usr/bin/chkpwr
+	rm -f /usr/include/chkpwd.h
+	rm -f /usr/share/man/man1/chkpwd.1.gz
+
+test:
+	$(CC) -Wall -DPAM_DEBUG -o test test.c
 

README.md

@@ -1,54 +1,89 @@
-# checkpw
+# chkusr
 
-checkpw is a program that checks the validity of a users password on a UNIX/[PAM](https://en.wikipedia.org/wiki/Pluggable_Authentication_Module)-based system.
+chkusr is a set of programs (chkgrp, chkpwd and chkpwr) to verify information about a user and/or group on UNIX based systems.
 
-Currently checkpw is only tested on Linux, but it should work on a [AIX](https://en.wikipedia.org/wiki/IBM_AIX), [DragonFly BSD](https://www.dragonflybsd.org/), [FreeBSD](https://www.freebsd.org/), [HP-UX](https://en.wikipedia.org/wiki/HP-UX), [Linux](https://kernel.org/), [macOS](https://en.wikipedia.org/wiki/MacOS), [NetBSD](https://netbsd.org/) and [Solaris](https://en.wikipedia.org/wiki/Oracle_Solaris) operating system too.
+## THE FOLLOWING DOCUMENTATION WILL NOT WORK ACTUALLY! YOU NEED TO READ THE CODE! SORRY...
 
-## The idea
+ * [The idea](#the-idea)
+    * [Requirements](#requirements)
+    * [Configuration](#configuration)
+    * [Building chkusr](#building-chkusr)
+    * [Installation](#installation)
+    * [Uninstall](#uninstall)
+  * [Programs](#programs)
+    * [chkgrp](#chkgrp)
+    * [chkpwd](#chkpwd)
+       * [Usage](#usage)
+       * [Return codes](#return-codes)
+       * [Examples](#examples)
+          * [Interactive mode asking for a username and a password](#interactive-mode-asking-for-a-username-and-a-password)
+          * [Interactive mode only asking for a password](#interactive-mode-only-asking-for-a-password)
+          * [None interactive mode with username and password provided as arguments to chkpwd](#none-interactive-mode-with-username-and-password-provided-as-arguments-to-chkpwd)
+          * [Request the result from the above commands](#request-the-result-from-the-above-commands)
+       * [Custom build](#custom-build)
+    * [chkpwr](#chkpwr)
+ * [Links](#links)
+ * [License](#license)
 
-I needed a program to verify passwords of users on Linux/UNIX systems using PAM that just returns 0 on success and 1 on error.
+### The idea
 
-## Building checkpw
+I needed some programs to verify some information about users and groups on a Linux/UNIX system just returning 0 on success and 1 on error. Nonetheless, some programs also return a message.
+
+#### Requirements
+
+You need the PAM development package installed. On Alpine it is named linux-pam-dev, on Debian based systems it is named libpam0g-dev. Not all programs require PAM but you need to edit the Makefile to disable PAM based programs in the build process.
+
+#### Configuration
+
+chkusr needs to be configured before compilation. Always look at config.h for configuration options. I did it this way because I need the programs as small and simple as possible, and I don't want to parse a configuration file.
+
+#### Building chkusr
 
 ```
-git clone https://git.xw3.org/xw3/checkpw.git
-cd checkpw
+git clone https://git.xw3.org/hanez/chkusr.git
+cd chkusr
 make
 ```
 
-The code only supports verifying passwords for user id 1000 by default. Look at the file checkpw.h for some compile time options!
+#### Installation
 
-### Custom build example
-
-Set MAX_UID and MIN_UID at compile time:
-
-```
-gcc -Wall -DMAX_UID=1000 -DMIN_UID=1000 -o checkpw checkpw.c -lpam -lpam_misc
-```
-
-## Installation
-
-**WARNING:** Install this software with care. checkpw could easily be used for bruteforcing passwords from local users!
+**WARNING:** Install this software with care. chkpwd could easily be used for bruteforcing passwords from local users!
 
 ```
 sudo make install
 ```
 
-checkpw is installed to /usr/bin/.
+chkusr programs are installed to /usr/bin/.
 
-checkpw.h is installed to /usr/include/ for use in other applications.
+chkpwd.h is installed to /usr/include/ for use in other applications.
 
-## Uninstall
+#### Uninstall
 
 ```
 sudo make uninstall
 ```
 
-## Usage
+### Programs
+
+#### chkgrp
+
+chkgrp is a program to verify if a user is a member of a group.
+
+More information will follow... Actually there are multiple programs with some different behavior. I will write more about this, but for now I will not.
+
+#### chkpwd
+
+chkpwd is a program that checks the validity of a users password on a UNIX/[PAM](https://en.wikipedia.org/wiki/Pluggable_Authentication_Module)-based system.
+
+Currently chkpwd is only tested on Linux, but it should work on a [AIX](https://en.wikipedia.org/wiki/IBM_AIX), [DragonFly BSD](https://www.dragonflybsd.org/), [FreeBSD](https://www.freebsd.org/), [HP-UX](https://en.wikipedia.org/wiki/HP-UX), [Linux](https://kernel.org/), [macOS](https://en.wikipedia.org/wiki/MacOS), [NetBSD](https://netbsd.org/) and [Solaris](https://en.wikipedia.org/wiki/Oracle_Solaris) operating system too.
+
+The code only supports verifying passwords for user id 1000 by default. Look at the file chkpwd.h for some compile time options!
+
+##### Usage
 
 ```
-checkpw -h
-Usage: checkpw [-u <username>] [-p <password>] [-v] [-V] [-h]
+chkpwd -h
+Usage: chkpwd [-u <username>] [-p <password>] [-v] [-V] [-h]
 
 Options:
   -u <username>  Set username.
@@ -58,50 +93,70 @@ Options:
   -h             Show this help.
 ```
 
-You can also use checkpw even without installing by just running the following command:
+You can also use chkpwd even without installing by just running the following command:
 
 ```
-./checkpk
+./chkpwd
 ```
 
-checkpw returns 0 on success, 1 otherwise.
+##### Return codes
 
-### Examples
+chk returns 0 on success, 1 otherwise.
 
+##### Examples
 
-#### Interactive mode asking for a username and a password
+###### Interactive mode asking for a username and a password
 
 ```
-checkpw
+chkpwd
 ```
 
-#### Interactive mode only asking for a password
+###### Interactive mode only asking for a password
 
 ```
-checkpw -u hanez
+chkpwd -u hanez
 ```
 
-#### None interactive mode with username and password provided as arguments to checkpw
+###### None interactive mode with username and password provided as arguments to chkpwd
 
 ```
-checkpw -u hanez -p password
+chkpwd -u hanez -p password
 ```
 
-#### Request the result from the above commands
+###### Request the result from the above commands
 
 ```
 echo $?
 ```
 
-## License
+##### Custom build
 
-checkpw is licensed under the Apache License, Version 2.0.
+Set MAX_UID and MIN_UID at compile time:
+
+```
+gcc -Wall -DMAX_UID=1000 -DMIN_UID=1000 -o chkpwd chkpwd.c -lpam -lpam_misc
+```
+
+#### chkpwr
+
+A program that checks if an input string validates a password rule. More to come... look at the code!
+
+### Links
+
+ - [https://git.xw3.org/hanez/chkusr](https://git.xw3.org/hanez/chkusr)
+ - [https://github.com/shadow-maint/shadow](https://github.com/shadow-maint/shadow)
+ - [https://github.com/linux-pam/linux-pam](https://github.com/linux-pam/linux-pam)
+ - [https://www.man7.org/linux/man-pages/man8/unix_chkpwd.8.html](https://www.man7.org/linux/man-pages/man8/unix_chkpwd.8.html)
+ - [https://cr.yp.to/checkpwd.html](https://cr.yp.to/checkpwd.html)
+ - [https://pamtester.sourceforge.net/](https://pamtester.sourceforge.net/)
+ - [https://github.com/AlexanderZhirov/chkpass](https://github.com/AlexanderZhirov/chkpass)
+ - [https://github.com/ViKingIX/pam_test](https://github.com/ViKingIX/pam_test)
+ - [https://github.com/Dareka826/chk_pw](https://github.com/Dareka826/chk_pw)
+
+### License
+
+chkusr is licensed under the Apache License, Version 2.0.
 
 See LICENSE for details.
 
-## Links
-
- - [Homepage of checkpw](https://git.xw3.org/xw3/checkpw)
- - [https://cr.yp.to/checkpwd.html](https://cr.yp.to/checkpwd.html)
- - [https://pamtester.sourceforge.net/](https://pamtester.sourceforge.net/)
 

checkpw.1

@@ -1,24 +0,0 @@
-.TH man 1 "01 Jan 2025" "checkpw 1.1.1" "checkpw man page"
-.SH NAME
-checkpw \- checks the validity of a users password on a UNIX/PAM-based system.
-.SH SYNOPSIS
-checkpw [OPTION]...
-.SH DESCRIPTION
-checkpw is a program that checks the validity of a users password on a UNIX/PAM-based system.
-.SH OPTIONS
-The options which apply to the checkpw command are:
-
-  -u <username>  Set username.
-  -p <password>  Set password.
-  -v             Enable verbose mode.
-  -V             Print program version.
-  -h             Show this help.
-
-checkpw runs in an interactive mode when no username and/or password are set. A missing username and/or password will then be asked for program execution.
-
-.SH SEE ALSO
-pam(3), pam_authenticate(3), PAM(8)
-.SH BUGS
-No known bugs.
-.SH AUTHOR
-Johannes Findeisen (you@hanez.org)

chkgrp-min.c

@@ -0,0 +1,48 @@
+/**
+ * chkgrp-min is a program that checks if a user is a member of a group.
+ *
+ * Author: Johannes Findeisen <you@hanez.org> - 2025
+ * Homepage: https://git.xw3.org/hanez/chkusr
+ * License: Apache-2.0 (see LICENSE)
+ */
+
+ #include "config.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <pwd.h>
+#include <grp.h>
+
+int main(int argc, char *argv[])
+{
+    if (argc != 3)
+        return 2;
+
+    if (strlen(argv[1]) > MAX_NAME || strlen(argv[2]) > MAX_NAME)
+        return 2;
+
+    struct passwd *pw = getpwnam(argv[1]);
+    if (!pw)
+        return 2;
+
+    struct group *gr = getgrnam(argv[2]);
+    if (!gr)
+        return 2;
+
+    if (pw->pw_gid == gr->gr_gid) {
+        puts("Yes");
+        return 0;
+    }
+
+    for (char **m = gr->gr_mem; *m; ++m) {
+        if (!strcmp(*m, argv[1])) {
+            puts("Yes");
+            return 0;
+        }
+    }
+
+    puts("No");
+    return 1;
+}
+

chkgrp-native-min-extended.c

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

chkgrp-native-min.c

@@ -0,0 +1,59 @@
+/**
+ * chkgrp-min-native is a program that checks if a user is a member of a group.
+ *
+ * Author: Johannes Findeisen <you@hanez.org> - 2025
+ * Homepage: https://git.xw3.org/hanez/chkusr
+ * License: Apache-2.0 (see LICENSE)
+ */
+
+#include "config.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+int main(int argc, char *argv[])
+{
+    if (argc != 3)
+        return 2;
+
+    const char *username = argv[1];
+    const char *groupname = argv[2];
+
+    if (strlen(username) > MAX_NAME || strlen(groupname) > MAX_NAME)
+        return 2;
+
+    FILE *fp = fopen("/etc/group", "r");
+    if (!fp)
+        return 2;
+
+    char line[MAX_LINE];
+    while (fgets(line, sizeof(line), fp)) {
+        char *grp = strtok(line, ":");
+        if (!grp || strcmp(grp, groupname) != 0)
+            continue;
+
+        strtok(NULL, ":"); // skip password
+        strtok(NULL, ":"); // skip GID
+
+        char *members = strtok(NULL, ":\n");
+        if (!members) break;
+
+        char *m = strtok(members, ",");
+        while (m) {
+            if (!strcmp(m, username)) {
+                puts("Yes");
+                fclose(fp);
+                return 0;
+            }
+            m = strtok(NULL, ",");
+        }
+
+        break; // group matched, no user found
+    }
+
+    fclose(fp);
+    puts("No");
+    return 1;
+}
+

chkgrp-native.c

@@ -0,0 +1,77 @@
+/**
+ * chkgrp-native is a program that checks if a user is a member of a group.
+ *
+ * Author: Johannes Findeisen <you@hanez.org> - 2025
+ * Homepage: https://git.xw3.org/hanez/chkusr
+ * License: Apache-2.0 (see LICENSE)
+ */
+
+#include "config.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+int main(int argc, char *argv[])
+{
+    if (argc != 3) {
+        fprintf(stderr, "Usage: %s <username> <groupname>\n", argv[0]);
+        return 2;
+    }
+
+    const char *username = argv[1];
+    const char *groupname = argv[2];
+
+    if (strlen(username) > MAX_NAME || strlen(groupname) > MAX_NAME) {
+        fprintf(stderr, "Error: Name too long (max %d characters).\n", MAX_NAME);
+        return 2;
+    }
+
+    FILE *fp = fopen("/etc/group", "r");
+    if (!fp) {
+        perror("Error opening /etc/group");
+        return 2;
+    }
+
+    char line[MAX_LINE];
+    int found = 0;
+
+    while (fgets(line, sizeof(line), fp)) {
+        char *grp_name = strtok(line, ":");
+        if (!grp_name) continue;
+
+        strtok(NULL, ":"); // skip password
+        strtok(NULL, ":"); // skip GID
+
+        char *members = strtok(NULL, ":\n");
+        if (!members) continue;
+
+        if (strcmp(grp_name, groupname) != 0)
+            continue;
+
+        // Group found, now check for user in member list
+        found = 1;
+        char *member = strtok(members, ",");
+        while (member) {
+            if (strcmp(member, username) == 0) {
+                fclose(fp);
+                puts("Yes");
+                return 0;
+            }
+            member = strtok(NULL, ",");
+        }
+
+        break; // no need to continue scanning
+    }
+
+    fclose(fp);
+
+    if (!found) {
+        fprintf(stderr, "Group '%s' not found.\n", groupname);
+        return 2;
+    }
+
+    puts("No");
+    return 1;
+}
+

chkgrp-ng.c

@@ -0,0 +1,152 @@
+/**
+ * chkgrp-ng is a program that checks if a user is a member of a group.
+ *
+ * Author: Johannes Findeisen <you@hanez.org> - 2025
+ * Homepage: https://git.xw3.org/hanez/chkusr
+ * License: Apache-2.0 (see LICENSE)
+ */
+
+#include "config.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+void print_help(const char *prog)
+{
+    printf("Usage: %s [OPTIONS] <username> <groupname>\n", prog);
+    printf("Options:\n");
+    printf("  --passwd PATH    Use custom /etc/passwd file\n");
+    printf("  --group PATH     Use custom /etc/group file\n");
+    printf("  -q               Quiet mode (no output)\n");
+    printf("  -h               Show this help message\n");
+}
+
+const char *get_arg(int *i, int argc, char *argv[], const char *opt)
+{
+    if (*i + 1 >= argc) {
+        fprintf(stderr, "Missing argument after %s\n", opt);
+        exit(2);
+    }
+    return argv[++(*i)];
+}
+
+int get_user_gid(const char *user, const char *passwd_path)
+{
+    FILE *fp = fopen(passwd_path, "r");
+    if (!fp) {
+        fprintf(stderr, "Error: Cannot open passwd file: %s\n", passwd_path);
+        return -1;
+    }
+
+    char line[MAX_LINE];
+    while (fgets(line, sizeof(line), fp)) {
+        char *name = strtok(line, ":");
+        if (!name || strcmp(name, user) != 0) continue;
+
+        strtok(NULL, ":"); // password
+        strtok(NULL, ":"); // UID
+        char *gid_str = strtok(NULL, ":");
+        fclose(fp);
+        return gid_str ? atoi(gid_str) : -1;
+    }
+
+    fclose(fp);
+    return -1;
+}
+
+int check_group(const char *user, const char *group, int user_gid,
+                const char *group_path)
+{
+    FILE *fp = fopen(group_path, "r");
+    if (!fp) {
+        fprintf(stderr, "Error: Cannot open group file: %s\n", group_path);
+        return -1;
+    }
+
+    char line[MAX_LINE];
+    while (fgets(line, sizeof(line), fp)) {
+        char *grp = strtok(line, ":");
+        if (!grp || strcmp(grp, group) != 0) continue;
+
+        strtok(NULL, ":"); // password
+        char *gid_str = strtok(NULL, ":");
+        if (!gid_str) break;
+
+        int group_gid = atoi(gid_str);
+        if (group_gid == user_gid) {
+            fclose(fp);
+            return 1;
+        }
+
+        char *members = strtok(NULL, ":\n");
+        if (!members) break;
+
+        char *m = strtok(members, ",");
+        while (m) {
+            if (strcmp(m, user) == 0) {
+                fclose(fp);
+                return 1;
+            }
+            m = strtok(NULL, ",");
+        }
+
+        fclose(fp);
+        return 0;
+    }
+
+    fclose(fp);
+    return -1;
+}
+
+int main(int argc, char *argv[])
+{
+    const char *passwd_file = "/etc/passwd";
+    const char *group_file  = "/etc/group";
+    int quiet = 0;
+
+    int i = 1;
+    const char *username = NULL, *groupname = NULL;
+
+    while (i < argc) {
+        if (!strcmp(argv[i], "--passwd")) {
+            passwd_file = get_arg(&i, argc, argv, "--passwd");
+        } else if (!strcmp(argv[i], "--group")) {
+            group_file = get_arg(&i, argc, argv, "--group");
+        } else if (!strcmp(argv[i], "-q")) {
+            quiet = 1;
+        } else if (!strcmp(argv[i], "-h")) {
+            print_help(argv[0]);
+            return 0;
+        } else if (!username) {
+            username = argv[i];
+        } else if (!groupname) {
+            groupname = argv[i];
+        } else {
+            fprintf(stderr, "Unexpected argument: %s\n", argv[i]);
+            return 2;
+        }
+        i++;
+    }
+
+    if (!username || !groupname ||
+        strlen(username) > MAX_NAME || strlen(groupname) > MAX_NAME) {
+        return 2;
+    }
+
+    int user_gid = get_user_gid(username, passwd_file);
+    if (user_gid < 0)
+        return 2;
+
+    int result = check_group(username, groupname, user_gid, group_file);
+    if (result == 1) {
+        if (!quiet) puts("Yes");
+        return 0;
+    } else if (result == 0) {
+        if (!quiet) puts("No");
+        return 1;
+    }
+
+    return 2;
+}
+

chkgrp.c

@@ -0,0 +1,75 @@
+/**
+ * chkgrp is a program that checks if a user is a member of a group.
+ *
+ * Author: Johannes Findeisen <you@hanez.org> - 2025
+ * Homepage: https://git.xw3.org/hanez/chkusr
+ * License: Apache-2.0 (see LICENSE)
+ */
+
+#include "config.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <pwd.h>
+#include <grp.h>
+#include <unistd.h>
+#include <errno.h>
+#include <limits.h>
+
+int main(int argc, char *argv[])
+{
+    if (argc != 3) {
+        fprintf(stderr, "Usage: %s <username> <groupname>\n", argv[0]);
+        return 2;
+    }
+
+    const char *username = argv[1];
+    const char *groupname = argv[2];
+
+    // Runtime check for max name length
+    long max_name_len = sysconf(_SC_LOGIN_NAME_MAX);
+    if (max_name_len <= 0 || max_name_len > 1024) {
+        max_name_len = MAX_NAME;
+    }
+
+    if (strlen(username) > (size_t)max_name_len) {
+        fprintf(stderr, "Error: Username too long (max %ld characters).\n",
+                max_name_len);
+        return 2;
+    }
+
+    if (strlen(groupname) > (size_t)max_name_len) {
+        fprintf(stderr, "Error: Group name too long (max %ld characters).\n",
+                max_name_len);
+        return 2;
+    }
+
+    struct passwd *pw = getpwnam(username);
+    if (!pw) {
+        fprintf(stderr, "Error: User '%s' not found.\n", username);
+        return 2;
+    }
+
+    struct group *gr = getgrnam(groupname);
+    if (!gr) {
+        fprintf(stderr, "Error: Group '%s' not found.\n", groupname);
+        return 2;
+    }
+
+    if (pw->pw_gid == gr->gr_gid) {
+        puts("Yes");
+        return 0;
+    }
+
+    for (char **members = gr->gr_mem; *members != NULL; members++) {
+        if (strcmp(*members, username) == 0) {
+            puts("Yes");
+            return 0;
+        }
+    }
+
+    puts("No");
+    return 1;
+}
+

chkpwd.1

@@ -0,0 +1,27 @@
+.TH checkpw 1 "June 2025" "chkpwd 1.4.0" "chkpwd man page"
+.SH NAME
+chkpwd \- checks the validity of a users password on a UNIX/PAM-based system.
+.SH SYNOPSIS
+chkpwd [OPTION]...
+.SH DESCRIPTION
+chkpwd is a program that checks the validity of a users password on a
+UNIX/PAM-based system.
+.SH OPTIONS
+The options which apply to the chkpwd command are:
+
+  -u <username>  Set username.
+  -p <password>  Set password.
+  -v             Enable verbose mode.
+  -V             Print program version.
+  -h             Show this help.
+
+chkpwd runs in an interactive mode when no username and/or password are set.
+A missing username and/or password will then be asked for while program
+execution.
+
+.SH SEE ALSO
+pam(3), pam_authenticate(3), PAM(8), pam_unix(8)
+.SH BUGS
+No known bugs.
+.SH AUTHOR
+Written by Johannes Findeisen <you@hanez.org>.

chkpwd.c

@@ -1,11 +1,15 @@
 /**
- * checkpw is a program that checks the validity of a users password on a
+ * chkpwd is a program that checks the validity of a users password on a
  * UNIX/PAM-based system.
  *
  * Author: Johannes Findeisen <you@hanez.org> - 2024
+ * Homepage: https://git.xw3.org/hanez/chkpwd
  * License: Apache-2.0 (see LICENSE)
  */
 
+#include "chkpwd.h"
+#include "config.h"
+
 #include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -13,8 +17,6 @@
 #include <termios.h>
 #include <unistd.h>
 
-#include "checkpw.h"
-
 // Function to prompt user for input, optionally hiding input
 void prompt_for_input(char *buffer, size_t size, const char *prompt,
                       bool hide_input)
@@ -80,28 +82,28 @@ int main(int argc, char *argv[])
 {
     bool verbose = false;
     bool version = false;
-    char password[MAX_PASSWORD_LEN] = {0};
-    char username[MAX_USERNAME_LEN] = {0};
+    char password[MAX_PASSWORD] = {0};
+    char username[MAX_NAME] = {0};
     int opt;
 
     // Parse command-line arguments
     while ((opt = getopt(argc, argv, "u:p:hvV")) != -1) {
         switch (opt) {
             case 'u':
-                if (strlen(optarg) >= MAX_USERNAME_LEN) {
+                if (strlen(optarg) >= MAX_NAME) {
                     fprintf(stderr, "Error: Username is too long (maximum %d characters).\n",
-                            MAX_USERNAME_LEN);
+                            MAX_NAME);
                     exit(1);
                 }
-                strncpy(username, optarg, MAX_USERNAME_LEN - 1);
+                strncpy(username, optarg, MAX_NAME - 1);
                 break;
             case 'p':
-                if (strlen(optarg) >= MAX_PASSWORD_LEN) {
+                if (strlen(optarg) >= MAX_PASSWORD) {
                     fprintf(stderr, "Error: Password is too long (maximum %d characters).\n",
-                            MAX_PASSWORD_LEN);
+                            MAX_PASSWORD);
                     exit(1);
                 }
-                strncpy(password, optarg, MAX_PASSWORD_LEN - 1);
+                strncpy(password, optarg, MAX_PASSWORD - 1);
                 break;
             case 'h':
                 print_usage(argv[0]);
@@ -157,7 +159,7 @@ int main(int argc, char *argv[])
         printf("User '%s' passed UID check (UID: %d).\n", username,
                pwd->pw_uid);
 
-    if (authenticate(username, password, verbose) == true) {
+    if (checkpw_authenticate(username, password, verbose) == true) {
         printf("Authenticated successfully.\n");
         return 0;
     } else {

chkpwd.h

@@ -1,34 +1,19 @@
 /**
- * checkpw.h is part of checkpw, a program that checks the validity of a users
- * password on a UNIX/PAM-based system.
+ * chkpwd.h is part of chkusr, a set of programs to verify information about
+ * a user on UNIX based systems.
  *
  * Author: Johannes Findeisen <you@hanez.org> - 2025
+ * Homepage: https://git.xw3.org/hanez/chkusr
  * License: Apache-2.0 (see LICENSE)
  */
 
 #include <pwd.h>
+#include <stdbool.h>
 #include <security/pam_appl.h>
 #include <security/pam_misc.h>
 
-#define VERSION "1.1.1"
-
-#ifndef MAX_PASSWORD_LEN
-#define MAX_PASSWORD_LEN 256
-#endif
-
-#ifndef MAX_USERNAME_LEN
-#define MAX_USERNAME_LEN 32
-#endif
-
-#ifndef MAX_UID
-#define MAX_UID 1000
-#endif
-
-#ifndef MIN_UID
-#define MIN_UID 1000
-#endif
-
-bool authenticate(const char *username, const char *password, bool verbose);
+bool checkpw_authenticate(const char *username, const char *password,
+                          bool verbose);
 
 int pam_conversation(int num_msg, const struct pam_message **msg,
                      struct pam_response **resp, void *appdata_ptr);
@@ -38,7 +23,8 @@ struct pam_credentials
     const char *password;
 };
 
-bool authenticate(const char *username, const char *password, bool verbose)
+bool checkpw_authenticate(const char *username, const char *password,
+                          bool verbose)
 {
     int retval;
     pam_handle_t *pamh = NULL;

chkpwr.c

@@ -0,0 +1,100 @@
+/**
+ * checkpwrule is a program that checks if an input string validates a
+ * password rule.
+ *
+ * Author: Johannes Findeisen <you@hanez.org> - 2024
+ * License: MIT (see LICENSE)
+ */
+
+#include "config.h"
+
+#include <stdio.h>
+#include <ctype.h>
+#include <string.h>
+
+// Return 1 if non-ASCII characters are found, 0 if all are ASCII
+int is_valid_ascii(char *str) {
+    for (int i = 0; i < strlen(str); i++) {
+        if ((unsigned char)str[i] > 127) {
+            return 1; // Non-ASCII character detected, return 1 (indicating invalid)
+        }
+    }
+    return 0; // All characters are ASCII
+}
+
+int is_valid(char *str) {
+    int lowercase_count = 0, uppercase_count = 0, digit_count = 0, special_count = 0;
+    int i;
+    int length = strlen(str);
+
+    // Check if the input contains any non-ASCII characters
+    if (is_valid_ascii(str)) {
+        printf("Password contains non-ASCII characters.\n");
+        return 1; // Invalid input, return 1 to signal failure
+    }
+
+    // Check if the length is within the allowed range
+    if (length < MIN_PASSWORD_LENGTH) {
+        printf("Password is too short! It must be at least %d characters long.\n", MIN_PASSWORD_LENGTH);
+        return 1;
+    }
+    if (length > MAX_PASSWORD_LENGTH) {
+        printf("Password exceeds the maximum length of %d characters.\n", MAX_PASSWORD_LENGTH);
+        return 1;
+    }
+
+    // Check each character of the string and count occurrences
+    for (i = 0; i < length; i++) {
+        if (islower(str[i])) {
+            lowercase_count++;
+        } else if (isupper(str[i])) {
+            uppercase_count++;
+        } else if (isdigit(str[i])) {
+            digit_count++;
+        } else if (ispunct(str[i])) { // Checks for special characters like !, @, #, etc.
+            special_count++;
+        }
+    }
+
+    // Check if all counts meet the required minimums
+    if (lowercase_count < MIN_LOWERCASE) {
+        printf("Password needs at least %d lowercase letters.\n", MIN_LOWERCASE);
+        return 1;
+    }
+    if (uppercase_count < MIN_UPPERCASE) {
+        printf("Password needs at least %d uppercase letters.\n", MIN_UPPERCASE);
+        return 1;
+    }
+    if (digit_count < MIN_DIGITS) {
+        printf("Password needs at least %d digits.\n", MIN_DIGITS);
+        return 1;
+    }
+    if (special_count < MIN_SPECIAL) {
+        printf("Password needs at least %d special characters.\n", MIN_SPECIAL);
+        return 1;
+    }
+
+    // If all conditions are met, return 0 (indicating success)
+    return 0;
+}
+
+int main(int argc, char *argv[]) {
+    if (argc != 2) {
+        printf("Usage: %s <string>\n", argv[0]);
+        return 1;
+    }
+
+    if (is_valid(argv[1]) == 0) {
+        printf("The string is valid.\n");
+        return 0; // Success
+    } else {
+        printf("The string is invalid. It must contain at least:\n");
+        printf("- %d lowercase letters\n", MIN_LOWERCASE);
+        printf("- %d uppercase letters\n", MIN_UPPERCASE);
+        printf("- %d digits\n", MIN_DIGITS);
+        printf("- %d special characters\n", MIN_SPECIAL);
+        printf("And be between %d and %d characters long.\n", MIN_PASSWORD_LENGTH, MAX_PASSWORD_LENGTH);
+        return 1; // Invalid password, return 1
+    }
+}
+

config.h

@@ -0,0 +1,56 @@
+/*
+ * Author: Johannes Findeisen <you@hanez.org> - 2025
+ * Homepage: https://git.xw3.org/hanez/chkusr
+ * License: Apache-2.0 (see LICENSE)
+ */
+
+#define VERSION "1.5.1"
+
+/* For chkgrp */
+#ifndef MAX_LINE
+#define MAX_LINE 1024
+#endif
+
+/* MAX_NAME is also used by chkpwd */
+#ifndef MAX_NAME
+#define MAX_NAME 256
+#endif
+
+/* For chkpwd; Also uses MAX_NAME from chkgrp above */
+#ifndef MAX_PASSWORD
+#define MAX_PASSWORD 256
+#endif
+
+#ifndef MAX_UID
+#define MAX_UID 1000
+#endif
+
+#ifndef MIN_UID
+#define MIN_UID 1000
+#endif
+
+/* For chkpwr */
+#ifndef MAX_PASSWORD_LENGTH
+#define MAX_PASSWORD_LENGTH 32
+#endif
+
+#ifndef MIN_PASSWORD_LENGTH
+#define MIN_PASSWORD_LENGTH 12
+#endif
+
+#ifndef MIN_LOWERCASE
+#define MIN_LOWERCASE 2
+#endif
+
+#ifndef MIN_UPPERCASE
+#define MIN_UPPERCASE 2
+#endif
+
+#ifndef MIN_DIGITS
+#define MIN_DIGITS 2
+#endif
+
+#ifndef MIN_SPECIAL
+#define MIN_SPECIAL 2
+#endif
+

lua/README.md

@@ -0,0 +1 @@
+This is experimental at the monent but I really will implement some programs from chkusr in Lua or write some wrappers for the C programs...

lua/checkgroup.lua

@@ -0,0 +1,79 @@
+-- This file is part of chkgrp that is a program that checks if a user is a
+-- member of a group.
+--
+-- Author: Johannes Findeisen <you@hanez.org> - 2025
+-- Homepage: https://git.xw3.org/hanez/chkgrp
+-- License: Apache-2.0 (see LICENSE)
+
+local checkgroup = {}
+
+local MAX_NAME = 256
+
+local function read_passwd_gid(username)
+    local f = io.open("/etc/passwd", "r")
+    if not f then return nil end
+
+    for line in f:lines() do
+        local fields = {}
+        for field in string.gmatch(line, "([^:]+)") do
+            table.insert(fields, field)
+        end
+        if fields[1] == username then
+            f:close()
+            return tonumber(fields[4])
+        end
+    end
+
+    f:close()
+    return nil
+end
+
+local function check_group_membership(username, groupname, user_gid)
+    local f = io.open("/etc/group", "r")
+    if not f then return nil end
+
+    for line in f:lines() do
+        local fields = {}
+        for field in string.gmatch(line, "([^:]+)") do
+            table.insert(fields, field)
+        end
+        if fields[1] == groupname then
+            local group_gid = tonumber(fields[3])
+            if group_gid == user_gid then
+                f:close()
+                return true
+            end
+
+            for member in string.gmatch(fields[4] or "", "[^,]+") do
+                if member == username then
+                    f:close()
+                    return true
+                end
+            end
+
+            f:close()
+            return false
+        end
+    end
+
+    f:close()
+    return nil
+end
+
+function checkgroup.is_user_in_group(username, groupname)
+    if not username or not groupname then
+        return nil
+    end
+
+    if #username > MAX_NAME or #groupname > MAX_NAME then
+        return nil
+    end
+
+    local gid = read_passwd_gid(username)
+    if not gid then return nil end
+
+    return check_group_membership(username, groupname, gid)
+end
+
+return checkgroup
+

lua/chkgrp-native-min-extended.lua

@@ -0,0 +1,89 @@
+#!/usr/bin/env lua
+
+-- This file is part of chkgrp that is a program that checks if a user is a
+-- member of a group.
+--
+-- Author: Johannes Findeisen <you@hanez.org> - 2025
+-- Homepage: https://git.xw3.org/hanez/chkgrp
+-- License: Apache-2.0 (see LICENSE)
+
+local MAX_NAME = 256
+
+local function read_passwd_gid(username)
+    local f = io.open("/etc/passwd", "r")
+    if not f then return nil end
+
+    for line in f:lines() do
+        local fields = {}
+        for field in string.gmatch(line, "([^:]+)") do
+            table.insert(fields, field)
+        end
+        if fields[1] == username then
+            f:close()
+            return tonumber(fields[4]) -- GID is 4th field
+        end
+    end
+
+    f:close()
+    return nil
+end
+
+local function check_group_membership(username, groupname, user_gid)
+    local f = io.open("/etc/group", "r")
+    if not f then return nil end
+
+    for line in f:lines() do
+        local fields = {}
+        for field in string.gmatch(line, "([^:]+)") do
+            table.insert(fields, field)
+        end
+        if fields[1] == groupname then
+            local group_gid = tonumber(fields[3])
+            if group_gid == user_gid then
+                f:close()
+                return true
+            end
+
+            for member in string.gmatch(fields[4] or "", "[^,]+") do
+                if member == username then
+                    f:close()
+                    return true
+                end
+            end
+
+            f:close()
+            return false
+        end
+    end
+
+    f:close()
+    return nil
+end
+
+local username = arg[1]
+local groupname = arg[2]
+
+if not username or not groupname then
+    os.exit(2)
+end
+
+if #username > MAX_NAME or #groupname > MAX_NAME then
+    os.exit(2)
+end
+
+local user_gid = read_passwd_gid(username)
+if not user_gid then
+    os.exit(2)
+end
+
+local result = check_group_membership(username, groupname, user_gid)
+if result == nil then
+    os.exit(2)
+elseif result == true then
+    print("Yes")
+    os.exit(0)
+else
+    print("No")
+    os.exit(1)
+end
+

lua/test.lua

@@ -0,0 +1,26 @@
+#!/usr/bin/env lua
+
+-- This file is part of chkgrp that is a program that checks if a user is a
+-- member of a group.
+--
+-- Author: Johannes Findeisen <you@hanez.org> - 2025
+-- Homepage: https://git.xw3.org/hanez/chkgrp
+-- License: Apache-2.0 (see LICENSE)
+
+local checkgroup = require("checkgroup")
+
+local user = arg[1]
+local group = arg[2]
+
+local result = checkgroup.is_user_in_group(user, group)
+
+if result == true then
+    print("Yes")
+    os.exit(0)
+elseif result == false then
+    print("No")
+    os.exit(1)
+else
+    os.exit(2)
+end
+