97 lines
2.6 KiB
C
97 lines
2.6 KiB
C
/*
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* checkpw is a program that checks the validity of a users password on a
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* Linux/PAM-based system.
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*
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* Usage: checkpw
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*
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* Returns 0 on success, 1 otherwise.
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*
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* License: MIT (see LICENSE)
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*/
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#include <security/pam_appl.h>
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#include <security/pam_misc.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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// Custom data structure to hold user-entered password
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struct pam_credentials {
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const char *password;
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};
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// PAM conversation function to supply the password
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int pam_conversation(int num_msg, const struct pam_message **msg,
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struct pam_response **resp, void *appdata_ptr) {
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struct pam_response *response = NULL;
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struct pam_credentials *credentials = (struct pam_credentials *)appdata_ptr;
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int i;
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response = (struct pam_response *)malloc(sizeof(struct pam_response) * num_msg);
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if (response == NULL) {
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return PAM_CONV_ERR;
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}
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for (i = 0; i < num_msg; i++) {
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if (msg[i]->msg_style == PAM_PROMPT_ECHO_OFF || msg[i]->msg_style == PAM_PROMPT_ECHO_ON) {
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response[i].resp = strdup(credentials->password);
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response[i].resp_retcode = 0;
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}
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}
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*resp = response;
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return PAM_SUCCESS;
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}
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int authenticate(const char *username, const char *password) {
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pam_handle_t *pamh = NULL;
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int retval;
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struct pam_credentials credentials = { password };
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struct pam_conv conv = { pam_conversation, &credentials };
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retval = pam_start("login", username, &conv, &pamh);
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if (retval == PAM_SUCCESS) {
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retval = pam_authenticate(pamh, 0); // Attempt to authenticate
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}
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if (retval == PAM_SUCCESS) {
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retval = pam_acct_mgmt(pamh, 0); // Check account validity
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}
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if (pam_end(pamh, retval) != PAM_SUCCESS) {
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pamh = NULL;
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fprintf(stderr, "Failed to release PAM authenticator\n");
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exit(1);
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}
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return (retval == PAM_SUCCESS ? 0 : 1); // 0 for success, 1 for failure
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}
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int main() {
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char username[256];
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char *password;
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// Prompt user for a username
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printf("Username: ");
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if (fgets(username, sizeof(username), stdin) == NULL) {
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fprintf(stderr, "Failed to read username\n");
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exit(1);
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}
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// Remove the trailing newline character if it exists
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username[strcspn(username, "\n")] = '\0';
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// Prompt user for a password
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password = getpass("Password: ");
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// Authenticate the user
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if (authenticate(username, password) == 0) {
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printf("Authenticated successfully.\n");
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return 0;
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} else {
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printf("Authentication failed.\n");
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return 1;
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}
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}
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