123 lines
3.1 KiB
C
123 lines
3.1 KiB
C
#define _POSIX_C_SOURCE 200809L
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#include <pwd.h>
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#include <security/pam_appl.h>
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#include <stdbool.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include "comm.h"
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#include "log.h"
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#include "password-buffer.h"
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#include "swaylock.h"
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static char *pw_buf = NULL;
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void initialize_pw_backend(int argc, char **argv) {
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if (getuid() != geteuid() || getgid() != getegid()) {
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swaylock_log(LOG_ERROR,
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"swaylock is setuid, but was compiled with the PAM"
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" backend. Run 'chmod a-s %s' to fix. Aborting.", argv[0]);
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exit(EXIT_FAILURE);
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}
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if (!spawn_comm_child()) {
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exit(EXIT_FAILURE);
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}
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}
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static int handle_conversation(int num_msg, const struct pam_message **msg,
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struct pam_response **resp, void *data) {
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/* PAM expects an array of responses, one for each message */
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struct pam_response *pam_reply =
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calloc(num_msg, sizeof(struct pam_response));
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if (pam_reply == NULL) {
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swaylock_log(LOG_ERROR, "Allocation failed");
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return PAM_ABORT;
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}
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*resp = pam_reply;
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for (int i = 0; i < num_msg; ++i) {
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switch (msg[i]->msg_style) {
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case PAM_PROMPT_ECHO_OFF:
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case PAM_PROMPT_ECHO_ON:
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pam_reply[i].resp = strdup(pw_buf); // PAM clears and frees this
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if (pam_reply[i].resp == NULL) {
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swaylock_log(LOG_ERROR, "Allocation failed");
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return PAM_ABORT;
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}
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break;
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case PAM_ERROR_MSG:
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case PAM_TEXT_INFO:
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break;
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}
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}
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return PAM_SUCCESS;
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}
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static const char *get_pam_auth_error(int pam_status) {
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switch (pam_status) {
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case PAM_AUTH_ERR:
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return "invalid credentials";
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case PAM_CRED_INSUFFICIENT:
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return "swaylock cannot authenticate users; check /etc/pam.d/swaylock "
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"has been installed properly";
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case PAM_AUTHINFO_UNAVAIL:
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return "authentication information unavailable";
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case PAM_MAXTRIES:
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return "maximum number of authentication tries exceeded";
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default:;
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static char msg[64];
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snprintf(msg, sizeof(msg), "unknown error (%d)", pam_status);
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return msg;
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}
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}
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void run_pw_backend_child(void) {
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struct passwd *passwd = getpwuid(getuid());
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char *username = passwd->pw_name;
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const struct pam_conv conv = {
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.conv = handle_conversation,
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.appdata_ptr = NULL,
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};
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pam_handle_t *auth_handle = NULL;
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if (pam_start("swaylock", username, &conv, &auth_handle) != PAM_SUCCESS) {
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swaylock_log(LOG_ERROR, "pam_start failed");
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exit(EXIT_FAILURE);
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}
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/* This code does not run as root */
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swaylock_log(LOG_DEBUG, "Prepared to authorize user %s", username);
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int pam_status = PAM_SUCCESS;
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while (1) {
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ssize_t size = read_comm_request(&pw_buf);
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if (size < 0) {
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exit(EXIT_FAILURE);
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} else if (size == 0) {
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break;
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}
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int pam_status = pam_authenticate(auth_handle, 0);
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password_buffer_destroy(pw_buf, size);
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pw_buf = NULL;
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bool success = pam_status == PAM_SUCCESS;
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if (!success) {
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swaylock_log(LOG_ERROR, "pam_authenticate failed: %s",
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get_pam_auth_error(pam_status));
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}
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if (!write_comm_reply(success)) {
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exit(EXIT_FAILURE);
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}
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}
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pam_setcred(auth_handle, PAM_REFRESH_CRED);
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if (pam_end(auth_handle, pam_status) != PAM_SUCCESS) {
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swaylock_log(LOG_ERROR, "pam_end failed");
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exit(EXIT_FAILURE);
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}
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exit((pam_status == PAM_SUCCESS) ? EXIT_SUCCESS : EXIT_FAILURE);
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}
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