feat: add support for fido yubikeys (#89)

* add support for fido keybind

* add to themes

* fix clang format

* Update ui.c

* docs: add misc stuff about the yubikey

---------

Co-authored-by: javalsai <jvssxxi@gmail.com>

README.md

@@ -27,10 +27,11 @@ kmscon -l --vt /dev/tty7 --font-name "Cascadia Code" -- /usr/bin/lidm
 
 ## Features
 
-- Simple as C, you only need a C compiler and standard unix libraries to build this.
-- Fully customizable, from strings, including action keys, to colors (I hope you know ansi escape codes)
-- Automatically detects xorg and wayland sessions, plus allowing to launch the default user shell (if enabled in config)
-- Starts with many init systems (systemd, dinit, runit, openrc and s6).
+- Simple as C, meant to depend only on standard libc and basic unix system headers.
+- Fully customizable: ALL strings, colors (with its ANSI keys) and most behavior.
+- Xorg[\*](https://github.com/javalsai/lidm/issues/79) and wayland sessions, while supporting the default user shell (if enabled in config)
+- Init agnostinc (systemd, dinit, runit, openrc and s6).
+- Supports [fido yubikeys](./docs/yubikey.md) (via pam_u2f).
 
 # Table of Contents
 

assets/man/lidm-config.5

@@ -69,13 +69,13 @@ Characters for the corners of the box (ctl = corner top left, cbr = corner botto
 .SS functions
 All these are of type \fBKEY\fP.
 .TP
-\fBpoweroff, reboot, refresh\fP
+\fBpoweroff, reboot, fido, refresh\fP
 Function key to use for such action.
 
 .SS strings
 Display strings to use for some elements.
 .TP
-\fBf_poweroff, f_reboot, f_refresh\fP
+\fBf_poweroff, f_reboot, f_fido, f_refresh\fP
 Text displayed to name such functions at the bottom of the screen.
 .TP
 \fBe_user, e_passwd\fP

docs/yubikey.md

@@ -0,0 +1,30 @@
+# Yubikeys
+
+Quick reference explaining how yubikeys work for now.
+
+# Enable
+
+Yubikeys are disabled by default, to enable them activate a keybinding for it (`[functions] fido`) in the config file.
+
+Note that pressing this configured keybinding has no difference from trying to log in with an empty password, there's virtually no difference.
+
+`pam_u2f` must be configured with a registered key (`pamu2fcfg`).
+
+# Extra
+
+All my yubikey knowledge comes from the [pr that implemented this](https://github.com/javalsai/lidm/pull/89), please refer to it for extra details. Contributions to this documentation are welcome (explaining more in detail, potential issues... really anything that improves this).
+
+Allegedly this pam module configuration should work:
+
+```pam
+#%PAM-1.0
+
+auth sufficient pam_u2f.so cue
+auth       requisite    pam_nologin.so
+auth       include      system-local-login
+account    include      system-local-login
+session    include      system-local-login
+password   include      system-local-login
+```
+
+Also, I recommend giving the [arch wiki](https://wiki.archlinux.org/title/YubiKey) a read anyways.

include/config.h

@@ -92,6 +92,7 @@ BUILD(chars, CHARS, TABLE_CHARS);
 #define TABLE_FUNCTIONS(F, name)        \
   F(enum keys, poweroff, KEY, F1, name) \
   F(enum keys, reboot, KEY, F2, name)   \
+  F(enum keys, fido, KEY, NONE, name)   \
   F(enum keys, refresh, KEY, F5, name)
 
 BUILD(functions, FUNCTIONS, TABLE_FUNCTIONS);
@@ -99,6 +100,7 @@ BUILD(functions, FUNCTIONS, TABLE_FUNCTIONS);
 #define TABLE_STRINGS(F, name)                             \
   F(char* NNULLABLE, f_poweroff, STRING, "poweroff", name) \
   F(char* NNULLABLE, f_reboot, STRING, "reboot", name)     \
+  F(char* NNULLABLE, f_fido, STRING, "fido", name)         \
   F(char* NNULLABLE, f_refresh, STRING, "refresh", name)   \
   F(char* NNULLABLE, e_user, STRING, "user", name)         \
   F(char* NNULLABLE, e_passwd, STRING, "password", name)   \

include/keys.h

@@ -32,9 +32,11 @@ enum keys {
   END,
   PAGE_UP,
   PAGE_DOWN,
+  NONE,
 };
 
 static const char* const KEY_NAMES[] = {
+    [NONE] = "NONE",
     [ESC] = "ESC",
     [F1] = "F1",
     [F2] = "F2",

include/ui.h

@@ -46,6 +46,8 @@ void setup(struct config* config);
 int load(struct Vector* users, struct Vector* sessions);
 void print_err(const char* /*msg*/);
 void print_errno(const char* /*descr*/);
+void print_pam_msg(const char* msg, int msg_style);
+void clear_pam_msg(void);
 
 void ui_update_field(enum input focused_input);
 void ui_update_ffield();

src/auth.c

@@ -17,6 +17,11 @@
 #include "unistd.h"
 #include "util.h"
 
+struct pam_conv_data {
+  char* password;
+  void (*display_pam_msg)(const char* msg, int msg_style);
+};
+
 int pam_conversation(int num_msg, const struct pam_message** msg,
                      struct pam_response** resp, void* appdata_ptr) {
   struct pam_response* reply =
@@ -24,13 +29,34 @@ int pam_conversation(int num_msg, const struct pam_message** msg,
   if (!reply) {
     return PAM_BUF_ERR;
   }
+
+  struct pam_conv_data* conv_data = (struct pam_conv_data*)appdata_ptr;
+
   for (size_t i = 0; i < num_msg; i++) {
     reply[i].resp = NULL;
     reply[i].resp_retcode = 0;
-    if (msg[i]->msg_style == PAM_PROMPT_ECHO_OFF ||
-        msg[i]->msg_style == PAM_PROMPT_ECHO_ON) {
-      char* input = (char*)appdata_ptr;
-      reply[i].resp = strdup(input);
+
+    switch (msg[i]->msg_style) {
+      case PAM_PROMPT_ECHO_OFF:
+      case PAM_PROMPT_ECHO_ON:
+        reply[i].resp = strdup(conv_data->password);
+        if (!reply[i].resp) {
+          for (size_t j = 0; j < i; j++)
+            free(reply[j].resp);
+          free(reply);
+          return PAM_BUF_ERR;
+        }
+        break;
+
+      case PAM_TEXT_INFO:
+      case PAM_ERROR_MSG:
+        if (conv_data->display_pam_msg && msg[i]->msg) {
+          conv_data->display_pam_msg(msg[i]->msg, msg[i]->msg_style);
+        }
+        break;
+
+      default:
+        break;
     }
   }
   *resp = reply;
@@ -54,7 +80,9 @@ void clear_screen() {
 
 pam_handle_t* get_pamh(char* user, char* passwd) {
   pam_handle_t* pamh = NULL;
-  struct pam_conv pamc = {pam_conversation, (void*)passwd};
+  struct pam_conv_data conv_data = {.password = passwd,
+                                    .display_pam_msg = print_pam_msg};
+  struct pam_conv pamc = {pam_conversation, (void*)&conv_data};
   int ret;
 
   char* pam_service_override = getenv("LIDM_PAM_SERVICE");
@@ -192,9 +220,10 @@ bool launch(char* user, char* passwd, struct session session, void (*cb)(void),
 
   pam_handle_t* pamh = get_pamh(user, passwd);
   if (pamh == NULL) {
-    print_err("error on pam authentication");
+    print_pam_msg("authentication failed", PAM_ERROR_MSG);
     return false;
   }
+  clear_pam_msg();
 
   bool* reach_session = shmalloc(sizeof(bool));
   if (reach_session == NULL) {

src/ui.c

@@ -5,6 +5,7 @@
 #include <errno.h>
 #include <limits.h>
 #include <pwd.h>
+#include <security/pam_appl.h>
 #include <signal.h>
 #include <stdbool.h>
 #include <stddef.h>
@@ -295,6 +296,21 @@ int load(struct Vector* users, struct Vector* sessions) {
           restore_all();
           reboot(RB_POWER_OFF);
           exit(0);
+        } else if (g_config->functions.fido != NONE &&
+                   ansi_code == g_config->functions.fido) {
+          bool successful_write = write_launch_state((struct LaunchState){
+              .username = st_user().username,
+              .session_opt =
+                  st_session(g_config->behavior.include_defshell).name,
+          });
+          if (!successful_write) log_puts("[E] failed to write launch state");
+
+          if (!launch(st_user().username, "",
+                      st_session(g_config->behavior.include_defshell),
+                      &restore_all, g_config)) {
+            print_passwd(utf8len(of_passwd.efield.content), true);
+            ui_update_cursor_focus();
+          }
         } else if (ansi_code == A_UP || ansi_code == A_DOWN) {
           st_ch_focus(ansi_code == A_DOWN ? 1 : -1);
         } else if (ansi_code == A_RIGHT || ansi_code == A_LEFT) {
@@ -509,6 +525,8 @@ static void print_box() {
 }
 
 static void print_footer() {
+  bool fido_enabled = g_config->functions.fido != NONE;
+
   size_t bsize = utf8len(g_config->strings.f_poweroff) +
                  utf8len(KEY_NAMES[g_config->functions.poweroff]) +
                  utf8len(g_config->strings.f_reboot) +
@@ -516,19 +534,31 @@ static void print_footer() {
                  utf8len(g_config->strings.f_refresh) +
                  utf8len(KEY_NAMES[g_config->functions.refresh]);
 
-  bsize += 2 * 2 + // 2 wide separators between 3 items
-           3 * 1;  // 3 thin separators inside every item
+  bsize += 2 * 2 + 3 * 1;
+
+  if (fido_enabled) {
+    bsize += utf8len(g_config->strings.f_fido) +
+             utf8len(KEY_NAMES[g_config->functions.fido]) + 2 + 1;
+  }
 
   uint row = window.ws_row - 1;
   uint col = window.ws_col - 2 - bsize;
-  printf(
-      "\x1b[%3$d;%4$dH%8$s \x1b[%1$sm%5$s\x1b[%2$sm  %9$s "
-      "\x1b[%1$sm%6$s\x1b[%2$sm  %10$s \x1b[%1$sm%7$s\x1b[%2$sm",
-      g_config->colors.e_key, g_config->colors.fg, row, col,
-      KEY_NAMES[g_config->functions.poweroff],
-      KEY_NAMES[g_config->functions.reboot],
-      KEY_NAMES[g_config->functions.refresh], g_config->strings.f_poweroff,
-      g_config->strings.f_reboot, g_config->strings.f_refresh);
+
+  printf("\x1b[%d;%dH%s \x1b[%sm%s\x1b[%sm  %s \x1b[%sm%s\x1b[%sm  ", row, col,
+         g_config->strings.f_poweroff, g_config->colors.e_key,
+         KEY_NAMES[g_config->functions.poweroff], g_config->colors.fg,
+         g_config->strings.f_reboot, g_config->colors.e_key,
+         KEY_NAMES[g_config->functions.reboot], g_config->colors.fg);
+
+  if (fido_enabled) {
+    printf("%s \x1b[%sm%s\x1b[%sm  ", g_config->strings.f_fido,
+           g_config->colors.e_key, KEY_NAMES[g_config->functions.fido],
+           g_config->colors.fg);
+  }
+
+  printf("%s \x1b[%sm%s\x1b[%sm", g_config->strings.f_refresh,
+         g_config->colors.e_key, KEY_NAMES[g_config->functions.refresh],
+         g_config->colors.fg);
 }
 
 void print_err(const char* msg) {
@@ -536,6 +566,21 @@ void print_err(const char* msg) {
                 msg, errno, strerror(errno));
 }
 
+void print_pam_msg(const char* msg, int msg_style) {
+  uint row = box_start.y + BOX_HEIGHT + 1;
+  const char* color =
+      (msg_style == PAM_ERROR_MSG) ? g_config->colors.err : g_config->colors.fg;
+  printf("\x1b[%d;%dH\x1b[K\x1b[%sm%.*s\x1b[%sm", row, box_start.x, color,
+         BOX_WIDTH, msg, g_config->colors.fg);
+  (void)fflush(stdout);
+}
+
+void clear_pam_msg(void) {
+  uint row = box_start.y + BOX_HEIGHT + 1;
+  printf("\x1b[%d;%dH\x1b[K", row, box_start.x);
+  (void)fflush(stdout);
+}
+
 void print_errno(const char* descr) {
   if (descr == NULL)
     (void)fprintf(stderr, "\x1b[%d;%dH\x1b[%smunknown error(%d): %s",

themes/default.ini

@@ -25,11 +25,13 @@
 [functions]
 # poweroff = F1
 # reboot = F2
+# fido = NONE
 # refresh = F5
 
 [strings]
 # f_poweroff = "poweroff"
 # f_reboot = "reboot"
+# f_fido = "fido"
 # f_refresh = "refresh"
 # e_user = "user"
 # e_passwd = "password"