fixes: improve login environment handling (#114)

* chore(organization): allow nested header and c files

* feat: add shell login "middleware" & etc:
  * lidm now calls `bash` (or other shells, depends on PACKAGE cfg) in
  login mode as a session wrapper to source most env (can be disabled)
  * this fixes a lot of env problems with all `/etc/profile` and more

Extra:
* implemented a musl compatible version of `execvpe` and now lidm should
  search for PATH everywhere it needs to
* `search_path` now also checks if the found binary is properly
  executable
* lidm now uses `confstr` for a decent PATH default if none is found
* logs are unbuffered for cases where debug logs appear empty (exit
  without handlers moment)

* chore: one-time evaluate certain makefile vars

---------

Co-authored-by: grialion <48643945+grialion@users.noreply.github.com>

src/auth.c

@@ -1,10 +1,11 @@
-// TODO: handle `fork() == -1`// TODO: handle `fork() == -1`s
+// TODO: handle `fork() == -1`
 
 #include <errno.h>
 #include <grp.h>
 #include <pwd.h>
 #include <security/pam_misc.h>
 #include <signal.h>
+#include <stddef.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -21,7 +22,8 @@
 #include "pam.h"
 #include "sessions.h"
 #include "ui.h"
-#include "util.h"
+#include "util/path.h"
+#include "util/vec.h"
 
 #define XORG_MESSAGE_LENGTH 16
 
@@ -80,16 +82,6 @@ static void source_paths(struct Vector* NNULLABLE vec_envlist,
   }
 }
 
-/*char *buf;*/
-/*size_t bsize = snprintf(NULL, 0, "/run/user/%d", pw->pw_uid) + 1;*/
-/*buf = malloc(bsize);*/
-/*snprintf(buf, bsize, "/run/user/%d", pw->pw_uid);*/
-/*setenv("XDG_RUNTIME_DIR", buf, true);*/
-/*setenv("XDG_SESSION_CLASS", "user", true);*/
-/*setenv("XDG_SESSION_ID", "1", true);*/
-/*setenv("XDG_SESSION_DESKTOP", , true);*/
-/*setenv("XDG_SEAT", "seat0", true);*/
-
 struct child_msg {
   char* msg;
   int _errno;
@@ -176,7 +168,8 @@ static void start_xorg_server(struct passwd* pw, char** NNULLABLE envlist,
 
 // TODO: add error msgs
 /// returns on completion
-static void launch_with_xorg_server(struct session_exec* NNULLABLE exec,
+static void launch_with_xorg_server(struct config* config,
+                                    struct session_exec* NNULLABLE exec,
                                     struct passwd* pw,
                                     char** NNULLABLE envlist) {
   int xorg_pipefd[2];
@@ -212,10 +205,14 @@ static void launch_with_xorg_server(struct session_exec* NNULLABLE exec,
   (void)fflush(NULL);
   pid_t xorg_session_pid = fork();
   if (xorg_session_pid == 0) {
-    int exit = session_exec_exec(exec, envlist);
-    perror("exec error");
+    if (config->behavior.bypass_shell_login)
+      session_exec_exec(exec, envlist);
+    else
+      session_exec_login_through_shell(exec, envlist);
+
+    perror("session exec error");
     (void)fputs("failure calling session\n", stderr);
-    _exit(exit);
+    _exit(EXIT_FAILURE);
   }
 
   // looks weird, waiting on -1 should wait on any child and then just check if
@@ -254,8 +251,8 @@ static void launch_with_xorg_server(struct session_exec* NNULLABLE exec,
     char _dummy;                              \
     read(pipefd[0], &_dummy, sizeof(_dummy)); \
   }
-inline static void forked(int pipefd[2], struct passwd* pw,
-                          char* NNULLABLE user,
+inline static void forked(struct config* config, int pipefd[2],
+                          struct passwd* pw, char* NNULLABLE user,
                           struct session* NNULLABLE session,
                           char** NNULLABLE envlist) {
   if (chdir(pw->pw_dir) == -1) SEND_ERR("chdir");
@@ -267,14 +264,26 @@ inline static void forked(int pipefd[2], struct passwd* pw,
   DUMMY_READ();
   close(pipefd[0]);
 
+  if (!getenv("PATH")) {
+    size_t path_size = confstr(_CS_PATH, NULL, 0);
+    char* path_env = malloc(path_size);
+    confstr(_CS_PATH, path_env, path_size);
+    setenv("PATH", path_env, 1);
+    free(path_env);
+  }
+
+  log_printf(" [I] using shell login?: %s",
+             config->behavior.bypass_shell_login ? "true" : "false");
   if (session->type == XORG) {
-    launch_with_xorg_server(&session->exec, pw, envlist);
+    launch_with_xorg_server(config, &session->exec, pw, envlist);
     _exit(EXIT_SUCCESS);
   } else {
-    int exit = session_exec_exec(&session->exec, envlist);
-    perror("exec error");
-    (void)fputs("failure calling session\n", stderr);
-    _exit(exit);
+    if (config->behavior.bypass_shell_login)
+      session_exec_exec(&session->exec, envlist);
+    else
+      session_exec_login_through_shell(&session->exec, envlist);
+    perror("session exec error");
+    _exit(EXIT_FAILURE);
   }
 }
 #undef SEND_MSG
@@ -325,7 +334,7 @@ bool launch(char* user, char* passwd, struct session session, void (*cb)(void),
 
   uint pid = fork();
   if (pid == 0)
-    forked(pipefd, pw, user, &session, envlist);
+    forked(config, pipefd, pw, user, &session, envlist);
   else {
     struct child_msg msg;
     read(pipefd[0], &msg, sizeof(struct child_msg));