1 files changed, 104 insertions, 0 deletions
diff --git a/command/su.c b/command/su.c
new file mode 100644
index 0000000..942f37e
--- /dev/null
+++ b/command/su.c
@@ -0,0 +1,104 @@
+#include "command.h"
+#include "lslib.h"
+
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+static struct {
+    bool clear_env;
+    bool update_env;
+    char* shell;
+    char* user;
+} flags;
+
+static bool restricted_shell(const char *shell) {
+	char *line;
+	int result = true;
+
+	while ((line = getusershell()) != NULL) {
+		if (strcmp(line, shell) == 0) {
+			result = false;
+			break;
+		}
+	}
+	endusershell();
+	return result;
+}
+
+static void help (void) {
+    printf("Usage: su [-lmp] [-s SH] [-] [USER [FILE ARGS]] \n\n");
+    printf("Run shell under USER (by default, root)\n\n");
+	printf("\t-,-l\tClear environment, go to home dir, run shell as login shell\n");
+	printf("\t-p,-m\tDo not set new $HOME, $SHELL, $USER, $LOGNAME\n");
+	printf("\t-s SH	Shell\tto use instead of user's default\n");
+}
+
+static int short_arg (char c, char* next) {
+    switch (c) {
+        case 'l':
+            flags.clear_env = true;
+            break;
+        case 'p':
+        case 'm':
+            flags.update_env = false;
+            break;
+        case 's':
+            check_arg(next);
+            flags.shell = next;
+            return ARG_USED;
+        default:
+            return ARG_INVALID;
+    
+    }
+    return ARG_UNUSED;
+}
+
+COMMAND (su) {
+     
+    int start, res;
+    uid_t cur_uid;
+    struct passwd* pw;
+
+    flags.clear_env = false;
+    flags.update_env = true;
+    flags.shell = NULL;
+    flags.user = "root";
+
+    start = parse_args(argc, argv, help, short_arg, NULL);
+
+    if (start < argc && streql(argv[start], "-")) {
+        flags.clear_env = true;
+        start++;
+    }
+
+    if (start < argc)
+        flags.user = argv[start++];
+
+    pw = xgetpwnam(flags.user);
+    cur_uid = getuid();
+
+    if (cur_uid != 0) {
+        res = prompt_password(pw, "Password: ");
+    } else {
+        res = PASSWORD_VALID;
+    }
+
+    if (res != PASSWORD_VALID) {
+        error("invalid password");
+    }
+
+    if (flags.shell && cur_uid != 0 && pw->pw_shell && restricted_shell(pw->pw_shell)) {
+        error_s("using restricted shell");
+        flags.shell = NULL;
+    }
+
+    if (!flags.shell)
+        flags.shell = pw->pw_shell;
+
+    change_identity(pw);
+    setup_environment(flags.shell, flags.update_env, flags.clear_env, pw);
+    exec_shell(flags.shell, flags.clear_env, (const char**) &argv[start]);
+
+    return EXIT_FAILURE; /* */
+}