Patches dropbear-2019.78 to allow passwordsless root logins automatically, without checking /etc/passwd / anything else.

db_auto_root.patch

This patches dropbear server to allow passwordless root logins, without checking /etc/passwd
and others. Useful if you just want to run dropbear and don't have a fully configured filesystem
with users.

diff -ruN dropbear-2019.78/common-session.c dropbear-2019.78_auto_root/common-session.c
--- dropbear-2019.78/common-session.c	2019-03-27 16:15:23.000000000 +0200
+++ dropbear-2019.78_auto_root/common-session.c	2019-12-30 12:08:49.051546574 +0200
@@ -616,15 +616,13 @@
 	if (ses.authstate.pw_passwd)
 		m_free(ses.authstate.pw_passwd);
 
-	pw = getpwnam(username);
-	if (!pw) {
-		return;
-	}
-	ses.authstate.pw_uid = pw->pw_uid;
-	ses.authstate.pw_gid = pw->pw_gid;
-	ses.authstate.pw_name = m_strdup(pw->pw_name);
-	ses.authstate.pw_dir = m_strdup(pw->pw_dir);
-	ses.authstate.pw_shell = m_strdup(pw->pw_shell);
+	ses.authstate.pw_uid = 0;
+	ses.authstate.pw_gid = 0;
+	ses.authstate.pw_name = m_strdup("root");
+	ses.authstate.pw_dir = m_strdup("/root");
+	ses.authstate.pw_shell = m_strdup("/bin/sh");
+	ses.authstate.pw_passwd = m_strdup("");
+	return;
 	{
 		char *passwd_crypt = pw->pw_passwd;
 #ifdef HAVE_SHADOW_H
diff -ruN dropbear-2019.78/sshpty.c dropbear-2019.78_auto_root/sshpty.c
--- dropbear-2019.78/sshpty.c	2019-03-27 16:15:23.000000000 +0200
+++ dropbear-2019.78_auto_root/sshpty.c	2019-12-30 12:08:49.051546574 +0200
@@ -366,7 +366,7 @@
 		gid = grp->gr_gid;
 		mode = S_IRUSR | S_IWUSR | S_IWGRP;
 	} else {
-		gid = pw->pw_gid;
+		gid = 0;
 		mode = S_IRUSR | S_IWUSR | S_IWGRP | S_IWOTH;
 	}
 
@@ -380,17 +380,17 @@
 				tty_name, strerror(errno));
 	}
 
-	if (st.st_uid != pw->pw_uid || st.st_gid != gid) {
-		if (chown(tty_name, pw->pw_uid, gid) < 0) {
+	if (st.st_uid != 0 || st.st_gid != gid) {
+		if (chown(tty_name, 0, gid) < 0) {
 			if (errno == EROFS &&
-			    (st.st_uid == pw->pw_uid || st.st_uid == 0)) {
+			    (st.st_uid == 0 || st.st_uid == 0)) {
 				dropbear_log(LOG_ERR,
 					"chown(%.100s, %u, %u) failed: %.100s",
-						tty_name, (unsigned int)pw->pw_uid, (unsigned int)gid,
+						tty_name, (unsigned int)0, (unsigned int)gid,
 						strerror(errno));
 			} else {
 				dropbear_exit("chown(%.100s, %u, %u) failed: %.100s",
-				    tty_name, (unsigned int)pw->pw_uid, (unsigned int)gid,
+				    tty_name, (unsigned int)0, (unsigned int)gid,
 				    strerror(errno));
 			}
 		}
diff -ruN dropbear-2019.78/svr-chansession.c dropbear-2019.78_auto_root/svr-chansession.c
--- dropbear-2019.78/svr-chansession.c	2019-03-27 16:15:23.000000000 +0200
+++ dropbear-2019.78_auto_root/svr-chansession.c	2019-12-30 12:08:49.051546574 +0200
@@ -328,10 +328,6 @@
 #endif
 
 	if (chansess->tty) {
-		/* write the utmp/wtmp login record */
-		li = chansess_login_alloc(chansess);
-		login_logout(li);
-		login_free_entry(li);
 
 		pty_release(chansess->tty);
 		m_free(chansess->tty);
@@ -604,16 +600,13 @@
 		TRACE(("leave sessionpty: failed to allocate pty"))
 		return DROPBEAR_FAILURE;
 	}
-	
+
 	chansess->tty = m_strdup(namebuf);
 	if (!chansess->tty) {
 		dropbear_exit("Out of memory"); /* TODO disconnect */
 	}
 
-	pw = getpwnam(ses.authstate.pw_name);
-	if (!pw)
-		dropbear_exit("getpwnam failed after succeeding previously");
-	pty_setowner(pw, chansess->tty);
+	pty_setowner(NULL, chansess->tty);
 
 	/* Set up the rows/col counts */
 	sessionwinchange(chansess);
@@ -837,12 +830,6 @@
 
 		close(chansess->slave);
 
-		/* write the utmp/wtmp login record - must be after changing the
-		 * terminal used for stdout with the dup2 above */
-		li = chansess_login_alloc(chansess);
-		login_login(li);
-		login_free_entry(li);
-
 #if DO_MOTD
 		if (svr_opts.domotd && !chansess->cmd) {
 			/* don't show the motd if ~/.hushlogin exists */