target: add option to set the root password

Add an option in the menuconfig to specify a root password.

If set to empty, no root password is created; otherwise, the password is
encrypted using MD5 (MD5 is not the default for crypt(3), DES-56 is, but
MD5 is widely available, not-so-strong, but not-so-weak either).

Add a check for 'mkpasswd' as a new dependency.

[Peter: fix typo/capitilization and simplify logic]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Arnout Vandecappelle <arnout@mind.be>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

support/dependencies/dependencies.sh

@@ -158,6 +158,7 @@ if grep ^BR2_TOOLCHAIN_BUILDROOT=y $CONFIG_FILE > /dev/null && \
        exit 1 ;
    fi
 fi
+
 if grep -q ^BR2_PACKAGE_CLASSPATH=y $CONFIG_FILE ; then
     for prog in javac jar; do
 	if ! which $prog > /dev/null ; then
@@ -166,3 +167,11 @@ if grep -q ^BR2_PACKAGE_CLASSPATH=y $CONFIG_FILE ; then
 	fi
     done
 fi
+
+if grep -E '^BR2_TARGET_GENERIC_ROOT_PASSWD=".+"$' $CONFIG_FILE > /dev/null 2>&1; then
+    if ! which mkpasswd > /dev/null 2>&1; then
+        /bin/echo -e "\nYou need the 'mkpasswd' utility to set the root password\n"
+        /bin/echo -e "(in Debian/ubuntu, 'mkpasswd' provided by the whois package)\n"
+        exit 1
+    fi
+fi

system/Config.in

@@ -12,6 +12,27 @@ config BR2_TARGET_GENERIC_ISSUE
        help
          Select system banner (/etc/issue) to be displayed at login.
 
+config BR2_TARGET_GENERIC_ROOT_PASSWD
+	string "Root password"
+	default ""
+	help
+	  Set the initial root password (in clear). It will be md5-encrypted.
+	  
+	  If set to empty (the default), then no root password will be set,
+	  and root will need no password to log in.
+	  
+	  WARNING! WARNING!
+	  Although pretty strong, MD5 is now an old hash function, and
+	  suffers from some weaknesses, which makes it susceptible to attacks.
+	  It is showing its age, so this root password should not be trusted
+	  to properly secure any product that can be shipped to the wide,
+	  hostile world.
+	  
+	  WARNING! WARNING!
+	  The password appears in clear in the .config file, and may appear
+	  in the build log! Avoid using a valuable password if either the
+	  .config file or the build log may be distributed!
+
 choice
 	prompt "/dev management"
 	default BR2_ROOTFS_DEVICE_CREATION_STATIC

system/system.mk

@@ -1,5 +1,9 @@
 TARGET_GENERIC_HOSTNAME:=$(call qstrip,$(BR2_TARGET_GENERIC_HOSTNAME))
 TARGET_GENERIC_ISSUE:=$(call qstrip,$(BR2_TARGET_GENERIC_ISSUE))
+TARGET_GENERIC_ROOT_PASSWD:=$(call qstrip,$(BR2_TARGET_GENERIC_ROOT_PASSWD))
+ifneq ($(TARGET_GENERIC_ROOT_PASSWD),)
+TARGET_GENERIC_ROOT_PASSWD_HASH=$(shell mkpasswd -m md5 "$(TARGET_GENERIC_ROOT_PASSWD)")
+endif
 TARGET_GENERIC_GETTY:=$(call qstrip,$(BR2_TARGET_GENERIC_GETTY_PORT))
 TARGET_GENERIC_GETTY_BAUDRATE:=$(call qstrip,$(BR2_TARGET_GENERIC_GETTY_BAUDRATE))
 TARGET_GENERIC_GETTY_TERM:=$(call qstrip,$(BR2_TARGET_GENERIC_GETTY_TERM))
@@ -14,6 +18,9 @@ target-generic-issue:
 	mkdir -p $(TARGET_DIR)/etc
 	echo "$(TARGET_GENERIC_ISSUE)" > $(TARGET_DIR)/etc/issue
 
+target-root-passwd:
+	$(SED) 's,^root:[^:]*:,root:$(TARGET_GENERIC_ROOT_PASSWD_HASH):,' $(TARGET_DIR)/etc/shadow
+
 target-generic-getty-busybox:
 	$(SED) '/# GENERIC_SERIAL$$/s~^.*#~$(TARGET_GENERIC_GETTY)::respawn:/sbin/getty -L $(TARGET_GENERIC_GETTY) $(TARGET_GENERIC_GETTY_BAUDRATE) $(TARGET_GENERIC_GETTY_TERM) #~' \
 		$(TARGET_DIR)/etc/inittab
@@ -40,6 +47,8 @@ ifneq ($(TARGET_GENERIC_ISSUE),)
 TARGETS += target-generic-issue
 endif
 
+TARGETS += target-root-passwd
+
 ifeq ($(BR2_ROOTFS_SKELETON_DEFAULT),y)
 ifeq ($(BR2_PACKAGE_SYSVINIT),y)
 TARGETS += target-generic-getty-sysvinit