diff mbox

[2/2,v4] system: allow/disallow root login, accept encoded passwords

Message ID a13aae8e9670b5cb069379dee94735deb3663f21.1427223149.git.yann.morin.1998@free.fr
State Changes Requested
Headers show

Commit Message

Yann E. MORIN March 24, 2015, 6:54 p.m. UTC 
From: Lorenzo Catucci <lorenzo@sancho.ccd.uniroma2.it>

Currently, there is only three possibilities regarding the root account:
  - it is enabled with no password (the default)
  - it is enabled, using a clear-text, user-provided password
  - it is disabled if the user sets the clear-text password to '*'

This is deemed insufficient in many cases, especially when the .config
file has to be published (e.g. for the GPL compliance, or any other
reason.).

Fix that in two ways:

  - add a bolean option that allows/diesaloows root login altogether,
    which defaults to 'y' to keep backward compatibility;

  - accept already-encoded passwords, which we recognise as starting
    with either of $1$, $5$ or $6$ (resp. for md5, sha256 or sha512).
    For backward-compatibility, we stil accept '*' to disable the
    account.

Signed-off-by: Lorenzo M. Catucci <lorenzo@sancho.ccd.uniroma2.it>
[yann.morin.1998@free.fr:
  - don't add a choice to select between clear-text/encoded password,
    use a single prompt;
  - differentiate in the password hook itself;
  - rewrite parts of the help entry;
  - rewrite and expand the commit log
]
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

---
Note: this can only go in if DES encoded is ditched, because its
character-space is the same as for clear-text passwords.
---
 system/Config.in | 28 +++++++++++++++++++---------
 system/system.mk | 24 ++++++++++++++++++++----
 2 files changed, 39 insertions(+), 13 deletions(-)

Comments

Lorenzo Catucci March 24, 2015, 9:20 p.m. UTC | #1 
Thank you, Yann!

On 24/03/2015 19:54, Yann E. MORIN wrote:
> From: Lorenzo Catucci <lorenzo@sancho.ccd.uniroma2.it>
> 
> Currently, there is only three possibilities regarding the root account:
>   - it is enabled with no password (the default)
>   - it is enabled, using a clear-text, user-provided password
>   - it is disabled if the user sets the clear-text password to '*'
> 
> This is deemed insufficient in many cases, especially when the .config
> file has to be published (e.g. for the GPL compliance, or any other
> reason.).
> 
> Fix that in two ways:
> 
>   - add a bolean option that allows/diesaloows root login altogether,
>     which defaults to 'y' to keep backward compatibility;
> 
>   - accept already-encoded passwords, which we recognise as starting
>     with either of $1$, $5$ or $6$ (resp. for md5, sha256 or sha512).
>     For backward-compatibility, we stil accept '*' to disable the
>     account.
> 

Works very well for me, especially since my primary need was a config option
disabling root login; still, you summarized very well the reason I'd rather
use a decent sha-512 encoded root password if I were to distribute my
applicance's config file.

Thank you once more, yours

	lorenzo
Thomas Petazzoni April 10, 2015, 8:39 p.m. UTC | #2 
Dear Yann E. MORIN,

On Tue, 24 Mar 2015 19:54:16 +0100, Yann E. MORIN wrote:

> Currently, there is only three possibilities regarding the root account:
>   - it is enabled with no password (the default)
>   - it is enabled, using a clear-text, user-provided password
>   - it is disabled if the user sets the clear-text password to '*'
> 
> This is deemed insufficient in many cases, especially when the .config
> file has to be published (e.g. for the GPL compliance, or any other
> reason.).
> 
> Fix that in two ways:
> 
>   - add a bolean option that allows/diesaloows root login altogether,

disallows.

>     which defaults to 'y' to keep backward compatibility;
> 
>   - accept already-encoded passwords, which we recognise as starting
>     with either of $1$, $5$ or $6$ (resp. for md5, sha256 or sha512).
>     For backward-compatibility, we stil accept '*' to disable the

still.


> @@ -70,9 +70,25 @@ TARGET_FINALIZE_HOOKS += SET_NETWORK
>  ifeq ($(BR2_ROOTFS_SKELETON_DEFAULT),y)
>  
>  define SYSTEM_ROOT_PASSWD
> -	[ -n "$(TARGET_GENERIC_ROOT_PASSWD)" ] && \
> -		TARGET_GENERIC_ROOT_PASSWD_HASH=$$($(MKPASSWD) -m "$(TARGET_GENERIC_PASSWD_METHOD)" "$(TARGET_GENERIC_ROOT_PASSWD)"); \
> -	$(SED) "s,^root:[^:]*:,root:$$TARGET_GENERIC_ROOT_PASSWD_HASH:," $(TARGET_DIR)/etc/shadow
> +	if [ "$(BR2_TARGET_ENABLE_ROOT_LOGIN)" = "y" ]; then \
> +		case '$(TARGET_GENERIC_ROOT_PASSWD)' in \
> +		("") \
> +			ROOT_PASSWD=""; \
> +		;; \
> +		("$$1$$"*|"$$5$$"*|"$$6$$"*) \
> +			ROOT_PASSWD='$(TARGET_GENERIC_ROOT_PASSWD)'; \
> +		;; \
> +		('*') \
> +			ROOT_PASSWD='*'; \
> +		;; \
> +		(*) \
> +			ROOT_PASSWD=$$($(MKPASSWD) -m "$(TARGET_GENERIC_PASSWD_METHOD)" "$(TARGET_GENERIC_ROOT_PASSWD)"); \
> +		;; \
> +		esac; \
> +	else \
> +		ROOT_PASSWD='*'; \
> +	fi; \
> +	$(SED) "s,^root:[^:]*:,root:$${ROOT_PASSWD}:," $(TARGET_DIR)/etc/shadow

Argh. Can we use make instead of turning Buildroot into a build system
written in shell ?

ifeq ($(BR2_TARGET_ENABLE_ROOT_LOGIN),)
SYSTEM_ROOT_PASSWORD = *
else
 ifeq ($(TARGET_GENERIC_ROOT_PASSWORD),)
  SYSTEM_ROOT_PASSWORD =
 # I believe we could simplify this, and assume that if the password
 # starts with $$, we have an already encoded password.
 else ifeq ($(or $(filter $$1$$%,$(TARGET_GENERIC_ROOT_PASSWORD)),$(filter $$5$$%,$(TARGET_GENERIC_ROOT_PASSWORD)),$(filter $$6$$%,$(TARGET_GENERIC_ROOT_PASSWORD)))
  SYSTEM_ROOT_PASSWORD = $(TARGET_GENERIC_ROOT_PASSWORD))
 else ifeq ($(TARGET_GENERIC_ROOT_PASSWORD),*)
  SYSTEM_ROOT_PASSWORD = $(TARGET_GENERIC_ROOT_PASSWORD))
 else
  SYSTEM_ROOT_PASSWORD = $(shell $(MKPASSWD) -m "$(TARGET_GENERIC_PASSWD_METHOD)" "$(TARGET_GENERIC_ROOT_PASSWD)")
 endif
endif

(Completely untested, of course).

Thanks,

Thomas
Yann E. MORIN April 10, 2015, 8:53 p.m. UTC | #3 
Thomas, All,

On 2015-04-10 22:39 +0200, Thomas Petazzoni spake thusly:
> On Tue, 24 Mar 2015 19:54:16 +0100, Yann E. MORIN wrote:
> > Currently, there is only three possibilities regarding the root account:
> >   - it is enabled with no password (the default)
> >   - it is enabled, using a clear-text, user-provided password
> >   - it is disabled if the user sets the clear-text password to '*'
> > 
> > This is deemed insufficient in many cases, especially when the .config
> > file has to be published (e.g. for the GPL compliance, or any other
> > reason.).
> > 
> > Fix that in two ways:
> > 
> >   - add a bolean option that allows/diesaloows root login altogether,
> 
> disallows.

OK.

> >     which defaults to 'y' to keep backward compatibility;
> > 
> >   - accept already-encoded passwords, which we recognise as starting
> >     with either of $1$, $5$ or $6$ (resp. for md5, sha256 or sha512).
> >     For backward-compatibility, we stil accept '*' to disable the
> 
> still.

Well, I was wrong on that one: if the password is '*', it is
crypt-encoded. We in fact could *not* use '*' to disable root login at
all... I'll rework that part, and since we now have the option to
explicitly allow/disallow (without typo) root logins, recognising that
magic value is not needed.

> > @@ -70,9 +70,25 @@ TARGET_FINALIZE_HOOKS += SET_NETWORK
> >  ifeq ($(BR2_ROOTFS_SKELETON_DEFAULT),y)
> >  
> >  define SYSTEM_ROOT_PASSWD
> > -	[ -n "$(TARGET_GENERIC_ROOT_PASSWD)" ] && \
> > -		TARGET_GENERIC_ROOT_PASSWD_HASH=$$($(MKPASSWD) -m "$(TARGET_GENERIC_PASSWD_METHOD)" "$(TARGET_GENERIC_ROOT_PASSWD)"); \
> > -	$(SED) "s,^root:[^:]*:,root:$$TARGET_GENERIC_ROOT_PASSWD_HASH:," $(TARGET_DIR)/etc/shadow
> > +	if [ "$(BR2_TARGET_ENABLE_ROOT_LOGIN)" = "y" ]; then \
> > +		case '$(TARGET_GENERIC_ROOT_PASSWD)' in \
> > +		("") \
> > +			ROOT_PASSWD=""; \
> > +		;; \
> > +		("$$1$$"*|"$$5$$"*|"$$6$$"*) \
> > +			ROOT_PASSWD='$(TARGET_GENERIC_ROOT_PASSWD)'; \
> > +		;; \
> > +		('*') \
> > +			ROOT_PASSWD='*'; \
> > +		;; \
> > +		(*) \
> > +			ROOT_PASSWD=$$($(MKPASSWD) -m "$(TARGET_GENERIC_PASSWD_METHOD)" "$(TARGET_GENERIC_ROOT_PASSWD)"); \
> > +		;; \
> > +		esac; \
> > +	else \
> > +		ROOT_PASSWD='*'; \
> > +	fi; \
> > +	$(SED) "s,^root:[^:]*:,root:$${ROOT_PASSWD}:," $(TARGET_DIR)/etc/shadow
> 
> Argh. Can we use make instead of turning Buildroot into a build system
> written in shell ?
> 
> ifeq ($(BR2_TARGET_ENABLE_ROOT_LOGIN),)
> SYSTEM_ROOT_PASSWORD = *
> else
>  ifeq ($(TARGET_GENERIC_ROOT_PASSWORD),)
>   SYSTEM_ROOT_PASSWORD =
>  # I believe we could simplify this, and assume that if the password
>  # starts with $$, we have an already encoded password.
>  else ifeq ($(or $(filter $$1$$%,$(TARGET_GENERIC_ROOT_PASSWORD)),$(filter $$5$$%,$(TARGET_GENERIC_ROOT_PASSWORD)),$(filter $$6$$%,$(TARGET_GENERIC_ROOT_PASSWORD)))
>   SYSTEM_ROOT_PASSWORD = $(TARGET_GENERIC_ROOT_PASSWORD))
>  else ifeq ($(TARGET_GENERIC_ROOT_PASSWORD),*)
>   SYSTEM_ROOT_PASSWORD = $(TARGET_GENERIC_ROOT_PASSWORD))
>  else
>   SYSTEM_ROOT_PASSWORD = $(shell $(MKPASSWD) -m "$(TARGET_GENERIC_PASSWD_METHOD)" "$(TARGET_GENERIC_ROOT_PASSWD)")
>  endif
> endif
> 
> (Completely untested, of course).

OK, will try to make it work (hint: it does not right now: missing
operand to the ifeq for md5/sha256/sha512 case). ;-)

Regards,
Yann E. MORIN.
diff mbox

Patch

diff --git a/system/Config.in b/system/Config.in
index 8621def..17a626b 100644
--- a/system/Config.in
+++ b/system/Config.in
@@ -179,26 +179,36 @@  endif
 
 if BR2_ROOTFS_SKELETON_DEFAULT
 
+config BR2_TARGET_ENABLE_ROOT_LOGIN
+	bool "Enable root login"
+	default "y"
+	help
+	  Enable root login password
+
 config BR2_TARGET_GENERIC_ROOT_PASSWD
 	string "Root password"
 	default ""
+	depends on BR2_TARGET_ENABLE_ROOT_LOGIN
 	help
-	  Set the initial root password (in clear). It will be md5-encrypted.
+	  Set the initial root password.
 
 	  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.
+	  If the password starts with any of $1$, $5$ or $6$, it is considered
+	  to be already crypt-encoded with respectively md5, sha256 or sha512.
+	  Any other value is taken to be a clear-text value, and is crypt-encoded
+	  as per the "Passwords encoding" scheme, above.
+
+	  Note: "$" signs in the hashed password must be doubled. For example,
+	  if the hashed password is "$1$longsalt$v35DIIeMo4yUfI23yditq0", then
+	  you must enter it as "$$1$$longsalt$$v35DIIeMo4yUfI23yditq0".
 
 	  WARNING! WARNING!
-	  The password appears in clear in the .config file, and may appear
+	  The password appears as-is 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!
+	  .config file or the build log may be distributed, or at the
+	  very least use a strong cryptographic hash for your password!
 
 choice
 	bool "/bin/sh"
diff --git a/system/system.mk b/system/system.mk
index 4a1eb4a..2ac5d08 100644
--- a/system/system.mk
+++ b/system/system.mk
@@ -34,7 +34,7 @@  endef
 TARGET_FINALIZE_HOOKS += SYSTEM_ISSUE
 endif
 
-ifneq ($(TARGET_GENERIC_ROOT_PASSWD),)
+ifneq ($(BR2_TARGET_ENABLE_ROOT_LOGIN),)
 TARGETS += host-mkpasswd
 endif
 
@@ -70,9 +70,25 @@  TARGET_FINALIZE_HOOKS += SET_NETWORK
 ifeq ($(BR2_ROOTFS_SKELETON_DEFAULT),y)
 
 define SYSTEM_ROOT_PASSWD
-	[ -n "$(TARGET_GENERIC_ROOT_PASSWD)" ] && \
-		TARGET_GENERIC_ROOT_PASSWD_HASH=$$($(MKPASSWD) -m "$(TARGET_GENERIC_PASSWD_METHOD)" "$(TARGET_GENERIC_ROOT_PASSWD)"); \
-	$(SED) "s,^root:[^:]*:,root:$$TARGET_GENERIC_ROOT_PASSWD_HASH:," $(TARGET_DIR)/etc/shadow
+	if [ "$(BR2_TARGET_ENABLE_ROOT_LOGIN)" = "y" ]; then \
+		case '$(TARGET_GENERIC_ROOT_PASSWD)' in \
+		("") \
+			ROOT_PASSWD=""; \
+		;; \
+		("$$1$$"*|"$$5$$"*|"$$6$$"*) \
+			ROOT_PASSWD='$(TARGET_GENERIC_ROOT_PASSWD)'; \
+		;; \
+		('*') \
+			ROOT_PASSWD='*'; \
+		;; \
+		(*) \
+			ROOT_PASSWD=$$($(MKPASSWD) -m "$(TARGET_GENERIC_PASSWD_METHOD)" "$(TARGET_GENERIC_ROOT_PASSWD)"); \
+		;; \
+		esac; \
+	else \
+		ROOT_PASSWD='*'; \
+	fi; \
+	$(SED) "s,^root:[^:]*:,root:$${ROOT_PASSWD}:," $(TARGET_DIR)/etc/shadow
 endef
 TARGET_FINALIZE_HOOKS += SYSTEM_ROOT_PASSWD