[Buildroot] [PATCH 1/1] scripts/mkusers: allow users with no password value set

[Buildroot] [PATCH 1/1] scripts/mkusers: allow users with no password value set

[James Knight]

The following allows a user definition to specify that a created user
entry should not have a password value set. Original implementation
allowed a user definition to provide a password value of "-" (no quotes)
to generate a crypt-encoded empty string value. In some cases, it may be
desired to have no value specified for a user's password. By using a
value "-" for a password, no value will be set in the shadow value.

Signed-off-by: James Knight <james.knight@rockwellcollins.com>
---
 docs/manual/makeusers-syntax.txt | 3 ++-
 support/scripts/mkusers          | 3 +++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/docs/manual/makeusers-syntax.txt b/docs/manual/makeusers-syntax.txt
index ffdb961..467e596 100644
--- a/docs/manual/makeusers-syntax.txt
+++ b/docs/manual/makeusers-syntax.txt
@@ -31,7 +31,8 @@ Where:
   then login is disabled. If prefixed with +=+, then it is interpreted
   as clear-text, and will be crypt-encoded (using MD5). If prefixed with
   +!=+, then the password will be crypt-encoded (using MD5) and login
-  will be disabled. If set to +*+, then login is not allowed.
+  will be disabled. If set to +*+, then login is not allowed. If set to 
+  +-+, then no password value will be set.
 - +home+ is the desired home directory for the user. If set to '-', no
   home directory will be created, and the user's home will be +/+.
   Explicitly setting +home+ to +/+ is not allowed.
diff --git a/support/scripts/mkusers b/support/scripts/mkusers
index 026519e..9c5c4dc 100755
--- a/support/scripts/mkusers
+++ b/support/scripts/mkusers
@@ -318,6 +318,9 @@ add_one_user() {
         *)  fail "home must be an absolute path\n";;
     esac
     case "${passwd}" in
+        -)
+            _passwd=""
+            ;;
         !=*)
             _passwd='!'"$( encode_password "${passwd#!=}" )"
             ;;
-- 
1.9.5.msysgit.1

[Buildroot] [PATCH 1/1] scripts/mkusers: allow users with no password value set

[Yann E. MORIN]

James, All,

On 2015-05-22 11:36 -0400, James Knight spake thusly:
> The following allows a user definition to specify that a created user
> entry should not have a password value set. Original implementation
> allowed a user definition to provide a password value of "-" (no quotes)
> to generate a crypt-encoded empty string value. In some cases, it may be
> desired to have no value specified for a user's password. By using a
> value "-" for a password, no value will be set in the shadow value.

I fail to see how that is different from using an empty password as
(without quotes): "="

From man 5 passwd:

    The encrypted password field may be blank, in which case no password
    is required to authenticate as the specified login name. However,
    some applications which read the /etc/passwd file may decide not to
    permit any access at all if the password field is blank.

Thus, I believe it is safest to store an encoded empty password rather
than set the password field empty.

Did I miss something?

Of course, the manual could be updated to reflect that a password-less
account should use "=" in the password field.

Regards,
Yann E. MORIN.

> Signed-off-by: James Knight <james.knight@rockwellcollins.com>
> ---
>  docs/manual/makeusers-syntax.txt | 3 ++-
>  support/scripts/mkusers          | 3 +++
>  2 files changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/docs/manual/makeusers-syntax.txt b/docs/manual/makeusers-syntax.txt
> index ffdb961..467e596 100644
> --- a/docs/manual/makeusers-syntax.txt
> +++ b/docs/manual/makeusers-syntax.txt
> @@ -31,7 +31,8 @@ Where:
>    then login is disabled. If prefixed with +=+, then it is interpreted
>    as clear-text, and will be crypt-encoded (using MD5). If prefixed with
>    +!=+, then the password will be crypt-encoded (using MD5) and login
> -  will be disabled. If set to +*+, then login is not allowed.
> +  will be disabled. If set to +*+, then login is not allowed. If set to 
> +  +-+, then no password value will be set.
>  - +home+ is the desired home directory for the user. If set to '-', no
>    home directory will be created, and the user's home will be +/+.
>    Explicitly setting +home+ to +/+ is not allowed.
> diff --git a/support/scripts/mkusers b/support/scripts/mkusers
> index 026519e..9c5c4dc 100755
> --- a/support/scripts/mkusers
> +++ b/support/scripts/mkusers
> @@ -318,6 +318,9 @@ add_one_user() {
>          *)  fail "home must be an absolute path\n";;
>      esac
>      case "${passwd}" in
> +        -)
> +            _passwd=""
> +            ;;
>          !=*)
>              _passwd='!'"$( encode_password "${passwd#!=}" )"
>              ;;
> -- 
> 1.9.5.msysgit.1
> 
> _______________________________________________
> buildroot mailing list
> buildroot at busybox.net
> http://lists.busybox.net/mailman/listinfo/buildroot

-- 
.-----------------.--------------------.------------------.--------------------.
|  Yann E. MORIN  | Real-Time Embedded | /"\ ASCII RIBBON | Erics' conspiracy: |
| +33 662 376 056 | Software  Designer | \ / CAMPAIGN     |  ___               |
| +33 223 225 172 `------------.-------:  X  AGAINST      |  \e/  There is no  |
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'------------------------------^-------^------------------^--------------------'

[Buildroot] [PATCH 1/1] scripts/mkusers: allow users with no password value set

[James Knight]

Yann,

> On 2015-05-22 11:36 -0400, James Knight spake thusly:
> > The following allows a user definition to specify that a created 
user
> > entry should not have a password value set. Original implementation
> > allowed a user definition to provide a password value of "-" (no 
quotes)
> > to generate a crypt-encoded empty string value. In some cases, it 
may be
> > desired to have no value specified for a user's password. By using a
> > value "-" for a password, no value will be set in the shadow value.
> 
> I fail to see how that is different from using an empty password as
> (without quotes): "="
> 
> From man 5 passwd:
> 
>     The encrypted password field may be blank, in which case no 
password
>     is required to authenticate as the specified login name. However,
>     some applications which read the /etc/passwd file may decide not 
to
>     permit any access at all if the password field is blank.
> 
> Thus, I believe it is safest to store an encoded empty password rather
> than set the password field empty.
> 
> Did I miss something?
> 
> Of course, the manual could be updated to reflect that a password-less
> account should use "=" in the password field.
> 
> Regards,
> Yann E. MORIN.

Logging into a session with an encoded empty password will prompt me to 
enter a password since it doesn't know the password is empty. In this 
case, I would simply just hit enter to supply an empty password and it 
would authenticate.

If I alternatively set the password field blank, my login session will 
not prompt a password and will just login (since it knows there is no 
password set). This is what I'm hoping to achieve for the current target 
I'm developing.

[Buildroot] [PATCH 1/1] scripts/mkusers: allow users with no password value set

[Yann E. MORIN]

James, All,

On 2015-05-23 06:11 +0000, James Knight spake thusly:
> > On 2015-05-22 11:36 -0400, James Knight spake thusly:
> > > The following allows a user definition to specify that a created 
> user
> > > entry should not have a password value set. Original implementation
> > > allowed a user definition to provide a password value of "-" (no 
> quotes)
> > > to generate a crypt-encoded empty string value. In some cases, it 
> may be
> > > desired to have no value specified for a user's password. By using a
> > > value "-" for a password, no value will be set in the shadow value.
> > 
> > I fail to see how that is different from using an empty password as
> > (without quotes): "="
> > 
> > From man 5 passwd:
> > 
> >     The encrypted password field may be blank, in which case no 
> password
> >     is required to authenticate as the specified login name. However,
> >     some applications which read the /etc/passwd file may decide not 
> to
> >     permit any access at all if the password field is blank.
> > 
> > Thus, I believe it is safest to store an encoded empty password rather
> > than set the password field empty.
> > 
> > Did I miss something?
> > 
> > Of course, the manual could be updated to reflect that a password-less
> > account should use "=" in the password field.
> > 
> > Regards,
> > Yann E. MORIN.
> 
> Logging into a session with an encoded empty password will prompt me to 
> enter a password since it doesn't know the password is empty. In this 
> case, I would simply just hit enter to supply an empty password and it 
> would authenticate.
> 
> If I alternatively set the password field blank, my login session will 
> not prompt a password and will just login (since it knows there is no 
> password set). This is what I'm hoping to achieve for the current target 
> I'm developing.

Ah, right, that's what I missed. OK.

Regards,
Yann E. MORIN.

-- 
.-----------------.--------------------.------------------.--------------------.
|  Yann E. MORIN  | Real-Time Embedded | /"\ ASCII RIBBON | Erics' conspiracy: |
| +33 662 376 056 | Software  Designer | \ / CAMPAIGN     |  ___               |
| +33 223 225 172 `------------.-------:  X  AGAINST      |  \e/  There is no  |
| http://ymorin.is-a-geek.org/ | _/*\_ | / \ HTML MAIL    |   v   conspiracy.  |
'------------------------------^-------^------------------^--------------------'

[Buildroot] [PATCH 1/1] scripts/mkusers: allow users with no password value set

[Yann E. MORIN]

James, All,

On 2015-05-22 11:36 -0400, James Knight spake thusly:
> The following allows a user definition to specify that a created user
> entry should not have a password value set. Original implementation
> allowed a user definition to provide a password value of "-" (no quotes)
> to generate a crypt-encoded empty string value. In some cases, it may be
> desired to have no value specified for a user's password. By using a
> value "-" for a password, no value will be set in the shadow value.

Well, that commit log was not completely explicit about what the goal
was. What about something like:

    Currently, it is not possible to create a password-less user, i.e. a
    user that can log without providing a password. All we can do is
    create a user with an empty password, but a pasword nonetheless.

    Accept '-' as the password field, meaning that no password is set,
    which allows a user to log in by just providing is login, and no
    password will even be asked.

If you have yet a better explanation, go for it! ;-)

> Signed-off-by: James Knight <james.knight@rockwellcollins.com>

With the commit log more explicit, you can add:

Acked-by: "Yann E. MORIN" <yann.morin.1998@free.fr>

Thanks! :-)

Regards,
Yann E. MORIN.

> ---
>  docs/manual/makeusers-syntax.txt | 3 ++-
>  support/scripts/mkusers          | 3 +++
>  2 files changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/docs/manual/makeusers-syntax.txt b/docs/manual/makeusers-syntax.txt
> index ffdb961..467e596 100644
> --- a/docs/manual/makeusers-syntax.txt
> +++ b/docs/manual/makeusers-syntax.txt
> @@ -31,7 +31,8 @@ Where:
>    then login is disabled. If prefixed with +=+, then it is interpreted
>    as clear-text, and will be crypt-encoded (using MD5). If prefixed with
>    +!=+, then the password will be crypt-encoded (using MD5) and login
> -  will be disabled. If set to +*+, then login is not allowed.
> +  will be disabled. If set to +*+, then login is not allowed. If set to 
> +  +-+, then no password value will be set.
>  - +home+ is the desired home directory for the user. If set to '-', no
>    home directory will be created, and the user's home will be +/+.
>    Explicitly setting +home+ to +/+ is not allowed.
> diff --git a/support/scripts/mkusers b/support/scripts/mkusers
> index 026519e..9c5c4dc 100755
> --- a/support/scripts/mkusers
> +++ b/support/scripts/mkusers
> @@ -318,6 +318,9 @@ add_one_user() {
>          *)  fail "home must be an absolute path\n";;
>      esac
>      case "${passwd}" in
> +        -)
> +            _passwd=""
> +            ;;
>          !=*)
>              _passwd='!'"$( encode_password "${passwd#!=}" )"
>              ;;
> -- 
> 1.9.5.msysgit.1
> 
> _______________________________________________
> buildroot mailing list
> buildroot at busybox.net
> http://lists.busybox.net/mailman/listinfo/buildroot

-- 
.-----------------.--------------------.------------------.--------------------.
|  Yann E. MORIN  | Real-Time Embedded | /"\ ASCII RIBBON | Erics' conspiracy: |
| +33 662 376 056 | Software  Designer | \ / CAMPAIGN     |  ___               |
| +33 223 225 172 `------------.-------:  X  AGAINST      |  \e/  There is no  |
| http://ymorin.is-a-geek.org/ | _/*\_ | / \ HTML MAIL    |   v   conspiracy.  |
'------------------------------^-------^------------------^--------------------'