adduser/passwd: too long username
Laszlo Papp
lpapp at kde.org
Tue Aug 5 13:21:49 UTC 2014
On Tue, Aug 5, 2014 at 2:14 PM, Laszlo Papp <lpapp at kde.org> wrote:
>
>
>
> On Tue, Aug 5, 2014 at 2:06 PM, tito <farmatito at tiscali.it> wrote:
>
>> On Tuesday 05 August 2014 14:47:53 you wrote:
>> > On Tue, Aug 5, 2014 at 1:42 PM, tito <farmatito at tiscali.it> wrote:
>> >
>> > > On Tuesday 05 August 2014 14:27:57 you wrote:
>> > > > I disagree. There is nothing to reject here. It fixes _my issue_ at
>> hand.
>> > > > If you want to fix other bugs in your system that you are facing in
>> > > > reality, by all means, fix them in a separate change.
>> > > >
>> > > > I definitely do not agree with dynamically allocated buffer for the
>> > > simple
>> > > > reasons of:
>> > > >
>> > > > 1) Slow.
>> > > > 2) You would still need a maximum anyway.
>> > > > 3) Needless code complication.
>> > > >
>> > > > Let us keep things simple and good, you know the good old KISS
>> principle.
>> > > >
>> > > > P.S.: please do not bikeshed.
>> > > >
>> > > >
>> > > > On Tue, Aug 5, 2014 at 1:17 PM, tito <farmatito at tiscali.it> wrote:
>> > > >
>> > > > > On Tuesday 05 August 2014 12:46:08 you wrote:
>> > > > > > Here is my tested fix without being to debug the busybox code,
>> so
>> > > only
>> > > > > code
>> > > > > > reading and understanding were my friends:
>> > > > > >
>> > > > > > commit 9610650b6ce2a4c1904f78a2dcdb47cad3d2e3d1
>> > > > > > Author: Laszlo Papp <lpapp at kde.org>
>> > > > > > Date: Tue Aug 5 11:42:24 2014 +0100
>> > > > > >
>> > > > > > Allow 256 bytes long usernames as per Unix standards
>> (usually)
>> > > > > >
>> > > > > > diff --git a/libpwdgrp/pwd_grp.c b/libpwdgrp/pwd_grp.c
>> > > > > > index 2060d78..368c252 100644
>> > > > > > --- a/libpwdgrp/pwd_grp.c
>> > > > > > +++ b/libpwdgrp/pwd_grp.c
>> > > > > > @@ -23,8 +23,8 @@
>> > > > > >
>> > >
>> /**********************************************************************/
>> > > > > > /* Sizes for statically allocated buffers. */
>> > > > > >
>> > > > > > -#define PWD_BUFFER_SIZE 256
>> > > > > > -#define GRP_BUFFER_SIZE 256
>> > > > > > +#define PWD_BUFFER_SIZE LOGIN_NAME_MAX+256
>> > > > > > +#define GRP_BUFFER_SIZE LOGIN_NAME_MAX+256
>> > > > > >
>> > > > > >
>> > >
>> /**********************************************************************/
>> > > > > > /* Prototypes for internal functions. */
>> > > > > >
>> > > > >
>> > > > > Hi,
>> > > > > yes I've thought also about this solution but rejected it because:
>> > > > >
>> > > > > 1) there will not be enough space to hold the home dir if named
>> the
>> > > same
>> > > > > as the user
>> > > > > so you need at least:
>> > > > >
>> > > > > #define PWD_BUFFER_SIZE LOGIN_NAME_MAX+ 6 (for home) +
>> LOGIN_NAME_MAX
>> > > (or
>> > > > > PATH_MAX?) + 256 (for the rest)
>> > > > >
>> > > > > yet this might not be enough as in my passwd file I see a 101
>> char
>> > > long
>> > > > > passwd.
>> > > > > Add the gecos fields (arbitrary lenght) to it and the default
>> > > shell
>> > > > > and we are short on space again.
>> > > > >
>> > > > > 2) same for #define GRP_BUFFER_SIZE LOGIN_NAME_MAX+256:
>> > > > > here you need to take into account the group member list with
>> > > > > an arbitrary number of members:
>> > > > >
>> > > > >
>> > > > > #define GRP_BUFFER_SIZE LOGIN_NAME_MAX+256+ LOGIN_NAME_MAX*n:
>> > > > >
>> > > > > The only clean solution to fix it forever is dynamically allocated
>> > > buffers
>> > > > > created at the time you read in the line from the passwd files.
>> > > > >
>> > > > > Ciao,
>> > > > > Tito
>> > > > >
>> > > > >
>> > > > > P.S.: please don't top post.
>> > > > >
>> > > > >
>> > > > > >
>> > > > > > On Tue, Aug 5, 2014 at 11:22 AM, Laszlo Papp <lpapp at kde.org>
>> wrote:
>> > > > > >
>> > > > > > > Yeah, mayhaps... Thanks for the prompt reply. I tried to
>> debug the
>> > > > > code,
>> > > > > > > but the busybox code here is a bit messy heavily abusing
>> macros in
>> > > C
>> > > > > and
>> > > > > > > all that. It ain't easy I must confess!
>> > > > > > >
>> > > > > > > For instance, see this section:
>> > > > > > >
>> > > > > > > http://git.busybox.net/busybox/tree/libpwdgrp/pwd_grp.c#n227
>> > > > > > >
>> > > > > > > The _source_ is included several times always getting a new
>> meaning
>> > > > > based
>> > > > > > > on some defines... Now, check this function:
>> > > > > > >
>> > > > > > >
>> > > http://git.busybox.net/busybox/tree/libpwdgrp/pwd_grp_internal.c#n20
>> > > > > > >
>> > > > > > > "resultbuf" will be always different depending on which
>> include it
>> > > is.
>> > > > > > > Since it is failing at the pw_name check in there, I wanted to
>> > > print it
>> > > > > > > out, but no easy joy there as printing it like that will yield
>> > > > > compilation
>> > > > > > > error when the file is being included next time from above.
>> > > > > > >
>> > > > > > > Right, I thought instead of doing some "#if a == b" hackery,
>> > > debugging
>> > > > > > > would be easier, BUT:
>> > > > > > >
>> > > > > > > 1) The default build is stripped, yuck!
>> > > > > > >
>> > > > > > > 2) The unstripped build cannot locate the symbols (*).
>> > > > > > >
>> > > > > > > So, I am giving up on this for now; this is not the type of
>> source
>> > > code
>> > > > > > > that is so pleasant to work with. ;-)
>> > > > > > >
>> > > > > > > Cheers, L.
>> > > > > > >
>> > > > > > > * (gdb) b main
>> > > > > > >
>> > > > > > > Breakpoint 2 at 0x407c71
>> > > > > > > (gdb) r
>> > > > > > > Starting program:
>> /home/lpapp/Projects/busybox/busybox_unstripped
>> > > > > deluser
>> > > > >
>> > >
>> fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
>> > > > > > > warning: Could not load shared library symbols for
>> linux-vdso.so.1.
>> > > > > > > Do you need "set solib-search-path" or "set sysroot"?
>> > > > > > >
>> > > > > > > Breakpoint 2, 0x0000000000407c71 in main ()
>> > > > > > > (gdb) list
>> > > > > > > No symbol table is loaded. Use the "file" command.
>> > > > > > > (gdb)
>> > > > > > >
>> > > > > > >
>> > > > > > >
>> > > > > > > On Mon, Aug 4, 2014 at 10:40 PM, tito <farmatito at tiscali.it>
>> > > wrote:
>> > > > > > >
>> > > > > > >> On Monday 04 August 2014 19:06:39 Laszlo Papp wrote:
>> > > > > > >> > Hi,
>> > > > > > >> >
>> > > > > > >> > sudo busybox adduser
>> > > > > > >> >
>> > > > > > >>
>> > > > >
>> > >
>> fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
>> > > > > > >> > passwd: unknown user
>> > > > > > >> >
>> > > > > > >>
>> > > > >
>> > >
>> fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
>> > > > > > >> >
>> > > > > > >> > Yet, the user is created in /etc/shadow:
>> > > > > > >> >
>> > > > > > >> >
>> > > > > > >>
>> > > > >
>> > >
>> fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff:!:16286:0:99999:7:::
>> > > > > > >> >
>> > > > > > >> > This is at least one issue, but there is another here:
>> > > > > > >> >
>> > > > > > >> > sudo busybox deluser
>> > > > > > >> >
>> > > > > > >>
>> > > > >
>> > >
>> fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
>> > > > > > >> > deluser: unknown user
>> > > > > > >> >
>> > > > > > >>
>> > > > >
>> > >
>> fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
>> > > > > > >> >
>> > > > > > >> > So, basically, once you create that long username, you
>> cannot
>> > > > > remove it
>> > > > > > >> > anymore with busybox and it keeps polluting your system.
>> > > > > > >> >
>> > > > > > >> > You have to gain other means to clean up! I am using this
>> > > version
>> > > > > over
>> > > > > > >> here:
>> > > > > > >> >
>> > > > > > >> > BusyBox v1.22.1 (2014-06-02 14:47:37 MSK) multi-call
>> binary.
>> > > > > > >> >
>> > > > > > >> > Could you please look into this and potentially fix it?
>> Thanks
>> > > in
>> > > > > > >> advance.
>> > > > > > >> >
>> > > > > > >> > Cheers, L.
>> > > > > > >> >
>> > > > > > >> Hi,
>> > > > > > >> if disabling libb's internal pwd/grp lib and by jumping
>> through
>> > > some
>> > > > > hops
>> > > > > > >> it
>> > > > > > >> works for me:
>> > > > > > >>
>> > > > > > >> I need to add the group first as my system's groupadd command
>> > > called
>> > > > > by
>> > > > > > >> bb's adduser
>> > > > > > >> supports only groupnames of max 32 chars.
>> > > > > > >>
>> > > > > > >> ./busybox addgroup
>> > > > > > >>
>> > > > >
>> > >
>> fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
>> > > > > > >> ./busybox adduser
>> > > > > > >>
>> > > > >
>> > >
>> fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
>> > > > > > >> -G
>> > > > > > >>
>> > > > >
>> > >
>> fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
>> > > > > > >> Adding user
>> > > > > > >>
>> > > > >
>> > >
>> `fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff'
>> > > > > > >> to group
>> > > > > > >>
>> > > > >
>> > >
>> `fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff'
>> > > > > > >> ...
>> > > > > > >> Adding user
>> > > > > > >>
>> > > > >
>> > >
>> fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
>> > > > > > >> to group
>> > > > > > >>
>> > > > >
>> > >
>> fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
>> > > > > > >> Done.
>> > > > > > >> Enter new UNIX password:
>> > > > > > >> Retype new UNIX password:
>> > > > > > >> passwd: password updated successfully
>> > > > > > >>
>> > > > > > >> and then I could also delete it:
>> > > > > > >>
>> > > > > > >> ./busybox deluser
>> > > > > > >>
>> > > > >
>> > >
>> fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
>> > > > > > >> ./busybox delgroup
>> > > > > > >>
>> > > > >
>> > >
>> fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
>> > > > > > >> delgroup: unknown group
>> > > > > > >>
>> > > > >
>> > >
>> fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
>> > > > > > >>
>> > > > > > >> (deluser correctly deleted also the group)
>> > > > > > >>
>> > > > > > >> I suspect that the buffer size used in libbpwdgrp/pwd_grp.c
>> is to
>> > > > > small:
>> > > > > > >>
>> > > > > > >> #define PWD_BUFFER_SIZE 256
>> > > > > > >> #define GRP_BUFFER_SIZE 256
>> > > > > > >>
>> > > > > > >> as it is meant for the whole struct pw passwd (or struct gr
>> group)
>> > > > > fields
>> > > > > > >> which could be easily be bigger:
>> > > > > > >>
>> > > > > > >> grep ffff* /etc/shadow | wc
>> > > > > > >> 1 1 240
>> > > > > > >> grep ffff* /etc/passwd | wc
>> > > > > > >> 1 2 286
>> > > > > > >>
>> > > > > > >> I think that the buffers' size must be increased for example
>> to:
>> > > > > > >>
>> > > > > > >> #define PWD_BUFFER_SIZE LOGIN_NAME_MAX+LOGIN_NAME_MAX+256
>> > > > > > >>
>> > > > > > >> we need one LOGIN_NAME_MAX size for the login and one more
>> for the
>> > > > > home
>> > > > > > >> dir
>> > > > > > >> if same as login, plus 256 for the remaining data (passwd,
>> gecos,
>> > > > > shell,
>> > > > > > >> etc).
>> > > > > > >>
>> > > > > > >> #define GRP_BUFFER_SIZE LOGIN_NAME_MAX+256+LOGIN_NAME_MAX*n
>> (?)
>> > > > > > >>
>> > > > > > >> we need one LOGIN_NAME_MAX size for the group name (for
>> which we
>> > > > > > >> actually enforce the same size as for the username) plus 256
>> for
>> > > the
>> > > > > > >> remaining data
>> > > > > > >> plus LOGIN_NAME_MAX * n group member names.
>> > > > > > >>
>> > > > > > >> So for my limited understanding using static buffers here is
>> > > rather
>> > > > > > >> difficult
>> > > > > > >> as the size of data is not easily predictable.
>> > > > > > >> I don't know how real libc manages it (maybe realloc on
>> ERANGE?)
>> > > > > > >>
>> > > > > > >> Your particular example for me is fixed by using.
>> > > > > > >>
>> > > > > > >> #define PWD_BUFFER_SIZE 1024
>> > > > > > >>
>> > > > > > >> #define GRP_BUFFER_SIZE 1024
>> > > > > > >>
>> > > > > > >> But to me it seems not an optimal solution,
>> > > > > > >> so other more experienced developers should
>> > > > > > >> take a look at it.
>> > > > > > >>
>> > > > > > >> Hope this helps.
>> > > > > > >> Ciao,
>> > > > > > >> Tito
>> > > > > > >>
>> > > > > > >> PS: in libbbpwdgrp functions we need to check for errors:
>> > > > > > >>
>> > > > > > >> 0 or ENOENT or ESRCH or EBADF or EPERM or ...
>> > > > > > >> The given name or gid was not found.
>> > > > > > >>
>> > > > > > >> EINTR A signal was caught.
>> > > > > > >>
>> > > > > > >> EIO I/O error.
>> > > > > > >>
>> > > > > > >> EMFILE The maximum number (OPEN_MAX) of files was open
>> > > already
>> > > > > in
>> > > > > > >> the calling process.
>> > > > > > >>
>> > > > > > >> ENFILE The maximum number of files was open already
>> in the
>> > > > > system.
>> > > > > > >>
>> > > > > > >> ENOMEM Insufficient memory to allocate group
>> structure.
>> > > > > > >>
>> > > > > > >> ERANGE Insufficient buffer space supplied.
>> > > > > > >>
>> > > > > > >> as for example the xgroup_study function in the addgroup
>> applet
>> > > > > > >> assigns a wrong gid if getgrgid fails for example for ERANGE
>> > > > > > >>
>> > > > > > >> /* Check if the desired gid is free
>> > > > > > >> * or find the first free one */
>> > > > > > >> while (1) {
>> > > > > > >> printf("gid %d\n", g->gr_gid);
>> > > > > > >> if (!getgrgid(g->gr_gid)) {
>> > > > > > >> return; /* found free group: return
>> */
>> > > > > > >> }
>> > > > > > >>
>> > > > > > >>
>> > > Hi,
>> > > I doubt it fixes your issue
>> >
>> >
>> > What you are basically telling me here that I submitted untested changes
>> > for my use cases, directly or indirectly. Either way, I refuse this
>> claim
>> > since I _did_ test the change for my use case.
>> >
>> >
>> > > because I tested the same fix and it did in fact
>> >
>> > fail. Please test:
>> > >
>> > > 1) ./busybox addgroup LONGUSERNAME (this fails in subtle ways as a
>> > > already in use gid is assigned)
>> > > 2) ./busybox adduser LONGUSERNAME -G LONGUSERNAME
>> > > 3) ./busybox deluser LONGUSERNAME
>> > > 4) ./busybox delgroup LONGUSERNAME
>> > >
>> >
>> > I do not see how this is any relevant to my initial steps. This is a
>> > completely different test step with a different issue. As I said
>> earlier,
>> > please welcome contributors rather than being blocker just because they
>> fix
>> > one particular and real bug, and not every "imaginary" use case that can
>> > just exist in the world out there.
>> >
>>
>> Hi,
>> there is nothing imaginary here, i just would like to point out that
>> due to the fact that busybox adduser program by default creates
>> a home dir with the same name as the user the buffer size you
>> propose in your fix may not be big enough to hold all the data
>> and that this fact will affect also other commands that use
>> the functions in libbbpwdgrp in subtle ways.
>> I of course welcome you as a contributor and by the way I have
>> no decisional power to accept or reject your patches (which is fine
>> for me), but nonetheless sometimes I disagree with you for the sake
>> of cleaner solutions (from my point of view).
>>
>
> This script disagrees with you:
>
> #!/bin/bash
>
> USERNAME='e'
> for i in {1..232}
> do
> USERNAME+='f'
> done
> echo $USERNAME
>
> ./busybox adduser -D $USERNAME
> ./busybox deluser $USERNAME
>
Furthermore, I am planning to use -H for now, so I am not in any way
affected by this (other than -H is broken here for some reason because it
does create the home folder in /etc/passwd, but that is discussion for
another thread).
If you really need to support home in practice now, too, I can add a
"2*foo" (not foo + foo though because it is ugly IMHO ;) ), but I do not
have the urgent need for it, however I do have the urgent need for the fix
I am proposing.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.busybox.net/pipermail/busybox/attachments/20140805/610b266d/attachment-0001.html>
More information about the busybox
mailing list