Re: bugs in pam_env

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Hello Antonio,

can you please report these as individual issues into the GitHub issue
tracker for the Linux PAM project?

The issue 1 is already reported by someone -

There it is actually questionable whether we should change the behavior
or the documentation as someone could already depend on the current


On Sat, 2017-02-25 at 09:54 +0000, Antonio Capanna wrote:
> Hi,
> I found some errors and unexpected/confusing behaviour in pam_env.
> 1)
> The user environment file is not parsed with the correct function,
> but it is parsed as a configuration file. This means that DEFAULT and
> OVERRIDE are recognized as special words and that parameter expansion
> is done.
> Please see pam_env.c at line 826.
> The parsing seems to work just because of unexpected behaviour #4
> below (that is, also in config file the syntax "variable=value" is
> honored, even if because of an error.)
> 2)
> > From what I understand, setting DEFAULT= deletes a variable if
> > OVERRIDE is empty or non-existing. But with some configuration
> > combinations you get inconsistent behaviour:
> this_variable_is_removedthis_one_is_removed_too
> DEFAULT=this_one_is_removed_as_well OVERRIDE=""
> DEFAULT=also_this_one_is_removed DEFAULT=
> OVERRIDE=but_this_one_is_added_as_empty_var OVERRIDE= DEFAULT=
> This happens because in pam_env.c, in function _parse_line,
> variable quoteflg is not properly handled (more specifically, it is
> decremented even when it shouldn't).
> 3)
> I don't know if it is a bug or not, but it's most definitely
> unexpected.If in the env file I write:
> export a=1
> it works. But:
> export  b=2   # note that there are two spacesexport    c=3 # note
> that there is a TAB character
> do not work. The parser in _parse_env_file (pam_env.c:220) does not
> handle anything different from a single space.
> 4)
> If in conf file I write:
> variable# or
> variable DEFAULT=
> the expected behaviour is to remove that variable from the
> environment. But the parser does not check for '=' signs, so if have
> this in the conf file (NOT in the env file):
> this_does_not_do_what_expected=yeah# or even this:
> neither_does_this=ohyeah!     DEFAULT=
> the module tries to remove the variable
> "this_does_not_do_what_expected=yeah" from the environment (as per
> debug log: remove variable "this_does_not_do_what_expected=yeah"),
> but it results in adding the variable
> "this_does_not_do_what_expected" instead, with value = "yeah".
> Note that this is the reason why the parsing of the user environment
> file seems to work.
> 5)
> The '#' char is recognized as comment even if it's not the first non-
> blank character in the line (differently from what written in the man
> page).Especially, a conf line like this one:
> variable DEFAULT="a#b"
> does not work, it results in an error (Unterminated quoted string:
> "a). If not supported, this should be at least mentioned in the
> manual.Note that the same problem is in the env file, because the
> line parsing function is the same (_assemble_line).
> 6)
> pam_env.c:74:/* This is a flag used to designate an empty string
> */static char quote='Z';
> but in function check_var (row 511):    if (&quote == var->defval) { 
>     /*       * This means that the empty string was given for defval
> value       * which indicates that a variable should be defined with
> no value       */      *var->defval = '\0';
> as it can be seen, the last line changes the value of quote. This
> does not seem to have ill effects, but it is not nice because quote
> becomes = '\0', which has also a special meaning different from quote
> itself (quote means the empty quoted string, '\0' means the empty
> unquoted string).
> 7)
> the "_parse_env_file" function in pam_env.c gets lines using function
> "_assemble_line", but then repeats a lot of the checks that have
> already been done (comments, empty lines, whitespaces at the
> beginning, ...)
> Regards
> _______________________________________________
> Pam-list mailing list
> Pam-list@xxxxxxxxxx
Tomas Mraz
No matter how far down the wrong road you've gone, turn back.
                                              Turkish proverb
(You'll never know whether the road is wrong though.)

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