With the new expansion code (word splitting during instead of after other
expansion processing), tracing the result of command substitution is no
longer possible, so stop trying.
The parsed internal representation of words consists of a byte string with a
list of nodes (commands in command substitution). Each unescaped CTLBACKQ or
CTLBACKQ | CTLQUOTE byte corresponds to an entry in the list.
If param in ${param#%##%%word} is not set, the word is not expanded (in a
deviation of POSIX shared with other ash variants and ksh93). Erroneously,
the pointer in the list of commands (argbackq) was not advanced. This caused
the wrong command to be executed later if the outer word contained another
command substitution.
Example:
echo "${unsetvar#$(echo a)}$(echo b)"
wrote "a" but should write "b".
MFC after: 1 week
Code like t=$(stat -f %m "$file") segfaulted if -T was active and a trap
was taken while the shell was waiting for the child process to finish.
What happened was that the dotrap() call in waitforjob() was hit. This
re-entered command execution (including expand.c) at a point not expected by
expbackq(), and global state (unallocated stack string and argbackq) was
corrupted.
To fix this, change expbackq() to prepare for command execution to be
re-entered.
Reported by: bdrewery
MFC after: 1 week
Renumber cluase 4 to 3, per what everybody else did when BSD granted
them permission to remove clause 3. My insistance on keeping the same
numbering for legal reasons is too pedantic, so give up on that point.
Submitted by: Jan Schaumann <jschauma@stevens.edu>
Pull Request: https://github.com/freebsd/freebsd/pull/96
Instead of changing the whole course to another POSIX-permitted way
for consistency and uniformity I decide to completely ignore missing
regex fucntionality and focus on fixing bugs in what we have now,
too many small obstacles we have choicing other way, counting ports.
Corresponding libc changes are backed out in r302824.
Forbid (temporary or permanent) modifications of the strings in NARG nodes
during expansion.
Tilde expansion now needs to copy the username for the terminating '\0'.
With the new expand.c code, the intermediate representation passed to the
pathname generation code only contains CTLESC, not CTLQUOTEMARK.
CTLQUOTEMARK now only occurs in the text of NARG nodes (output of the
parser).
This avoids the need to add and remove CTLESC bytes if pathname generation
will not be performed (set -f).
Side effect: the order of operations is slightly different: pathname
generation in ${$+* $(CMD)} will not see filesystem changes from CMD.
This simplifies the code and should be faster in some cases.
Side effect: the order of operations is different so that the value of IFS
used when IFS is modified during expansion (${IFS:=...}, ${IFS=...} or
$((...IFS=...))) may be different. Note that this order is highly unportable
between shells.
This simplifies the code (e.g. allowing use of qsort(3) instead of a
hand-rolled mergesort) and should have better cache properties.
The waste of unused args arrays after resizes is approximately the same as
the savings from getting rid of the next pointers.
At the same time, remove a piece of global state and move some duplicated
code into a function.
Shell syntax is too complicated to detect command substitution and unquoted
operators reliably without implementing much of sh's parser. Therefore, have
sh do this detection.
While changing sh's support anyway, also read input from a pipe instead of
arguments to avoid {ARG_MAX} limits and improve privacy, and output count
and length using 16 instead of 8 digits.
The basic concept is:
execl("/bin/sh", "sh", "-c", "freebsd_wordexp ${1:+\"$1\"} -f "$2",
"", flags & WRDE_NOCMD ? "-p" : "", <pipe with words>);
The WRDE_BADCHAR error is still implemented in libc. POSIX requires us to
fail strings containing unquoted braces with code WRDE_BADCHAR. Since this
is normally not a syntax error in sh, there is still a need for checking
code in libc, we_check().
The new we_check() is an optimistic check that all the characters
<newline> | & ; < > ( ) { }
are quoted. To avoid duplicating too much sh logic, such characters are
permitted when quoting characters are seen, even if the quoting characters
may themselves be quoted. This code reports all WRDE_BADCHAR errors; bad
characters that get past it and are a syntax error in sh return WRDE_SYNTAX.
Although many implementations of WRDE_NOCMD erroneously allow some command
substitutions (and ours even documented this), there appears to be code that
relies on its security (codesearch.debian.net shows quite a few uses).
Passing untrusted data to wordexp() still exposes a denial of service
possibility and a fairly large attack surface.
Reviewed by: wblock (man page only)
MFC after: 2 weeks
Relnotes: yes
Security: fixes command execution with wordexp(untrusted, WRDE_NOCMD)
POSIX requires this to prevent entering function definitions in history but
this implementation does nothing except retain the option's value. In ksh88,
function definitions were usually entered in the history file, even when
they came from ~/.profile and the $ENV file, to allow displaying their
definitions.
This is also the first option that does not have a letter.
The initial check for a matching ] was incorrect if a ] may be consumed by a
[:class:]. The subsequent loop assumed that there must be a ].
Remove the initial check and make the loop cope with a missing ].
Found with afl-fuzz.
MFC after: 1 week
EXP_REDIR was supposed to generate pathnames in redirection if exactly one
file matches, as permitted but not required by POSIX in interactive mode. It
is unlikely this will be implemented.
No functional change is intended.
MFC after: 1 week
EXP_REDIR was not being checked for while expanding positional parameters in
redirection, so CTL* bytes were not being prefixed where they should be.
MFC after: 1 week
Currently, there can be no more than INT_MAX positional parameters. Make
sure to treat all higher ones as unset to avoid incorrect results and
crashes.
On 64-bit systems, our atoi() takes the low 32 bits of the strtol() and
sign-extends them.
On 32-bit systems, the call to atoi() returned INT_MAX for too high values
and there is not enough address space for so many positional parameters, so
there was no issue.
Redo expari() like evalvar(). This makes the logic more understandable and
avoids possible problems if arithmetic expansion occurs if CTLESC characters
are not generated (looking backwards for CTLARI is not generally possible in
that case but the old code tried anyway).
This adds an extra argstr() recursion.
It now passes WARNS=7 with clang on i386.
GCC 4.2.1 does not understand setjmp() properly so will always trigger
-Wuninitialized. I will not add the volatile keywords to suppress this.
Expand here documents at the same point other redirections are expanded but
use a non-fork subshell environment (like simple command substitutions) for
compatibility. Substitition errors result in an empty here document like
before.
As a result, a fork is avoided for short (<4K) expanded here documents.
Unexpanded here documents (with quoted end marker after <<) are not affected
by this change. They already only forked when >4K.
Side effects:
* Order of expansion is slightly different.
* Slow expansions are not executed in parallel with the redirected command.
* A non-fork subshell environment is subtly different from a forked process.
This improves performance for globs where a slash or another component
follows a component with metacharacters by eliminating unnecessary attempts
to open directories that are not.
