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crypt uses uninit/unalloced/freed memory as salt #15091

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p5pRT opened this issue Dec 15, 2015 · 15 comments
Closed

crypt uses uninit/unalloced/freed memory as salt #15091

p5pRT opened this issue Dec 15, 2015 · 15 comments

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@p5pRT
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@p5pRT p5pRT commented Dec 15, 2015

Migrated from rt.perl.org#126922 (status was 'resolved')

Searchable as RT126922$

@p5pRT
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@p5pRT p5pRT commented Dec 15, 2015

From @bulk88

Created by @bulk88

There seems to be no bounds checking for minimum length of things in
Perl_pp_crypt. Either win32_crypt/des_fcrypt are flawed (not correctly
processing C empty string as arguments), or Perl_pp_crypt is flawed by
not bounds checking for minimum string length before handing off the
char *s to libc's crypt function, well in this case p5p's win32
equivalent of libc crypt. IDK what the minimum string length policy is
on POSIX crypt.

Submitted to security list since a hashing function that uses uninit
memory as a seed can be used to do interesting things (collisions/perf
degrade, or less permutations to brute force crack it).

---------------------------------------------------------------------
C​:\p523\src>drmemory -- perl -e"my$var=substr(chr
256,0,0);my$dummy=crypt 0,$var;"
Dr.M Dr. Memory version 1.9.0
Dr.M Running "perl "-emy$var=substr(chr 256,0,0);my$dummy=crypt
0,$var;""
Dr.M
Dr.M Error #1​: UNINITIALIZED READ​: reading register al
Dr.M # 0 perl523.dll!des_fcrypt [c​:\p523\src\win32\fcrypt.c​:489]
Dr.M # 1 perl523.dll!win32_crypt [c​:\p523\src\win32\win32.c​:2486]
Dr.M # 2 perl523.dll!PerlProcCrypt [c​:\p523\src\win32\perlhost.h​:1530]
Dr.M # 3 perl523.dll!Perl_pp_crypt [c​:\p523\src\pp.c​:3668]
Dr.M # 4 perl523.dll!Perl_runops_standard [c​:\p523\src\run.c​:41]
Dr.M # 5 perl523.dll!RunPerl [c​:\p523\src\win32\perllib.c​:258]
Dr.M # 6 __tmainCRTStartup
[f​:\dd\vctools\crt\crtw32\dllstuff\crtexe.c​:626]
Dr.M # 7 KERNEL32.dll!BaseThreadInitThunk
Dr.M Note​: @​0​:00​:02.355 in thread 5068
Dr.M Note​: instruction​: test %al %al
Dr.M
Dr.M ERRORS FOUND​:
Dr.M 0 unique, 0 total unaddressable access(es)
Dr.M 1 unique, 1 total uninitialized access(es)
Dr.M 0 unique, 0 total invalid heap argument(s)
Dr.M 0 unique, 0 total GDI usage error(s)
Dr.M 0 unique, 0 total handle leak(s)
Dr.M 0 unique, 0 total warning(s)
Dr.M 0 unique, 0 total, 0 byte(s) of leak(s)
Dr.M 0 unique, 0 total, 0 byte(s) of possible leak(s)
Dr.M ERRORS IGNORED​:
Dr.M 5 potential leak(s) (suspected false positives)
Dr.M (details​: C​:\Users\Owner\AppData\Roaming\Dr.
Memory\DrMemory-perl.exe.1720.000\potential_errors.txt)
Dr.M 10 unique, 10 total, 300 byte(s) of still-reachable
allocation(s)
Dr.M (re-run with "-show_reachable" for details)
Dr.M Details​: C​:\Users\Owner\AppData\Roaming\Dr.
Memory\DrMemory-perl.exe.17
20.000\results.txt

---------------------------------------------------------------------
char *
des_fcrypt(const char *buf, const char *salt, char *buff)
  {
  unsigned int i,j,x,y;
  unsigned long Eswap0,Eswap1;
  unsigned long out[2],ll;
  des_cblock key;
  des_key_schedule ks;
  unsigned char bb[9];
  unsigned char *b=bb;
  unsigned char c,u;

  /* eay 25/08/92
  * If you call crypt("pwd","*") as often happens when you
  * have * as the pwd field in /etc/passwd, the function
  * returns *\0XXXXXXXXX
  * The \0 makes the string look like * so the pwd "*" would
  * crypt to "*". This was found when replacing the crypt in
  * our shared libraries. People found that the disbled
  * accounts effectivly had no passwd :-(. */
  x=buff[0]=((salt[0] == '\0')?(char)'A'​:salt[0]);
  Eswap0=con_salt[x];
  x=buff[1]=((salt[1] == '\0')?(char)'A'​:salt[1]);<<<<<<<<<<<<<<LINE 489
  Eswap1=con_salt[x]<<4;

  for (i=0; i<8; i++)

-------------------------------------------------------------------
PP(pp_crypt)
{
#ifdef HAS_CRYPT
  dSP; dTARGET;
  dPOPTOPssrl;
  STRLEN len;
  const char *tmps = SvPV_const(left, len);

  if (DO_UTF8(left)) {
  /* If Unicode, try to downgrade.
  * If not possible, croak.
  * Yes, we made this up. */
  SV* const tsv = newSVpvn_flags(tmps, len, SVf_UTF8|SVs_TEMP);

  sv_utf8_downgrade(tsv, FALSE);
  tmps = SvPV_const(tsv, len);
  }
# ifdef USE_ITHREADS
# ifdef HAS_CRYPT_R
  if (!PL_reentrant_buffer->_crypt_struct_buffer) {
  /* This should be threadsafe because in ithreads there is only
  * one thread per interpreter. If this would not be true,
  * we would need a mutex to protect this malloc. */
  PL_reentrant_buffer->_crypt_struct_buffer =
  (struct crypt_data *)safemalloc(sizeof(struct crypt_data));
#if defined(__GLIBC__) || defined(__EMX__)
  if (PL_reentrant_buffer->_crypt_struct_buffer) {
  PL_reentrant_buffer->_crypt_struct_buffer->initialized = 0;
  /* work around glibc-2.2.5 bug */
PL_reentrant_buffer->_crypt_struct_buffer->current_saltbits = 0;
  }
#endif
  }
# endif /* HAS_CRYPT_R */
# endif /* USE_ITHREADS */
# ifdef FCRYPT
  sv_setpv(TARG, fcrypt(tmps, SvPV_nolen_const(right)));
# else
  sv_setpv(TARG, PerlProc_crypt(tmps, SvPV_nolen_const(right)));
<<<<<<<<<<<<<<<<<<<<<<LINE 3668
# endif
  SvUTF8_off(TARG);
  SETTARG;
  RETURN;
#else
  DIE(aTHX_
  "The crypt() function is unimplemented due to excessive paranoia.");
#endif
}
-------------------------------------------------------------------------

Callstack

-------------------------------------------------------------------------
  perl523.dll!des_fcrypt(const char * buf, const char * salt, char *
buff) Line 489 C
  perl523.dll!win32_crypt(const char * txt, const char * salt) Line
2486 C
  perl523.dll!PerlProcCrypt(IPerlProc * piPerl, const char * clear,
const char * salt) Line 1530 C++
  perl523.dll!Perl_pp_crypt(interpreter * my_perl) Line 3668 C
  perl523.dll!Perl_runops_standard(interpreter * my_perl) Line 41 C
  perl523.dll!S_run_body(interpreter * my_perl, long oldscope) Line
2464 C
  perl523.dll!perl_run(interpreter * my_perl) Line 2387 C
  perl523.dll!RunPerl(int argc, char * * argv, char * * env) Line
258 C++
  perl.exe!__tmainCRTStartup() Line 626 C
  kernel32.dll!@​BaseThreadInitThunk@​12�() Unknown
  ntdll.dll!___RtlUserThreadStart@​8�() Unknown
  ntdll.dll!__RtlUserThreadStart@​8�() Unknown
-------------------------------------------------------------------------

Dumps of SVs.

SV * left from perl523.dll!Perl_pp_crypt(interpreter * my_perl) Line
3668 C

SV = PVIV(0x2adde4) at 0x2af374
  REFCNT = 1
  FLAGS = 0x8005505 (IOK,POK,READONLY,pIOK,pPOK)
  IV = 0
  PV = 0x2b5054 "0"\0
  CUR = 1
  LEN = 3

SV * right from perl523.dll!Perl_pp_crypt(interpreter * my_perl) Line
3668 C

SV = PV(0x290884) at 0x2af314
  REFCNT = 1
  FLAGS = 0x20004403 (POK,pPOK,UTF8)
  PV = 0x2b37d4 ""\0 [UTF8 ""]
  CUR = 0
  LEN = 2

Perl Info

Flags:
     category=core
     severity=high

Site configuration information for perl 5.23.5:

Configured by Owner at Fri Dec 11 22:33:57 2015.

Summary of my perl5 (revision 5 version 23 subversion 5) configuration:
   Local Commit: 8300cd2ba7e87391e21c6a94c00c193b077f3221
   Ancestor: ab36d597128b4016dda4ce194191e3237cf3f6a1
   Platform:
     osname=MSWin32, osvers=6.1, archname=MSWin32-x86-multi-thread
     uname=''
     config_args='undef'
     hint=recommended, useposix=true, d_sigaction=undef
     useithreads=define, usemultiplicity=define
     use64bitint=undef, use64bitall=undef, uselongdouble=undef
     usemymalloc=n, bincompat5005=undef
   Compiler:
     cc='cl', ccflags ='-nologo -GF -W3 -O1 -MD -Zi -DNDEBUG -GL -DWIN32 
-D_CONSOLE -DNO_STRICT -D_CRT_SECURE_NO_DEPRECATE 
-D_CRT_NONSTDC_NO_DEPRECATE  -DPERL_TEXTMODE_SCRIPTS 
-DPERL_IMPLICIT_CONTEXT -DPERL_IMPLICIT_SYS -DWIN32_NO_REGISTRY',
     optimize='-O1 -MD -Zi -DNDEBUG -GL',
     cppflags='-DWIN32'
     ccversion='18.00.31101', gccversion='', gccosandvers=''
     intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=1234, 
doublekind=3
     d_longlong=undef, longlongsize=8, d_longdbl=define, longdblsize=8, 
longdblkind=0
     ivtype='long', ivsize=4, nvtype='double', nvsize=8, 
Off_t='__int64', lseeksize=8
     alignbytes=8, prototype=define
   Linker and Libraries:
     ld='link', ldflags ='-nologo -nodefaultlib -debug -opt:ref,icf 
-ltcg         -libpath:"c:\perl\lib\CORE"         -machine:x86 
-subsystem:console,"5.01"'
     libpth=\lib
     libs=oldnames.lib kernel32.lib user32.lib gdi32.lib winspool.lib 
comdlg32.lib advapi32.lib shell32.lib ole32.lib oleaut32.lib 
netapi32.lib uuid.lib ws2_32.lib mpr.lib winmm.lib version.lib 
odbc32.lib odbccp32.lib comctl32.lib msvcrt.lib
     perllibs=oldnames.lib kernel32.lib user32.lib gdi32.lib 
winspool.lib comdlg32.lib advapi32.lib shell32.lib ole32.lib 
oleaut32.lib netapi32.lib uuid.lib ws2_32.lib mpr.lib winmm.lib 
version.lib odbc32.lib odbccp32.lib comctl32.lib msvcrt.lib
     libc=msvcrt.lib, so=dll, useshrplib=true, libperl=perl523.lib
     gnulibc_version=''
   Dynamic Linking:
     dlsrc=dl_win32.xs, dlext=dll, d_dlsymun=undef, ccdlflags=' '
     cccdlflags=' ', lddlflags='-dll -nologo -nodefaultlib -debug 
-opt:ref,icf -ltcg         -libpath:"c:\perl\lib\CORE"  -machine:x86 
-subsystem:console,"5.01"'

Locally applied patches:
     e871160f42ac868768134e1f539f4c2406c18308
     8300cd2ba7e87391e21c6a94c00c193b077f3221


@INC for perl 5.23.5:
     C:/p523/src/lib
     .


Environment for perl 5.23.5:
     HOME (unset)
     LANG (unset)
     LANGUAGE (unset)
     LD_LIBRARY_PATH (unset)
     LOGDIR (unset)
     PATH=C:\Program Files\Dr. 
Memory\bin;C:\sp520\c\bin;C:\Windows\system32;C:\Program Files\Microsoft 
Visual Studio 12.0\VC\BIN;C:\Program Files\Windows 
Kits\8.1\bin\x86;C:\Windows;C:\Program Files\ActiveState Komodo Edit 
9;C:\Program Files\Git\bin;
     PERL_BADLANG (unset)
     SHELL (unset)


@p5pRT
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@p5pRT p5pRT commented Dec 15, 2015

From @iabyn

On Tue, Dec 15, 2015 at 04​:58​:14AM -0800, bulk88 wrote​:

# New Ticket Created by bulk88
# Please include the string​: [perl #126922]
# in the subject line of all future correspondence about this issue.
# <URL​: https://rt-archive.perl.org/perl5/Ticket/Display.html?id=126922 >

This is a bug report for perl from bulk88@​hotmail.com,
generated with the help of perlbug 1.40 running under perl 5.23.5.

-----------------------------------------------------------------
[Please describe your issue here]

There seems to be no bounds checking for minimum length of things in
Perl_pp_crypt. Either win32_crypt/des_fcrypt are flawed (not correctly
processing C empty string as arguments), or Perl_pp_crypt is flawed by
not bounds checking for minimum string length before handing off the
char *s to libc's crypt function, well in this case p5p's win32
equivalent of libc crypt. IDK what the minimum string length policy is
on POSIX crypt.

I don't know what POSIX formally states, but the linux manpage for crypt
is amiguous.

Valgrind shows that a salt of length < 2 isn't causing any illegal accesses,
and crpyt() is returning NULL for a length(salt) < 2.

So I would lean towards win32_crypt/des_fcrypt being wrong for not
detecting a short salt.

--
But Pity stayed his hand. "It's a pity I've run out of bullets",
he thought. -- "Bored of the Rings"

@p5pRT
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@p5pRT p5pRT commented Dec 15, 2015

The RT System itself - Status changed from 'new' to 'open'

@p5pRT
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@p5pRT p5pRT commented Dec 15, 2015

From zefram@fysh.org

bulk88 wrote​:

There seems to be no bounds checking for minimum length of things in
Perl_pp_crypt.

There is no minimum length. crypt(3) takes two nul-terminated string
arguments. An excessively short salt string can produce silly output,
but not a boundary excursion.

          Either win32\_crypt/des\_fcrypt are flawed \(not correctly 

processing C empty string as arguments),

Yes, that's a clear flaw.

-zefram

@p5pRT
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@p5pRT p5pRT commented Dec 17, 2015

From @tonycoz

On Tue Dec 15 10​:44​:28 2015, zefram@​fysh.org wrote​:

bulk88 wrote​:

There seems to be no bounds checking for minimum length of things in
Perl_pp_crypt.

There is no minimum length. crypt(3) takes two nul-terminated string
arguments. An excessively short salt string can produce silly output,
but not a boundary excursion.

POSIX requires that the salt be at least two bytes long.

http​://pubs.opengroup.org/onlinepubs/9699919799/functions/crypt.html

          Either win32\_crypt/des\_fcrypt are flawed \(not correctly 

processing C empty string as arguments),

Yes, that's a clear flaw.

The attached validates the salt and adds some tests.

The error behaviour is modelled on the glibc crypt()​:

tony@​mars​:.../git/bse$ perl -le 'print crypt("abc", "!!") || $!'
Invalid argument
tony@​mars​:.../git/bse$ perl -le 'print crypt("abc", "") || $!'
Invalid argument
tony@​mars​:.../git/bse$ perl -le 'print crypt("abc", "//") || $!'
//dOFYpvAsViA

Tony

@p5pRT
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@p5pRT p5pRT commented Dec 17, 2015

From @tonycoz

0001-perl-126922-avoid-access-to-uninitialized-memory-in-.patch
From 1ff6c0fee48071c865f383e2d8168e99b7fb2a3a Mon Sep 17 00:00:00 2001
From: Tony Cook <tony@develop-help.com>
Date: Thu, 17 Dec 2015 11:15:31 +1100
Subject: [perl #126922] avoid access to uninitialized memory in win32 crypt()

Previously the Win32 crypt implementation() would access the first
and second characters of the salt, even if the salt was zero length.

Add validation that will detect both a short salt and invalid
characters in the salt.
---
 MANIFEST        |  1 +
 t/win32/crypt.t | 41 +++++++++++++++++++++++++++++++++++++++++
 win32/fcrypt.c  | 14 ++++++++++++++
 3 files changed, 56 insertions(+)
 create mode 100644 t/win32/crypt.t

diff --git a/MANIFEST b/MANIFEST
index 2adf881..a0fc308 100644
--- a/MANIFEST
+++ b/MANIFEST
@@ -5576,6 +5576,7 @@ t/uni/universal.t		See if Unicode in calls to UNIVERSAL works
 t/uni/upper.t			See if Unicode casing works
 t/uni/variables.t		See that the rules for variable names work
 t/uni/write.t			See if Unicode formats work
+t/win32/crypt.t			Test Win32 crypt for compatibility
 t/win32/fs.t			Test Win32 link for compatibility
 t/win32/popen.t			Test for stdout races in backticks, etc
 t/win32/runenv.t		Test if Win* perl honors its env variables
diff --git a/t/win32/crypt.t b/t/win32/crypt.t
new file mode 100644
index 0000000..f0e89ab
--- /dev/null
+++ b/t/win32/crypt.t
@@ -0,0 +1,41 @@
+#!./perl
+
+BEGIN {
+    chdir 't' if -d 't';
+    @INC = '../lib';
+    require "./test.pl";
+    eval 'use Errno';
+    die $@ if $@ and !is_miniperl();
+}
+
+my @bad_salts =
+   (
+    [ '',   'zero-length' ],
+    [ 'a',  'length 1' ],
+    [ '!a', 'bad first character' ],
+    [ 'a!', 'bad second character' ],
+    [ '@a', 'fencepost before A' ],
+    [ '[a', 'fencepost after Z' ],
+    [ '`a', 'fencepost before a' ],
+    [ '{a', 'fencepost after z' ],
+    [ '-a', 'fencepost before .' ],
+    [ ':a', 'fencepost after 9' ],
+   );
+
+my @good_salts = qw(aa zz AA ZZ .. 99);
+
+plan tests => 2 * @bad_salts + 1 + @good_salts;
+
+for my $bad_salt (@bad_salts) {
+    my ($salt, $what) = @$bad_salt;
+    $! = 0;
+    is(crypt("abc", $salt), undef, "bad salt ($what)");
+    is(0+$!, &Errno::EINVAL, "check errno ($what)");
+}
+
+is(crypt("abcdef", "ab"), "abDMWw5NL.afs", "sanity check result");
+
+# just to check we're not rejecting any good salts
+for my $good_salt (@good_salts) {
+    isnt(crypt("abcdef", $good_salt), undef, "good salt $good_salt");
+}
diff --git a/win32/fcrypt.c b/win32/fcrypt.c
index fd42d75..4433e68 100644
--- a/win32/fcrypt.c
+++ b/win32/fcrypt.c
@@ -1,6 +1,7 @@
 /* fcrypt.c */
 /* Copyright (C) 1993 Eric Young - see README for more details */
 #include <stdio.h>
+#include <errno.h>
 
 /* Eric Young.
  * This version of crypt has been developed from my MIT compatable
@@ -464,6 +465,14 @@ unsigned const char cov_2char[64]={
 0x73,0x74,0x75,0x76,0x77,0x78,0x79,0x7A
 };
 
+/* the salt for classic DES crypt (which is all we implement here)
+   permits [./0-9A-Za-z], since '.' and '/' immediately preceed
+   '0' we don't need individual checks for '.' and '/' 
+*/
+#define good_for_salt(c) \
+    ((c) >= '.' && (c) <= '9' || (c) >= 'A' && (c) <= 'Z' ||  \
+     (c) >= 'a' && (c) <= 'z')
+
 char *
 des_fcrypt(const char *buf, const char *salt, char *buff)
 	{
@@ -476,6 +485,11 @@ des_fcrypt(const char *buf, const char *salt, char *buff)
 	unsigned char *b=bb;
 	unsigned char c,u;
 
+        if (!good_for_salt(salt[0]) || !good_for_salt(salt[1])) {
+            errno = EINVAL;
+            return NULL;
+        }
+
 	/* eay 25/08/92
 	 * If you call crypt("pwd","*") as often happens when you
 	 * have * as the pwd field in /etc/passwd, the function
-- 
1.9.5.msysgit.0

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@p5pRT p5pRT commented Dec 19, 2015

From @bulk88

Subject​: [perl #126922] crypt uses uninit/unalloced/freed memory as salt
From​: perl5-security-report@​perl.org
To​: bulk88@​hotmail.com
Date​: Wed, 16 Dec 2015 16​:21​:44 -0800

On Tue Dec 15 10​:44​:28 2015, zefram@​fysh.org wrote​:

bulk88 wrote​:

There seems to be no bounds checking for minimum length of things in
Perl_pp_crypt.

There is no minimum length. crypt(3) takes two nul-terminated string
arguments. An excessively short salt string can produce silly output,
but not a boundary excursion.

POSIX requires that the salt be at least two bytes long.

http​://pubs.opengroup.org/onlinepubs/9699919799/functions/crypt.html

          Either win32\_crypt/des\_fcrypt are flawed \(not correctly 

processing C empty string as arguments),

Yes, that's a clear flaw.

The attached validates the salt and adds some tests.

The error behaviour is modelled on the glibc crypt()​:

tony@​mars​:.../git/bse$ perl -le 'print crypt("abc", "!!") || $!'
Invalid argument
tony@​mars​:.../git/bse$ perl -le 'print crypt("abc", "") || $!'
Invalid argument
tony@​mars​:.../git/bse$ perl -le 'print crypt("abc", "//") || $!'
//dOFYpvAsViA

Tony

Couldn't that win32/crypt.t test be for all OSes, not just Win32?

Another question generic question unrelated to the uninit memory read, if the input character set for the salt is only 60 chars out of 256, or %23, isn't that a very bad entropy reduction? If I read the POSIX document you linked, it says only the first 2 bytes of the salt string are used, is that correct? Or POSIX crypt stopped being crypto-secure a long time and is in the family as perl rand()?

I'll note glibc filters charset https://sourceware.org/git/?p=glibc.git;a=blob;f=crypt/crypt_util.c;h=05f6a56257b44a5923af7552c499eee20f37cba9;hb=HEAD#l581

glibc seems to only use the first 2 bytes https://sourceware.org/git/?p=glibc.git;a=blob;f=crypt/crypt_util.c;h=05f6a56257b44a5923af7552c499eee20f37cba9;hb=HEAD#l604

Your patch fixed the uninit memory read report from Dr Mem with the one liner q|perl -e"my$var=substr(chr256,0,0);my$dummy=crypt 0,$var;"| . Out of curiosity, i ran win32/crypt.t on the unpatched perl. Result below

C​:\p523\src\t>drmemory -- perl -I..\lib win32/crypt.t
Dr.M Dr. Memory version 1.9.0
Dr.M Running "perl -I..\lib win32/crypt.t"
1..27
Dr.M
Dr.M Error #1​: UNINITIALIZED READ​: reading register al
Dr.M # 0 perl523.dll!des_fcrypt [c​:\p523\src\win32\fcrypt.c​:489]

Dr.M # 1 perl523.dll!win32_crypt [c​:\p523\src\win32\win32.c​:2486]

Dr.M # 2 perl523.dll!PerlProcCrypt [c​:\p523\src\win32\perlhost.h​:15
30]
Dr.M # 3 perl523.dll!Perl_pp_crypt [c​:\p523\src\pp.c​:3668]
Dr.M # 4 perl523.dll!Perl_runops_standard [c​:\p523\src\run.c​:41]
Dr.M # 5 perl523.dll!RunPerl [c​:\p523\src\win32\perllib.c​:258
]
Dr.M # 6 __tmainCRTStartup [f​:\dd\vctools\crt\crtw32\dllstu
ff\crtexe.c​:626]
Dr.M # 7 KERNEL32.dll!BaseThreadInitThunk
Dr.M Note​: @​0​:00​:10.702 in thread 1192
Dr.M Note​: instruction​: test %al %al
not ok 1 - bad salt (zero-length)
# Failed test 1 - bad salt (zero-length) at win32/crypt.t line 32
# got "Ao.bTQLzE83bs"
# expected undef
not ok 2 - check errno (zero-length)
# Failed test 2 - check errno (zero-length) at win32/crypt.t line 33
# got "0"
# expected "22"
not ok 3 - bad salt (length 1)
# Failed test 3 - bad salt (length 1) at win32/crypt.t line 32
# got "aAI3uM763cGMY"
# expected undef
not ok 4 - check errno (length 1)
# Failed test 4 - check errno (length 1) at win32/crypt.t line 33
# got "0"
# expected "22"
not ok 5 - bad salt (bad first character)
# Failed test 5 - bad salt (bad first character) at win32/crypt.t line 32
# got "!aywdxyygOYLw"
# expected undef
not ok 6 - check errno (bad first character)
# Failed test 6 - check errno (bad first character) at win32/crypt.t line 33
# got "0"
# expected "22"
not ok 7 - bad salt (bad second character)
# Failed test 7 - bad salt (bad second character) at win32/crypt.t line 32
# got "a!uoC5noeqDXE"
# expected undef
not ok 8 - check errno (bad second character)
# Failed test 8 - check errno (bad second character) at win32/crypt.t line 33
# got "0"
# expected "22"
not ok 9 - bad salt (fencepost before A)
# Failed test 9 - bad salt (fencepost before A) at win32/crypt.t line 32
# got "@​ajAyahtsZls6"
# expected undef
not ok 10 - check errno (fencepost before A)
# Failed test 10 - check errno (fencepost before A) at win32/crypt.t line 33
# got "0"
# expected "22"
not ok 11 - bad salt (fencepost after Z)
# Failed test 11 - bad salt (fencepost after Z) at win32/crypt.t line 32
# got "[aqSURRK/uV3A"
# expected undef
not ok 12 - check errno (fencepost after Z)
# Failed test 12 - check errno (fencepost after Z) at win32/crypt.t line 33
# got "0"
# expected "22"
not ok 13 - bad salt (fencepost before a)
# Failed test 13 - bad salt (fencepost before a) at win32/crypt.t line 32
# got "`aTaMzmfjIpJ6"
# expected undef
not ok 14 - check errno (fencepost before a)
# Failed test 14 - check errno (fencepost before a) at win32/crypt.t line 33
# got "0"
# expected "22"
not ok 15 - bad salt (fencepost after z)
# Failed test 15 - bad salt (fencepost after z) at win32/crypt.t line 32
# got "{aywdxyygOYLw"
# expected undef
not ok 16 - check errno (fencepost after z)
# Failed test 16 - check errno (fencepost after z) at win32/crypt.t line 33
# got "0"
# expected "22"
not ok 17 - bad salt (fencepost before .)
# Failed test 17 - bad salt (fencepost before .) at win32/crypt.t line 32
# got "-aywdxyygOYLw"
# expected undef
not ok 18 - check errno (fencepost before .)
# Failed test 18 - check errno (fencepost before .) at win32/crypt.t line 33
# got "0"
# expected "22"
not ok 19 - bad salt (fencepost after 9)
# Failed test 19 - bad salt (fencepost after 9) at win32/crypt.t line 32
# got "​:a0QeMflQunsk"
# expected undef
not ok 20 - check errno (fencepost after 9)
# Failed test 20 - check errno (fencepost after 9) at win32/crypt.t line 33
# got "0"
# expected "22"
ok 21 - sanity check result
ok 22 - good salt aa
ok 23 - good salt zz
ok 24 - good salt AA
ok 25 - good salt ZZ
ok 26 - good salt ..
ok 27 - good salt 99
Dr.M
Dr.M ERRORS FOUND​:
Dr.M 0 unique, 0 total unaddressable access(es)
Dr.M 1 unique, 1 total uninitialized access(es)
Dr.M 0 unique, 0 total invalid heap argument(s)
Dr.M 0 unique, 0 total GDI usage error(s)
Dr.M 0 unique, 0 total handle leak(s)
Dr.M 0 unique, 0 total warning(s)
Dr.M 0 unique, 0 total, 0 byte(s) of leak(s)
Dr.M 0 unique, 0 total, 0 byte(s) of possible leak(s)
Dr.M ERRORS IGNORED​:
Dr.M 16 potential leak(s) (suspected false positives)
Dr.M (details​: C​:\Users\Owner\AppData\Roaming\Dr. Memory\DrMemory-p
erl.exe.3012.000\potential_errors.txt)
Dr.M 10 unique, 10 total, 300 byte(s) of still-reachable allocati
on(s)
Dr.M (re-run with "-show_reachable" for details)
Dr.M Details​: C​:\Users\Owner\AppData\Roaming\Dr. Memory\DrMemory-perl.exe.30
12.000\results.txt

C​:\p523\src\t>
 

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@p5pRT p5pRT commented Dec 19, 2015

From @tonycoz

On Sat Dec 19 11​:53​:43 2015, bulk88 wrote​:

Couldn't that win32/crypt.t test be for all OSes, not just Win32?

Not all other OS implementations support classic DES crypt(), for example see https://rt-archive.perl.org/perl5/Ticket/Display.html?id=121591.

The tests in t/op/crypt.t attempt to test perl's interface to the underlying crypt implementation, the new tests attempt to test the win32 specific implementation.

Another question generic question unrelated to the uninit memory read,
if the input character set for the salt is only 60 chars out of 256,
or %23, isn't that a very bad entropy reduction? If I read the POSIX
document you linked, it says only the first 2 bytes of the salt string
are used, is that correct? Or POSIX crypt stopped being crypto-secure
a long time and is in the family as perl rand()?

The classic DES crypt() hasn't been considered secure for many years, which is why many implementations support extensions that use other algorithms.

I'll note glibc filters charset
https://sourceware.org/git/?p=glibc.git;a=blob;f=crypt/crypt_util.c;h=05f6a56257b44a5923af7552c499eee20f37cba9;hb=HEAD#l581

It's doing pretty much what I did - rejecting invalid characters.

glibc seems to only use the first 2 bytes
https://sourceware.org/git/?p=glibc.git;a=blob;f=crypt/crypt_util.c;h=05f6a56257b44a5923af7552c499eee20f37cba9;hb=HEAD#l604

As does the win32 implementation.

Your patch fixed the uninit memory read report from Dr Mem with the
one liner q|perl -e"my$var=substr(chr256,0,0);my$dummy=crypt 0,$var;"|
. Out of curiosity, i ran win32/crypt.t on the unpatched perl. Result
below

C​:\p523\src\t>drmemory -- perl -I..\lib win32/crypt.t
Dr.M Dr. Memory version 1.9.0
Dr.M Running "perl -I..\lib win32/crypt.t"
1..27
Dr.M
Dr.M Error #1​: UNINITIALIZED READ​: reading register al
Dr.M # 0 perl523.dll!des_fcrypt
[c​:\p523\src\win32\fcrypt.c​:489]
(mostly failing tests ommitted)

Cool.

We have another Win32 specific security issue outstanding.

Does this issue require a CVE?

Tony

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@p5pRT p5pRT commented Dec 26, 2015

From @bulk88

Tony Cook via RT wrote​:

Cool.

We have another Win32 specific security issue outstanding.

Does this issue require a CVE?

Tony
I'd like for this ticket to be made public sooner than later. This
memory corruption/segv bug ticket is the cause of the SEGVs in
perl11/cperl#95 and CI smoke
https://ci.appveyor.com/project/rurban/cperl/build/5.22.2.728/job/6d2y5prny5ukq6or#L6653
. The patch in this ticket seems to have fixed the SEGV for me when I
apply it to cperl.

I dont have much comment on a CVE, its not my thing to decide. The only
thing I can say is, I think (didnt read the failure mode too deeply), if
there is a coding error and an app was passing empty string as the salt
to crypt, the salt used would be predictable if you can predict what the
bytes will be in the tail of the empty string PV buffer from Win32
malloc. One byte would be null (empty string term), and the 2nd byte
either uninit 0s (fresh VM block from OS), or contents of previous
memory allocation at that addr or semi-predictable malloc bookkeeping.
The other argument is, des implemented crypt()
((26+26+12)*(26+26+12)=4096 possible salts, a 12 bit encryption key) is
not secure in any way, and it is simply obfuscation, not encryption,
obfuscation can always be reversed, hence this isn't a security bug.
That is my thinking, but I am not the person to ask on security questions.

Another question, is the result of crypt() on POSIX required to be
stable between reboots? Can it be serialized to disk and guaranteed to
be the same after a reboot on the same OS version? If the app that was
passing by mistake empty string as salt, it stores serialized the hash
number (that is what crypt returns kind of) to disk using uninit memory
as the salt, reboots and ASLR/memory randomization changes things, then
recomputes a different input with empty string as hash, a collision can
occur since the salt of "empty string" in perl lang has different values
between reboots and caused 2 different inputs that shouldn't have had
the same hash number, have the same hash number because of different
salts in C but they were the same salt in perl lang ("").

I am not sure if anyone but TonyC will respond to this ticket before it
is made public due to a lack of eyes on the security list.

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@p5pRT p5pRT commented Dec 26, 2015

From @iabyn

On Fri, Dec 25, 2015 at 10​:09​:53PM -0500, bulk88 wrote​:

Another question, is the result of crypt() on POSIX required to be stable
between reboots? Can it be serialized to disk and guaranteed to be the same
after a reboot on the same OS version?

The main purpose of having crypt() built-in to perl was to make it easy to
write admin scripts that could create new password hashes, or test
existing password hashes, for the user account "database" in /etc/password
on traditional UNIX systems.

The hashed password and the two salt characters for a newly-created user
or password would be stored as 2+11 characters in a field in
/etc/password.

To create a new password, a script would create 2 random salt chars ($salt
say), then store crypt($pass,$salt) and $salt in /etc/password.

To check a password, ($hash,$salt) would be read from /etc/password, then
(crypt($pass,$salt) eq $hash) would be tested for.

I suspect that any code which failed to pass a 2-char salt to crypt()
would have been spotted almost immediately, as it would either fail to
generate new accounts that can logged in with, or would fail to
authenticate users.

Also, I suspect the use of crypt() on win32 systems is vanishingly small,
and the use of crypt() on *any* system is rare now, since the hashing
algorithm for user passwords on UNIX systems changed to more secure
functions years ago.

So I don't think a CVE is required.

--
Counsellor Troi states something other than the blindingly obvious.
  -- Things That Never Happen in "Star Trek" #16

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@p5pRT p5pRT commented Jan 1, 2016

From @rjbs

* Dave Mitchell <davem@​iabyn.com> [2015-12-26T06​:02​:53]

So I don't think a CVE is required.

Sorry for my delayed reply. The holidays have kept me busy.

I tentatively agree. As the one who is likely to deal with a CVE, I know that
I have a bias against having a CVE. ;-) Accordingly, I ask for feedback.

If we have any objections, please let them be stated by the 4th. Failing that,
let us make this public.

--
rjbs

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@p5pRT p5pRT commented Jan 5, 2016

From @rjbs

I have moved this ticket from perl5-security to perl5.

--
rjbs

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@p5pRT p5pRT commented Jan 5, 2016

From [Unknown Contact. See original ticket]

I have moved this ticket from perl5-security to perl5.

--
rjbs

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@p5pRT p5pRT commented Jan 5, 2016

From @tonycoz

On Wed Dec 16 16​:21​:43 2015, tonyc wrote​:

The attached validates the salt and adds some tests.

The error behaviour is modelled on the glibc crypt()​:

tony@​mars​:.../git/bse$ perl -le 'print crypt("abc", "!!") || $!'
Invalid argument
tony@​mars​:.../git/bse$ perl -le 'print crypt("abc", "") || $!'
Invalid argument
tony@​mars​:.../git/bse$ perl -le 'print crypt("abc", "//") || $!'
//dOFYpvAsViA

Applied as d691474 and added to maint-votes.

Tony

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@p5pRT p5pRT commented Jan 5, 2016

@tonycoz - Status changed from 'open' to 'resolved'

@p5pRT p5pRT closed this Jan 5, 2016
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