CVE-2018-18314 (published 2018-12-07T21:29Z)

Perl before 5.26.3 has a buffer overflow via a crafted regular expression that triggers invalid write operations.

Severity: HIGH
CVSS v2 base score: 7.5 (AV:N/AC:L/Au:N/C:P/I:P/A:P)
CVSS v3 base score: 9.8, CRITICAL (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H)

Weakness information:
cwe_id: CWE-119
cwe_name: Improper Restriction of Operations within the Bounds of a Memory Buffer
description: The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.
extended_description: 
            Certain languages allow direct addressing of memory locations and do not automatically ensure that these locations are valid for the memory buffer that is being referenced. This can cause read or write operations to be performed on memory locations that may be associated with other variables, data structures, or internal program data.
         
         

Fix information:
repo_url: https://github.com/Perl/perl5
commit_details: repo_url: https://github.com/Perl/perl5
author: Yves Orton
author_date: 2017-06-26 13:19:55+02:00
msg: fix #131649 - extended charclass can trigger assert

The extended charclass parser makes some assumptions during the
first pass which are only true on well structured input, and it
does not properly catch various errors. later on the code assumes
that things the first pass will let through are valid, when in
fact they should trigger errors.
repository: repo_url: https://github.com/Perl/perl5
repo_name: Perl/perl5
description: 🐪 The Perl programming language
repo_language: Perl
owner: Perl
file_changes: filename: perldiag.pod
change_type: ModificationType.MODIFY
diff: @@ -5945,7 +5945,7 @@ yourself.
 a perl4 interpreter, especially if the next 2 tokens are "use strict"
 or "my $var" or "our $var".
 
-=item Syntax error in (?[...]) in regex m/%s/
+=item Syntax error in (?[...]) in regex; marked by <-- HERE in m/%s/
 
 (F) Perl could not figure out what you meant inside this construct; this
 notifies you that it is giving up trying.
@@ -6441,6 +6441,31 @@ to find out why that isn't happening.
 (F) The unexec() routine failed for some reason.  See your local FSF
 representative, who probably put it there in the first place.
 
+=item Unexpected ']' with no following ')' in (?[... in regex; marked by <-- HERE in m/%s/
+
+(F) While parsing an extended character class a ']' character was encountered
+at a point in the definition where the only legal use of ']' is to close the
+character class definition as part of a '])', you may have forgotten the close
+paren, or otherwise confused the parser.
+
+=item Expecting close paren for nested extended charclass in regex; marked by <-- HERE in m/%s/
+
+(F) While parsing a nested extended character class like:
+
+    (?[ ... (?flags:(?[ ... ])) ... ])
+                             ^
+
+we expected to see a close paren ')' (marked by ^) but did not.
+
+=item Expecting close paren for wrapper for nested extended charclass in regex; marked by <-- HERE in m/%s/
+
+(F) While parsing a nested extended character class like:
+
+    (?[ ... (?flags:(?[ ... ])) ... ])
+                              ^
+
+we expected to see a close paren ')' (marked by ^) but did not.
+
 =item Unexpected binary operator '%c' with no preceding operand in regex;
 marked by S<<-- HERE> in m/%s/
 

programming_language: Perl
filename: perlrecharclass.pod
change_type: ModificationType.MODIFY
diff: @@ -1128,8 +1128,8 @@ hence both of the following work:
 Any contained POSIX character classes, including things like C<\w> and C<\D>
 respect the C<E<sol>a> (and C<E<sol>aa>) modifiers.
 
-C<< (?[ ]) >> is a regex-compile-time construct.  Any attempt to use
-something which isn't knowable at the time the containing regular
+Note that C<< (?[ ]) >> is a regex-compile-time construct.  Any attempt
+to use something which isn't knowable at the time the containing regular
 expression is compiled is a fatal error.  In practice, this means
 just three limitations:
 

programming_language: Perl
filename: regcomp.c
change_type: ModificationType.MODIFY
diff: @@ -14947,8 +14947,9 @@ S_handle_regex_sets(pTHX_ RExC_state_t *pRExC_state, SV** return_invlist,
                                     TRUE /* Force /x */ );
 
             switch (*RExC_parse) {
-                case '?':
-                    if (RExC_parse[1] == '[') nest_depth++, RExC_parse++;
+                case '(':
+                    if (RExC_parse[1] == '?' && RExC_parse[2] == '[')
+                        nest_depth++, RExC_parse+=2;
                     /* FALLTHROUGH */
                 default:
                     break;
@@ -15005,9 +15006,9 @@ S_handle_regex_sets(pTHX_ RExC_state_t *pRExC_state, SV** return_invlist,
                 }
 
                 case ']':
-                    if (nest_depth--) break;
-                    RExC_parse++;
-                    if (*RExC_parse == ')') {
+                    if (RExC_parse[1] == ')') {
+                        RExC_parse++;
+                        if (nest_depth--) break;
                         node = reganode(pRExC_state, ANYOF, 0);
                         RExC_size += ANYOF_SKIP;
                         nextchar(pRExC_state);
@@ -15019,20 +15020,25 @@ S_handle_regex_sets(pTHX_ RExC_state_t *pRExC_state, SV** return_invlist,
 
                         return node;
                     }
-                    goto no_close;
+                    /* We output the messages even if warnings are off, because we'll fail
+                     * the very next thing, and these give a likely diagnosis for that */
+                    if (posix_warnings && av_tindex_skip_len_mg(posix_warnings) >= 0) {
+                        output_or_return_posix_warnings(pRExC_state, posix_warnings, NULL);
+                    }
+                    RExC_parse++;
+                    vFAIL("Unexpected ']' with no following ')' in (?[...");
             }
 
             RExC_parse += UTF ? UTF8SKIP(RExC_parse) : 1;
         }
 
-      no_close:
         /* We output the messages even if warnings are off, because we'll fail
          * the very next thing, and these give a likely diagnosis for that */
         if (posix_warnings && av_tindex_skip_len_mg(posix_warnings) >= 0) {
             output_or_return_posix_warnings(pRExC_state, posix_warnings, NULL);
         }
 
-        FAIL("Syntax error in (?[...])");
+        vFAIL("Syntax error in (?[...])");
     }
 
     /* Pass 2 only after this. */
@@ -15212,12 +15218,14 @@ redo_curchar:
                      * inversion list, and RExC_parse points to the trailing
                      * ']'; the next character should be the ')' */
                     RExC_parse++;
-                    assert(UCHARAT(RExC_parse) == ')');
+                    if (UCHARAT(RExC_parse) != ')')
+                        vFAIL("Expecting close paren for nested extended charclass");
 
                     /* Then the ')' matching the original '(' handled by this
                      * case: statement */
                     RExC_parse++;
-                    assert(UCHARAT(RExC_parse) == ')');
+                    if (UCHARAT(RExC_parse) != ')')
+                        vFAIL("Expecting close paren for wrapper for nested extended charclass");
 
                     RExC_parse++;
                     RExC_flags = save_flags;

programming_language: C
filename: regcomp
change_type: ModificationType.MODIFY
diff: @@ -59,21 +59,21 @@ Unmatched [ in regex; marked by <-- HERE in m/abc[ <-- HERE ﬁ[.00./ at - line
 qr/(?[[[:word]]])/;
 EXPECT
 Assuming NOT a POSIX class since there is no terminating ':' in regex; marked by <-- HERE in m/(?[[[:word <-- HERE ]]])/ at - line 2.
-syntax error in (?[...]) in regex m/(?[[[:word]]])/ at - line 2.
+Unexpected ']' with no following ')' in (?[... in regex; marked by <-- HERE in m/(?[[[:word]] <-- HERE ])/ at - line 2.
 ########
 # NAME qr/(?[ [[:digit: ])/
 # OPTION fatal
 qr/(?[[[:digit: ])/;
 EXPECT
 Assuming NOT a POSIX class since no blanks are allowed in one in regex; marked by <-- HERE in m/(?[[[:digit: ] <-- HERE )/ at - line 2.
-syntax error in (?[...]) in regex m/(?[[[:digit: ])/ at - line 2.
+syntax error in (?[...]) in regex; marked by <-- HERE in m/(?[[[:digit: ]) <-- HERE / at - line 2.
 ########
 # NAME qr/(?[ [:digit: ])/
 # OPTION fatal
 qr/(?[[:digit: ])/
 EXPECT
 Assuming NOT a POSIX class since no blanks are allowed in one in regex; marked by <-- HERE in m/(?[[:digit: ] <-- HERE )/ at - line 2.
-syntax error in (?[...]) in regex m/(?[[:digit: ])/ at - line 2.
+syntax error in (?[...]) in regex; marked by <-- HERE in m/(?[[:digit: ]) <-- HERE / at - line 2.
 ########
 # NAME [perl #126141]
 # OPTION fatal

programming_language: Perl
filename: reg_mesg.t
change_type: ModificationType.MODIFY
diff: @@ -234,8 +234,9 @@ my @death =
  '/\b{gc}/' => "'gc' is an unknown bound type {#} m/\\b{gc{#}}/",
  '/\B{gc}/' => "'gc' is an unknown bound type {#} m/\\B{gc{#}}/",
 
- '/(?[[[::]]])/' => "Syntax error in (?[...]) in regex m/(?[[[::]]])/",
- '/(?[[[:w:]]])/' => "Syntax error in (?[...]) in regex m/(?[[[:w:]]])/",
+
+ '/(?[[[::]]])/' => "Unexpected ']' with no following ')' in (?[... {#} m/(?[[[::]]{#}])/",
+ '/(?[[[:w:]]])/' => "Unexpected ']' with no following ')' in (?[... {#} m/(?[[[:w:]]{#}])/",
  '/(?[[:w:]])/' => "",
  '/([.].*)[.]/'   => "",    # [perl #127582]
  '/[.].*[.]/'     => "",    # [perl #127604]
@@ -258,11 +259,12 @@ my @death =
  '/(?[ \p{foo} ])/' => 'Can\'t find Unicode property definition "foo" {#} m/(?[ \p{foo}{#} ])/',
  '/(?[ \p{ foo = bar } ])/' => 'Can\'t find Unicode property definition "foo = bar" {#} m/(?[ \p{ foo = bar }{#} ])/',
  '/(?[ \8 ])/' => 'Unrecognized escape \8 in character class {#} m/(?[ \8{#} ])/',
- '/(?[ \t ]/' => 'Syntax error in (?[...]) in regex m/(?[ \t ]/',
- '/(?[ [ \t ]/' => 'Syntax error in (?[...]) in regex m/(?[ [ \t ]/',
- '/(?[ \t ] ]/' => 'Syntax error in (?[...]) in regex m/(?[ \t ] ]/',
- '/(?[ [ ] ]/' => 'Syntax error in (?[...]) in regex m/(?[ [ ] ]/',
- '/(?[ \t + \e # This was supposed to be a comment ])/' => 'Syntax error in (?[...]) in regex m/(?[ \t + \e # This was supposed to be a comment ])/',
+ '/(?[ \t ]/' => "Unexpected ']' with no following ')' in (?[... {#} m/(?[ \\t ]{#}/",
+ '/(?[ [ \t ]/' => "Syntax error in (?[...]) {#} m/(?[ [ \\t ]{#}/",
+ '/(?[ \t ] ]/' => "Unexpected ']' with no following ')' in (?[... {#} m/(?[ \\t ]{#} ]/",
+ '/(?[ [ ] ]/' => "Syntax error in (?[...]) {#} m/(?[ [ ] ]{#}/",
+ '/(?[ \t + \e # This was supposed to be a comment ])/' =>
+    "Syntax error in (?[...]) {#} m/(?[ \\t + \\e # This was supposed to be a comment ]){#}/",
  '/(?[ ])/' => 'Incomplete expression within \'(?[ ])\' {#} m/(?[ {#}])/',
  'm/(?[[a-\d]])/' => 'False [] range "a-\d" {#} m/(?[[a-\d{#}]])/',
  'm/(?[[\w-x]])/' => 'False [] range "\w-" {#} m/(?[[\w-{#}x]])/',
@@ -452,10 +454,10 @@ my @death_utf8 = mark_as_utf8(
 
  '/ネ\p{}ネ/' => 'Empty \p{} {#} m/ネ\p{{#}}ネ/',
 
- '/ネ(?[[[:ネ]]])ネ/' => "Syntax error in (?[...]) in regex m/ネ(?[[[:ネ]]])ネ/",
- '/ネ(?[[[:ネ: ])ネ/' => "Syntax error in (?[...]) in regex m/ネ(?[[[:ネ: ])ネ/",
- '/ネ(?[[[::]]])ネ/' => "Syntax error in (?[...]) in regex m/ネ(?[[[::]]])ネ/",
- '/ネ(?[[[:ネ:]]])ネ/' => "Syntax error in (?[...]) in regex m/ネ(?[[[:ネ:]]])ネ/",
+ '/ネ(?[[[:ネ]]])ネ/' => "Unexpected ']' with no following ')' in (?[... {#} m/ネ(?[[[:ネ]]{#}])ネ/",
+ '/ネ(?[[[:ネ: ])ネ/' => "Syntax error in (?[...]) {#} m/ネ(?[[[:ネ: ])ネ{#}/",
+ '/ネ(?[[[::]]])ネ/' => "Unexpected ']' with no following ')' in (?[... {#} m/ネ(?[[[::]]{#}])ネ/",
+ '/ネ(?[[[:ネ:]]])ネ/' => "Unexpected ']' with no following ')' in (?[... {#} m/ネ(?[[[:ネ:]]{#}])ネ/",
  '/ネ(?[[:ネ:]])ネ/' => "",
  '/ネ(?[ネ])ネ/' =>  'Unexpected character {#} m/ネ(?[ネ{#}])ネ/',
  '/ネ(?[ + [ネ] ])/' => 'Unexpected binary operator \'+\' with no preceding operand {#} m/ネ(?[ +{#} [ネ] ])/',
@@ -468,8 +470,9 @@ my @death_utf8 = mark_as_utf8(
  '/(?[ \x{ネ} ])ネ/' => 'Non-hex character {#} m/(?[ \x{ネ{#}} ])ネ/',
  '/(?[ \p{ネ} ])/' => 'Can\'t find Unicode property definition "ネ" {#} m/(?[ \p{ネ}{#} ])/',
  '/(?[ \p{ ネ = bar } ])/' => 'Can\'t find Unicode property definition "ネ = bar" {#} m/(?[ \p{ ネ = bar }{#} ])/',
- '/ネ(?[ \t ]/' => 'Syntax error in (?[...]) in regex m/ネ(?[ \t ]/',
- '/(?[ \t + \e # ネ This was supposed to be a comment ])/' => 'Syntax error in (?[...]) in regex m/(?[ \t + \e # ネ This was supposed to be a comment ])/',
+ '/ネ(?[ \t ]/' => "Unexpected ']' with no following ')' in (?[... {#} m/ネ(?[ \\t ]{#}/",
+ '/(?[ \t + \e # ネ This was supposed to be a comment ])/' =>
+    "Syntax error in (?[...]) {#} m/(?[ \\t + \\e # ネ This was supposed to be a comment ]){#}/",
  'm/(*ネ)ネ/' => q<Unknown verb pattern 'ネ' {#} m/(*ネ){#}ネ/>,
  '/\cネ/' => "Character following \"\\c\" must be printable ASCII",
  '/\b{ネ}/' => "'ネ' is an unknown bound type {#} m/\\b{ネ{#}}/",

programming_language: Perl
filename: regex_sets.t
change_type: ModificationType.MODIFY
diff: @@ -158,13 +158,13 @@ for my $char ("٠", "٥", "٩") {
 	eval { $_ = '/(?[(\c]) /'; qr/$_/ };
 	like($@, qr/^Syntax error/, '/(?[(\c]) / should not panic');
 	eval { $_ = '(?[\c#]' . "\n])"; qr/$_/ };
-	like($@, qr/^Syntax error/, '/(?[(\c]) / should not panic');
+	like($@, qr/^Unexpected/, '/(?[(\c]) / should not panic');
 	eval { $_ = '(?[(\c])'; qr/$_/ };
 	like($@, qr/^Syntax error/, '/(?[(\c])/ should be a syntax error');
 	eval { $_ = '(?[(\c]) ]\b'; qr/$_/ };
-	like($@, qr/^Syntax error/, '/(?[(\c]) ]\b/ should be a syntax error');
+	like($@, qr/^Unexpected/, '/(?[(\c]) ]\b/ should be a syntax error');
 	eval { $_ = '(?[\c[]](])'; qr/$_/ };
-	like($@, qr/^Syntax error/, '/(?[\c[]](])/ should be a syntax error');
+	like($@, qr/^Unexpected/, '/(?[\c[]](])/ should be a syntax error');
 	like("\c#", qr/(?[\c#])/, '\c# should match itself');
 	like("\c[", qr/(?[\c[])/, '\c[ should match itself');
 	like("\c\ ", qr/(?[\c\])/, '\c\ should match itself');

programming_language: Perl