TEAMCR@K

* 공통 사항: 취약한 bash 버전의 쉘을 사용하고 있어야 함

1. 파싱 오류로 인한 보안 취약점 노출: 특정 프로세스를 생성하는 등의 행위를 하는 모듈이 동작해야 함 (Ex: Enabled CGI module on the apache web server)

2. 메모리 실행 오류로 인한 보안 취약점 노출: 위의 공통 사항과 동일

Bug-Description:

When bash is parsing a function definition that contains a here-document
delimited by end-of-file (or end-of-string), it leaves the closing delimiter
uninitialized.  This can result in an invalid memory access when the parsed
function is later copied.

*** ../bash-4.3.28/make_cmd.c	2011-12-16 08:08:01.000000000 -0500
--- make_cmd.c	2014-10-02 11:24:23.000000000 -0400
***************
*** 693,696 ****
--- 693,697 ----
    temp->redirector = source;
    temp->redirectee = dest_and_filename;
+   temp->here_doc_eof = 0;
    temp->instruction = instruction;
    temp->flags = 0;
*** ../bash-4.3.28/copy_cmd.c	2009-09-11 16:28:02.000000000 -0400
--- copy_cmd.c	2014-10-02 11:24:23.000000000 -0400
***************
*** 127,131 ****
      case r_reading_until:
      case r_deblank_reading_until:
!       new_redirect->here_doc_eof = savestring (redirect->here_doc_eof);
        /*FALLTHROUGH*/
      case r_reading_string:
--- 127,131 ----
      case r_reading_until:
      case r_deblank_reading_until:
!     new_redirect->here_doc_eof = redirect->here_doc_eof ? savestring (redirect->here_doc_eof) : 0;

Bug-Description:

A combination of nested command substitutions and function importing from
the environment can cause bash to execute code appearing in the environment
variable value following the function definition.

*** ../bash-4.3.29/parse.y	2014-10-01 12:58:43.000000000 -0400
--- parse.y	2014-10-03 14:48:59.000000000 -0400
***************
*** 2539,2542 ****
--- 2539,2552 ----
  }
  
+ char *
+ parser_remaining_input ()
+ {
+   if (shell_input_line == 0)
+     return 0;
+   if (shell_input_line_index < 0 || shell_input_line_index >= shell_input_line_len)
+     return '\0';	/* XXX */
+   return (shell_input_line + shell_input_line_index);
+ }
+ 

Bug-Description:

Under certain circumstances, bash can incorrectly save a lookahead character and
return it on a subsequent call, even when reading a new line.

Patch (apply with `patch -p0'):

*** ../bash-4.3.25/parse.y	2014-07-30 10:14:31.000000000 -0400
--- parse.y	2014-09-25 20:20:21.000000000 -0400
***************
*** 2954,2957 ****
--- 2954,2959 ----
    word_desc_to_read = (WORD_DESC *)NULL;
  
+   eol_ungetc_lookahead = 0;
+ 
    current_token = '\n';		/* XXX */
    last_read_token = '\n';
*** ../bash-4.3.25/y.tab.c	2014-07-30 10:14:32.000000000 -0400
--- y.tab.c	2014-09-25 20:21:48.000000000 -0400
***************
*** 5266,5269 ****
--- 5266,5271 ----
    word_desc_to_read = (WORD_DESC *)NULL;
  
+   eol_ungetc_lookahead = 0;
+ 
    current_token = '\n';		/* XXX */
    last_read_token = '\n';

Bug-Description:

There are two local buffer overflows in parse.y that can cause the shell
to dump core when given many here-documents attached to a single command
or many nested loops.

Patch (apply with `patch -p0'):

*** ../bash-4.3-patched/parse.y	2014-09-25 23:02:35.000000000 -0400
--- parse.y	2014-09-29 16:47:03.000000000 -0400
***************
*** 169,172 ****
--- 169,175 ----
  static int reserved_word_acceptable __P((int));
  static int yylex __P((void));
+ 
+ static void push_heredoc __P((REDIRECT *));
+ static char *mk_alexpansion __P((char *));
  static int alias_expand_token __P((char *));
  static int time_command_acceptable __P((void));
***************
*** 266,270 ****
  /* Variables to manage the task of reading here documents, because we need to
     defer the reading until after a complete command has been collected. */
! static REDIRECT *redir_stack[10];
  int need_here_doc;
  
--- 269,275 ----
  /* Variables to manage the task of reading here documents, because we need to
     defer the reading until after a complete command has been collected. */
! #define HEREDOC_MAX 16
! 
! static REDIRECT *redir_stack[HEREDOC_MAX];
  int need_here_doc;
+ 
+ static void push_heredoc __P((REDIRECT *));
+ static char *mk_alexpansion __P((char *));

+ static void

+ push_heredoc (r)
+      REDIRECT *r;
+ {
+   if (need_here_doc >= HEREDOC_MAX)
+     {
+       last_command_exit_value = EX_BADUSAGE;
+       need_here_doc = 0;
+       report_syntax_error (_("maximum here-document count exceeded"));
+       reset_parser ();
+       exit_shell (last_command_exit_value);
+     }
+   redir_stack[need_here_doc++] = r;
+ }
+ 

Bug-Description:

There are two local buffer overflows in parse.y that can cause the shell
to dump core when given many here-documents attached to a single command
or many nested loops.

*** ../bash-4.3-patched/parse.y	2014-09-25 23:02:35.000000000 -0400
--- parse.y	2014-09-29 16:47:03.000000000 -0400
***************
*** 169,172 ****
--- 169,175 ----
  static int reserved_word_acceptable __P((int));
  static int yylex __P((void));
+ 
+ static void push_heredoc __P((REDIRECT *));
+ static char *mk_alexpansion __P((char *));
  static int alias_expand_token __P((char *));
  static int time_command_acceptable __P((void));
***************
*** 266,270 ****
  /* Variables to manage the task of reading here documents, because we need to
     defer the reading until after a complete command has been collected. */
! static REDIRECT *redir_stack[10];
  int need_here_doc;
  
--- 269,275 ----
  /* Variables to manage the task of reading here documents, because we need to
     defer the reading until after a complete command has been collected. */
! #define HEREDOC_MAX 16
! 
! static REDIRECT *redir_stack[HEREDOC_MAX];
  int need_here_doc;
  
***************
*** 308,312 ****
     index is decremented after a case, select, or for command is parsed. */
  #define MAX_CASE_NEST	128
! static int word_lineno[MAX_CASE_NEST];
  static int word_top = -1;
  
--- 313,317 ----
     index is decremented after a case, select, or for command is parsed. */
  #define MAX_CASE_NEST	128
! static int word_lineno[MAX_CASE_NEST+1];
  static int word_top = -1;
  

! #line 785 "/usr/src/local/chet/src/bash/bash-4.3.28/parse.y"
      {
  			  (yyval.command) = make_for_command ((yyvsp[(2) - (6)].word), add_string_to_list ("\"$@\"", (WORD_LIST *)NULL), (yyvsp[(5) - (6)].command), word_lineno[word_top]);
***************
*** 2707,2711 ****

http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2014-6271

https://securityblog.redhat.com/2014/09/24/bash-specially-crafted-environment-variables-code-injection-attack/

env x='() { : ; } ; echo vulnerable'