1 From 31106a073882656a2a5ab56c4ce2847e9a334c3c Mon Sep 17 00:00:00 2001

     2 From: Daniel Stenberg <[email protected]>

     3 Date: Wed, 28 Sep 2016 10:15:34 +0200

     4 Subject: [PATCH] aprintf: detect wrap-around when growing allocation

     5 

     6 On 32bit systems we could otherwise wrap around after 2GB and allocate 0

     7 bytes and crash.

     8 

     9 CVE-2016-8618

    10 

    11 Bug: https://curl.haxx.se/docs/adv_20161102D.html

    12 Reported-by: Cure53

    13 ---

    14  lib/mprintf.c | 9 ++++++---

    15  1 file changed, 6 insertions(+), 3 deletions(-)

    16 

    17 --- lib/mprintf.c

    18 +++ lib/mprintf.c

    19 @@ -1034,20 +1034,23 @@ static int alloc_addbyter(int output, FILE *data)

    20      }

    21      infop->alloc = 32;

    22      infop->len =0;

    23    }

    24    else if(infop->len+1 >= infop->alloc) {

    25 -    char *newptr;

    26 +    char *newptr = NULL;

    27 +    size_t newsize = infop->alloc*2;

    28  

    29 -    newptr = realloc(infop->buffer, infop->alloc*2);

    30 +    /* detect wrap-around or other overflow problems */

    31 +    if(newsize > infop->alloc)

    32 +      newptr = realloc(infop->buffer, newsize);

    33  

    34      if(!newptr) {

    35        infop->fail = 1;

    36        return -1; /* fail */

    37      }

    38      infop->buffer = newptr;

    39 -    infop->alloc *= 2;

    40 +    infop->alloc = newsize;

    41    }

    42  

    43    infop->buffer[ infop->len ] = outc;

    44  

    45    infop->len++;

    46 -- 

    47 2.9.3

    48