[BRLY-LOGOFAIL-2023-015] Out-of-bounds Read in DXE driver

Summary

Binarly REsearch Team has discovered a OOB Read vulnerability in DXE driver. Improper validation of PNG chunk length during PNG file processing in AMI firmware leads to OOB read.

Vulnerability Information

 
• BINARLY internal vulnerability identifier: BRLY-LOGOFAIL-2023-015  
• CVSS v3.1: 3.2 Low AV:L/AC:L/PR:H/UI:N/S:C/C:N/I:L/A:N

Affected modules with confirmed impact by Binarly REsearch Team

Potential impact

This vulnerability will not lead to exploitation, however, it may lead to unexpected behaviour during PNG file processing.

Vulnerability description

The pseudocode of the vulnerable function is shown below:

unsigned __int64 __fastcall GetChunk(_DWORD *Length, _QWORD *ChunkPtr, _DWORD *ChunkType, _DWORD *a4)
{
  unsigned __int64 v5; // rbx
  unsigned __int8 *ZeroPool; // rax
  unsigned __int8 *v10; // rdi
  __int64 v11; // rdx
  unsigned __int8 *v12; // rcx
  __int64 v13; // r9
  __int64 v14; // r8
  __int64 v15; // rdx
  __int64 v16; // r8
  unsigned __int8 *v17; // rcx
  __int64 v18; // rdx
  int v19; // ecx
  UINTN Length1; // rcx
  _BYTE *v21; // rax
  __int64 v22; // r8
  __int64 v23; // r10
  __int64 v24; // r9
  __int64 v25; // rdx
  unsigned __int8 *v26; // rcx
  int v27; // ecx
  int v28; // eax
  unsigned __int8 *v30; // [rsp+20h] [rbp-28h] BYREF

  v5 = 0i64;
  ZeroPool = (unsigned __int8 *)AllocateZeroPool(4ui64);
  v30 = ZeroPool;
  v10 = ZeroPool;
  if ( ZeroPool )
  {
    v11 = GlobalImagePtr;
    v12 = ZeroPool;
    v13 = 4i64;
    v14 = GlobalImagePtr - (_QWORD)ZeroPool;
    do
    {
      *v12 = v12[v14];
      ++v12;
      --v13;
    }
    while ( v13 );
    v15 = v11 + 4;
    v16 = 4i64;
    *Length = ZeroPool[3] + ((ZeroPool[2] + ((ZeroPool[1] + (*ZeroPool << 8)) << 8)) << 8);
    v17 = ZeroPool;
    do
    {
      *v17 = v17[v15 - (_QWORD)ZeroPool];
      ++v17;
      --v16;
    }
    while ( v16 );
    v18 = v15 + 4;
    v19 = ZeroPool[1] + (*ZeroPool << 8);
    GlobalImagePtr = v18;
    *ChunkType = ZeroPool[3] + ((ZeroPool[2] + (v19 << 8)) << 8);
    Length1 = (unsigned int)*Length;
    if ( (_DWORD)Length1 )
    {
      v21 = AllocateZeroPool(Length1);
      *ChunkPtr = v21;
      if ( !v21 )
      {
        v5 = 0x8000000000000009ui64;
LABEL_18:
        sub_4654(&v30);
        return v5;
      }
      LODWORD(Length1) = *Length;
      v18 = GlobalImagePtr;
      if ( *Length )
      {
        v22 = 0i64;
        v23 = (unsigned int)Length1;
        do
        {
          v21[v22] = *(_BYTE *)(v22 + v18);
          ++v22;
          --v23;
        }
        while ( v23 );
      }
    }
    else
    {
      *ChunkPtr = 0i64;
    }
    v24 = 4i64;
    // BRLY-LOGOFAIL-2023-015: Length is read from chunk and added without validation to GlobalImagePtr (v25)
    v25 = (unsigned int)Length1 + v18;
    v26 = v10;
    do
    {
      *v26 = v26[v25 - (_QWORD)v10];
      ++v26;
      --v24;
    }
    while ( v24 );
    v27 = v10[2];
    v28 = v10[1];
    GlobalImagePtr = v25 + 4;
    *a4 = v10[3] + ((v27 + ((v28 + (*v10 << 8)) << 8)) << 8);
    goto LABEL_18;
  }
  return 0x8000000000000009ui64;
}

As we can see from the pseudocode, a PNG chunk length (stored in the variable Length1) is used without validation to update the GlobalImagePtr variable pointer.

Disclosure timeline

This bug is subject to a 90 day disclosure deadline. After 90 days elapsed or a patch has been made broadly available (whichever is earlier), the bug report will become visible to the public.

Acknowledgements

Binarly REsearch Team