Header bannerHeader banner
Advisory ID:
BRLY-LOGOFAIL-2023-011

[BRLY-LOGOFAIL-2023-011] Memory contents leak / information disclosure vulnerability in DXE driver

June 20, 2024
Severity:
Medium
CVSS Score
6
Public Disclosure Date:
June 19, 2024
CVE ID:
CVE-2023-40238

Summary

BINARLY efiXplorer team has discovered multiple memory leaks / information disclosure vulnerabilities in the DXE driver due to improper input validation during PCX file processing in Insyde firmware.

Vendors Affected

Affected Products

Yoga 7 14IAL7
,

Potential Impact

An attacker with local privileged access can exploit this vulnerability to read the contents of the physical memory and use this information to exploit other vulnerabilities in DXE. A malicious code installed as a result of the vulnerability exploitation in a DXE driver could survive across an operating system (OS) boot process and runtime or modify NVRAM area on SPI flash storage (to gain persistence on target platform). Additionally, this vulnerability potentially could be used by threat actors to bypass OS security mechanisms (modify privileged memory or runtime variables), influence on the OS boot process, and in some cases would allow an attacker to hook or modify EFI Runtime services.

Summary

BINARLY efiXplorer team has discovered multiple memory leaks / information disclosure vulnerabilities in the DXE driver due to improper input validation during PCX file processing in Insyde firmware.

Vulnerability Information

     
  • BINARLY internal vulnerability identifier: BRLY-LOGOFAIL-2023-011  
  • Insyde PSIRT assigned CVE identifier: CVE-2023-40238  
  • CVSS v3.1: 6.0 Medium AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:N/A:N

Affected modules with confirmed impact by Binarly team

Module name Module GUID Module SHA256
PcxDecoderDxe a8f634a5-28f1-4456-a9d5-7e24b99bdb65 31106727d3ca68626e174fb6d592187c2583bd9b6bb4080b02af419e1f515896

Potential impact

An attacker with local privileged access can exploit this vulnerability to read the contents of the physical memory and use this information to exploit other vulnerabilities in DXE. A malicious code installed as a result of the vulnerability exploitation in a DXE driver could survive across an operating system (OS) boot process and runtime or modify NVRAM area on SPI flash storage (to gain persistence on target platform). Additionally, this vulnerability potentially could be used by threat actors to bypass OS security mechanisms (modify privileged memory or runtime variables), influence on the OS boot process, and in some cases would allow an attacker to hook or modify EFI Runtime services.

Vulnerability description

The pseudocode of the vulnerable function is shown below:

unsigned __int64 __fastcall DecodePCX(
        PCXHeader *Image,
        __int64 ImageSize,
        __int64 *a3,
        unsigned __int64 *a4,
        _QWORD *a5,
        unsigned __int64 *a6)
{
  __int64 v6; // rbx
  unsigned __int64 v8; // r14
  __int64 Index; // rbp
  unsigned __int64 v10; // rsi
  __int64 v11; // r15
  char *v12; // rdx
  unsigned __int64 i; // rcx
  char v14; // al
  unsigned __int64 v15; // r15
  __int64 v16; // rcx
  __int64 v17; // rax
  __int64 v18; // rdx
  __int64 v19; // rcx
  __int64 v20; // r8
  __int64 v21; // r9
  __int64 v22; // r12
  unsigned __int64 v23; // r14
  __int64 v24; // rcx
  __int64 v25; // rax
  __int64 v26; // rdx
  unsigned __int64 v27; // rcx
  unsigned __int64 v28; // r8
  EFI_PHYSICAL_ADDRESS v29; // rsi
  _QWORD *v30; // rax
  __int64 v31; // r9
  unsigned __int64 v32; // r10
  EFI_PHYSICAL_ADDRESS v34; // r15
  unsigned __int64 v35; // rax
  unsigned __int64 v36; // r11
  EFI_PHYSICAL_ADDRESS v37; // r15
  char v38; // al
  __int64 v40; // rcx
  __int64 v41; // rdx
  unsigned __int64 v42; // rdx
  unsigned __int64 j; // r8
  __int64 bytes_per_line; // [rsp+20h] [rbp-458h]
  unsigned __int64 v45; // [rsp+30h] [rbp-448h]
  _BYTE v46[1080]; // [rsp+40h] [rbp-438h]
  unsigned __int64 Total; // [rsp+480h] [rbp+8h]

  v6 = 0i64;
  v8 = 0i64;
  Index = 0i64;
  v10 = 0i64;
  if ( *&Image->id != 1290 )
    return 0x8000000000000003ui64;
  if ( Image->encoding != 1 )
    return 0x8000000000000003ui64;
  if ( Image->bits_per_px != 8 )
    return 0x8000000000000003ui64;
    
  // Root cause for all vulnerabilities is here:
  // Image->planes and Image->bytes_per_line are not validated
  // => Total is controllable by the attacker
  // It will lead to OOB Reads further

  // BRLY-LOGOFAIL-2023-011: Improper input validation leads to OOB Read vulnerabilities
    
  *a6 = Image->x_max - Image->x_min + 1;
  v11 = Image->y_max - Image->y_min + 1;
  *a5 = v11;
  bytes_per_line = Image->bytes_per_line;
  v12 = Image + ImageSize - 767;
  Total = bytes_per_line * Image->planes;
  for ( i = 0i64; i < 0x100; ++i )
  {
    v46[4 * i + 2] = *(v12 - 1);
    v14 = *v12;
    v12 += 3;
    v46[4 * i + 1] = v14;
    v46[4 * i] = *(v12 - 2);
    v46[4 * i + 3] = 0;
  }
  v15 = 4 * *a6 * v11;
  v45 = v15;
  if ( v15 >= 0x100000000i64 )
    return 0x8000000000000003ui64;
  if ( sub_964(i, v12, a3, a4) )
    v17 = sub_9B4(v16, (v15 >> 12) + ((v15 & 0xFFF) != 0));
  else
    v17 = sub_9EC(v16, v15);
  v22 = v17;
  if ( v17 )
  {
    if ( (Image->planes - 3) > 1u || Image->bits_per_px != 8 )
    {
      v40 = *a6;
      if ( *a5 * *a6 )
      {
        do
        {
          // Vulnerability:
          // if v10 == v40, the Index will be incremented by a controllable
          // number of times since attacker is controlling
          // Total = Image->bytes_per_line * Image->planes;
          // and fields Image->bytes_per_line and Image->planes are unvalidated
          // So, we have OOB Read here: Image->Buffer[Index]
          if ( v10 == v40 )
          {
            if ( v10 < Total )
            {
              v40 = *a6;
              Index += Total - v10;
            }
            v10 = 0i64;
          }
          v41 = Image->Buffer[Index];
          if ( (Image->Buffer[Index] & 0xC0) == 0xC0 )
          {
            v42 = v41 & 0x3F;
            ++Index;
            for ( j = 0i64; j < v42; ++j )
            {
              ++v10;
              *(v17 + 4 * v8++) = *&v46[4 * Image->Buffer[Index]];
              v40 = *a6;
              if ( v10 == *a6 )
                break;
            }
          }
          else
          {
            *(v17 + 4 * v8++) = *&v46[4 * v41];
            v40 = *a6;
            ++v10;
          }
          ++Index;
        }
        while ( v8 < *a5 * v40 );
      }
      *a3 = v17;
      *a4 = v15;
      return 0i64;
    }
    v23 = Total + 50;
    if ( sub_964(v19, v18, v20, v21) )
      v25 = sub_9B4(v24, (v23 >> 12) + ((v23 & 0xFFF) != 0));
    else
      v25 = sub_9EC(v24, v23);
    v29 = v25;
    if ( v25 )
      v29 = sub_310(v25, v23);
    if ( v29 )
    {
      v30 = a5;
      v31 = 0i64;
      if ( *a5 )
      {
        v32 = Total;
        while ( 1 )
        {
          v27 = 0i64;
          if ( v32 )
          {
            do
            {
              // Vulnerability:
              // The Index will be incremented by a controllable
              // number of times since attacker is controlling
              // Total = Image->bytes_per_line * Image->planes;
              // and fields Image->bytes_per_line and Image->planes are unvalidated
              // So, we have OOB Read here: Image->Buffer[Index]
              v28 = Image->Buffer[Index];
              v26 = 1i64;
              if ( (Image->Buffer[Index] & 0xC0) == 0xC0 )
              {
                LOBYTE(v28) = Image->Buffer[Index + 1];
                v26 = Image->Buffer[Index++] & 0x3F;
              }
              while ( v27 < v32 )
              {
                if ( !v26-- )
                  break;
                *(v27 + v29) = v28;
                ++v27;
              }
              ++Index;
            }
            while ( v27 < v32 );
            v30 = a5;
          }
          if ( Image->planes == 3 )
          {
            v28 = 0i64;
            if ( *a6 )
            {
              v34 = v29 + 2 * bytes_per_line;
              do
              {
                v26 = v34 + v28;
                *(v22 + 4 * (v28 + v31 * *a6) + 2) = *(v34 + v28 - 2 * bytes_per_line);
                *(v22 + 4 * (v28 + v31 * *a6) + 1) = *(v34 + v28 - bytes_per_line);
                v27 = v28 + v31 * *a6;
                *(v22 + 4 * v27) = *(v34 + v28);
                v35 = v28 + v31 * *a6;
                ++v28;
                *(v22 + 4 * v35 + 3) = -1;
              }
              while ( v28 < *a6 );
LABEL_37:
              v30 = a5;
              v32 = Total;
            }
          }
          else
          {
            v36 = 0i64;
            if ( *a6 )
            {
              v37 = v29 + 2 * bytes_per_line;
              v28 = -bytes_per_line;
              do
              {
                v26 = v37 + v36;
                *(v22 + 4 * (v36 + v31 * *a6) + 2) = *(v37 + v36 - 2 * bytes_per_line);
                *(v22 + 4 * (v36 + v31 * *a6) + 1) = *(v37 + v36 - bytes_per_line);
                *(v22 + 4 * (v36 + v31 * *a6)) = *(v37 + v36);
                v38 = *(v37 + v36 + bytes_per_line);
                v27 = v36 + v31 * *a6;
                ++v36;
                *(v22 + 4 * v27 + 3) = v38;
              }
              while ( v36 < *a6 );
              goto LABEL_37;
            }
          }
          if ( ++v31 >= *v30 )
          {
            v23 = Total + 50;
            v15 = v45;
            break;
          }
        }
      }
      *a3 = v22;
      *a4 = v15;
      if ( sub_964(v27, v26, v28, v31) )
      {
        LOBYTE(v6) = (v23 & 0xFFF) != 0;
        gBS->FreePages(v29, (v23 >> 12) + v6);
      }
      else
      {
        (gBS->FreePool)(v29);
      }
      return 0i64;
    }
  }
  return 0x8000000000000009ui64;
}

As we can see from the pseudocode, Image->planes and Image->bytes_per_line values are not validated. As a result, the Total value is controllable by the attacker and unchecked value.

The fact that Total is controlled by the attacker and unchecked can lead to OOB read at 3 locations (documented in the pseudocode above).

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.

Disclosure Activity Date (YYYY-mm-dd)
Lenovo PSIRT is notified 2023-06-21
Lenovo ID (LEN-132940) is assigned 2023-06-22
CERT/CC is notified 2023-07-10
Insyde PSIRT confirmed reported issues 2023-09-10
Insyde PSIRT assigned CVE ID 2023-11-27
Insyde advisory release date 2023-12-06
BINARLY public disclosure date 2024-06-19

Acknowledgements

BINARLY efiXplorer team

Tags
Vulnerability
supply chain
FWHunt
See if you are impacted now with our Firmware Vulnerability Scanner