Zoom RCE from Pwn2Own 2021

undefined4 __fastcall AESDecode(undefined4 *param_1, undefined4 *param_2) {
  char cVar1;
  int iVar2;
  undefined4 uVar3;
  int iVar4;
  LogMessage *this;
  int extraout_EDX;
  int iVar5;
  LogMessage local_180 [176];
  LogMessage local_d0 [176];
  int local_20;
  undefined4 *local_1c;
  int local_18;
  int local_14;
  undefined4 local_8;
  undefined4 uStack4;
  
  uStack4 = 0x170;
  local_8 = 0x101ba696;
  iVar5 = 0;
  local_14 = 0;
  local_1c = param_2;
  cVar1 = FUN_101ba34a();

  if (cVar1 == '\0') {
    return 1;
  }

  if ((*(uint *)(extraout_EDX + 4) < 0x20) || (*(uint *)(extraout_EDX + 0xc) < 0x10)) {
    iVar5 = logging::GetMinLogLevel();
    
    if (iVar5 < 2) {
      logging::LogMessage::LogMessage
                (local_d0, "c:\\ZoomCode\\client_sdk_2019_kof\\Common\\include\\zoom_crypto_util.h",
                 0x1d6, 1);
      local_8 = 0;
      local_14 = 1;
      uVar3 = log_message(iVar5 + 8, "[AESDecode] Failed. Key len or IV len is incorrect.", " ");
      log_message(uVar3);
      logging::LogMessage::~LogMessage(local_d0);

      return 1;
    }

    return 1;
  }

  local_14 = param_1[2];
  local_18 = 0;
  iVar2 = EVP_CIPHER_CTX_new();

  if (iVar2 == 0) {
    return 0xc;
  }

  local_20 = iVar2;
  EVP_CIPHER_CTX_reset(iVar2);
  uVar3 = EVP_aes_256_cbc(0, *local_1c, local_1c[2], 0);
  iVar4 = EVP_CipherInit_ex(iVar2, uVar3);

  if (iVar4 < 1) {
    iVar2 = logging::GetMinLogLevel();

    if (iVar2 < 2) {
      logging::LogMessage::LogMessage
                (local_d0,"c:\\ZoomCode\\client_sdk_2019_kof\\Common\\include\\zoom_crypto_util.h",
                 0x1e8, 1);
      iVar5 = 2;
      local_8 = 1;
      local_14 = 2;
      uVar3 = log_message(iVar2 + 8, "[AESDecode] EVP_CipherInit_ex Failed.", " ");
      log_message(uVar3);
    }
LAB_101ba758:
    if (iVar5 == 0) goto LAB_101ba852;
    this = local_d0;
  } else {
    iVar4 = EVP_CipherUpdate(iVar2, local_14, &local_18, *param_1, param_1[1]);

    if (iVar4 < 1) {
      iVar2 = logging::GetMinLogLevel();

      if (iVar2 < 2) {
        logging::LogMessage::LogMessage
                  (local_d0,"c:\\ZoomCode\\client_sdk_2019_kof\\Common\\include\\zoom_crypto_util.h",
                  0x1f0, 1);
        iVar5 = 4;
        local_8 = 2;
        local_14 = 4;
        uVar3 = log_message(iVar2 + 8, "[AESDecode] EVP_CipherUpdate Failed.", " ");
        log_message(uVar3);
      }
      goto LAB_101ba758;
    }

    param_1[3] = local_18;
    iVar4 = EVP_CipherFinal_ex(iVar2, local_14 + local_18, &local_18);

    if (0 < iVar4) {
      param_1[3] = param_1[3] + local_18;
      EVP_CIPHER_CTX_free(iVar2);
      return 0;
    }

    iVar2 = logging::GetMinLogLevel();
    if (iVar2 < 2) {
      logging::LogMessage::LogMessage
                (local_180,"c:\\ZoomCode\\client_sdk_2019_kof\\Common\\include\\zoom_crypto_util.h",
                 0x1fb, 1);
      iVar5 = 8;
      local_8 = 3;
      local_14 = 8;
      uVar3 = log_message(iVar2 + 8, "[AESDecode] EVP_CipherFinal_ex Failed.", " ");
      log_message(uVar3);
    }

    if (iVar5 == 0) goto LAB_101ba852;
    this = local_180;
  }
  
  logging::LogMessage::~LogMessage(this);
LAB_101ba852:
  EVP_CIPHER_CTX_free(local_20);
  return 0xc;
}

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https://sector7.computest.nl/post/2021-08-zoom/ 

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