From 16bb1de3a6addec1c07b9ffc3fcd616744a3f15c Mon Sep 17 00:00:00 2001 From: Mounir IDRASSI Date: Sat, 5 Aug 2023 10:55:46 +0200 Subject: Security: ensure that XTS primary key is different from secondary key when creating volumes This is unlikely to happen thanks to random generator properties but we much add this check to prevent an attack described in page 3 of https://csrc.nist.gov/csrc/media/Projects/crypto-publication-review-project/documents/initial-comments/sp800-38e-initial-public-comments-2021.pdf --- src/Common/Volumes.c | 9 +++++++++ src/Core/VolumeCreator.cpp | 5 +++++ 2 files changed, 14 insertions(+) diff --git a/src/Common/Volumes.c b/src/Common/Volumes.c index 40be21c8..5b1d4065 100644 --- a/src/Common/Volumes.c +++ b/src/Common/Volumes.c @@ -909,6 +909,15 @@ int CreateVolumeHeaderInMemory (HWND hwndDlg, BOOL bBoot, char *header, int ea, retVal = ERR_CIPHER_INIT_WEAK_KEY; goto err; } + + // check that first half of keyInfo.master_keydata is different from the second half. If they are the same return error + // cf CCSS,NSA comment at page 3: https://csrc.nist.gov/csrc/media/Projects/crypto-publication-review-project/documents/initial-comments/sp800-38e-initial-public-comments-2021.pdf + if (memcmp (keyInfo.master_keydata, &keyInfo.master_keydata[bytesNeeded/2], bytesNeeded/2) == 0) + { + crypto_close (cryptoInfo); + retVal = ERR_CIPHER_INIT_WEAK_KEY; + goto err; + } } else { diff --git a/src/Core/VolumeCreator.cpp b/src/Core/VolumeCreator.cpp index d5caa846..5f19a66d 100644 --- a/src/Core/VolumeCreator.cpp +++ b/src/Core/VolumeCreator.cpp @@ -298,6 +298,11 @@ namespace VeraCrypt // Master data key MasterKey.Allocate (options->EA->GetKeySize() * 2); RandomNumberGenerator::GetData (MasterKey); + // check that first half of MasterKey is different from its second half. If they are the same, through an exception + // cf CCSS,NSA comment at page 3: https://csrc.nist.gov/csrc/media/Projects/crypto-publication-review-project/documents/initial-comments/sp800-38e-initial-public-comments-2021.pdf + if (memcmp (MasterKey.Ptr(), MasterKey.Ptr() + MasterKey.Size() / 2, MasterKey.Size() / 2) == 0) + throw AssertionFailed (SRC_POS); + headerOptions.DataKey = MasterKey; // PKCS5 salt -- cgit v1.2.3