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Use 12 bytes nonce for crypto #2174

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merged 2 commits into from
Aug 17, 2020
Merged

Use 12 bytes nonce for crypto #2174

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dd6a8b0
Use 12 bytes nonce for crypto
pan-apple Aug 14, 2020
f8a002e
Absolute check
pan-apple Aug 14, 2020
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43 changes: 31 additions & 12 deletions src/transport/SecureSession.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,7 @@

#include <core/CHIPEncoding.h>
#include <crypto/CHIPCryptoPAL.h>
#include <support/BufBound.h>
#include <support/CodeUtils.h>
#include <transport/MessageHeader.h>
#include <transport/SecureSession.h>
Expand All @@ -36,6 +37,8 @@ namespace {

const char * kManualKeyExchangeChannelInfo = "Manual Key Exchanged Channel";

constexpr size_t kAESCCMIVLen = 12;

} // namespace

using namespace Crypto;
Expand Down Expand Up @@ -104,33 +107,46 @@ void SecureSession::Reset(void)
memset(mKey, 0, sizeof(mKey));
}

uint64_t SecureSession::GetIV(const MessageHeader & header)
CHIP_ERROR SecureSession::GetIV(const MessageHeader & header, uint8_t * iv, size_t len)
{
// The message ID is a 4 byte value. It's assumed that the security
// session will be rekeyed before (or on) message ID rollover.
uint64_t IV = header.GetMessageId() & 0xffffffff;
CHIP_ERROR err = CHIP_NO_ERROR;
uint64_t nodeID = 0;
uint32_t messageID = 0;

BufBound bbuf(iv, len);

VerifyOrExit(len == kAESCCMIVLen, err = CHIP_ERROR_INVALID_ARGUMENT);

if (header.GetSourceNodeId().HasValue())
{
uint64_t nodeID = header.GetSourceNodeId().Value();
IV |= nodeID & 0xffffffff00000000;
IV |= (nodeID & 0xffffffff) << 32;
nodeID = header.GetSourceNodeId().Value();
}
return IV;

VerifyOrExit(bbuf.Put(&nodeID, sizeof(nodeID)) == sizeof(nodeID), err = CHIP_ERROR_NO_MEMORY);

messageID = header.GetMessageId();
VerifyOrExit(bbuf.Put(&messageID, sizeof(messageID)) == sizeof(nodeID) + sizeof(messageID), err = CHIP_ERROR_NO_MEMORY);
VerifyOrExit(bbuf.Fit(), err = CHIP_ERROR_NO_MEMORY);

exit:
return err;
}

CHIP_ERROR SecureSession::Encrypt(const unsigned char * input, size_t input_length, unsigned char * output, MessageHeader & header)
{
CHIP_ERROR error = CHIP_NO_ERROR;
uint64_t tag = 0;
uint64_t IV = SecureSession::GetIV(header);
uint8_t IV[kAESCCMIVLen];

VerifyOrExit(mKeyAvailable, error = CHIP_ERROR_INVALID_USE_OF_SESSION_KEY);
VerifyOrExit(input != NULL, error = CHIP_ERROR_INVALID_ARGUMENT);
VerifyOrExit(input_length > 0, error = CHIP_ERROR_INVALID_ARGUMENT);
VerifyOrExit(output != NULL, error = CHIP_ERROR_INVALID_ARGUMENT);

error = AES_CCM_encrypt(input, input_length, NULL, 0, mKey, sizeof(mKey), (const unsigned char *) &IV, sizeof(IV), output,
error = GetIV(header, IV, sizeof(IV));
SuccessOrExit(error);

error = AES_CCM_encrypt(input, input_length, NULL, 0, mKey, sizeof(mKey), (const unsigned char *) IV, sizeof(IV), output,
(unsigned char *) &tag, sizeof(tag));
SuccessOrExit(error);

Expand All @@ -146,15 +162,18 @@ CHIP_ERROR SecureSession::Decrypt(const unsigned char * input, size_t input_leng
CHIP_ERROR error = CHIP_NO_ERROR;
size_t taglen = header.GetTagLength();
const uint8_t * tag = header.GetTag();
uint64_t IV = SecureSession::GetIV(header);
uint8_t IV[kAESCCMIVLen];

VerifyOrExit(mKeyAvailable, error = CHIP_ERROR_INVALID_USE_OF_SESSION_KEY);
VerifyOrExit(input != NULL, error = CHIP_ERROR_INVALID_ARGUMENT);
VerifyOrExit(input_length > 0, error = CHIP_ERROR_INVALID_ARGUMENT);
VerifyOrExit(output != NULL, error = CHIP_ERROR_INVALID_ARGUMENT);

error = GetIV(header, IV, sizeof(IV));
SuccessOrExit(error);

error = AES_CCM_decrypt(input, input_length, NULL, 0, (const unsigned char *) tag, taglen, mKey, sizeof(mKey),
(const unsigned char *) &IV, sizeof(IV), output);
(const unsigned char *) IV, sizeof(IV), output);
exit:
return error;
}
Expand Down
2 changes: 1 addition & 1 deletion src/transport/SecureSession.h
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Original file line number Diff line number Diff line change
Expand Up @@ -129,7 +129,7 @@ class DLL_EXPORT SecureSession
bool mKeyAvailable;
uint8_t mKey[kAES_CCM128_Key_Length];

static uint64_t GetIV(const MessageHeader & header);
static CHIP_ERROR GetIV(const MessageHeader & header, uint8_t * iv, size_t len);
};

} // namespace chip
Expand Down