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Error handling of ccm assosiate data length. #3719

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soloicesky opened this issue Sep 27, 2020 · 1 comment · Fixed by #3772
Closed

Error handling of ccm assosiate data length. #3719

soloicesky opened this issue Sep 27, 2020 · 1 comment · Fixed by #3772
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@soloicesky
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soloicesky commented Sep 27, 2020 •
edited

Note: This is just a template, so feel free to use/remove the unnecessary things

Description

  • Type: Bug | Enhancement\Feature Request
  • Priority: Blocker | Major | Minor

Bug

OS
Mbed OS|linux|windows|

mbed TLS build:
Version: x.x.x or git commit id
OS version: x.x.x
Configuration: please attach config.h file where possible
Compiler and options (if you used a pre-built binary, please indicate how you obtained it):
Additional environment information:

Peer device TLS stack and version
OpenSSL|GnuTls|Chrome|NSS(Firefox)|SecureChannel (IIS/Internet Explorer/Edge)|Other
Version:

Expected behavior

Actual behavior

Steps to reproduce

Enhancement\Feature Request

Justification - why does the library need this feature?

Suggested enhancement

Question

Please first check for answers in the Mbed TLS knowledge Base. If you can't find the answer you're looking for then please use the Mbed TLS mailing list
I found an issue in ccm implementation. code block as follows:
image
I think as your intent
Line#178 should be add_len >= 0xFF00
otherwise
line#224 to line#225 is conflicting with standard when aad_len = 0xFF00. because per standard aad_len should encoded as six octets but current is 2.
image
@yanesca
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yanesca commented Sep 28, 2020

Thank you for reporting this bug!

@yanesca yanesca added the bug label Sep 28, 2020
frestr pushed a commit to frestr/mbedtls that referenced this issue Oct 8, 2020
Fix additional data length field check for CCM
5e940c6 
The CCM specification (NIST SP 800-38C) mandates that the formatting of
the additional data length l(a) changes when it is greater _or equal_ to
2^16 - 2^8 (>= 0xFF00). Since such lengths are not supported in mbed TLS,
the operation should fail in such cases.

This commit fixes an off-by-one error which allowed encryption/decryption
to be executed when l(a) was equal to 0xFF00, resulting in an
incorrect/non-standard length format being used.

Fixes Mbed-TLS#3719.

Signed-off-by: Fredrik Strupe <fredrik.strupe@silabs.com>
@frestr frestr mentioned this issue Oct 8, 2020
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Fix additional data length field check for CCM frestr/mbedtls
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@soloicesky @yanesca