mbed-tls December 2020

mbed-tls@lists.trustedfirmware.org

7 participants
14 discussions

Re: [mbed-tls] mbedtls undefined behaviour

by Gilles Peskine

Hi Андрей, The behavior you describe is a bug. But there isn't enough information to tell whether the bug is in Mbed TLS, in asio-standalone, in some other third-party code, or in your application. Some things to consider: * Are you using blocking or non-blocking I/O? * Are you using TLS or DTLS? What protocol version, what cipher suite and what extensions are negotiated? * Does your application call mbedtls_ssl_write() and mbedtls_ssl_read() again with the same buffer if they return MBEDTLS_ERR_SSL_WANT_READ or MBEDTLS_ERR_SSL_WANT_WRITE? * Do you close the TLS connection if mbedtls_ssl_xxx() returns an error other than WANT_XXX (or XXX_IN_PROGRESS if you use these features)? * What is the value of MBEDTLS_SSL_MAX_CONTENT_LEN (or MBEDTLS_SSL_OUT_CONTENT_LEN if it's defined)? * What operating system are you using? * Is this a client or a server? What TLS stack does the other side run? You'll give others the most chance to help you if you post small, complete code to reproduce the problem. I realize this may be difficult. A good intermediate way to see what is going on would be to post debug logs. To get debug logs, make sure that MBEDTLS_DEBUG_C is enabled and call these functions before opening the TLS connection: mbedtls_ssl_conf_dbg(&ssl_conf, my_debug, stdout); mbedtls_debug_set_threshold(2); See https://tls.mbed.org/kb/how-to/mbedtls-tutorial for a sample version of my_debug(). Calls to bio_send() are shown in the logs as => flush output message length: %d, out_left: %d ssl->f_send() returned %d <= flush output If they don't show expected numbers, the rest of the logs should give a clue as to why. Hope this helps, -- Gilles Peskine Mbed TLS developer On 09/12/2020 22:17, Сысоев Андрей via mbed-tls wrote: > Hello. > > I need a little help with mbedtls 2.16.3. > I'm using it under x86-64 with asio-standalone. > > Here's a standard situation: > - I call mbedtls_ssl_write() to write let's say 8192 bytes of payload > - it calls my own bio_send() with (8192+21) bytes as len parameter > - bio_send() returns len=(8192+21), indicating transport data > correctly written > - mbedtls_ssl_write() returns 8192, indicating payload send > GOOD: next I use this value to shift application buffer (erase first > 8192 bytes), then send next chunk > > BUT after some time of running this situation happens: > - once again, a call to mbedtls_ssl_write() to write let's say 8192 > bytes of payload > - it calls bio_send() with smaller number, about 5500 bytes as len > parameter (?? but OK) > - bio_send() returns len=5500, indicating transport data correctly > written > - mbedtls_ssl_write() returns 8192 (??? why not 5500 ???), indicating > payload send > BAD: next I use this value to shift application buffer (erase first > 8192 bytes), this leads to data loss of (8192-5500)=2692 bytes and > ruins protocol > > As you can see, mbedtls_ssl_write() incorrectly reports about sent > application data (8192 instead of 5500) - is this a bug? How can such > situation happen under normal operation? > > Thanks in advance. >

5 years, 2 months

mbedtls undefined behaviour

by Сысоев Андрей

Hello. I need a little help with mbedtls 2.16.3. I'm using it under x86-64 with asio-standalone. Here's a standard situation: - I call mbedtls_ssl_write() to write let's say 8192 bytes of payload - it calls my own bio_send() with (8192+21) bytes as len parameter - bio_send() returns len=(8192+21), indicating transport data correctly written - mbedtls_ssl_write() returns 8192, indicating payload send GOOD: next I use this value to shift application buffer (erase first 8192 bytes), then send next chunk BUT after some time of running this situation happens: - once again, a call to mbedtls_ssl_write() to write let's say 8192 bytes of payload - it calls bio_send() with smaller number, about 5500 bytes as len parameter (?? but OK) - bio_send() returns len=5500, indicating transport data correctly written - mbedtls_ssl_write() returns 8192 (??? why not 5500 ???), indicating payload send BAD: next I use this value to shift application buffer (erase first 8192 bytes), this leads to data loss of (8192-5500)=2692 bytes and ruins protocol As you can see, mbedtls_ssl_write() incorrectly reports about sent application data (8192 instead of 5500) - is this a bug? How can such situation happen under normal operation? Thanks in advance.

5 years, 2 months

Re: [mbed-tls] Implementing MbedTLS on "xilinx zu7 zynq ultrascale+soc"

by Gilles Peskine

Hi Farhad, Mbed TLS currently supports hardware acceleration through alternative implementations of the corresponding modules or functions. See https://tls.mbed.org/kb/development/hw_acc_guidelines . This mechanism is available for symmetric cryptography and partially for RSA and ECC. There is some work in progress on a new mechanism for hardware acceleration through the psa_xxx() API, which will be available for all algorithms. You can follow the work in progress on the “Unified driver interface: API design and prototype” epic at https://github.com/ARMmbed/mbedtls/projects/2#column-8543266 . Hope this helps, -- Gilles Peskine Mbed TLS developer On 04/12/2020 11:20, saghili via mbed-tls wrote: > Dear Sir/Madam, > > Our platform is a quad core Cortex A53 running PetaLinux. > In our hardware, "AF_ALG" module has performance accelerations > available through the Linux crypto drivers. > Is it possible that we have "AF_ALG" for offloading crypto operations? > > Best regards, > Farhad

5 years, 2 months

Implementing MbedTLS on "xilinx zu7 zynq ultrascale+soc"

by saghili

Dear Sir/Madam, Our platform is a quad core Cortex A53 running PetaLinux. In our hardware, "AF_ALG" module has performance accelerations available through the Linux crypto drivers. Is it possible that we have "AF_ALG" for offloading crypto operations? Best regards, Farhad

5 years, 2 months

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mbed-tls December 2020