August 2022 - mbed-tls - lists.trustedfirmware.org

by Subramanian Gopi Krishnan

Hi, I have an inhouse developed secure authentication program that uses certificate for authentication. I have used mbedtls library for the x.509 certificate verification purpose. In our custom PKI we have only three level of certificates, Root-CA -> Intermediate-CA -> Device-Cert. The embedded device has very limited memory, so instead of sending whole certificate chain, the devices communicates intermediate_CA and device cert (in der format base64 encoded) in separate packet. Root-CA will be available on node as trusted-ca. Intermediate is verified against Root; then device cert is verified against intermediate. The problem is, the poc developed on linux platform is working fine - but on embedded platform I encounter either 0x3b00(parsing failed) or 0x2700(with flag 8). Also the error code are inconsistent. I verified the integrity of packet with certificate using crc16. So no chance of certificate getting corrupted. Also verified the certificate's base64 format integrity using crc16. All certificates are sha256WithRSAEncryption; RSA Public-Key: (4096 bit) Attached config.h on target platform for reference - could you help me if anything wrong with configuration. While trying to trace, the flag was set from x509_crt.c from below code. /* No parent? We're done here */ if( parent == NULL ) { printf("NO_PARENT\r\n"); *flags |= MBEDTLS_X509_BADCERT_NOT_TRUSTED; return( 0 ); } Any clue would be helpful. Thanks, Gopi Krishnan

7 months, 2 weeks

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Get size of available application data without calling mbedtls_ssl_read()

by Bruckner, Jan

Hi all, I'd like to know if there is some way to retrieve the currently available number of bytes of application data without calling mbedtls_ssl_read()? I'm writing a "TLS socket" for higher layers to use and would like to notify them when new application data is available, tell them how much it is, but leave it up to them when and how much to retrieve. I'd like to prevent having to buffer all application data inside my TLS socket, because that would mean copying it once from mbedtls' buffer to my socket and then again from there to the application whenever it actually requests the data. After a quick look into the sources, it seems like, if at all, this might be possible for single records. But all related fields are private and I could not find any API for this. Issue #551 [1] seems related, but is more about peeking into the application data, while I would be fine with knowing just the size of available application data. Thanks for any hints on how I could achieve this. Best regards, Jan [1] https://github.com/Mbed-TLS/mbedtls/issues/551 ________________________________ This message is for the designated recipient only and may contain privileged, proprietary, or otherwise private information. If you have received it in error, please notify the sender immediately and delete the original. Any other use of the email by you is prohibited.

2 years, 1 month

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Question about handshake MTU

by Martin Man

Hi guys, I use mbedtls for years (since 2.10 IIRC) upgrading to latest available as time goes by. For DTLS that is. I remember a case in the past where a link would have a small MTU (around 500 bytes) and I had to tune ssl_context.handshake.mtu to a lower value to successfully complete handshakes. I do not remember exactly why, but I did not want to actually restrict maximum value via mbedtls_ssl_set_mtu, maybe it was even ignored back then for handshakes… but Now when working on migration to 3.2.1 (gave some time to 3x releases to stabilize) I noticed that the whole ssl_context.handshake member is now private and inaccessible, which I guess is fine. Could somebody with more knowledge of the code recommend what is the best strategy for DTLS app where MTU may not always be 1400? thanks a lot for your time, Martin

2 years, 2 months

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HMAC and CMAC Verification

by Ahmed Mohammed

Hello, I am wondering if there are APIs for Hmac and Cmac verification? from md.h and cmac.h, Hmac and Cmac generation functionalities are provided in a single and streaming approach. But is there a plan to add verification APIs for future releases maybe? Kind regards, Ahmed Mohammed

2 years, 3 months

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User configuration

by Ahmed Mohammed

Hello, What is the difference between these two macros in include/mbedtls/build_info.h: MBEDTLS_CONFIG_FILE MBEDTLS_USER_CONFIG_FILE In other words, why would I have two different user configuration files? Or I misunderstand the difference between such files. Kind regards, Ahmed Mohammed

2 years, 3 months

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OID Issue

by Subramanian Gopi Krishnan

Hi, We have developed a propriety protocol that authenticate node using certificate. In our PKI, we have four level of certificates as ROOT_CA, PROXY_CA, LOCAL_CA, and DEVICE_CERTIFICATE. Parsing of trusted CA certificate is getting success. However, verifying PROXY_CA against ROOT_CA fails with below error code. MBEDTLS_ERR_X509_UNKNOWN_SIG_ALG + MBEDTLS_ERR_OID_NOT_FOUND I have viewed the certificates transacted using OpenSSL command, the ASN1 OID is ECDSA_SHA384. Though, I have enabled the algorithm, it is failing. Any support would be appreciated. Attached the config.h for your reference. Thanks, Gopi Krishnan

2 years, 4 months

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Adding option to disable the zeroisation of internal buffers

by joel.petersson＠dirac.com

After recently updating mbedtls I noticed a considerable slowdown (over 70% on my cortex-m7 board) in the sha256 implementation, and after some digging I found the offending commit: https://github.com/Mbed-TLS/mbedtls/commit/76749aea784cfec245390d0d6f0ab0a2… I understand the motivation behind the commit, but I think it may not be relevant to all use cases. So my question is if an option to disable the clearing of internal buffers in mbedtls_config.h would be a reasonable improvement? Or would that be considered to much of a foot gun? Regards, Joel Petersson

2 years, 4 months

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support of Certificate exchange between client and server in Mbedtls

by Anupma Jain

Hi, In Embed tls version 2.28, is there any support to validate client certificate fields like for example: validity of certificate, CA validation or role extraction ? If support is present then, how can we enable that ? Please help me with this.Thanks in advance. Regards Anupma

2 years, 4 months

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mbed-tls August 2022