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Re: [mbed-tls] mbedtls_hmac_drbg_seed fails, returns MBEDTLS_ERR_ENTROPY_SOURCE_FAILED

by Gilles Peskine

Hi Jeff, It looks like you're using an old version of Mbed TLS. mbedtls_hmac_drbg_seed used to set ctx->entropy_len to entropy_len * 3 / 2, but this changed (https://github.com/ARMmbed/mbed-crypto/pull/238) to making a call to mbedtls_entropy_func for entropy_len and then one again for entropy_len / 2, precisely to avoid the scenario you're describing where the HMAC_DRBG module would request more entropy than the entropy can deliver in a single call. Please upgrade to the latest release of Mbed TLS, or the latest 2.16 release if you want a long-time support branch. The version you're using is old and has known vulnerabilities. -- Gilles Peskine Mbed TLS developer On 06/04/2021 13:59, Thompson, Jeff via mbed-tls wrote: > > ï¿½ > > The call flow is mbedtls_hmac_drbg -> mbedtls_hmac_drbg_reseed -> > mbedtls_entropy_func where the parameter, len, is 48 and > MBEDTLS_ENTROPY_BLOCK_SIZE is 32. I see that mbedtls_hmac_drbg_seed > sets ï¿½ctx->entropy_len = entropy_len * 3 / 2, which explains the size > difference. Iï¿½ve probably mis-configured (see attached) in order to > use TLS-ECDHE-RSA-WITH-AES-128-CBC-SHA, because other ciphers take too > long. > > ï¿½ > > *Jeff Thompson*ï¿½| ï¿½Senior Electrical Engineer-Firmware > +1 704 752 6513 x1394 > www.invue.com <www.invue.com> > > ï¿½ > >

5 years

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mbedtls_hmac_drbg_seed fails, returns MBEDTLS_ERR_ENTROPY_SOURCE_FAILED

by Thompson, Jeff

The call flow is mbedtls_hmac_drbg -> mbedtls_hmac_drbg_reseed -> mbedtls_entropy_func where the parameter, len, is 48 and MBEDTLS_ENTROPY_BLOCK_SIZE is 32. I see that mbedtls_hmac_drbg_seed sets ctx->entropy_len = entropy_len * 3 / 2, which explains the size difference. I've probably mis-configured (see attached) in order to use TLS-ECDHE-RSA-WITH-AES-128-CBC-SHA, because other ciphers take too long. Jeff Thompson | Senior Electrical Engineer-Firmware +1 704 752 6513 x1394 www.invue.com [cid:image001.gif@01D72ABA.56C4A310]

5 years

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Re: [mbed-tls] Mbed TLS mbedtls_ssl_config (struct) Question

by Manuel Pegourie-Gonnard

Hi Keith, Those are good questions, and the short answer is everything should work in a multi-threaded environment if Mbed TLS was built with threading support (for example, enabling MBEDTLS_THREADING_C and MBEDTLS_THREADING_PTHREAD in config.h). Now for some more details: regarding mbedtls_ssl_config, it is indeed treated as read-only by all function in the SSL/TLS module, except of course those functions that are explicitly meant to modify it (those whose name starts with mbedtls_ssl_conf_). So, if you set it up in the main thread and then use it in other threads, everything will be fine regarding the top-level structure itself (for sub-structures see below), regardless of whether threading support is enabled. For the DRBG contexts, you're right that each time we draw from them, they need to update their state. However, this is protected by a mutex if threading support was enabled at compile-time. A similar thing goes for private keys : RSA private keys are protected by a mutex if threading support is enabled (using them mutates state used for side-channel countermeasures), and ECDSA private keys are safe too. X.509 structures are always treated as read-only. Regarding documentation: we did recently expand the documentation on DRBGs: https://github.com/ARMmbed/mbedtls/commit/f305d92480c81c6eb02934a4e1af58152… Regarding SSL, I agree this should be better documented. If you'd like to open a PR to add documentation that would have answered your question, that would be very welcome. Regards, Manuel ________________________________ From: mbed-tls <mbed-tls-bounces(a)lists.trustedfirmware.org> on behalf of Keith Cancel via mbed-tls <mbed-tls(a)lists.trustedfirmware.org> Sent: 02 April 2021 06:43 To: mbed-tls(a)lists.trustedfirmware.org <mbed-tls(a)lists.trustedfirmware.org> Subject: [mbed-tls] Mbed TLS mbedtls_ssl_config (struct) Question Hello, I hope this a simple question regarding mbedtls_ssl_config. So it seems this structure is meant to be shared/used for multiple connections. However, if I have multiple threads is it treated as a read only structure by all the library code, or does it update some state at times? Similar thing regarding the mbedtls_x509_crt struct and mbedtls_ctr_drbg_context which also seem to be added to the config when I setup the config. I was hoping that once set I don’t have to worry about any mutexs/locks being used by the library under the hood. Mainly, that once the configuration is set in the main thread it state is never updated again. What made me curious about this is the fact the RNG seems to be part of the configuration and a CPRNG will generally have state that needs to change. Moreover, I can’t really find a clear answer looking at the docs. Thanks, Keith Cancel -- mbed-tls mailing list mbed-tls(a)lists.trustedfirmware.org https://lists.trustedfirmware.org/mailman/listinfo/mbed-tls

5 years

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Mbed TLS mbedtls_ssl_config (struct) Question

by Keith Cancel

Hello, I hope this a simple question regarding mbedtls_ssl_config. So it seems this structure is meant to be shared/used for multiple connections. However, if I have multiple threads is it treated as a read only structure by all the library code, or does it update some state at times? Similar thing regarding the mbedtls_x509_crt struct and mbedtls_ctr_drbg_context which also seem to be added to the config when I setup the config. I was hoping that once set I don’t have to worry about any mutexs/locks being used by the library under the hood. Mainly, that once the configuration is set in the main thread it state is never updated again. What made me curious about this is the fact the RNG seems to be part of the configuration and a CPRNG will generally have state that needs to change. Moreover, I can’t really find a clear answer looking at the docs. Thanks, Keith Cancel

5 years

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MbedTLS handshark faild "The certificate is not correctly signed bythe trusted CA"

by chen

Hello, I run a client that has been ported MbedTLS, but the client connect server faild. I check the debug log, the end client state is 15. In the client state 3, the client receive only one certificate from server, and the log printing "Certificate verification flags 8". Here are part of logs: ..\MbedTLS\library\ssl_tls.c:4232: dumping 'input record from network' (4467 bytes) ..\MbedTLS\library\ssl_tls.c:4232: 0000: 16 03 03 11 6e 0b 00 11 6a 00 11 67 00 05 c2 30 ....n...j..g...0 ..\MbedTLS\library\ssl_tls.c:4232: 0010: -------- omit some network input data -------- ..\MbedTLS\library\ssl_tls.c:4232: 0ff0: 38 a0 36 a0 34 86 32 68 74 74 70 3a 2f 2f 63 72 8.6.4.2http://cr ..\MbedTLS\library\ssl_tls.c:3624: handshake message: msglen = 4462, type = 11, hslen = 4462 ..\MbedTLS\library\ssl_tls.c:4385: <= read record ..\MbedTLS\library\ssl_tls.c:5606: peer certificate #1: ..\MbedTLS\library\ssl_tls.c:5606: cert. version : 3 ..\MbedTLS\library\ssl_tls.c:5606: serial number : F0:57:5F:65:80:A9:70:B4:F9:8E:42:91:AE:D0:70:27 ..\MbedTLS\library\ssl_tls.c:5606: issuer name : C=GB, ST=Greater Manchester, L=Salford, O=Sectigo Limited, CN=Sectigo RSA Domain Validation Secure Server CA ..\MbedTLS\library\ssl_tls.c:5606: subject name : CN=*.xxxxxxxx.com ..\MbedTLS\library\ssl_tls.c:5606: issued on : 2020-06-01 00:00:00 ..\MbedTLS\library\ssl_tls.c:5606: expires on : 2021-05-26 23:59:59 ..\MbedTLS\library\ssl_tls.c:5606: signed using : RSA with SHA-256 ..\MbedTLS\library\ssl_tls.c:5606: RSA key size : 2048 bits ..\MbedTLS\library\ssl_tls.c:5606: basic constraints : CA=false ..\MbedTLS\library\ssl_tls.c:5606: subject alt name : *.xxxxxxxx.com, xxxxxxxx.com ..\MbedTLS\library\ssl_tls.c:5606: key usage : Digital Signature, Key Encipherment ..\MbedTLS\library\ssl_tls.c:5606: ext key usage : TLS Web Server Authentication, TLS Web Client Authentication ..\MbedTLS\library\ssl_tls.c:5606: value of 'crt->rsa.N' (2048 bits) is: ..\MbedTLS\library\ssl_tls.c:5606: af b7 73 1a f9 8a 2d 5e a2 e8 0f fd 89 5d 60 1d ..\MbedTLS\library\ssl_tls.c:5606: -------- omit some bits -------- ..\MbedTLS\library\ssl_tls.c:5606: e6 8e f8 3e ed ec 8e dd ec 46 48 85 9a b4 c8 71 ..\MbedTLS\library\ssl_tls.c:5606: value of 'crt->rsa.E' (17 bits) is: ..\MbedTLS\library\ssl_tls.c:5606: 01 00 01 ..\MbedTLS\library\ssl_tls.c:5757: x509_verify_cert() returned -9984 (-0x2700) ..\MbedTLS\library\ssl_tls.c:5851: ! Certificate verification flags 8 ..\MbedTLS\library\ssl_tls.c:5863: <= parse certificate At the client side, I download certificate of server, and get CA and root CA base on this certificate. Loading any one of these certificates into the client can't connect server. I did a test with another server. The different of the handshark is that the server issued two certificates, one is server's cert and another is CA cert. Loading CA or root CA into the client both can connect server successfully. problems: 1. Must the server send CA certificate in handshake phase? 2. The client holds CA certificate, dose MbedTLS client support downloading CA base on server's certificate? 3. In the source code, the certificate chain only contains the certificate issued by the server during handshake, not the CA certificate downloaded by the client according to the server certificate? Thank you very much for the answers. Best regards, berry chen

5 years

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Re: [mbed-tls] C/assembly option

by Gilles Peskine

Hi Raoul, Do I understand correctly that the problem with Mbed TLS as it is now is that you need MBEDTLS_HAVE_ASM enabled for AESNI and disabled for bignum? Would you want even more granularity? In principle, we could create a new compile-time option MBEDTLS_MPI_ASM, defaulting to what it does now (enabled if MBEDTLS_HAVE_ASM if the platform is one of the known ones) but overridable in either direction. However I don't like it much because we're trying to cut down on compilation options to reduce the maintenance burden: each compilation option adds complexity which makes it harder to understand all interactions between different parts of the library, and adds some testing burden. Symmetric and asymmetric crypto are mostly decoupled, so this one wouldn't be too bad, but it all adds up. In the long term, I expect that the different cryptographic algorithms will become more decoupled, with a possibility to treat each one as a black box that could be implemented by a hardware driver, and with a uniform mechanism to select drivers (or maybe they should be called engines). The evolution of the crypto part of the library to PSA is going in this direction. But we aren't there yet. Sorry that I don't have a more satisfying answer here. -- Gilles Peskine Mbed TLS developer On 31/03/2021 09:13, Raoul Strackx via mbed-tls wrote: > Hi all, > > We have a product that requires very strong security measures. When > compiling the mbedtls library, we face the following issue: Compiling C > code with LVI-mitigations is often much faster than relying on automatic > LVI mitigations on assembly code. The MPI functions are a good example > where we wish to rely on C source code. For other functions, we need to > rely on assembly code in order to mitigate other vulnerabilities (e.g., > we require AESNI assembly instructions over C implementations of AES). > Currently there isn't an option to choose between C/assembly per function. > > What would be an acceptable solution for this? > > greetings, > > Raoul > > >

5 years

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Minimum development environment: 2021 edition

by Gilles Peskine

Hello, In a nutshell: 1. Must Mbed TLS support Python 3.4 to configure and test, or can 3.6 be enough? 2. Must the supplied CMake scripts support 2.8.12.2, or can 3.5.2 be enough? This thread is about minimum tool versions to configure, build and test Mbed TLS (excluding TLS interoperability testing and some maintainer scripts) on Linux and similar (Unix-like) platforms. (This is not about the set of platforms where Mbed TLS will _run_, which is as close to “anything with CHAR_BIT==8 and sizeof(size_t) >= 4” as we can make it.) Our general guideline is that Mbed TLS should build out of the box on supported versions of major desktop and server operating systems. In practice, this has tended to mean supporting tool versions from RHEL/CentOS, SLES and Ubuntu LTS releases (but not necessarily extended security maintenance releases). Last year (https://lists.trustedfirmware.org/pipermail/mbed-tls/2020-April/thread.html) we concluded that we should support the following minimum versions, which will remain supported in the Mbed TLS 2.16 long-time support (LTS) branch: clang 3.8 cmake 2.8.12.2 gcc 4.4 make 3.81 python 3.4 (in 2.16: only to build the unit tests, not to configure) Since then, RHEL 6 and Ubuntu 16.04 have reached their end of life, the CentOS world has changed considerably. Looking at maintained platforms after April 2021 (https://github.com/ARMmbed/mbedtls/issues/2896#issuecomment-603471273), our current goal for the upcoming Mbed TLS 2.x LTS (last release before 3.0) is: clang 6.0 cmake 2.8.12.2 (or 3.5.2? or 3.10.2?) gcc 4.8 make 3.82 python 3.6 (or 3.4.10?) Regarding Python: is there any demand for supporting Python versions older than 3.6? Python 3 is required to fine-tune the library configuration (it is not needed if you use the default config.h or a handwritten one) and build the unit tests. Regarding CMake: it is increasingly problematic for us to support CMake 2.8.12, which is only required for RHEL 7: other distributions under consideration have at least CMake 3.5. There is an ongoing effort to improve our CMake scripts to make it easier to integrate Mbed TLS into a larger project, but it is difficult to preserve backward compatibility with 2.8.12. Would it be acceptable to require CMake >= 3.5? CMake >= 3.10.2? If you have any constraints that are not captured here or if you have an opinion regarding Python and CMake versions, please let us know quickly. -- Gilles Peskine Mbed TLS developer

5 years

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C/assembly option

by Raoul Strackx

Hi all, We have a product that requires very strong security measures. When compiling the mbedtls library, we face the following issue: Compiling C code with LVI-mitigations is often much faster than relying on automatic LVI mitigations on assembly code. The MPI functions are a good example where we wish to rely on C source code. For other functions, we need to rely on assembly code in order to mitigate other vulnerabilities (e.g., we require AESNI assembly instructions over C implementations of AES). Currently there isn't an option to choose between C/assembly per function. What would be an acceptable solution for this? greetings, Raoul

5 years

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Mbed TLS releases: 2.26.0, 2.16.10 and 2.7.19

by Dave Rodgman

Hi Mbed TLS users, We have released Mbed TLS versions 2.7.19, 2.16.10 and 2.26.0. These releases of Mbed TLS address several security issues, provide bug fixes, and bring other minor changes. Full details are available in the release notes (https://github.com/ARMmbed/mbedtls/releases/tag/mbedtls-2.26.0, https://github.com/ARMmbed/mbedtls/releases/tag/mbedtls-2.16.10, https://github.com/ARMmbed/mbedtls/releases/tag/mbedtls-2.7.19). We recommend all users to consider whether they are impacted, and to upgrade appropriately. Please note that there will be no further releases on the 2.7 branch, as this is now out of the three year support period. Dave Rodgman

5 years, 1 month

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OCSP

by Giuseppe Modugno

Is there any support for OCSP stapling in mbedTLS? Is there any roadmap for implementing it?

5 years, 1 month

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mbed-tls