Hello,
I am a Student and for my bachelor thesis I am working on a tool that
is able to detect whether a server is vulnerable regarding
Bleichenbacher's attack or not, testing multiple side channels.
For this I am looking for a TLS implementation that has the TCP
protocol integrated and generates the TCP messages.
I was wondering if mbed-tls has the TCP integrated in the
implementation or not.
If so, I could make use of this information, too.
Thanks and kind regards,
Anastasija
Hello,
We couldn't see word swap in the output from both the end. Issue doesn't look related to the endianness.
Could you please confirm that the code used for ECDHE key exchange is proper?
SHARED_SECRET (Computed on Client):
11 36 F7 DB 2B 14 BB 86
1C A0 FC DF 6D 4D 17 70
BE 4F D8 58 C2 11 67 10
42 D7 47 EB 14 4B 10 5E
SHARED_SECRET(Computed on Sever):
c6 96 d9 f0 ec 37 be 9e
1a 60 a4 5f 88 f2 13 d3
bb 98 15 3f 3b d9 81 37
c6 10 12 85 e5 8b 49 16
Thanks,
LIJIN T V
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Today's Topics:
1. ECDHE Shared Secret is computed differently (T V LIJIN (EXT))
2. Re: ECDHE Shared Secret is computed differently (Brian D.)
3. How does the bignum.c works? (Shariful Alam)
----------------------------------------------------------------------
Message: 1
Date: Thu, 24 Jun 2021 13:35:03 +0000
From: "T V LIJIN (EXT)" <lijin.tv(a)kone.com>
To: "mbed-tls(a)lists.trustedfirmware.org"
<mbed-tls(a)lists.trustedfirmware.org>
Subject: [mbed-tls] ECDHE Shared Secret is computed differently
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Hello ,
We are trying to perform an ECDHE key exchange between two devices running on different platforms.[one on Linux and another on RTOS]
Both the devices use the same code to compute the ECDHE shared secret. The peer public parameters are exchanged in the base64 format and passed to the functions correctly , but the final shared secret computed seems to be different on both ends.
We have tested the same source code on Visual studio and found working.
I have attached the source files
Could you please comment on why the computed shared secret are different on both the ends?
Thanks,
LIJIN T V
Hello,
Can someone please briefly explain how does the bignum.c library works in
terms of RSA? I understand that this is too broad a question to ask. but If
someone can briefly explain the basic working mechanism it will be a great
help.
Thanks,
Shariful
Hi Linjin,
I am not part of the mbed-tls staff but I developed a lot with mbed library and I had your same problem. Try to check the byte order, I had issues when computing the shared secret because I had the little endian from the other side but mbed uses big endian.
Try to do a quick test and this could resolve your problem, let me know!
Bye,
Brian
24 giu 2021, 15:35 da mbed-tls(a)lists.trustedfirmware.org:
> Hello ,
> We are trying to perform an ECDHE key exchange between two devices running on different platforms.[one on Linux and another on RTOS]
> Both the devices use the same code to compute the ECDHE shared secret. The peer public parameters are exchanged in the base64 format and passed to the functions correctly , but the final shared secret computed seems to be different on both ends.
> We have tested the same source code on Visual studio and found working.
> I have attached the source files
>
> Could you please comment on why the computed shared secret are different on both the ends?
>
> Thanks,
> LIJIN T V
>
Hello ,
We are trying to perform an ECDHE key exchange between two devices running on different platforms.[one on Linux and another on RTOS]
Both the devices use the same code to compute the ECDHE shared secret. The peer public parameters are exchanged in the base64 format and passed to the functions correctly , but the final shared secret computed seems to be different on both ends.
We have tested the same source code on Visual studio and found working.
I have attached the source files
Could you please comment on why the computed shared secret are different on both the ends?
Thanks,
LIJIN T V
Hi Andrey,
Thank you for your interest in Mbed TLS! In general we welcome
contributions to the project. Unfortunately, our limiting factor is
bandwidth for review. In 2021 the Mbed TLS team has grown, so we have
more time for reviews, but we are still struggling to catch up with the
large backlog.
There is already an old attempt to add unencrypted PKCS#8 writing
support (https://github.com/ARMmbed/mbedtls/issues/1695
<https://github.com/ARMmbed/mbedtls/issues/1695>). There is a long
pending request for encrypted PKCS#8 writing support
(https://github.com/ARMmbed/mbedtls/issues/1372
<https://github.com/ARMmbed/mbedtls/issues/1372>) but I'm not aware of
any prior implementation.
We would be glad to have your contribution, but I must be honest and say
it might take us several months to get around to it.
Best regards,
--
Gilles Peskine
Mbed TLS developer
On 09/06/2021 22:46, Андрей Макаров via mbed-tls wrote:
> Recently I used mbedtls library in my working project. In accordance
> with the needs of the project, I added some functions to mbedtls for
> saving and loading keys in plain and encrypted pem and der forms.
> The changes are still raw and should be brought up to pull request
> requirements - there are no tests, since the functions tested as part
> of a working project which uses mbedtls. I can, over time, finalize
> the changes to a pull request, but it will take some time and effort
> that you don't want to waste unnecessarily — this will have to be done
> at my home time.
> If there is an interest for this work, then I will try to do it, but
> if few people need it or do not coincide with the general direction of
> development of the project, then I would not bother.
> To be done: 1) added mbedtls_pk_write_key_pkcs8_der() write
> non-encrypted pkcs8 der key 2) added mbedtls_pk_write_key_pkcs8_pem()
> write non-encrypted pkcs8 pem key 3) added
> mbedtls_pk_write_key_encrypted_pem() write legacy encryped pem file
> with DEK-Info header 4) added
> mbedtls_pk_write_key_pkcs8_encrypted_der() write to encrypted pkcs8
> der key; pkcs5 pbes1, pkcs12 and pbes2 schemes are supported 5) added
> mbedtls_pk_write_key_pkcs8_encrypted_pem() same as above but pem key
> 6) changed mbedtls_pem_read_buffer() which reads legacy encrypted pem
> formats (with DEK-Info header) now it uses mbedtls_cipher_… functions
> which allow to use any supported cipher rather than four enforced (was
> limited to des-cbc, des-ede3-cbc, ars-128-cbc and aes-256-cbc) 7)
> changed pk_parse_key_pkcs8_encrypted_der() 7.1) added pkcs5 pbes1
> support MD5-DES-CB CpbeWithMD5AndDES-CBC) and SHA1-DES-CBC
> (pbeWithSHA1AndDES-CBC) 7.2) changed pkcs12 pbe (use same cipher for
> all SHA1-DES2-EDE-CBC (pbeWithSHAAnd2-KeyTripleDES-CBC),
> SHA1-DES3-EDE-CBC (pbeWithSHAAnd3-KeyTripleDES-CBC) and SHA1-RC4-128
> (pbeWithSHA1And128BitRC4); (the special
> mbedtls_pkcs12_pbe_sha1_rc4_128() is not used now and may be removed)
> 7.3) changed pkcs5 pbes2 support: added AES-128-CBC and AES-256-CBC
> ciphers Some «preview» is available at fork
> https://github.com/loafer-mka/mbedtls
> <https://github.com/loafer-mka/mbedtls>, branch ‘dev_clean’ Of course,
> many changes relate to obsolete formats, and may be undesirable … also
> I do not touch PSK at all.
> Please, give me some feedback — try to finish this with tests, pull
> request, etc or not. ----------- Regards, Andrey
>
Just finishing off this thread:
The issue appeared due to an invalid pointer access else where in the
application that coincided with the mbedtls_ssl_set_bio function.
Working on resolution now.
Thanks for all the help, pointers & hints from the list!
On 2021-06-08 2:27 p.m., Ron Eggler via mbed-tls wrote:
>
> Yes, there's some kind of "memory magic" going on here:
>
> The task got terminated due to "Load from invalid memory"
>
> and I see:
>
> |Instruction at 0x6310604d is trying to load data at 0x4, which is an
> invalid memory area. You are probably dereferencing a NULL pointer.|
>
> |and i got some trace back addresses that point to:|
>
> *
>
> mbedtls_aes_crypt_ecb
>
> *
>
> mbedtls_ctr_drbg_random_with_add
>
> *
>
> mbedtls_ssl_handshake_step
>
> *
>
> mbedtls_ssl_handshake
>
>
> ||
>
> On 2021-06-08 11:43 a.m., Gilles Peskine via mbed-tls wrote:
>> Hi Ron,
>>
>> This behavior can't be explained by the library code and the code you
>> posted alone. There has to be something wrong elsewhere.
>>
>> Check that you aren't exceeding a limitation such as the stack size or
>> the size of executable and data sections. If it can be an issue on your
>> platform, check that load addresses are correct and sections don't
>> overlap. Make sure there's no overlap with any device memory mapping either.
>>
>> Make sure that the whole binary is compiled with consistent settings.
>> The layout of mbedtls_ssl_context can be influenced by the Mbed TLS
>> configuration, so make sure that there's a single copy of
>> mbedtls/config.h and both Mbed TLS itself and your application were
>> built against that copy. The layout of mbedtls_ssl_context can also be
>> influenced by compiler settings on some platforms (e.g. structure
>> packing options), so make sure those are consistent across your build.
>>
>> That's all I can think of for now. It may help to add a lot of printf
>> debugging with %p on various addresses, and compare these addresses with
>> what you know about memory mappings on that platform. Good luck!
>>
>
Recently I used mbedtls library in my working project.
In accordance with the needs of the project, I added some functions to mbedtls
for saving and loading keys in plain and encrypted pem and der forms.
The changes are still raw and should be brought up to pull request requirements - there
are no tests, since the functions tested as part of a working project which uses mbedtls.
I can, over time, finalize the changes to a pull request, but it will take some time and
effort that you don't want to waste unnecessarily — this will have to be done at my home time.
If there is an interest for this work, then I will try to do it, but if few people need
it or do not coincide with the general direction of development of the project, then I
would not bother.
To be done:
1) added mbedtls_pk_write_key_pkcs8_der()
write non-encrypted pkcs8 der key
2) added mbedtls_pk_write_key_pkcs8_pem()
write non-encrypted pkcs8 pem key
3) added mbedtls_pk_write_key_encrypted_pem()
write legacy encryped pem file with DEK-Info header
4) added mbedtls_pk_write_key_pkcs8_encrypted_der()
write to encrypted pkcs8 der key; pkcs5 pbes1, pkcs12 and pbes2 schemes are supported
5) added mbedtls_pk_write_key_pkcs8_encrypted_pem()
same as above but pem key
6) changed mbedtls_pem_read_buffer()
which reads legacy encrypted pem formats (with DEK-Info header)
now it uses mbedtls_cipher_… functions which allow to use any supported cipher rather than four
enforced (was limited to des-cbc, des-ede3-cbc, ars-128-cbc and aes-256-cbc)
7) changed pk_parse_key_pkcs8_encrypted_der()
7.1) added pkcs5 pbes1 support MD5-DES-CB CpbeWithMD5AndDES-CBC) and SHA1-DES-CBC (pbeWithSHA1AndDES-CBC)
7.2) changed pkcs12 pbe (use same cipher for all SHA1-DES2-EDE-CBC (pbeWithSHAAnd2-KeyTripleDES-CBC),
SHA1-DES3-EDE-CBC (pbeWithSHAAnd3-KeyTripleDES-CBC) and SHA1-RC4-128 (pbeWithSHA1And128BitRC4);
(the special mbedtls_pkcs12_pbe_sha1_rc4_128() is not used now and may be removed)
7.3) changed pkcs5 pbes2 support: added AES-128-CBC and AES-256-CBC ciphers
Some «preview» is available at fork https://github.com/loafer-mka/mbedtls, branch ‘dev_clean’
Of course, many changes relate to obsolete formats, and may be undesirable … also I do not touch PSK at all.
Please, give me some feedback — try to finish this with tests, pull request, etc or not.
-----------
Regards,
Andrey
Dear All,
I am having multiple queries regarding session resumption and renegotiation.
I understand that normally session resumption is used at every new
connection and session renegotiation is used on live connection.
Our domain standards recommends to use session resumption to change session
key ( or keyblock
key_block = PRF(SecurityParameters.master_secret,
"key expansion",
SecurityParameters.server_random +
SecurityParameters.client_random);
) at regular intervals without closing connection and session renegotiation
to change master key at regular interval using session renegotiation. This
is due to the fact that the connection will be long lasting.
Query 1:
I understand that mbedtls currently does not support session resumption on
live connection. Is there any plan to include it in the near future? ( may
be similar to openssl SSL_renegotiate_abbreviated api)
Query 3:
If the application wants to know if session renegotiation has happened as
part of mbedtls_tls_read and mbedtls_tls_write, is there any callback/API
for that?
--> I am only thinking of using session->start comparison in application to
know if session is renegotiated. Is there any better method?
Query 4:
Our requirement is to understand and log security event in case failure due
to certificate verification fail (revoked/expired etc..) currently we use
mbedtls_ssl_get_verify_result api for same
There is a case when certificate becomes expired/revoked while doing
session renegotiation, mbedtls_ssl_get_verify_result api returns value 0 in
above case
I am thinking in case of session renegotiation, a valid session will always
be available (it will not be NULL in the method below) and session
renegotiation failure information will be available with session_negotiate
pointer instead of session pointer in the below function.
uint32_t mbedtls_ssl_get_verify_result( const mbedtls_ssl_context *ssl )
{
if( ssl->session != NULL )
return( ssl->session->verify_result );
if( ssl->session_negotiate != NULL )
return( ssl->session_negotiate->verify_result );
return( 0xFFFFFFFF );
}
Am I using the right API to get certificate verify_result?
should mbedtls_ssl_get_verify_result api checks give priority to
session_negotiate then session? I think when there is a failure, the result
will always be with session_negotiate, when success session_negotiate
becomes NULL and session_negotiate pointers will be assigned to session
pointers.
uint32_t mbedtls_ssl_get_verify_result( const mbedtls_ssl_context *ssl )
{
if( ssl->session_negotiate != NULL )
return( ssl->session_negotiate->verify_result );
if( ssl->session != NULL )
return( ssl->session->verify_result );
return( 0xFFFFFFFF );
}
Kind request to guide me
Thanks in advance
Regards
Hardik Dave