July 2020 - mbed-tls - lists.trustedfirmware.org

DTS session resumption and fragmentation

by Fatima, Fariya

Hi all, I have configured the max fragment length at the client and server to both 512. With this setting when I try to reconnect using a saved session at the client side, the ssl handshake doesn’t seem to happen. Below is the comment in the server code. /* We don't support fragmentation of ClientHello (yet?) */ The mbedtls code I am using is version 2.16.6. Are there any plans to support fragmentation of clienthello? Do let me know Regards, Fariya

4 years, 3 months

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DTLS session resumption

by Fatima, Fariya

Hi, I do not quite have enough knowledge on DTLS session resumption .. nevertheless here's my question: a) Difference between the features: MBEDTLS_SSL_COOKIE_C and MBEDTLS_SSL_SESSION_TICKETS? b) Enabling the feature MBEDTLS_SSL_SESSION_TICKETS would be sufficient to resume an earlier established DTLS session quickly (i.e avoid the whole TLS handshake done the last time)? c) How do I test this - i.e initiate connection from client and server, break the connection and then make the client connect to the server again? Not sure what additional steps are required on client side. Any callbacks to be registered in the code? Regards, Fariya

4 years, 3 months

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Re: [mbed-tls] SSH client sample (Gilles Peskine)

by Christie Su

Hi Gilles, I checked one you recommended and looks like it is very complicated. Do you have any sample project(SSH client) based on MbedTLS+LWIP? Thanks, Christie -----Original Message----- From: mbed-tls <mbed-tls-bounces(a)lists.trustedfirmware.org> On Behalf Of mbed-tls-request(a)lists.trustedfirmware.org Sent: July-22-20 11:35 AM To: mbed-tls(a)lists.trustedfirmware.org Subject: mbed-tls Digest, Vol 5, Issue 15 Send mbed-tls mailing list submissions to mbed-tls(a)lists.trustedfirmware.org To subscribe or unsubscribe via the World Wide Web, visit https://lists.trustedfirmware.org/mailman/listinfo/mbed-tls or, via email, send a message with subject or body 'help' to mbed-tls-request(a)lists.trustedfirmware.org You can reach the person managing the list at mbed-tls-owner(a)lists.trustedfirmware.org When replying, please edit your Subject line so it is more specific than "Re: Contents of mbed-tls digest..." Today's Topics: 1. Problem with decrypt aes 128 in ecb mode. HELP ME! (dany_banik2000(a)yahoo.com) 2. Re: SSH client sample (Gilles Peskine) 3. Re: patches for low memory (Gilles Peskine) ---------------------------------------------------------------------- Message: 1 Date: Wed, 22 Jul 2020 14:42:33 +0000 (UTC) From: "dany_banik2000(a)yahoo.com" <dany_banik2000(a)yahoo.com> To: mbed-tls(a)lists.trustedfirmware.org Subject: [mbed-tls] Problem with decrypt aes 128 in ecb mode. HELP ME! Message-ID: <1371131400.5486983.1595428953399(a)mail.yahoo.com> Content-Type: text/plain; charset="utf-8" I developed a server application that obtains the data from a dht11 sensor, I encrypt it with aes 128 and publish it on the server. The client application makes a request to the server, and I would like to decrypt the answer. When I want to display decrypted message, it shows garbage The message retrieved from the server is in hex. I think that must to convert hex in binary, but i don’t know how can do it… -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.trustedfirmware.org/pipermail/mbed-tls/attachments/20200722/a5…> ------------------------------ Message: 2 Date: Wed, 22 Jul 2020 17:10:18 +0200 From: Gilles Peskine <gilles.peskine(a)arm.com> To: mbed-tls(a)lists.trustedfirmware.org Subject: Re: [mbed-tls] SSH client sample Message-ID: <4a7265ac-7b3e-33ef-7222-4cd29c3cda08(a)arm.com> Content-Type: text/plain; charset=windows-1252 Hi Christie, Libssh2 (https://github.com/libssh2/libssh2) supports Mbed TLS. I've never used it or investigated it, so I can't vouch for it, I just know that it's there. -- Gilles Peskine Mbed TLS developer On 21/07/2020 18:40, Christie Su via mbed-tls wrote: > > Hi, > > ï¿½ > > I am using FRDM-K64F with LWIP+mbedTLS for our control system. Now, I > want to develop the SSH client(or telnet 22) to access my SSH server. > > ï¿½ > > Could you give me some indications how to do it? Or do you have any > sample project? > > ï¿½ > > Thanks, > > ï¿½ > > Christie > > ------------------------------ Message: 3 Date: Wed, 22 Jul 2020 17:34:44 +0200 From: Gilles Peskine <gilles.peskine(a)arm.com> To: mbed-tls(a)lists.trustedfirmware.org Subject: Re: [mbed-tls] patches for low memory Message-ID: <152f6571-6972-8262-c38d-d200dcc7c0b7(a)arm.com> Content-Type: text/plain; charset=utf-8 Hi Nick, A TLS stack in 6kB of RAM sounds impressive, congratulations! We'd certainly be interested in all the improvements you can contribute. The process is documented in CONTRIBUTING.md (https://github.com/ARMmbed/mbedtls/blob/development/CONTRIBUTING.md). I just need to warn you that the limiting factor is reviewers' time. For a significant contribution, it may take a while before the Mbed TLS team can look at it in detail. Small patches are usually easier than large ones: if something only takes half an hour to review, someone will probably do it when they're stuck on some other task. If a review takes several days, it needs to be scheduled. It would probably be better to discuss the general nature of the changes on this mailing list first. Is a new compilation option needed? Is an API change needed? What is the risk that the change might break existing code? How is the new code tested? etc. Which version of Mbed TLS have you been using? We've made a few changes that are of interest to low-memory platforms recently, such as the option MBEDTLS_SSL_VARIABLE_BUFFER_LENGTH to resize SSL buffers after the handshake (new in 2.22). I don't know what the issue with the incoming SSL packet header length could be. If you could give precise steps to reproduce the issue, this would be very helpful. Eventually we'd want to construct a test in tests/ssl-opt.sh for this. -- Gilles Peskine Mbed TLS developer On 17/07/2020 21:00, Nick Setzer via mbed-tls wrote: > > Hi, I have been working with Mbed TLS for the last 6 months in an > extremely low memory use case. This library has been an absolute joy > to work with because of how flexible it is. I have an interesting use > case with how little RAM I have to work with (around 6kb on one > microprocessor) and I have made some changes that I thought would be > of interest. I'm not sure if I should submit them as a single > changeset or a set of changes. I'll describe the changes and if there > is interest I can clean them up for submission. > > The first change that I made was for a scenario with two > microprocessors communicating over a UART. I was already using TLS > offloading so that the private key was on one processor (with only 6kb > of RAM free) and the SSL context stored on the other. I required > generating a CSR and thus made some changes to the CSR code to be able > to generate the CSR using a similar private key offloading strategy. > > I found an issue with downloading firmware for OTA from openssl web > servers. This is a little tricky to describe. The server was not > responsive to requests for reducing the max fragment length, which > forced me to use MBEDTLS_SSL_MAX_CONTENT_LEN set to 16384. But I > needed to have multiple ssl sessions open for other activities and did > not have enough RAM to hold multiple large buffers. I have made a set > of changes to allow setting the content length when the ssl context is > initialized, as well as setting different IN and OUT content lengths > to save memory. This change allowed me to set up one session with 16kb > for the IN content length, and then 4kb for OUT content length, while > a second session could use 2kb for a total of 24kb instead of 64kb. > > Related to the openssl issue, I found that the incoming ssl packet > header length can sometimes be 8 or 16 bytes larger than expected > depending on which AES method is selected. I'm not actually sure what > the best way to solve this is. One way may be to change > MBEDTLS_SSL_HEADER_LEN from 13 to 29 bytes. However I ended up solving > it by adding 16 to both MBEDTLS_SSL_IN_BUFFER_LEN and > MBEDTLS_SSL_OUT_BUFFER_LEN. This way I could handle the larger ssl > header as well as receive the content body. > > If these three changes sound interesting I can start work on cleaning > up the code to be less specific to my company and then submit the > changes. Also I would like to know if there is any process I should be > following when submitting these changes. > > Thanks, > > Nick Setzer > SimpliSafe, Inc. > 294 Washington Street, 9th Floor > Boston, MA 02108 > ------------------------------ Subject: Digest Footer mbed-tls mailing list mbed-tls(a)lists.trustedfirmware.org https://lists.trustedfirmware.org/mailman/listinfo/mbed-tls ------------------------------ End of mbed-tls Digest, Vol 5, Issue 15 ***************************************

4 years, 4 months

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Re: [mbed-tls] [Mbed-tls-announce] Force push on the master branch

by Gilles Peskine

On 20/07/2020 12:21, Scott Branden via mbed-tls wrote: > Although this particular change doesn't affect me - rewriting history is a > bad idea. > > Why not simply commit a revert back to a cleaner point on "master" branch > and then commit the new changes you want from there? > > Then history is not lost on master branch. Mbed TLS used to follow the Git Flow model: day-to-day work happens on the 'development' branch, and there's a 'master' branch which always points to the latest commit on master that's a tagged release. A release is done by tagging a commit on 'development' and fast-forwarding 'master' to it. But after the 2.16 LTS release, we made 'master' follow the 2.16 LTS branch rather than 'development'. I think this was a mistake, but it's too late to change this, the question is what we do now with the existing situation. A force-push on 'master' would not erase history from the face of the world. The history is still there in 'mbedtls-2.16'. It is no longer possible to fast-forward 'master' to any commit on 'development'. No amount of revert or merge commits on 'master' will make it be the same commit as some a release made from 'development'. Without a force-push, all we can hope is to have 'master' have the same content as a release. This means that getting the same release would give you the same content, but different history, depending on whether tyou get it from 'master' or 'development'. This would also mean a more complicated release process. Another solution would be to do a merge of 'master' into 'development', ignoring all changes from the 'master' side. But this would mess up the history on 'development'. Is this more complicated release process, or this messy history, worth it, just to avoid a force-push? > Or, with the BLM movement some repos are stopping use of master branch. > github seems to be encourage it going forware: > https://www.zdnet.com/article/github-to-replace-master-with-alternative-ter… > > So another option: stop using "master" branch. You could even create a > tag/rename and then delete the branch name to avoid any confusions. History > won't be rewritten then, just a little "hidden". > And start using a new "main" branch. You can push you entire commit series > there without revering anything on master branch. Sure, we can create a new branch name. But then we'd still have to keep a branch with the old name, for the sake of existing setups that pull from 'master'. Or else we should make a commit on 'master' that removes every file and instead adds a README that says "pull from 'main' instead". -- Gilles Peskine Mbed TLS developer

4 years, 4 months

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Re: [mbed-tls] patches for low memory

by Gilles Peskine

On 22/07/2020 17:35, Gilles Peskine via mbed-tls wrote: > I just need to warn you that the limiting factor is reviewers' time. For a > significant contribution, it may take a while before the Mbed TLS team > can look at it in detail. Small patches are usually easier than large > ones: if something only takes half an hour to review, someone will > probably do it when they're stuck on some other task. If a review takes > several days, it needs to be scheduled. As an aside, Mbed TLS is under the governance of TrustedFirmware. Currently, only Arm employees are consider trusted reviewers, but this is not by policy, it's only due to the history of the project (until a few months ago, Mbed TLS was governed by Arm). We (as in, the Arm employees working on Mbed TLS) welcome design and code reviews from everyone. We don't yet have a formal process for becoming a “trusted” reviewer, beyond the general principles of TrustedFirmware. But a required part of that process will undoubtedly be to have done some reviews before. As every project, there is an informal, unwritten culture. If there's interest, we can try to document our review culture in writing. If I had to sum it up in one sentence, I'd say that if a reviewer should reject code that they don't understand: it's the job of the patch author to convince reviewers that the patch is good. “I don't see anything wrong” is not a good enough standard. -- Gilles Peskine Mbed TLS developer

4 years, 4 months

1
0
0 0

Re: [mbed-tls] patches for low memory

by Gilles Peskine

Hi Nick, A TLS stack in 6kB of RAM sounds impressive, congratulations! We'd certainly be interested in all the improvements you can contribute. The process is documented in CONTRIBUTING.md (https://github.com/ARMmbed/mbedtls/blob/development/CONTRIBUTING.md). I just need to warn you that the limiting factor is reviewers' time. For a significant contribution, it may take a while before the Mbed TLS team can look at it in detail. Small patches are usually easier than large ones: if something only takes half an hour to review, someone will probably do it when they're stuck on some other task. If a review takes several days, it needs to be scheduled. It would probably be better to discuss the general nature of the changes on this mailing list first. Is a new compilation option needed? Is an API change needed? What is the risk that the change might break existing code? How is the new code tested? etc. Which version of Mbed TLS have you been using? We've made a few changes that are of interest to low-memory platforms recently, such as the option MBEDTLS_SSL_VARIABLE_BUFFER_LENGTH to resize SSL buffers after the handshake (new in 2.22). I don't know what the issue with the incoming SSL packet header length could be. If you could give precise steps to reproduce the issue, this would be very helpful. Eventually we'd want to construct a test in tests/ssl-opt.sh for this. -- Gilles Peskine Mbed TLS developer On 17/07/2020 21:00, Nick Setzer via mbed-tls wrote: > > Hi, I have been working with Mbed TLS for the last 6 months in an > extremely low memory use case. This library has been an absolute joy > to work with because of how flexible it is. I have an interesting use > case with how little RAM I have to work with (around 6kb on one > microprocessor) and I have made some changes that I thought would be > of interest. I'm not sure if I should submit them as a single > changeset or a set of changes. I'll describe the changes and if there > is interest I can clean them up for submission. > > The first change that I made was for a scenario with two > microprocessors communicating over a UART. I was already using TLS > offloading so that the private key was on one processor (with only 6kb > of RAM free) and the SSL context stored on the other. I required > generating a CSR and thus made some changes to the CSR code to be able > to generate the CSR using a similar private key offloading strategy. > > I found an issue with downloading firmware for OTA from openssl web > servers. This is a little tricky to describe. The server was not > responsive to requests for reducing the max fragment length, which > forced me to use MBEDTLS_SSL_MAX_CONTENT_LEN set to 16384. But I > needed to have multiple ssl sessions open for other activities and did > not have enough RAM to hold multiple large buffers. I have made a set > of changes to allow setting the content length when the ssl context is > initialized, as well as setting different IN and OUT content lengths > to save memory. This change allowed me to set up one session with 16kb > for the IN content length, and then 4kb for OUT content length, while > a second session could use 2kb for a total of 24kb instead of 64kb. > > Related to the openssl issue, I found that the incoming ssl packet > header length can sometimes be 8 or 16 bytes larger than expected > depending on which AES method is selected. I'm not actually sure what > the best way to solve this is. One way may be to change > MBEDTLS_SSL_HEADER_LEN from 13 to 29 bytes. However I ended up solving > it by adding 16 to both MBEDTLS_SSL_IN_BUFFER_LEN and > MBEDTLS_SSL_OUT_BUFFER_LEN. This way I could handle the larger ssl > header as well as receive the content body. > > If these three changes sound interesting I can start work on cleaning > up the code to be less specific to my company and then submit the > changes. Also I would like to know if there is any process I should be > following when submitting these changes. > > Thanks, > > Nick Setzer > SimpliSafe, Inc. > 294 Washington Street, 9th Floor > Boston, MA 02108 >

4 years, 4 months

1
0
0 0

Re: [mbed-tls] SSH client sample

by Gilles Peskine

Hi Christie, Libssh2 (https://github.com/libssh2/libssh2) supports Mbed TLS. I've never used it or investigated it, so I can't vouch for it, I just know that it's there. -- Gilles Peskine Mbed TLS developer On 21/07/2020 18:40, Christie Su via mbed-tls wrote: > > Hi, > > ï¿½ > > I am using FRDM-K64F with LWIP+mbedTLS for our control system. Now, I > want to develop the SSH client(or telnet 22) to access my SSH server. > > ï¿½ > > Could you give me some indications how to do it? Or do you have any > sample project? > > ï¿½ > > Thanks, > > ï¿½ > > Christie > >

4 years, 4 months

1
0
0 0

Problem with decrypt aes 128 in ecb mode. HELP ME!

by dany_banik2000＠yahoo.com

I developed a server application that obtains the data from a dht11 sensor, I encrypt it with aes 128 and publish it on the server. The client application makes a request to the server, and I would like to decrypt the answer. When I want to display decrypted message, it shows garbage The message retrieved from the server is in hex. I think that must to convert hex in binary, but i don’t know how can do it…

4 years, 4 months

1
0
0 0

SSH client sample

by Christie Su

Hi, I am using FRDM-K64F with LWIP+mbedTLS for our control system. Now, I want to develop the SSH client(or telnet 22) to access my SSH server. Could you give me some indications how to do it? Or do you have any sample project? Thanks, Christie

4 years, 4 months

1
0
0 0

patches for low memory

by Nick Setzer

Hi, I have been working with Mbed TLS for the last 6 months in an extremely low memory use case. This library has been an absolute joy to work with because of how flexible it is. I have an interesting use case with how little RAM I have to work with (around 6kb on one microprocessor) and I have made some changes that I thought would be of interest. I'm not sure if I should submit them as a single changeset or a set of changes. I'll describe the changes and if there is interest I can clean them up for submission. The first change that I made was for a scenario with two microprocessors communicating over a UART. I was already using TLS offloading so that the private key was on one processor (with only 6kb of RAM free) and the SSL context stored on the other. I required generating a CSR and thus made some changes to the CSR code to be able to generate the CSR using a similar private key offloading strategy. I found an issue with downloading firmware for OTA from openssl web servers. This is a little tricky to describe. The server was not responsive to requests for reducing the max fragment length, which forced me to use MBEDTLS_SSL_MAX_CONTENT_LEN set to 16384. But I needed to have multiple ssl sessions open for other activities and did not have enough RAM to hold multiple large buffers. I have made a set of changes to allow setting the content length when the ssl context is initialized, as well as setting different IN and OUT content lengths to save memory. This change allowed me to set up one session with 16kb for the IN content length, and then 4kb for OUT content length, while a second session could use 2kb for a total of 24kb instead of 64kb. Related to the openssl issue, I found that the incoming ssl packet header length can sometimes be 8 or 16 bytes larger than expected depending on which AES method is selected. I'm not actually sure what the best way to solve this is. One way may be to change MBEDTLS_SSL_HEADER_LEN from 13 to 29 bytes. However I ended up solving it by adding 16 to both MBEDTLS_SSL_IN_BUFFER_LEN and MBEDTLS_SSL_OUT_BUFFER_LEN. This way I could handle the larger ssl header as well as receive the content body. If these three changes sound interesting I can start work on cleaning up the code to be less specific to my company and then submit the changes. Also I would like to know if there is any process I should be following when submitting these changes. Thanks, Nick Setzer SimpliSafe, Inc. 294 Washington Street, 9th Floor Boston, MA 02108

4 years, 4 months

1
0
0 0

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mbed-tls July 2020