Fix premature fopen() call in mbedtls_entropy_write_seed_file

[militant-daos]

Signed-off-by: Victor Krasnoshchok ct3da21164@protonmail.ch

Description

The PR fixes potential seed file corruption in case if path param of mbedtls_entropy_write_seed_file is equal to MBEDTLS_PLATFORM_STD_NV_SEED_FILE (or vice versa; i.e. the same file is used to read from and to write to).

Status

READY

Requires Backporting

Yes

• 2.16
• 2.7

Migrations

NO

Steps to test

1. Define MBEDTLS_ENTROPY_NV_SEED in the active config (config.h);
2. Edit test_suite_entropy.data in such a way to make entropy_seed_file define the same name as MBEDTLS_PLATFORM_STD_NV_SEED_FILE (seedfile by default);
3. Build and run test_suite_entropy target - NV-file related tests should pass.

[yanesca]

@militant-daos Thank you very much for contributing to Mbed TLS!

Could you please add an entry to test_suite_entropy.data with a non-regression test as you described it in step 2. of reproducing the issue? (We are testing a configuration in the CI that takes care of step 1 and 3.)

[militant-daos]

@militant-daos Thank you very much for contributing to Mbed TLS!

Could you please add an entry to test_suite_entropy.data with a non-regression test as you described it in step 2. of reproducing the issue? (We are testing a configuration in the CI that takes care of step 1 and 3.)

Sure, will update the suite.

[yanesca]

Looks good to me!

[yanesca]

The failure in the CI is only a glitch in the infrastructure.

[yanesca]

@militant-daos Could you please add a signed-by line to the last commit message?

[militant-daos]

@militant-daos Could you please add a signed-by line to the last commit message?

Sorry, I forgot to do that yesterday (I will create a pre-commit hook for this), thanks for pointing out. Added.

[yanesca]

Thank you, looks good to me!

[yanesca]

@militant-daos Now that the main PR is approved, could you please create the backports as well?

Also, we normally credit contributors in our ChangeLog. Please feel free to add a file with your entry in ChangeLog.d if you would like to be mentioned there. There is a readme about writing changelog entries in that directory as well.

[militant-daos]

@yanesca sure, will do. But first I need to reinstall my dev. environment, so this may take a while (I'll push the corresponding changes tomorrow)

[yanesca]

LGTM.

[yanesca]

The 2.16 backport looks good to me too, we can merge them as soon as the 2.7 backport is ready too.

[militant-daos]

@yanesca please take a look at #3821 - I've finally created the backport for 2.7. I'm sorry that it took so long, I hope that such things won't happen in future. Thanks in advance.

[gilles-peskine-arm]

Since the only missing thing was an approved 2.7 backport, this pull request is ready for merge. I just want to re-run the pr-merge CI first.