[FS#814] When LEDE is compiled with GCC 7 on at least ar71xx and brcm47xx, Dropbear won't accept connections

[LEDE Bugs]

The following task has a new comment added:

FS#814 - When LEDE is compiled with GCC 7 on at least ar71xx and brcm47xx, Dropbear won't accept connections
User who did this - Baptiste Jonglez (bjonglez)

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Here is the discussion from the mailing for reference:


Had a really quick play with this and as I suspected it's related to compiler
optimization flags.  In essence, if I compile with '-Os' then dropbear plays
dumb, with my usual (but different from default) of '-O2' then dropbear, gcc 7
& mips get on fine, irrespective of target -march settings.

So as further totally wild guesses and on the basis 'ssh -vvv' shows things
hanging during the initial ECDH key exchange, I'm going to guess this is
happening somewhere in the libtommath/crypt libraries.



I checked the bundled libtom* in dropbear:

bundled: libtomcrypt is 1.16, libtommath is 0.40
latest: libtomcrypt is 1.17, libtommath is 1.0

There are various fixes since the bundled version:
https://github.com/libtom/libtommath/releases



Confirmed that with the latest libtom*, dropbear works well on MIPS & GCC 7.

This repo is based on dropbear 2017.75.

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More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=814#comment2940