Re: improve ssl error code, 2147483650

On 07/03/2024 02:12, David Zhang wrote:
> The SSL_CTX_load_verify_locations function in OpenSSL will return NULL
> if there is a system error, such as "No such file or directory" in this
> case:
>
> const char *ERR_reason_error_string(unsigned long e)
> {
>     ERR_STRING_DATA d, *p = NULL;
>     unsigned long l, r;
>
>     if (!RUN_ONCE(&err_string_init, do_err_strings_init)) {
>         return NULL;
>     }
>
>     /*
>      * ERR_reason_error_string() can't safely return system error strings,
>      * since openssl_strerror_r() needs a buffer for thread safety, and we
>      * haven't got one that would serve any sensible purpose.
>      */
>     if (ERR_SYSTEM_ERROR(e))
>         return NULL;

That's pretty unfortunate. As typical with OpenSSL, this stuff is not
very well documented, but I think we could do something like this in
SSLerrmessage():

if (ERR_SYSTEM_ERROR(e))
errreason = strerror(ERR_GET_REASON(e));

ERR_SYSTEM_ERROR only exists in OpenSSL 3.0 and above, and the only
documentation I could find was in this one obscure place in the man
pages:
https://www.openssl.org/docs/man3.2/man3/BIO_dgram_get_local_addr_enable.html.
But as a best-effort thing, it would still be better than "SSL error
code 2147483650".

> It would be better to perform a simple SSL file check before passing the
> SSL file to OpenSSL APIs so that the system error can be captured and a
> meaningful message provided to the end user.

That feels pretty ugly. I agree it would catch most of the common
mistakes in practice, so maybe we should just hold our noses and do it
anyway, if the above ERR_SYSTEM_ERROR() method doesn't work.

It's sad that we cannot pass a file descriptor or in-memory copy of the
file contents to those functions.

--
Heikki Linnakangas
Neon (https://neon.tech)