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ussl.wrap_socket fails with mbedtls_ssl_handshake errors on ESP32 #5808
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I have good news and bad news for you ;-)
The good news is that I'm working on a PR to fix the obscure mbedtls error numbers. Here's what my version (using ESP_IDFv4) says:MicroPython v1.12-307-gad004db66-dirty on 2020-03-26; ESP32 module with ESP32 Type "help()" for more information. >>> import ussl, usocket >>> s = usocket.socket() >>> s.connect(('185.8.236.214', 443)) >>> s = ussl.wrap_socket(s, server_hostname="aladinonline.androworks.org") Traceback (most recent call last): File "<stdin>", line 1, in <module> OSError: RSA - The publicration failed : BIGNUM - Memory allocation failedThe bad news, other than the funny typo, is that the error is due to too small a buffer. MP uses the asymmetric buffer sizes and that puts a limit on the RSA key size, or something like that (someone please correct me). This is a well-known issue with TLS and constrained memory devices. I believe the buffer sizes are fixed at compile time (that's a mbedtls limitation).
Hope this helps.
In some cases, the
ussl.wrap_socketfunction fails with a nondescript error:This doesn't seem to be a network problem as requests to other pages work well in the same session. This is in fact the only page I've run into this issue with, and I can't figure out what's wrong with its TLS setup.
I initially ran into this when using the
urllib.urequest.urlopenfunction and I believed this was a micropython-lib bug, so I didn't post the issue here (original issue was micropython/micropython-lib#374), but I found out later that the bug wasn't present in the Micropython version 1.12 and that it was probably introduced by commit 3032ae1, which switches the version of ESP-IDF used to build Micropython for ESP32. Even though I managed to replicate the bug only using the undocumented parameterserver_hostnameofwrap_socketfunction, I really think this is a bug in Micropython (or some underlying library), not in micropython-lib.