SSL_WANT(3ossl)

📦 version 3.5.0, in opensuse-leap 16.0

💅 SSL_WANT(3ossl) — bestie's guide to "what does this SSL thing even want from me"

okay so this is the OpenSSL manual page for the whole SSL_want family of functions, and honestly? it's giving "I just need to know what you need from me" energy. let's get into it 🫶

✨ NAME ✨

SSL_want, SSL_want_nothing, SSL_want_read, SSL_want_write, SSL_want_x509_lookup, SSL_want_retry_verify, SSL_want_async, SSL_want_async_job, SSL_want_client_hello_cb — these are the girlies that obtain state information about a TLS/SSL I/O operation. 💅

🌸 SYNOPSIS 🌸

#include <openssl/ssl.h>

int SSL_want(const SSL *ssl);
int SSL_want_nothing(const SSL *ssl);
int SSL_want_read(const SSL *ssl);
int SSL_want_write(const SSL *ssl);
int SSL_want_x509_lookup(const SSL *ssl);
int SSL_want_retry_verify(const SSL *ssl);
int SSL_want_async(const SSL *ssl);
int SSL_want_async_job(const SSL *ssl);
int SSL_want_client_hello_cb(const SSL *ssl);

like, every single one takes a const SSL *ssl and hands you back an int, no cap ✨

🦋 DESCRIPTION 🦋

So SSL_want() returns state information for the SSL object ssl. And bestie, listen — ssl MUST NOT be NULL. like, do not do that. that's not the vibe. 😭

The other SSL_want_*() calls are literally just shortcuts for the possible states that SSL_want() can return. same energy, less typing. iconic behavior fr 💅

🎀 NOTES 🎀

okay so SSL_want() peeks at the internal state information of the SSL object. the values it returns are, like, similar to what SSL_get_error(3) gives you — but here's the plot twist 🔥: SSL_get_error(3) also evaluates the error queue, whereas SSL_want() gets its results by examining an internal state flag only.

which means… that info is only valid for normal operation under nonblocking I/O. periodt. error conditions are not handled here — those have to be treated using SSL_get_error(3), no exceptions. 🙈

and the result returned by SSL_want() should always be consistent with the result of SSL_get_error(3). like they should be matching outfits, always. 👑

💖 RETURN VALUES 💖

these are the return values that can currently occur for SSL_want() — buckle up, there's a bunch:

  • SSL_NOTHING — there's no data to be written or to be read. nothing to do, honestly restful of it 🌸
  • SSL_WRITING — there are data in the SSL buffer that must be written to the underlying BIO layer in order to complete the actual SSL_*() operation. a call to SSL_get_error(3) should return SSL_ERROR_WANT_WRITE.
  • SSL_READING — more data must be read from the underlying BIO layer in order to complete the actual SSL_*() operation. a call to SSL_get_error(3) should return SSL_ERROR_WANT_READ.
  • SSL_X509_LOOKUP — the operation did not complete because an application callback set by SSL_CTX_set_client_cert_cb() has asked to be called again. a call to SSL_get_error(3) should return SSL_ERROR_WANT_X509_LOOKUP.
  • SSL_RETRY_VERIFY — the operation did not complete because a certificate verification callback has asked to be called again via SSL_set_retry_verify(3). a call to SSL_get_error(3) should return SSL_ERROR_WANT_RETRY_VERIFY.
  • SSL_ASYNC_PAUSED — an asynchronous operation partially completed and was then paused. see SSL_get_all_async_fds(3). a call to SSL_get_error(3) should return SSL_ERROR_WANT_ASYNC.
  • SSL_ASYNC_NO_JOBS — the asynchronous job could not be started because there were no async jobs available in the pool (see ASYNC_init_thread(3)). a call to SSL_get_error(3) should return SSL_ERROR_WANT_ASYNC_JOB.
  • SSL_CLIENT_HELLO_CB — the operation did not complete because an application callback set by SSL_CTX_set_client_hello_cb() has asked to be called again. a call to SSL_get_error(3) should return SSL_ERROR_WANT_CLIENT_HELLO_CB.

and for the shortcut girlies 💅: SSL_want_nothing(), SSL_want_read(), SSL_want_write(), SSL_want_x509_lookup(), SSL_want_retry_verify(), SSL_want_async(), SSL_want_async_job(), and SSL_want_client_hello_cb() all return 1 when the corresponding condition is true, or 0 otherwise. yes/no, slay, done. ✨

🌈 QUIC-SPECIFIC CONSIDERATIONS 🌈

For QUIC, these functions relate only to the TLS handshake layer. that's it, that's the whole note, don't overthink it 🧚

⭐ SEE ALSO ⭐

go read those, iykyk 🫶

👑 HISTORY 👑

The SSL_want_client_hello_cb() function and the SSL_CLIENT_HELLO_CB return value were added in OpenSSL 1.1.1. she's relatively new here but she's thriving 💜

Copyright 2001-2023 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at <https://www.openssl.org/source/license.html>.

okay bye bestie, this page was brought to you by OpenSSL 3.5.0, dated 2026-09-25, and yes that's the SSL_WANT(3ossl) manual page in the flesh 💖 go forth and check your return values ✨🎀🦋

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