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SSL_accept

Section: OpenSSL (3)
Updated: 2017-05-25
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NAME

SSL_accept - wait for a TLS/SSL client to initiate a TLS/SSL handshake

SYNOPSIS

 #include <openssl/ssl.h>

 int SSL_accept(SSL *ssl);

DESCRIPTION

SSL_accept() waits for a TLS/SSL client to initiate the TLS/SSL handshake. The communication channel must already have been set and assigned to the ssl by setting an underlying BIO.

NOTES

The behaviour of SSL_accept() depends on the underlying BIO.

If the underlying BIO is blocking, SSL_accept() will only return once the handshake has been finished or an error occurred.

If the underlying BIO is non-blocking, SSL_accept() will also return when the underlying BIO could not satisfy the needs of SSL_accept() to continue the handshake, indicating the problem by the return value -1. In this case a call to SSL_get_error() with the return value of SSL_accept() will yield SSL_ERROR_WANT_READ or SSL_ERROR_WANT_WRITE. The calling process then must repeat the call after taking appropriate action to satisfy the needs of SSL_accept(). The action depends on the underlying BIO. When using a non-blocking socket, nothing is to be done, but select() can be used to check for the required condition. When using a buffering BIO, like a BIO pair, data must be written into or retrieved out of the BIO before being able to continue.

RETURN VALUES

The following return values can occur:

0: The TLS/SSL handshake was not successful but was shut down controlled and by the specifications of the TLS/SSL protocol. Call SSL_get_error() with the return value ret to find out the reason.
1: The TLS/SSL handshake was successfully completed, a TLS/SSL connection has been established.
<0: The TLS/SSL handshake was not successful because a fatal error occurred either at the protocol level or a connection failure occurred. The shutdown was not clean. It can also occur of action is need to continue the operation for non-blocking BIOs. Call SSL_get_error() with the return value ret to find out the reason.