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Diffstat (limited to 'secure/lib/libcrypto/man/SSL_read.3')
| -rw-r--r-- | secure/lib/libcrypto/man/SSL_read.3 | 271 |
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diff --git a/secure/lib/libcrypto/man/SSL_read.3 b/secure/lib/libcrypto/man/SSL_read.3 new file mode 100644 index 0000000000000..32519b574dae2 --- /dev/null +++ b/secure/lib/libcrypto/man/SSL_read.3 @@ -0,0 +1,271 @@ +.\" Automatically generated by Pod::Man 4.09 (Pod::Simple 3.35) +.\" +.\" Standard preamble: +.\" ======================================================================== +.de Sp \" Vertical space (when we can't use .PP) +.if t .sp .5v +.if n .sp +.. +.de Vb \" Begin verbatim text +.ft CW +.nf +.ne \\$1 +.. +.de Ve \" End verbatim text +.ft R +.fi +.. +.\" Set up some character translations and predefined strings. \*(-- will +.\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left +.\" double quote, and \*(R" will give a right double quote. \*(C+ will +.\" give a nicer C++. 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Always turn off hyphenation; it makes +.\" way too many mistakes in technical documents. +.if n .ad l +.nh +.SH "NAME" +SSL_read_ex, SSL_read, SSL_peek_ex, SSL_peek \&\- read bytes from a TLS/SSL connection +.SH "SYNOPSIS" +.IX Header "SYNOPSIS" +.Vb 1 +\& #include <openssl/ssl.h> +\& +\& int SSL_read_ex(SSL *ssl, void *buf, size_t num, size_t *readbytes); +\& int SSL_read(SSL *ssl, void *buf, int num); +\& +\& int SSL_peek_ex(SSL *ssl, void *buf, size_t num, size_t *readbytes); +\& int SSL_peek(SSL *ssl, void *buf, int num); +.Ve +.SH "DESCRIPTION" +.IX Header "DESCRIPTION" +\&\fISSL_read_ex()\fR and \fISSL_read()\fR try to read \fBnum\fR bytes from the specified \fBssl\fR +into the buffer \fBbuf\fR. On success \fISSL_read_ex()\fR will store the number of bytes +actually read in \fB*readbytes\fR. +.PP +\&\fISSL_peek_ex()\fR and \fISSL_peek()\fR are identical to \fISSL_read_ex()\fR and \fISSL_read()\fR +respectively except no bytes are actually removed from the underlying \s-1BIO\s0 during +the read, so that a subsequent call to \fISSL_read_ex()\fR or \fISSL_read()\fR will yield +at least the same bytes. +.SH "NOTES" +.IX Header "NOTES" +In the paragraphs below a \*(L"read function\*(R" is defined as one of \fISSL_read_ex()\fR, +\&\fISSL_read()\fR, \fISSL_peek_ex()\fR or \fISSL_peek()\fR. +.PP +If necessary, a read function will negotiate a \s-1TLS/SSL\s0 session, if not already +explicitly performed by \fISSL_connect\fR\|(3) or \fISSL_accept\fR\|(3). If the +peer requests a re-negotiation, it will be performed transparently during +the read function operation. The behaviour of the read functions depends on the +underlying \s-1BIO.\s0 +.PP +For the transparent negotiation to succeed, the \fBssl\fR must have been +initialized to client or server mode. This is being done by calling +\&\fISSL_set_connect_state\fR\|(3) or \fISSL_set_accept_state()\fR before the first +invocation of a read function. +.PP +The read functions work based on the \s-1SSL/TLS\s0 records. The data are received in +records (with a maximum record size of 16kB). Only when a record has been +completely received, can it be processed (decryption and check of integrity). +Therefore data that was not retrieved at the last read call can still be +buffered inside the \s-1SSL\s0 layer and will be retrieved on the next read +call. If \fBnum\fR is higher than the number of bytes buffered then the read +functions will return with the bytes buffered. If no more bytes are in the +buffer, the read functions will trigger the processing of the next record. +Only when the record has been received and processed completely will the read +functions return reporting success. At most the contents of one record will +be returned. As the size of an \s-1SSL/TLS\s0 record may exceed the maximum packet size +of the underlying transport (e.g. \s-1TCP\s0), it may be necessary to read several +packets from the transport layer before the record is complete and the read call +can succeed. +.PP +If \fB\s-1SSL_MODE_AUTO_RETRY\s0\fR has been switched off and a non-application data +record has been processed, the read function can return and set the error to +\&\fB\s-1SSL_ERROR_WANT_READ\s0\fR. +In this case there might still be unprocessed data available in the \fB\s-1BIO\s0\fR. +If read ahead was set using \fISSL_CTX_set_read_ahead\fR\|(3), there might also still +be unprocessed data available in the \fB\s-1SSL\s0\fR. +This behaviour can be controlled using the \fISSL_CTX_set_mode\fR\|(3) call. +.PP +If the underlying \s-1BIO\s0 is \fBblocking\fR, a read function will only return once the +read operation has been finished or an error occurred, except when a +non-application data record has been processed and \fB\s-1SSL_MODE_AUTO_RETRY\s0\fR is +not set. +Note that if \fB\s-1SSL_MODE_AUTO_RETRY\s0\fR is set and only non-application data is +available the call will hang. +.PP +If the underlying \s-1BIO\s0 is \fBnon-blocking\fR, a read function will also return when +the underlying \s-1BIO\s0 could not satisfy the needs of the function to continue the +operation. +In this case a call to \fISSL_get_error\fR\|(3) with the +return value of the read function will yield \fB\s-1SSL_ERROR_WANT_READ\s0\fR or +\&\fB\s-1SSL_ERROR_WANT_WRITE\s0\fR. +As at any time it's possible that non-application data needs to be sent, +a read function can also cause write operations. +The calling process then must repeat the call after taking appropriate action +to satisfy the needs of the read function. +The action depends on the underlying \s-1BIO.\s0 +When using a non-blocking socket, nothing is to be done, but \fIselect()\fR can be +used to check for the required condition. +When using a buffering \s-1BIO,\s0 like a \s-1BIO\s0 pair, data must be written into or +retrieved out of the \s-1BIO\s0 before being able to continue. +.PP +\&\fISSL_pending\fR\|(3) can be used to find out whether there +are buffered bytes available for immediate retrieval. +In this case the read function can be called without blocking or actually +receiving new data from the underlying socket. +.SH "RETURN VALUES" +.IX Header "RETURN VALUES" +\&\fISSL_read_ex()\fR and \fISSL_peek_ex()\fR will return 1 for success or 0 for failure. +Success means that 1 or more application data bytes have been read from the \s-1SSL\s0 +connection. +Failure means that no bytes could be read from the \s-1SSL\s0 connection. +Failures can be retryable (e.g. we are waiting for more bytes to +be delivered by the network) or non-retryable (e.g. a fatal network error). +In the event of a failure call \fISSL_get_error\fR\|(3) to find out the reason which +indicates whether the call is retryable or not. +.PP +For \fISSL_read()\fR and \fISSL_peek()\fR the following return values can occur: +.IP "> 0" 4 +.IX Item "> 0" +The read operation was successful. +The return value is the number of bytes actually read from the \s-1TLS/SSL\s0 +connection. +.IP "<= 0" 4 +.IX Item "<= 0" +The read operation was not successful, because either the connection was closed, +an error occurred or action must be taken by the calling process. +Call \fISSL_get_error\fR\|(3) with the return value \fBret\fR to find out the reason. +.Sp +Old documentation indicated a difference between 0 and \-1, and that \-1 was +retryable. +You should instead call \fISSL_get_error()\fR to find out if it's retryable. +.SH "HISTORY" +.IX Header "HISTORY" +\&\fISSL_read_ex()\fR and \fISSL_peek_ex()\fR were added in OpenSSL 1.1.1. +.SH "SEE ALSO" +.IX Header "SEE ALSO" +\&\fISSL_get_error\fR\|(3), \fISSL_write_ex\fR\|(3), +\&\fISSL_CTX_set_mode\fR\|(3), \fISSL_CTX_new\fR\|(3), +\&\fISSL_connect\fR\|(3), \fISSL_accept\fR\|(3) +\&\fISSL_set_connect_state\fR\|(3), +\&\fISSL_pending\fR\|(3), +\&\fISSL_shutdown\fR\|(3), \fISSL_set_shutdown\fR\|(3), +\&\fIssl\fR\|(7), \fIbio\fR\|(7) +.SH "COPYRIGHT" +.IX Header "COPYRIGHT" +Copyright 2000\-2018 The OpenSSL Project Authors. All Rights Reserved. +.PP +Licensed under the OpenSSL license (the \*(L"License\*(R"). You may not use +this file except in compliance with the License. You can obtain a copy +in the file \s-1LICENSE\s0 in the source distribution or at +<https://www.openssl.org/source/license.html>. |