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Diffstat (limited to 'upstream/debian-unstable/man3/SSL_read.3ssl')
| -rw-r--r-- | upstream/debian-unstable/man3/SSL_read.3ssl | 198 |
1 files changed, 198 insertions, 0 deletions
diff --git a/upstream/debian-unstable/man3/SSL_read.3ssl b/upstream/debian-unstable/man3/SSL_read.3ssl new file mode 100644 index 00000000..178f5c78 --- /dev/null +++ b/upstream/debian-unstable/man3/SSL_read.3ssl @@ -0,0 +1,198 @@ +.\" -*- mode: troff; coding: utf-8 -*- +.\" Automatically generated by Pod::Man 5.01 (Pod::Simple 3.43) +.\" +.\" 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 +.. +.\" \*(C` and \*(C' are quotes in nroff, nothing in troff, for use with C<>. +.ie n \{\ +. ds C` "" +. ds C' "" +'br\} +.el\{\ +. ds C` +. ds C' +'br\} +.\" +.\" Escape single quotes in literal strings from groff's Unicode transform. +.ie \n(.g .ds Aq \(aq +.el .ds Aq ' +.\" +.\" If the F register is >0, we'll generate index entries on stderr for +.\" titles (.TH), headers (.SH), subsections (.SS), items (.Ip), and index +.\" entries marked with X<> in POD. Of course, you'll have to process the +.\" output yourself in some meaningful fashion. +.\" +.\" Avoid warning from groff about undefined register 'F'. +.de IX +.. +.nr rF 0 +.if \n(.g .if rF .nr rF 1 +.if (\n(rF:(\n(.g==0)) \{\ +. if \nF \{\ +. de IX +. tm Index:\\$1\t\\n%\t"\\$2" +.. +. if !\nF==2 \{\ +. nr % 0 +. nr F 2 +. \} +. \} +.\} +.rr rF +.\" ======================================================================== +.\" +.IX Title "SSL_READ 3SSL" +.TH SSL_READ 3SSL 2024-02-03 3.1.5 OpenSSL +.\" For nroff, turn off justification. 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" +\&\fBSSL_read_ex()\fR and \fBSSL_read()\fR try to read \fBnum\fR bytes from the specified \fBssl\fR +into the buffer \fBbuf\fR. On success \fBSSL_read_ex()\fR will store the number of bytes +actually read in \fB*readbytes\fR. +.PP +\&\fBSSL_peek_ex()\fR and \fBSSL_peek()\fR are identical to \fBSSL_read_ex()\fR and \fBSSL_read()\fR +respectively except no bytes are actually removed from the underlying BIO during +the read, so that a subsequent call to \fBSSL_read_ex()\fR or \fBSSL_read()\fR will yield +at least the same bytes. +.SH NOTES +.IX Header "NOTES" +In the paragraphs below a "read function" is defined as one of \fBSSL_read_ex()\fR, +\&\fBSSL_read()\fR, \fBSSL_peek_ex()\fR or \fBSSL_peek()\fR. +.PP +If necessary, a read function will negotiate a TLS/SSL session, if not already +explicitly performed by \fBSSL_connect\fR\|(3) or \fBSSL_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 BIO. +.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 +\&\fBSSL_set_connect_state\fR\|(3) or \fBSSL_set_accept_state()\fR before the first +invocation of a read function. +.PP +The read functions work based on the SSL/TLS 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 SSL 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 SSL/TLS record may exceed the maximum packet size +of the underlying transport (e.g. TCP), 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 \fBSSL_MODE_AUTO_RETRY\fR has been switched off and a non-application data +record has been processed, the read function can return and set the error to +\&\fBSSL_ERROR_WANT_READ\fR. +In this case there might still be unprocessed data available in the \fBBIO\fR. +If read ahead was set using \fBSSL_CTX_set_read_ahead\fR\|(3), there might also still +be unprocessed data available in the \fBSSL\fR. +This behaviour can be controlled using the \fBSSL_CTX_set_mode\fR\|(3) call. +.PP +If the underlying BIO 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 \fBSSL_MODE_AUTO_RETRY\fR is +not set. +Note that if \fBSSL_MODE_AUTO_RETRY\fR is set and only non-application data is +available the call will hang. +.PP +If the underlying BIO is \fBnonblocking\fR, a read function will also return when +the underlying BIO could not satisfy the needs of the function to continue the +operation. +In this case a call to \fBSSL_get_error\fR\|(3) with the +return value of the read function will yield \fBSSL_ERROR_WANT_READ\fR or +\&\fBSSL_ERROR_WANT_WRITE\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 BIO. +When using a nonblocking socket, nothing is to be done, but \fBselect()\fR 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. +.PP +\&\fBSSL_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" +\&\fBSSL_read_ex()\fR and \fBSSL_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 SSL +connection. +Failure means that no bytes could be read from the SSL 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 \fBSSL_get_error\fR\|(3) to find out the reason which +indicates whether the call is retryable or not. +.PP +For \fBSSL_read()\fR and \fBSSL_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 TLS/SSL +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 \fBSSL_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 \fBSSL_get_error()\fR to find out if it's retryable. +.SH "SEE ALSO" +.IX Header "SEE ALSO" +\&\fBSSL_get_error\fR\|(3), \fBSSL_write_ex\fR\|(3), +\&\fBSSL_CTX_set_mode\fR\|(3), \fBSSL_CTX_new\fR\|(3), +\&\fBSSL_connect\fR\|(3), \fBSSL_accept\fR\|(3) +\&\fBSSL_set_connect_state\fR\|(3), +\&\fBSSL_pending\fR\|(3), +\&\fBSSL_shutdown\fR\|(3), \fBSSL_set_shutdown\fR\|(3), +\&\fBssl\fR\|(7), \fBbio\fR\|(7) +.SH HISTORY +.IX Header "HISTORY" +The \fBSSL_read_ex()\fR and \fBSSL_peek_ex()\fR functions were added in OpenSSL 1.1.1. +.SH COPYRIGHT +.IX Header "COPYRIGHT" +Copyright 2000\-2020 The OpenSSL Project Authors. All Rights Reserved. +.PP +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>. |