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Diffstat (limited to 'secure/lib/libssl/man/SSL_read.3')
| -rw-r--r-- | secure/lib/libssl/man/SSL_read.3 | 247 |
1 files changed, 247 insertions, 0 deletions
diff --git a/secure/lib/libssl/man/SSL_read.3 b/secure/lib/libssl/man/SSL_read.3 new file mode 100644 index 0000000..8fc6323 --- /dev/null +++ b/secure/lib/libssl/man/SSL_read.3 @@ -0,0 +1,247 @@ +.\" Automatically generated by Pod::Man 2.28 (Pod::Simple 3.28) +.\" +.\" 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 \- read bytes from a TLS/SSL connection. +.SH "SYNOPSIS" +.IX Header "SYNOPSIS" +.Vb 1 +\& #include <openssl/ssl.h> +\& +\& int SSL_read(SSL *ssl, void *buf, int num); +.Ve +.SH "DESCRIPTION" +.IX Header "DESCRIPTION" +\&\fISSL_read()\fR tries to read \fBnum\fR bytes from the specified \fBssl\fR into the +buffer \fBbuf\fR. +.SH "NOTES" +.IX Header "NOTES" +If necessary, \fISSL_read()\fR 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 \fISSL_read()\fR operation. The behaviour of \fISSL_read()\fR 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 call to an \fISSL_read()\fR or \fISSL_write\fR\|(3) +function. +.PP +\&\fISSL_read()\fR works based on the \s-1SSL/TLS\s0 records. The data are received in +records (with a maximum record size of 16kB for SSLv3/TLSv1). Only when a +record has been completely received, it can be processed (decryption and +check of integrity). Therefore data that was not retrieved at the last +call of \fISSL_read()\fR can still be buffered inside the \s-1SSL\s0 layer and will be +retrieved on the next call to \fISSL_read()\fR. If \fBnum\fR is higher than the +number of bytes buffered, \fISSL_read()\fR will return with the bytes buffered. +If no more bytes are in the buffer, \fISSL_read()\fR will trigger the processing +of the next record. Only when the record has been received and processed +completely, \fISSL_read()\fR will return reporting success. At most the contents +of the 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 \fISSL_read()\fR can succeed. +.PP +If the underlying \s-1BIO\s0 is \fBblocking\fR, \fISSL_read()\fR will only return, once the +read operation has been finished or an error occurred, except when a +renegotiation take place, in which case a \s-1SSL_ERROR_WANT_READ\s0 may occur. +This behaviour can be controlled with the \s-1SSL_MODE_AUTO_RETRY\s0 flag of the +\&\fISSL_CTX_set_mode\fR\|(3) call. +.PP +If the underlying \s-1BIO\s0 is \fBnon-blocking\fR, \fISSL_read()\fR will also return +when the underlying \s-1BIO\s0 could not satisfy the needs of \fISSL_read()\fR +to continue the operation. In this case a call to +\&\fISSL_get_error\fR\|(3) with the +return value of \fISSL_read()\fR will yield \fB\s-1SSL_ERROR_WANT_READ\s0\fR or +\&\fB\s-1SSL_ERROR_WANT_WRITE\s0\fR. As at any time a re-negotiation is possible, a +call to \fISSL_read()\fR can also cause write operations! The calling process +then must repeat the call after taking appropriate action to satisfy the +needs of \fISSL_read()\fR. 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 +\&\fISSL_read()\fR can be called without blocking or actually receiving new +data from the underlying socket. +.SH "WARNING" +.IX Header "WARNING" +When an \fISSL_read()\fR operation has to be repeated because of +\&\fB\s-1SSL_ERROR_WANT_READ\s0\fR or \fB\s-1SSL_ERROR_WANT_WRITE\s0\fR, it must be repeated +with the same arguments. +.SH "RETURN VALUES" +.IX Header "RETURN VALUES" +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 +The read operation was not successful. The reason may either be a clean +shutdown due to a \*(L"close notify\*(R" alert sent by the peer (in which case +the \s-1SSL_RECEIVED_SHUTDOWN\s0 flag in the ssl shutdown state is set +(see \fISSL_shutdown\fR\|(3), +\&\fISSL_set_shutdown\fR\|(3)). It is also possible, that +the peer simply shut down the underlying transport and the shutdown is +incomplete. Call \fISSL_get_error()\fR with the return value \fBret\fR to find out, +whether an error occurred or the connection was shut down cleanly +(\s-1SSL_ERROR_ZERO_RETURN\s0). +.Sp +SSLv2 (deprecated) does not support a shutdown alert protocol, so it can +only be detected, whether the underlying connection was closed. It cannot +be checked, whether the closure was initiated by the peer or by something +else. +.IP "<0" 4 +.IX Item "<0" +The read operation was not successful, because either an error occurred +or action must be taken by the calling process. Call \fISSL_get_error()\fR with the +return value \fBret\fR to find out the reason. +.SH "SEE ALSO" +.IX Header "SEE ALSO" +\&\fISSL_get_error\fR\|(3), \fISSL_write\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\|(3), \fIbio\fR\|(3) |
