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351 lines
11 KiB
C
351 lines
11 KiB
C
/*++
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* NAME
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* tls_bio_ops 3
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* SUMMARY
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* TLS network BIO management
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* SYNOPSIS
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* #include <tls.h>
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* #include <tls_private.h>
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*
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* int tls_bio_connect(fd, timeout, context)
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* int fd;
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* int timeout;
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* TLS_SESS_STATE *context;
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*
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* int tls_bio_accept(fd, timeout, context)
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* int fd;
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* int timeout;
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* TLS_SESS_STATE *context;
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*
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* int tls_bio_shutdown(fd, timeout, context)
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* int fd;
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* int timeout;
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* TLS_SESS_STATE *context;
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*
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* int tls_bio_read(fd, buf, len, timeout, context)
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* int fd;
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* void *buf;
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* int len;
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* int timeout;
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* TLS_SESS_STATE *context;
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*
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* int tls_bio_write(fd, buf, len, timeout, context)
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* int fd;
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* void *buf;
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* int len;
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* int timeout;
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* TLS_SESS_STATE *context;
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* DESCRIPTION
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* This layer synchronizes the TLS network buffers with the network
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* while performing TLS handshake or input/output operations.
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*
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* When the TLS layer is active, it converts plain-text
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* data from Postfix into encrypted network data and vice versa.
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* However, to handle network timeout conditions, Postfix
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* needs to maintain control over network input/output. This
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* rules out the usual approach of placing the TLS layer
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* between the application and the network socket.
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*
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* As shown below, Postfix reads/writes plain-text data from/to
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* the TLS layer. The TLS layer informs Postfix when it needs
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* to read/write encrypted data from/to the network; Postfix
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* then reads/writes encrypted data from/to the TLS layer and
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* takes care of the network socket I/O.
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*
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* The TLS layer to network interface is realized with a BIO pair:
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*
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* Postfix | TLS layer
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* |
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* smtp/smtpd |
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* /\ || |
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* || \/ |
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* vstream read/write <===> TLS read/write/etc
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* | /\ ||
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* | || \/
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* | BIO pair (internal_bio)
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* | BIO pair (network_bio)
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* | /\ ||
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* | || \/
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* socket read/write <===> BIO read/write
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* /\ || |
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* || \/ |
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* network |
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*
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* The Postfix VSTREAM read/write operations invoke the SSL
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* read/write operations to send and retrieve plain-text data. Inside
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* the TLS layer the data are converted to/from TLS protocol.
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*
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* Whenever an SSL operation reports success, or whenever it
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* indicates that network input/output needs to happen, Postfix
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* uses the BIO read/write routines to synchronize the
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* network_bio buffer with the network. Writing data to the
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* network has precedence over reading from the network. This
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* is necessary to avoid deadlock.
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*
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* The BIO pair buffer size is set to 8192 bytes. This is much
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* larger than the typical Path MTU, and avoids sending tiny TCP
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* segments. It is also larger than the default VSTREAM_BUFSIZE
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* (4096, see vstream.h), so that large write operations can
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* be handled within one request. The internal buffer in the
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* network/network_bio handling layer is set to the same
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* value, since this seems to be reasonable. The code is
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* however able to handle arbitrary values smaller or larger
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* than the buffer size in the BIO pair.
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*
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* tls_bio_connect() performs the SSL_connect() operation while
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* synchronizing the network_bio buffer with the network.
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*
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* tls_bio_accept() performs the SSL_accept() operation while
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* synchronizing the network_bio buffer with the network.
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*
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* tls_bio_shutdown() performs the SSL_shutdown() operation while
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* synchronizing the network_bio buffer with the network.
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*
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* tls_bio_read() performs the SSL_read() operation while
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* synchronizing the network_bio buffer with the network.
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*
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* tls_bio_write() performs the SSL_write() operation while
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* synchronizing the network_bio buffer with the network.
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*
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* Arguments:
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* .IP fd
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* Network socket.
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* .IP buf
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* Read/write buffer.
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* .IP len
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* Read/write request size.
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* .IP timeout
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* Read/write timeout.
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* .IP TLScontext
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* TLS session state.
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* DIAGNOSTICS
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* The result value is -1 in case of a network read/write
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* error, otherwise it is the result value of the TLS operation.
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* LICENSE
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* .ad
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* .fi
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* This software is free. You can do with it whatever you want.
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* The original author kindly requests that you acknowledge
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* the use of his software.
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* AUTHOR(S)
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* Originally written by:
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* Lutz Jaenicke
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* BTU Cottbus
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* Allgemeine Elektrotechnik
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* Universitaetsplatz 3-4
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* D-03044 Cottbus, Germany
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*
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* Updated by:
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* Wietse Venema
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* IBM T.J. Watson Research
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* P.O. Box 704
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* Yorktown Heights, NY 10598, USA
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*
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* Victor Duchovni
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* Morgan Stanley
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*--*/
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/* System library. */
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#include "StdAfx.h"
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#ifdef USE_TLS
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/* TLS library. */
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#include "tls.h"
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#include "tls_private.h"
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/* Application-specific. */
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#define NETLAYER_BUFFERSIZE 8192
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/* network_biopair_interop - synchronize network with BIO pair */
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static int network_biopair_interop(ACL_SOCKET fd, int timeout, BIO *network_bio)
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{
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const char *myname = "network_biopair_interop";
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int want_write;
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int num_write;
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int write_pos;
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int from_bio;
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int want_read;
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int num_read;
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int to_bio;
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char buffer[NETLAYER_BUFFERSIZE];
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/*
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* To avoid deadlock, write all pending data to the network before
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* attempting to read from the network.
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*/
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while ((want_write = (int) BIO_ctrl_pending(network_bio)) > 0) {
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if (want_write > (int) sizeof(buffer))
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want_write = (int) sizeof(buffer);
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from_bio = BIO_read(network_bio, buffer, want_write);
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/*
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* Write the complete buffer contents to the network.
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*/
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for (write_pos = 0; write_pos < from_bio; /* see below */ ) {
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if (timeout > 0 && acl_write_wait(fd, timeout) < 0)
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return (-1);
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num_write = acl_socket_write(fd, buffer + write_pos, from_bio - write_pos, 0, 0, 0);
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if (num_write <= 0) {
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if ((num_write < 0) && (timeout > 0) && (errno == ACL_EAGAIN || errno == ACL_EINTR)) {
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acl_msg_warn("%s: write() returns EAGAIN on a writable file descriptor!", myname);
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acl_msg_warn("%s: pausing to avoid going into a tight select/write loop!", myname);
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sleep(1);
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} else {
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acl_msg_warn("%s: error writing %d bytes to the network: %s",
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myname, from_bio - write_pos, acl_last_serror());
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return (-1);
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}
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} else {
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write_pos += num_write;
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}
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}
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}
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/*
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* Read data from the network into the BIO pair.
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*/
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while ((want_read = (int) BIO_ctrl_get_read_request(network_bio)) > 0) {
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if (want_read > (int) sizeof(buffer))
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want_read = (int) sizeof(buffer);
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if (timeout > 0 && acl_read_wait(fd, timeout) < 0)
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return (-1);
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num_read = acl_socket_read(fd, buffer, want_read, 0, 0, 0);
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if (num_read == 0)
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/* FIX 200412 Cannot return a zero read count. */
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return (-1);
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if (num_read < 0) {
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if ((num_read < 0) && (timeout > 0) && (errno == ACL_EAGAIN || errno == ACL_EINTR)) {
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acl_msg_warn("%s: read() returns EAGAIN on a readable file descriptor!", myname);
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acl_msg_warn("%s: pausing to avoid going into a tight select/write loop!", myname);
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sleep(1);
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} else {
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acl_msg_warn("%s: error reading %d bytes from the network: %s",
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myname, want_read, acl_last_serror());
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return (-1);
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}
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} else {
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to_bio = BIO_write(network_bio, buffer, num_read);
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if (to_bio != num_read)
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acl_msg_panic("%s: BIO_write error: to_bio != num_read", myname);
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}
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}
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return (0);
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}
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/* tls_bio - perform SSL input/output operation with extreme prejudice */
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int tls_bio(ACL_SOCKET fd, int timeout, TLS_SESS_STATE *TLScontext,
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int (*hsfunc) (SSL *),
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int (*rfunc) (SSL *, void *, int),
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int (*wfunc) (SSL *, const void *, int),
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void *buf, int num)
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{
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const char *myname = "tls_bio";
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int status = 0;
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int err;
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int retval = 0;
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int biop_retval;
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int done;
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/*
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* If necessary, retry the SSL handshake or read/write operation after
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* handling any pending network I/O.
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*/
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for (done = 0; done == 0; /* void */ ) {
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if (hsfunc) {
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#if 1
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status = hsfunc(TLScontext->con);
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#else
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status = SSL_do_handshake(TLScontext->con);
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#endif
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} else if (rfunc)
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status = rfunc(TLScontext->con, buf, num);
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else if (wfunc)
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status = wfunc(TLScontext->con, buf, num);
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else
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acl_msg_panic("%s: nothing to do here", myname);
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err = SSL_get_error(TLScontext->con, status);
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#if (OPENSSL_VERSION_NUMBER <= 0x0090581fL)
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/*
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* There is a bug up to and including OpenSSL-0.9.5a: if an error
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* occurs while checking the peers certificate due to some
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* certificate error (e.g. as happend with a RSA-padding error), the
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* error is put onto the error stack. If verification is not
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* enforced, this error should be ignored, but the error-queue is not
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* cleared, so we can find this error here. The bug has been fixed on
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* May 28, 2000.
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*
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* This bug so far has only manifested as 4800:error:0407006A:rsa
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* routines:RSA_padding_check_PKCS1_type_1:block type is not
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* 01:rsa_pk1.c:100: 4800:error:04067072:rsa
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* routines:RSA_EAY_PUBLIC_DECRYPT:padding check
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* failed:rsa_eay.c:396: 4800:error:0D079006:asn1 encoding
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* routines:ASN1_verify:bad get asn1 object call:a_verify.c:109: so
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* that we specifically test for this error. We print the errors to
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* the logfile and automatically clear the error queue. Then we retry
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* to get another error code. We cannot do better, since we can only
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* retrieve the last entry of the error-queue without actually
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* cleaning it on the way.
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*
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* This workaround is secure, as verify_result is set to "failed"
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* anyway.
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*/
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if (err == SSL_ERROR_SSL) {
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if (ERR_peek_error() == 0x0407006AL) {
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tls_print_errors();
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acl_msg_info("OpenSSL <= 0.9.5a workaround called: certificate errors ignored");
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err = SSL_get_error(TLScontext->con, status);
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}
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}
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#endif
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/*
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* Find out if we must retry the operation and/or if there is pending
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* network I/O.
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*
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* XXX If we're the first to invoke SSL_shutdown(), then the operation
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* isn't really complete when the call returns. We could hide that
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* anomaly here and repeat the call.
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*/
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switch (err) {
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case SSL_ERROR_NONE: /* success */
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retval = status;
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done = 1;
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/* FALLTHROUGH */
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case SSL_ERROR_WANT_WRITE: /* flush/update buffers */
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case SSL_ERROR_WANT_READ:
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biop_retval = network_biopair_interop(fd, timeout, TLScontext->network_bio);
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if (biop_retval < 0)
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return (-1); /* network read/write error */
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break;
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/*
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* With tls_timed_read() and tls_timed_write() the caller is the
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* VSTREAM library module which is unaware of TLS, so we log the
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* TLS error stack here. In a better world, each VSTREAM I/O
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* object would provide an error reporting method in addition to
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* the timed_read and timed_write methods, so that we would not
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* need to have ad-hoc code like this.
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*/
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case SSL_ERROR_SSL:
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if (rfunc || wfunc)
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tls_print_errors();
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/* FALLTHROUGH */
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default:
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retval = status;
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done = 1;
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break;
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}
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}
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return (retval);
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}
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#endif
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