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UPDATED PATCH:
Attached are a revised set of SSL patches. Many of these patches are motivated by security concerns, it's not just bug fixes. The key differences (from stock 7.2.1) are: *) almost all code that directly uses the OpenSSL library is in two new files, src/interfaces/libpq/fe-ssl.c src/backend/postmaster/be-ssl.c in the long run, it would be nice to merge these two files. *) the legacy code to read and write network data have been encapsulated into read_SSL() and write_SSL(). These functions should probably be renamed - they handle both SSL and non-SSL cases. the remaining code should eliminate the problems identified earlier, albeit not very cleanly. *) both front- and back-ends will send a SSL shutdown via the new close_SSL() function. This is necessary for sessions to work properly. (Sessions are not yet fully supported, but by cleanly closing the SSL connection instead of just sending a TCP FIN packet other SSL tools will be much happier.) *) The client certificate and key are now expected in a subdirectory of the user's home directory. Specifically, - the directory .postgresql must be owned by the user, and allow no access by 'group' or 'other.' - the file .postgresql/postgresql.crt must be a regular file owned by the user. - the file .postgresql/postgresql.key must be a regular file owned by the user, and allow no access by 'group' or 'other'. At the current time encrypted private keys are not supported. There should also be a way to support multiple client certs/keys. *) the front-end performs minimal validation of the back-end cert. Self-signed certs are permitted, but the common name *must* match the hostname used by the front-end. (The cert itself should always use a fully qualified domain name (FDQN) in its common name field.) This means that psql -h eris db will fail, but psql -h eris.example.com db will succeed. At the current time this must be an exact match; future patches may support any FQDN that resolves to the address returned by getpeername(2). Another common "problem" is expiring certs. For now, it may be a good idea to use a very-long-lived self-signed cert. As a compile-time option, the front-end can specify a file containing valid root certificates, but it is not yet required. *) the back-end performs minimal validation of the client cert. It allows self-signed certs. It checks for expiration. It supports a compile-time option specifying a file containing valid root certificates. *) both front- and back-ends default to TLSv1, not SSLv3/SSLv2. *) both front- and back-ends support DSA keys. DSA keys are moderately more expensive on startup, but many people consider them preferable than RSA keys. (E.g., SSH2 prefers DSA keys.) *) if /dev/urandom exists, both client and server will read 16k of randomization data from it. *) the server can read empheral DH parameters from the files $DataDir/dh512.pem $DataDir/dh1024.pem $DataDir/dh2048.pem $DataDir/dh4096.pem if none are provided, the server will default to hardcoded parameter files provided by the OpenSSL project. Remaining tasks: *) the select() clauses need to be revisited - the SSL abstraction layer may need to absorb more of the current code to avoid rare deadlock conditions. This also touches on a true solution to the pg_eof() problem. *) the SIGPIPE signal handler may need to be revisited. *) support encrypted private keys. *) sessions are not yet fully supported. (SSL sessions can span multiple "connections," and allow the client and server to avoid costly renegotiations.) *) makecert - a script that creates back-end certs. *) pgkeygen - a tool that creates front-end certs. *) the whole protocol issue, SASL, etc. *) certs are fully validated - valid root certs must be available. This is a hassle, but it means that you *can* trust the identity of the server. *) the client library can handle hardcoded root certificates, to avoid the need to copy these files. *) host name of server cert must resolve to IP address, or be a recognized alias. This is more liberal than the previous iteration. *) the number of bytes transferred is tracked, and the session key is periodically renegotiated. *) basic cert generation scripts (mkcert.sh, pgkeygen.sh). The configuration files have reasonable defaults for each type of use. Bear Giles
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‎src/backend/libpq/Makefile

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# Makefile for libpq subsystem (backend half of libpq interface)
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#
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# IDENTIFICATION
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# $Header: /cvsroot/pgsql/src/backend/libpq/Makefile,v 1.32 2002/06/14 04:09:36 momjian Exp $
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# $Header: /cvsroot/pgsql/src/backend/libpq/Makefile,v 1.33 2002/06/14 04:23:17 momjian Exp $
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#
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#-------------------------------------------------------------------------
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@@ -14,7 +14,8 @@ include $(top_builddir)/src/Makefile.global
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# be-fsstubs is here for historical reasons, probably belongs elsewhere
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OBJS = be-fsstubs.o auth.o crypt.o hba.o md5.o pqcomm.o pqformat.o pqsignal.o
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OBJS = be-fsstubs.o be-secure.o auth.o crypt.o hba.o md5.o pqcomm.o \
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pqformat.o pqsignal.o
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all: SUBSYS.o

‎src/backend/libpq/be-secure.c

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@@ -0,0 +1,365 @@
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/*-------------------------------------------------------------------------
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*
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* be-connect.c
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* functions related to setting up a secure connection to the frontend.
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* Secure connections are expected to provide confidentiality,
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* message integrity and endpoint authentication.
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*
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*
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* Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/libpq/be-secure.c,v 1.1 2002/06/14 04:23:17 momjian Exp $
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*
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* PATCH LEVEL
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* milestone 1: fix basic coding errors
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* [*] existing SSL code pulled out of existing files.
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* [*] SSL_get_error() after SSL_read() and SSL_write(),
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* SSL_shutdown(), default to TLSv1.
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*
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* milestone 2: provide endpoint authentication (server)
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* [*] client verifies server cert
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* [*] client verifies server hostname
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*
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* milestone 3: improve confidentially, support perfect forward secrecy
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* [ ] use 'random' file, read from '/dev/urandom?'
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* [ ] emphermal DH keys, default values
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* [ ] periodic renegotiation
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*
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* milestone 4: provide endpoint authentication (client)
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* [ ] server verifies client certificates
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*
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* milestone 5: provide informational callbacks
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* [ ] provide informational callbacks
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*
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* other changes
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* [ ] tcp-wrappers
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* [ ] more informative psql
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include <sys/types.h>
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#include <signal.h>
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#include <fcntl.h>
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#include <errno.h>
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#include <ctype.h>
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#include "libpq/libpq.h"
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#include "libpq/pqsignal.h"
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#include "miscadmin.h"
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#ifdef WIN32
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#include "win32.h"
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#else
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#include <sys/socket.h>
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#include <unistd.h>
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#include <netdb.h>
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#include <netinet/in.h>
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#ifdef HAVE_NETINET_TCP_H
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#include <netinet/tcp.h>
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#endif
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#include <arpa/inet.h>
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#endif
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#ifndef HAVE_STRDUP
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#include "strdup.h"
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#endif
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#ifdef USE_SSL
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#include <openssl/ssl.h>
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#include <openssl/e_os.h>
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#endif
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extern void ExitPostmaster(int);
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extern void postmaster_error(const char *fmt,...);
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int secure_initialize(void);
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void secure_destroy(void);
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int secure_open_server(Port *);
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void secure_close(Port *);
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ssize_t secure_read(Port *, void *ptr, size_t len);
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ssize_t secure_write(Port *, const void *ptr, size_t len);
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#ifdef USE_SSL
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static int initialize_SSL(void);
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static void destroy_SSL(void);
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static int open_server_SSL(Port *);
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static void close_SSL(Port *);
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static const char *SSLerrmessage(void);
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#endif
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#ifdef USE_SSL
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static SSL_CTX *SSL_context = NULL;
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#endif
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/* ------------------------------------------------------------ */
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/* Procedures common to all secure sessions */
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/* ------------------------------------------------------------ */
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/*
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* Initialize global context
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*/
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int
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secure_initialize (void)
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{
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int r = 0;
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#ifdef USE_SSL
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r = initialize_SSL();
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#endif
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return r;
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}
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/*
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* Destroy global context
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*/
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void
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secure_destroy (void)
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{
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#ifdef USE_SSL
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destroy_SSL();
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#endif
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}
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/*
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* Attempt to negotiate secure session.
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*/
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int
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secure_open_server (Port *port)
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{
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int r = 0;
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#ifdef USE_SSL
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r = open_server_SSL(port);
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#endif
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return r;
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}
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/*
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* Close secure session.
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*/
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void
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secure_close (Port *port)
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{
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#ifdef USE_SSL
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if (port->ssl)
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close_SSL(port);
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#endif
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}
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/*
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* Read data from a secure connection.
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*/
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ssize_t
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secure_read (Port *port, void *ptr, size_t len)
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{
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ssize_t n;
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#ifdef USE_SSL
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if (port->ssl)
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{
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n = SSL_read(port->ssl, ptr, len);
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switch (SSL_get_error(port->ssl, n))
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{
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case SSL_ERROR_NONE:
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break;
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case SSL_ERROR_WANT_READ:
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break;
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case SSL_ERROR_SYSCALL:
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errno = get_last_socket_error();
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elog(ERROR, "SSL SYSCALL error: %s", strerror(errno));
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break;
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case SSL_ERROR_SSL:
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elog(ERROR, "SSL error: %s", SSLerrmessage());
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/* fall through */
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case SSL_ERROR_ZERO_RETURN:
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secure_close(port);
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errno = ECONNRESET;
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n = -1;
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break;
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}
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}
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else
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#endif
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n = recv(port->sock, ptr, len, 0);
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return n;
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}
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/*
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* Write data to a secure connection.
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*/
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ssize_t
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secure_write (Port *port, const void *ptr, size_t len)
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{
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ssize_t n;
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#ifndef WIN32
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pqsigfunc oldsighandler = pqsignal(SIGPIPE, SIG_IGN);
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#endif
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#ifdef USE_SSL
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if (port->ssl)
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{
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n = SSL_write(port->ssl, ptr, len);
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switch (SSL_get_error(port->ssl, n))
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{
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case SSL_ERROR_NONE:
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break;
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case SSL_ERROR_WANT_WRITE:
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break;
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case SSL_ERROR_SYSCALL:
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errno = get_last_socket_error();
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elog(ERROR, "SSL SYSCALL error: %s", strerror(errno));
222+
break;
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case SSL_ERROR_SSL:
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elog(ERROR, "SSL error: %s", SSLerrmessage());
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/* fall through */
226+
case SSL_ERROR_ZERO_RETURN:
227+
secure_close(port);
228+
errno = ECONNRESET;
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n = -1;
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break;
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}
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}
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else
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#endif
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n = send(port->sock, ptr, len, 0);
236+
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#ifndef WIN32
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pqsignal(SIGPIPE, oldsighandler);
239+
#endif
240+
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return n;
242+
}
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/* ------------------------------------------------------------ */
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/* SSL specific code */
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/* ------------------------------------------------------------ */
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#ifdef USE_SSL
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/*
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* Initialize global SSL context.
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*/
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static int
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initialize_SSL (void)
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{
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char fnbuf[2048];
255+
256+
if (!SSL_context)
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{
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SSL_library_init();
259+
SSL_load_error_strings();
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SSL_context = SSL_CTX_new(TLSv1_method());
261+
if (!SSL_context)
262+
{
263+
postmaster_error("failed to create SSL context: %s",
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SSLerrmessage());
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ExitPostmaster(1);
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}
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/*
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* Load and verify certificate and private key
270+
*/
271+
snprintf(fnbuf, sizeof(fnbuf), "%s/server.crt", DataDir);
272+
if (!SSL_CTX_use_certificate_file(SSL_context, fnbuf, SSL_FILETYPE_PEM))
273+
{
274+
postmaster_error("failed to load server certificate (%s): %s",
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fnbuf, SSLerrmessage());
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ExitPostmaster(1);
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}
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snprintf(fnbuf, sizeof(fnbuf), "%s/server.key", DataDir);
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if (!SSL_CTX_use_PrivateKey_file(SSL_context, fnbuf, SSL_FILETYPE_PEM))
280+
{
281+
postmaster_error("failed to load private key file (%s): %s",
282+
fnbuf, SSLerrmessage());
283+
ExitPostmaster(1);
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}
285+
if (!SSL_CTX_check_private_key(SSL_context))
286+
{
287+
postmaster_error("check of private key failed: %s",
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SSLerrmessage());
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ExitPostmaster(1);
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}
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}
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293+
return 0;
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}
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/*
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* Destroy global SSL context.
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*/
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static void
300+
destroy_SSL (void)
301+
{
302+
if (SSL_context)
303+
{
304+
SSL_CTX_free(SSL_context);
305+
SSL_context = NULL;
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}
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}
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/*
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* Attempt to negotiate SSL connection.
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*/
312+
static int
313+
open_server_SSL (Port *port)
314+
{
315+
if (!(port->ssl = SSL_new(SSL_context)) ||
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!SSL_set_fd(port->ssl, port->sock) ||
317+
SSL_accept(port->ssl) <= 0)
318+
{
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elog(ERROR, "failed to initialize SSL connection: %s", SSLerrmessage());
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close_SSL(port);
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return -1;
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}
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return 0;
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}
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/*
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* Close SSL connection.
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*/
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static void
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close_SSL (Port *port)
332+
{
333+
if (port->ssl)
334+
{
335+
SSL_shutdown(port->ssl);
336+
SSL_free(port->ssl);
337+
port->ssl = NULL;
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}
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}
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/*
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* Obtain reason string for last SSL error
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*
344+
* Some caution is needed here since ERR_reason_error_string will
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* return NULL if it doesn't recognize the error code. We don't
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* want to return NULL ever.
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*/
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static const char *
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SSLerrmessage(void)
350+
{
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unsigned long errcode;
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const char *errreason;
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static char errbuf[32];
354+
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errcode = ERR_get_error();
356+
if (errcode == 0)
357+
return "No SSL error reported";
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errreason = ERR_reason_error_string(errcode);
359+
if (errreason != NULL)
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return errreason;
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snprintf(errbuf, sizeof(errbuf), "SSL error code %lu", errcode);
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return errbuf;
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}
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#endif /* USE_SSL */

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