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crypto.c
813 lines (712 loc) · 21.6 KB
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crypto.c
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/* nbdkit
* Copyright (C) 2017-2022 Red Hat Inc.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* * Neither the name of Red Hat nor the names of its contributors may be
* used to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
* PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <stdint.h>
#include <stdbool.h>
#include <inttypes.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/types.h>
#include <assert.h>
#include "cleanup.h"
#include "internal.h"
#include "realpath.h"
#include "strndup.h"
#ifdef HAVE_GNUTLS
#include <gnutls/gnutls.h>
#include <gnutls/x509.h>
#if defined HAVE_GNUTLS_TRANSPORT_IS_KTLS_ENABLED && \
defined HAVE_GNUTLS_SOCKET_H
#define TRY_KTLS 1
#else
#define TRY_KTLS 0
#endif
#if TRY_KTLS
#include <gnutls/socket.h>
#endif
static int crypto_auth;
#define CRYPTO_AUTH_CERTIFICATES 1
#define CRYPTO_AUTH_PSK 2
static gnutls_certificate_credentials_t x509_creds;
static gnutls_psk_server_credentials_t psk_creds;
static void print_gnutls_error (int err, const char *fs, ...)
ATTRIBUTE_FORMAT_PRINTF(2, 3);
static void
print_gnutls_error (int err, const char *fs, ...)
{
va_list args;
fprintf (stderr, "%s: GnuTLS error: ", program_name);
va_start (args, fs);
vfprintf (stderr, fs, args);
va_end (args);
fprintf (stderr, ": %s\n", gnutls_strerror (err));
}
/* Try to load certificates from 'path'. Returns true if successful.
* If it's not a certicate directory it returns false. Exits on
* other errors.
*/
static int
load_certificates (const char *path)
{
CLEANUP_FREE char *ca_cert_filename = NULL;
CLEANUP_FREE char *server_cert_filename = NULL;
CLEANUP_FREE char *server_key_filename = NULL;
CLEANUP_FREE char *ca_crl_filename = NULL;
int err;
if (asprintf (&ca_cert_filename, "%s/ca-cert.pem", path) == -1) {
perror ("asprintf");
exit (EXIT_FAILURE);
}
if (asprintf (&server_cert_filename, "%s/server-cert.pem", path) == -1) {
perror ("asprintf");
exit (EXIT_FAILURE);
}
if (asprintf (&server_key_filename, "%s/server-key.pem", path) == -1) {
perror ("asprintf");
exit (EXIT_FAILURE);
}
if (asprintf (&ca_crl_filename, "%s/ca-crl.pem", path) == -1) {
perror ("asprintf");
exit (EXIT_FAILURE);
}
/* Our test for a certificate directory is that ca-cert.pem,
* server-cert.pem and server-key.pem must all exist in the path.
*/
if (access (ca_cert_filename, R_OK) == -1)
return 0;
if (access (server_cert_filename, R_OK) == -1)
return 0;
if (access (server_key_filename, R_OK) == -1)
return 0;
/* Any problem past here is a hard error. */
err = gnutls_certificate_allocate_credentials (&x509_creds);
if (err < 0) {
print_gnutls_error (err, "allocating credentials");
exit (EXIT_FAILURE);
}
err = gnutls_certificate_set_x509_trust_file (x509_creds, ca_cert_filename,
GNUTLS_X509_FMT_PEM);
if (err < 0) {
print_gnutls_error (err, "loading %s", ca_cert_filename);
exit (EXIT_FAILURE);
}
if (access (ca_crl_filename, R_OK) == 0) {
err = gnutls_certificate_set_x509_crl_file (x509_creds, ca_crl_filename,
GNUTLS_X509_FMT_PEM);
if (err < 0) {
print_gnutls_error (err, "loading %s", ca_crl_filename);
exit (EXIT_FAILURE);
}
}
err = gnutls_certificate_set_x509_key_file (x509_creds,
server_cert_filename,
server_key_filename,
GNUTLS_X509_FMT_PEM);
if (err < 0) {
print_gnutls_error (err, "loading server certificate and key (%s, %s)",
server_cert_filename, server_key_filename);
exit (EXIT_FAILURE);
}
debug ("successfully loaded TLS certificates from %s", path);
return 1;
}
static int
start_certificates (void)
{
/* Try to locate the certificates directory and load them. */
if (tls_certificates_dir == NULL) {
const char *home;
CLEANUP_FREE char *path = NULL;
#ifndef WIN32
#define RUNNING_AS_NON_ROOT_FOR_CERTIFICATES_DIR (geteuid () != 0)
#else
#define RUNNING_AS_NON_ROOT_FOR_CERTIFICATES_DIR 0
#endif
if (RUNNING_AS_NON_ROOT_FOR_CERTIFICATES_DIR) {
home = getenv ("HOME");
if (home) {
if (asprintf (&path, "%s/.pki/%s", home, PACKAGE_NAME) == -1) {
perror ("asprintf");
exit (EXIT_FAILURE);
}
if (load_certificates (path))
goto found_certificates;
free (path);
if (asprintf (&path, "%s/.config/pki/%s", home, PACKAGE_NAME) == -1) {
perror ("asprintf");
exit (EXIT_FAILURE);
}
if (load_certificates (path))
goto found_certificates;
}
}
else { /* geteuid () == 0 */
if (load_certificates (root_tls_certificates_dir))
goto found_certificates;
}
}
else {
if (load_certificates (tls_certificates_dir))
goto found_certificates;
}
return -1;
found_certificates:
#ifdef HAVE_GNUTLS_CERTIFICATE_SET_KNOWN_DH_PARAMS
gnutls_certificate_set_known_dh_params (x509_creds, GNUTLS_SEC_PARAM_MEDIUM);
#endif
return 0;
}
static int
start_psk (void)
{
int err;
CLEANUP_FREE char *abs_psk_file = NULL;
/* Make sure the path to the PSK file is absolute. */
abs_psk_file = realpath (tls_psk, NULL);
if (abs_psk_file == NULL) {
perror (tls_psk);
exit (EXIT_FAILURE);
}
err = gnutls_psk_allocate_server_credentials (&psk_creds);
if (err < 0) {
print_gnutls_error (err, "allocating PSK credentials");
exit (EXIT_FAILURE);
}
/* Note that this function makes a copy of the string.
* CLEANUP_FREE macro above will free abs_psk_file when
* we return, but this is safe.
*/
gnutls_psk_set_server_credentials_file (psk_creds, abs_psk_file);
return 0;
}
/* Initialize crypto. This also handles the command line parameters
* and loading the server certificate.
*/
void
crypto_init (bool tls_set_on_cli)
{
int err, r;
const char *what;
err = gnutls_global_init ();
if (err < 0) {
print_gnutls_error (err, "initializing GnuTLS");
exit (EXIT_FAILURE);
}
if (tls == 0) /* --tls=off */
return;
/* --tls-psk overrides certificates. */
if (tls_psk != NULL) {
what = "Pre-Shared Keys (PSK)";
r = start_psk ();
if (r == 0)
crypto_auth = CRYPTO_AUTH_PSK;
}
else {
what = "X.509 certificates";
r = start_certificates ();
if (r == 0)
crypto_auth = CRYPTO_AUTH_CERTIFICATES;
}
if (r == 0) {
debug ("TLS enabled using: %s", what);
return;
}
/* If we get here, we didn't manage to load the PSK file /
* certificates. If --tls=require was given on the command line
* then that's a problem.
*/
if (tls == 2) { /* --tls=require */
fprintf (stderr,
"%s: --tls=require but could not load TLS certificates.\n"
"Try setting ‘--tls-certificates=/path/to/certificates’ or read\n"
"the \"TLS\" section in nbdkit(1).\n",
program_name);
exit (EXIT_FAILURE);
}
/* If --tls=on was given on the command line, warn before we turn
* TLS off.
*/
if (tls == 1 && tls_set_on_cli) { /* explicit --tls=on */
fprintf (stderr,
"%s: warning: --tls=on but could not load TLS certificates.\n"
"TLS will be disabled and TLS connections will be rejected.\n"
"Try setting ‘--tls-certificates=/path/to/certificates’ or read\n"
"the \"TLS\" section in nbdkit(1).\n",
program_name);
}
tls = 0;
debug ("TLS disabled: could not load TLS certificates");
}
void
crypto_free (void)
{
if (tls > 0) {
switch (crypto_auth) {
case CRYPTO_AUTH_CERTIFICATES:
gnutls_certificate_free_credentials (x509_creds);
break;
case CRYPTO_AUTH_PSK:
gnutls_psk_free_server_credentials (psk_creds);
break;
}
}
gnutls_global_deinit ();
}
/* Read buffer from GnuTLS and either succeed completely
* (returns > 0), read an EOF (returns 0), or fail (returns -1).
*/
static int
crypto_recv (void *vbuf, size_t len)
{
GET_CONN;
gnutls_session_t session = conn->crypto_session;
char *buf = vbuf;
ssize_t r;
bool first_read = true;
assert (session != NULL);
while (len > 0) {
r = gnutls_record_recv (session, buf, len);
if (r < 0) {
if (r == GNUTLS_E_INTERRUPTED || r == GNUTLS_E_AGAIN)
continue;
nbdkit_error ("gnutls_record_recv: %s", gnutls_strerror (r));
errno = EIO;
return -1;
}
if (r == 0) {
if (first_read)
return 0;
/* Partial record read. This is an error. */
errno = EBADMSG;
return -1;
}
first_read = false;
buf += r;
len -= r;
}
return 1;
}
/* If this send()'s length is so large that it is going to require
* multiple TCP segments anyway, there's no need to try and merge it
* with any corked data from a previous send that used SEND_MORE.
*/
#define MAX_SEND_MORE_LEN (64 * 1024)
/* Write buffer to GnuTLS and either succeed completely
* (returns 0) or fail (returns -1). flags is ignored for now.
*/
static int
crypto_send (const void *vbuf, size_t len, int flags)
{
GET_CONN;
gnutls_session_t session = conn->crypto_session;
const char *buf = vbuf;
ssize_t r;
assert (session != NULL);
if (len + gnutls_record_check_corked (session) > MAX_SEND_MORE_LEN) {
if (gnutls_record_uncork (session, GNUTLS_RECORD_WAIT) < 0)
return -1;
}
else if (flags & SEND_MORE)
gnutls_record_cork (session);
while (len > 0) {
r = gnutls_record_send (session, buf, len);
if (r < 0) {
if (r == GNUTLS_E_INTERRUPTED || r == GNUTLS_E_AGAIN)
continue;
return -1;
}
buf += r;
len -= r;
}
if (!(flags & SEND_MORE) &&
gnutls_record_uncork (session, GNUTLS_RECORD_WAIT) < 0)
return -1;
return 0;
}
/* There's no place in the NBD protocol to send back errors from
* close, so this function ignores errors.
*/
static void
crypto_close (int how)
{
GET_CONN;
gnutls_session_t session = conn->crypto_session;
int sockin, sockout;
assert (session != NULL);
if (how == SHUT_WR)
gnutls_bye (session, GNUTLS_SHUT_WR);
else {
gnutls_transport_get_int2 (session, &sockin, &sockout);
gnutls_bye (session, GNUTLS_SHUT_RDWR);
if (sockin >= 0)
closesocket (sockin);
if (sockout >= 0 && sockin != sockout)
closesocket (sockout);
gnutls_deinit (session);
conn->crypto_session = NULL;
}
}
#ifdef WIN32
/* Push/pull functions. Only required for Windows, because on Unix we
* can use the default send(2) and recv(2). Note these are actually
* calling the wrappers win_send and win_recv in windows-compat.h
*/
static ssize_t
push (gnutls_transport_ptr_t ptr, const void *buf, size_t n)
{
ssize_t r;
r = send ((intptr_t) ptr, buf, n, 0);
/* XXX call gnutls_transport_set_errno here */
return r;
}
static ssize_t
pull (gnutls_transport_ptr_t ptr, void *buf, size_t n)
{
ssize_t r;
r = recv ((intptr_t) ptr, buf, n, 0);
/* XXX call gnutls_transport_set_errno here */
return r;
}
static int
pull_timeout (gnutls_transport_ptr_t ptr, unsigned ms)
{
#if 0
/* XXX This is what you're supposed to do, but I couldn't get it to
* work.
*/
return gnutls_system_recv_timeout (ptr, ms);
#endif
return 1;
}
#endif /* WIN32 */
/* Turn GnuTLS debug messages into nbdkit debug messages
* when nbdkit -D nbdkit.tls.log > 0
*/
NBDKIT_DLL_PUBLIC int nbdkit_debug_tls_log = 0;
static void
tls_log (int level, const char *msg)
{
size_t len;
CLEANUP_FREE char *copy = NULL;
/* Strip trailing \n added by GnuTLS. */
len = strlen (msg);
if (len > 0 && msg[len-1] == '\n') {
copy = strndup (msg, len-1);
msg = copy;
}
nbdkit_debug ("gnutls: %d: %s", level, msg);
}
/* Print additional information about the session using
* nbdkit -D nbdkit.tls.session=1
*
* https://gnutls.org/manual/html_node/Obtaining-session-information.html
*/
NBDKIT_DLL_PUBLIC int nbdkit_debug_tls_session = 0;
static void
debug_x590_cert (gnutls_session_t session)
{
const gnutls_datum_t *cert_list;
unsigned int i, cert_list_size = 0;
cert_list = gnutls_certificate_get_peers (session, &cert_list_size);
if (cert_list == NULL) {
/* Note unless you use --tls-verify-peer you will always see the
* following message.
*/
nbdkit_debug ("TLS: no peer certificates found");
return;
}
nbdkit_debug ("TLS: peer provided %u certificate(s)", cert_list_size);
for (i = 0; i < cert_list_size; ++i) {
int ret;
gnutls_x509_crt_t cert;
gnutls_datum_t cinfo;
/* This is for debugging; best-effort is okay */
ret = gnutls_x509_crt_init (&cert);
if (ret != 0)
continue;
ret = gnutls_x509_crt_import (cert, &cert_list[i], GNUTLS_X509_FMT_DER);
if (ret != 0) {
gnutls_x509_crt_deinit (cert);
continue;
}
ret = gnutls_x509_crt_print (cert, GNUTLS_CRT_PRINT_ONELINE, &cinfo);
if (ret == 0) {
nbdkit_debug ("TLS: %s", cinfo.data);
gnutls_free (cinfo.data);
}
gnutls_x509_crt_deinit (cert);
}
}
static void
debug_session (gnutls_session_t session)
{
gnutls_credentials_type_t cred;
gnutls_kx_algorithm_t kx;
bool dhe = false, ecdh = false;
int grp;
const char *desc, *username, *hint;
#if TRY_KTLS
gnutls_transport_ktls_enable_flags_t ktls_enabled;
#endif
if (nbdkit_debug_tls_session <= 0)
return;
desc = gnutls_session_get_desc (session);
if (desc) nbdkit_debug ("TLS session: %s", desc);
#if TRY_KTLS
ktls_enabled = gnutls_transport_is_ktls_enabled (session);
switch (ktls_enabled) {
case GNUTLS_KTLS_RECV:
nbdkit_debug ("TLS: kTLS enabled for receive only"); break;
case GNUTLS_KTLS_SEND:
nbdkit_debug ("TLS: kTLS enabled for send only"); break;
case GNUTLS_KTLS_DUPLEX:
nbdkit_debug ("TLS: kTLS enabled full duplex"); break;
default:
if ((int) ktls_enabled == 0)
nbdkit_debug ("TLS: kTLS disabled");
else
nbdkit_debug ("TLS: kTLS enabled unknown setting: %d",
(int) ktls_enabled);
}
#endif
kx = gnutls_kx_get (session);
cred = gnutls_auth_get_type (session);
switch (cred) {
case GNUTLS_CRD_SRP:
nbdkit_debug ("TLS: authentication: SRP (Secure Remote Password)");
#ifdef HAVE_GNUTLS_SRP_SERVER_GET_USERNAME
username = gnutls_srp_server_get_username (session);
#else
username = NULL;
#endif
if (username)
nbdkit_debug ("TLS: SRP session username: %s", username);
break;
case GNUTLS_CRD_PSK:
nbdkit_debug ("TLS: authentication: PSK (Pre-Shared Key)");
hint = gnutls_psk_client_get_hint (session);
if (hint)
nbdkit_debug ("TLS: PSK hint: %s", hint);
username = gnutls_psk_server_get_username (session);
if (username)
nbdkit_debug ("TLS: PSK username: %s", username);
if (kx == GNUTLS_KX_ECDHE_PSK)
ecdh = true;
else if (kx == GNUTLS_KX_DHE_PSK)
dhe = true;
break;
case GNUTLS_CRD_ANON:
nbdkit_debug ("TLS: authentication: anonymous");
if (kx == GNUTLS_KX_ANON_ECDH)
ecdh = true;
else if (kx == GNUTLS_KX_ANON_DH)
dhe = true;
break;
case GNUTLS_CRD_CERTIFICATE:
nbdkit_debug ("TLS: authentication: certificate");
if (gnutls_certificate_type_get (session) == GNUTLS_CRT_X509)
debug_x590_cert (session);
if (kx == GNUTLS_KX_DHE_RSA || kx == GNUTLS_KX_DHE_DSS)
dhe = true;
else if (kx == GNUTLS_KX_ECDHE_RSA || kx == GNUTLS_KX_ECDHE_ECDSA)
ecdh = true;
break;
default:
nbdkit_debug ("TLS: authentication: unknown (%d)", (int) cred);
}
#ifdef HAVE_GNUTLS_GROUP_GET
grp = gnutls_group_get (session);
#else
grp = 0;
#endif
if (grp) {
nbdkit_debug ("TLS: negotiated group: "
#ifdef HAVE_GNUTLS_GROUP_GET_NAME
"%s", gnutls_group_get_name (grp));
#else
"%d", grp);
#endif
}
else {
if (ecdh)
nbdkit_debug ("TLS: ephemeral ECDH using curve %s",
gnutls_ecc_curve_get_name (gnutls_ecc_curve_get (session)));
else if (dhe)
nbdkit_debug ("TLS: ephemeral DH using prime of %d bits",
gnutls_dh_get_prime_bits (session));
}
}
/* Upgrade an existing connection to TLS. Also this should do access
* control if enabled. The protocol code ensures this function can
* only be called once per connection.
*/
int
crypto_negotiate_tls (int sockin, int sockout)
{
GET_CONN;
gnutls_session_t session;
CLEANUP_FREE char *priority = NULL;
int err;
/* Create the GnuTLS session. */
err = gnutls_init (&session, GNUTLS_SERVER);
if (err < 0) {
nbdkit_error ("gnutls_init: %s", gnutls_strerror (err));
return -1;
}
if (nbdkit_debug_tls_log > 0)
gnutls_global_set_log_level (nbdkit_debug_tls_log);
gnutls_global_set_log_function (tls_log);
switch (crypto_auth) {
case CRYPTO_AUTH_CERTIFICATES:
/* Associate the session with the server credentials (key, cert). */
err = gnutls_credentials_set (session, GNUTLS_CRD_CERTIFICATE,
x509_creds);
if (err < 0) {
nbdkit_error ("gnutls_credentials_set: %s", gnutls_strerror (err));
goto error;
}
/* If verify peer is enabled, tell GnuTLS to request the client
* certificates. (Note the default is to not request or verify
* certificates).
*/
if (tls_verify_peer) {
#ifdef HAVE_GNUTLS_SESSION_SET_VERIFY_CERT
gnutls_certificate_server_set_request (session, GNUTLS_CERT_REQUEST);
gnutls_session_set_verify_cert (session, NULL, 0);
#else
abort (); /* Checked when we set the flag in main() */
#endif
}
priority = strdup (TLS_PRIORITY);
if (priority == NULL) {
nbdkit_error ("strdup: %m");
goto error;
}
break;
case CRYPTO_AUTH_PSK:
/* Associate the session with the server PSK credentials. */
err = gnutls_credentials_set (session, GNUTLS_CRD_PSK, psk_creds);
if (err < 0) {
nbdkit_error ("gnutls_credentials_set: %s", gnutls_strerror (err));
goto error;
}
if (asprintf (&priority,
"%s:+ECDHE-PSK:+DHE-PSK:+PSK", TLS_PRIORITY) == -1) {
nbdkit_error ("asprintf: %m");
goto error;
}
break;
default:
abort ();
}
assert (priority != NULL);
err = gnutls_priority_set_direct (session, priority, NULL);
if (err < 0) {
nbdkit_error ("failed to set TLS session priority to %s: %s",
priority, gnutls_strerror (err));
goto error;
}
/* Set up GnuTLS so it reads and writes on the raw sockets. */
gnutls_transport_set_int2 (session, sockin, sockout);
#ifdef WIN32
gnutls_transport_set_push_function (session, push);
gnutls_transport_set_pull_function (session, pull);
gnutls_transport_set_pull_timeout_function (session, pull_timeout);
#endif
/* Perform the handshake. */
debug ("starting TLS handshake");
gnutls_handshake_set_timeout (session,
GNUTLS_DEFAULT_HANDSHAKE_TIMEOUT);
do {
err = gnutls_handshake (session);
} while (err < 0 && gnutls_error_is_fatal (err) == 0);
if (err < 0) {
gnutls_handshake_description_t in, out;
/* Get some additional debug information about where in the
* handshake protocol it failed. You have to look up these codes in
* <gnutls/gnutls.h>.
*/
in = gnutls_handshake_get_last_in (session);
out = gnutls_handshake_get_last_out (session);
nbdkit_error ("gnutls_handshake: %s (%d/%d)",
gnutls_strerror (err), (int) in, (int) out);
goto error;
}
debug ("TLS handshake completed");
debug_session (session);
/* Set up the connection recv/send/close functions so they call
* GnuTLS wrappers instead.
*/
conn->crypto_session = session;
conn->recv = crypto_recv;
conn->send = crypto_send;
conn->close = crypto_close;
return 0;
error:
gnutls_deinit (session);
return -1;
}
#else /* !HAVE_GNUTLS */
/* GnuTLS was not available at compile time. These are stub versions
* of the above functions which either do nothing or report errors as
* appropriate.
*/
void
crypto_init (bool tls_set_on_cli)
{
if (tls > 0) {
fprintf (stderr,
"%s: TLS cannot be enabled because "
"this binary was compiled without GnuTLS.\n",
program_name);
exit (EXIT_FAILURE);
}
tls = 0;
debug ("TLS disabled: nbdkit was not compiled with GnuTLS support");
}
void
crypto_free (void)
{
/* nothing */
}
int
crypto_negotiate_tls (int sockin, int sockout)
{
/* Should never be called because tls == 0. */
abort ();
}
#endif /* !HAVE_GNUTLS */