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qemu/ui/vnc-auth-sasl.c

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/*
* QEMU VNC display driver: SASL auth protocol
*
* Copyright (C) 2009 Red Hat, Inc
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include "qemu/osdep.h"
#include "qapi/error.h"
#include "authz/base.h"
#include "vnc.h"
#include "trace.h"
/* Max amount of data we send/recv for SASL steps to prevent DOS */
#define SASL_DATA_MAX_LEN (1024 * 1024)
void vnc_sasl_client_cleanup(VncState *vs)
{
if (vs->sasl.conn) {
vs->sasl.runSSF = false;
vs->sasl.wantSSF = false;
vs->sasl.waitWriteSSF = 0;
vs->sasl.encodedLength = vs->sasl.encodedOffset = 0;
vs->sasl.encoded = NULL;
g_free(vs->sasl.username);
g_free(vs->sasl.mechlist);
vs->sasl.username = vs->sasl.mechlist = NULL;
sasl_dispose(&vs->sasl.conn);
vs->sasl.conn = NULL;
}
}
size_t vnc_client_write_sasl(VncState *vs)
{
size_t ret;
VNC_DEBUG("Write SASL: Pending output %p size %zd offset %zd "
"Encoded: %p size %d offset %d\n",
vs->output.buffer, vs->output.capacity, vs->output.offset,
vs->sasl.encoded, vs->sasl.encodedLength, vs->sasl.encodedOffset);
if (!vs->sasl.encoded) {
int err;
err = sasl_encode(vs->sasl.conn,
(char *)vs->output.buffer,
vs->output.offset,
(const char **)&vs->sasl.encoded,
&vs->sasl.encodedLength);
if (err != SASL_OK)
return vnc_client_io_error(vs, -1, NULL);
vs->sasl.encodedRawLength = vs->output.offset;
vs->sasl.encodedOffset = 0;
}
ret = vnc_client_write_buf(vs,
vs->sasl.encoded + vs->sasl.encodedOffset,
vs->sasl.encodedLength - vs->sasl.encodedOffset);
if (!ret)
return 0;
vs->sasl.encodedOffset += ret;
if (vs->sasl.encodedOffset == vs->sasl.encodedLength) {
bool throttled = vs->force_update_offset != 0;
size_t offset;
if (vs->sasl.encodedRawLength >= vs->force_update_offset) {
vs->force_update_offset = 0;
} else {
vs->force_update_offset -= vs->sasl.encodedRawLength;
}
if (throttled && vs->force_update_offset == 0) {
trace_vnc_client_unthrottle_forced(vs, vs->ioc);
}
offset = vs->output.offset;
buffer_advance(&vs->output, vs->sasl.encodedRawLength);
if (offset >= vs->throttle_output_offset &&
vs->output.offset < vs->throttle_output_offset) {
trace_vnc_client_unthrottle_incremental(vs, vs->ioc,
vs->output.offset);
}
vs->sasl.encoded = NULL;
vs->sasl.encodedOffset = vs->sasl.encodedLength = 0;
}
/* Can't merge this block with one above, because
* someone might have written more unencrypted
* data in vs->output while we were processing
* SASL encoded output
*/
if (vs->output.offset == 0) {
if (vs->ioc_tag) {
g_source_remove(vs->ioc_tag);
}
vs->ioc_tag = qio_channel_add_watch(
vs->ioc, G_IO_IN | G_IO_HUP | G_IO_ERR,
vnc_client_io, vs, NULL);
}
return ret;
}
size_t vnc_client_read_sasl(VncState *vs)
{
size_t ret;
uint8_t encoded[4096];
const char *decoded;
unsigned int decodedLen;
int err;
ret = vnc_client_read_buf(vs, encoded, sizeof(encoded));
if (!ret)
return 0;
err = sasl_decode(vs->sasl.conn,
(char *)encoded, ret,
&decoded, &decodedLen);
if (err != SASL_OK)
return vnc_client_io_error(vs, -1, NULL);
VNC_DEBUG("Read SASL Encoded %p size %ld Decoded %p size %d\n",
encoded, ret, decoded, decodedLen);
buffer_reserve(&vs->input, decodedLen);
buffer_append(&vs->input, decoded, decodedLen);
return decodedLen;
}
static int vnc_auth_sasl_check_access(VncState *vs)
{
const void *val;
int rv;
Error *err = NULL;
bool allow;
rv = sasl_getprop(vs->sasl.conn, SASL_USERNAME, &val);
if (rv != SASL_OK) {
trace_vnc_auth_fail(vs, vs->auth, "Cannot fetch SASL username",
sasl_errstring(rv, NULL, NULL));
return -1;
}
if (val == NULL) {
trace_vnc_auth_fail(vs, vs->auth, "No SASL username set", "");
return -1;
}
vs->sasl.username = g_strdup((const char*)val);
trace_vnc_auth_sasl_username(vs, vs->sasl.username);
if (vs->vd->sasl.authzid == NULL) {
trace_vnc_auth_sasl_acl(vs, 1);
return 0;
}
allow = qauthz_is_allowed_by_id(vs->vd->sasl.authzid,
vs->sasl.username, &err);
if (err) {
trace_vnc_auth_fail(vs, vs->auth, "Error from authz",
error_get_pretty(err));
error_free(err);
return -1;
}
trace_vnc_auth_sasl_acl(vs, allow);
return allow ? 0 : -1;
}
static int vnc_auth_sasl_check_ssf(VncState *vs)
{
const void *val;
int err, ssf;
if (!vs->sasl.wantSSF)
return 1;
err = sasl_getprop(vs->sasl.conn, SASL_SSF, &val);
if (err != SASL_OK)
return 0;
ssf = *(const int *)val;
trace_vnc_auth_sasl_ssf(vs, ssf);
if (ssf < 56)
return 0; /* 56 is good for Kerberos */
/* Only setup for read initially, because we're about to send an RPC
* reply which must be in plain text. When the next incoming RPC
* arrives, we'll switch on writes too
*
* cf qemudClientReadSASL in qemud.c
*/
vs->sasl.runSSF = 1;
/* We have a SSF that's good enough */
return 1;
}
/*
* Step Msg
*
* Input from client:
*
* u32 clientin-length
* u8-array clientin-string
*
* Output to client:
*
* u32 serverout-length
* u8-array serverout-strin
* u8 continue
*/
static int protocol_client_auth_sasl_step_len(VncState *vs, uint8_t *data, size_t len);
static int protocol_client_auth_sasl_step(VncState *vs, uint8_t *data, size_t len)
{
uint32_t datalen = len;
const char *serverout;
unsigned int serveroutlen;
int err;
char *clientdata = NULL;
/* NB, distinction of NULL vs "" is *critical* in SASL */
if (datalen) {
clientdata = (char*)data;
clientdata[datalen-1] = '\0'; /* Wire includes '\0', but make sure */
datalen--; /* Don't count NULL byte when passing to _start() */
}
err = sasl_server_step(vs->sasl.conn,
clientdata,
datalen,
&serverout,
&serveroutlen);
trace_vnc_auth_sasl_step(vs, data, len, serverout, serveroutlen, err);
if (err != SASL_OK &&
err != SASL_CONTINUE) {
trace_vnc_auth_fail(vs, vs->auth, "Cannot step SASL auth",
sasl_errdetail(vs->sasl.conn));
sasl_dispose(&vs->sasl.conn);
vs->sasl.conn = NULL;
goto authabort;
}
if (serveroutlen > SASL_DATA_MAX_LEN) {
trace_vnc_auth_fail(vs, vs->auth, "SASL data too long", "");
sasl_dispose(&vs->sasl.conn);
vs->sasl.conn = NULL;
goto authabort;
}
if (serveroutlen) {
vnc_write_u32(vs, serveroutlen + 1);
vnc_write(vs, serverout, serveroutlen + 1);
} else {
vnc_write_u32(vs, 0);
}
/* Whether auth is complete */
vnc_write_u8(vs, err == SASL_CONTINUE ? 0 : 1);
if (err == SASL_CONTINUE) {
/* Wait for step length */
vnc_read_when(vs, protocol_client_auth_sasl_step_len, 4);
} else {
if (!vnc_auth_sasl_check_ssf(vs)) {
trace_vnc_auth_fail(vs, vs->auth, "SASL SSF too weak", "");
goto authreject;
}
/* Check username whitelist ACL */
if (vnc_auth_sasl_check_access(vs) < 0) {
goto authreject;
}
trace_vnc_auth_pass(vs, vs->auth);
vnc_write_u32(vs, 0); /* Accept auth */
/*
* Delay writing in SSF encoded mode until pending output
* buffer is written
*/
if (vs->sasl.runSSF)
vs->sasl.waitWriteSSF = vs->output.offset;
start_client_init(vs);
}
return 0;
authreject:
vnc_write_u32(vs, 1); /* Reject auth */
vnc_write_u32(vs, sizeof("Authentication failed"));
vnc_write(vs, "Authentication failed", sizeof("Authentication failed"));
vnc_flush(vs);
vnc_client_error(vs);
return -1;
authabort:
vnc_client_error(vs);
return -1;
}
static int protocol_client_auth_sasl_step_len(VncState *vs, uint8_t *data, size_t len)
{
uint32_t steplen = read_u32(data, 0);
if (steplen > SASL_DATA_MAX_LEN) {
trace_vnc_auth_fail(vs, vs->auth, "SASL step len too large", "");
vnc_client_error(vs);
return -1;
}
if (steplen == 0)
return protocol_client_auth_sasl_step(vs, NULL, 0);
else
vnc_read_when(vs, protocol_client_auth_sasl_step, steplen);
return 0;
}
/*
* Start Msg
*
* Input from client:
*
* u32 clientin-length
* u8-array clientin-string
*
* Output to client:
*
* u32 serverout-length
* u8-array serverout-strin
* u8 continue
*/
#define SASL_DATA_MAX_LEN (1024 * 1024)
static int protocol_client_auth_sasl_start(VncState *vs, uint8_t *data, size_t len)
{
uint32_t datalen = len;
const char *serverout;
unsigned int serveroutlen;
int err;
char *clientdata = NULL;
/* NB, distinction of NULL vs "" is *critical* in SASL */
if (datalen) {
clientdata = (char*)data;
clientdata[datalen-1] = '\0'; /* Should be on wire, but make sure */
datalen--; /* Don't count NULL byte when passing to _start() */
}
err = sasl_server_start(vs->sasl.conn,
vs->sasl.mechlist,
clientdata,
datalen,
&serverout,
&serveroutlen);
trace_vnc_auth_sasl_start(vs, data, len, serverout, serveroutlen, err);
if (err != SASL_OK &&
err != SASL_CONTINUE) {
trace_vnc_auth_fail(vs, vs->auth, "Cannot start SASL auth",
sasl_errdetail(vs->sasl.conn));
sasl_dispose(&vs->sasl.conn);
vs->sasl.conn = NULL;
goto authabort;
}
if (serveroutlen > SASL_DATA_MAX_LEN) {
trace_vnc_auth_fail(vs, vs->auth, "SASL data too long", "");
sasl_dispose(&vs->sasl.conn);
vs->sasl.conn = NULL;
goto authabort;
}
if (serveroutlen) {
vnc_write_u32(vs, serveroutlen + 1);
vnc_write(vs, serverout, serveroutlen + 1);
} else {
vnc_write_u32(vs, 0);
}
/* Whether auth is complete */
vnc_write_u8(vs, err == SASL_CONTINUE ? 0 : 1);
if (err == SASL_CONTINUE) {
/* Wait for step length */
vnc_read_when(vs, protocol_client_auth_sasl_step_len, 4);
} else {
if (!vnc_auth_sasl_check_ssf(vs)) {
trace_vnc_auth_fail(vs, vs->auth, "SASL SSF too weak", "");
goto authreject;
}
/* Check username whitelist ACL */
if (vnc_auth_sasl_check_access(vs) < 0) {
goto authreject;
}
trace_vnc_auth_pass(vs, vs->auth);
vnc_write_u32(vs, 0); /* Accept auth */
start_client_init(vs);
}
return 0;
authreject:
vnc_write_u32(vs, 1); /* Reject auth */
vnc_write_u32(vs, sizeof("Authentication failed"));
vnc_write(vs, "Authentication failed", sizeof("Authentication failed"));
vnc_flush(vs);
vnc_client_error(vs);
return -1;
authabort:
vnc_client_error(vs);
return -1;
}
static int protocol_client_auth_sasl_start_len(VncState *vs, uint8_t *data, size_t len)
{
uint32_t startlen = read_u32(data, 0);
if (startlen > SASL_DATA_MAX_LEN) {
trace_vnc_auth_fail(vs, vs->auth, "SASL start len too large", "");
vnc_client_error(vs);
return -1;
}
if (startlen == 0)
return protocol_client_auth_sasl_start(vs, NULL, 0);
vnc_read_when(vs, protocol_client_auth_sasl_start, startlen);
return 0;
}
static int protocol_client_auth_sasl_mechname(VncState *vs, uint8_t *data, size_t len)
{
char *mechname = g_strndup((const char *) data, len);
trace_vnc_auth_sasl_mech_choose(vs, mechname);
if (strncmp(vs->sasl.mechlist, mechname, len) == 0) {
if (vs->sasl.mechlist[len] != '\0' &&
vs->sasl.mechlist[len] != ',') {
goto fail;
}
} else {
char *offset = strstr(vs->sasl.mechlist, mechname);
if (!offset) {
goto fail;
}
if (offset[-1] != ',' ||
(offset[len] != '\0'&&
offset[len] != ',')) {
goto fail;
}
}
g_free(vs->sasl.mechlist);
vs->sasl.mechlist = mechname;
vnc_read_when(vs, protocol_client_auth_sasl_start_len, 4);
return 0;
fail:
trace_vnc_auth_fail(vs, vs->auth, "Unsupported mechname", mechname);
vnc_client_error(vs);
g_free(mechname);
return -1;
}
static int protocol_client_auth_sasl_mechname_len(VncState *vs, uint8_t *data, size_t len)
{
uint32_t mechlen = read_u32(data, 0);
if (mechlen > 100) {
trace_vnc_auth_fail(vs, vs->auth, "SASL mechname too long", "");
vnc_client_error(vs);
return -1;
}
if (mechlen < 1) {
trace_vnc_auth_fail(vs, vs->auth, "SASL mechname too short", "");
vnc_client_error(vs);
return -1;
}
vnc_read_when(vs, protocol_client_auth_sasl_mechname,mechlen);
return 0;
}
static char *
vnc_socket_ip_addr_string(QIOChannelSocket *ioc,
bool local,
Error **errp)
{
SocketAddress *addr;
char *ret;
if (local) {
addr = qio_channel_socket_get_local_address(ioc, errp);
} else {
addr = qio_channel_socket_get_remote_address(ioc, errp);
}
if (!addr) {
return NULL;
}
if (addr->type != SOCKET_ADDRESS_TYPE_INET) {
error_setg(errp, "Not an inet socket type");
qapi_free_SocketAddress(addr);
return NULL;
}
ret = g_strdup_printf("%s;%s", addr->u.inet.host, addr->u.inet.port);
qapi_free_SocketAddress(addr);
return ret;
}
void start_auth_sasl(VncState *vs)
{
const char *mechlist = NULL;
sasl_security_properties_t secprops;
int err;
Error *local_err = NULL;
char *localAddr, *remoteAddr;
int mechlistlen;
/* Get local & remote client addresses in form IPADDR;PORT */
localAddr = vnc_socket_ip_addr_string(vs->sioc, true, &local_err);
if (!localAddr) {
trace_vnc_auth_fail(vs, vs->auth, "Cannot format local IP",
error_get_pretty(local_err));
goto authabort;
}
remoteAddr = vnc_socket_ip_addr_string(vs->sioc, false, &local_err);
if (!remoteAddr) {
trace_vnc_auth_fail(vs, vs->auth, "Cannot format remote IP",
error_get_pretty(local_err));
g_free(localAddr);
goto authabort;
}
err = sasl_server_new("vnc",
NULL, /* FQDN - just delegates to gethostname */
NULL, /* User realm */
localAddr,
remoteAddr,
NULL, /* Callbacks, not needed */
SASL_SUCCESS_DATA,
&vs->sasl.conn);
g_free(localAddr);
g_free(remoteAddr);
localAddr = remoteAddr = NULL;
if (err != SASL_OK) {
trace_vnc_auth_fail(vs, vs->auth, "SASL context setup failed",
sasl_errstring(err, NULL, NULL));
vs->sasl.conn = NULL;
goto authabort;
}
/* Inform SASL that we've got an external SSF layer from TLS/x509 */
if (vs->auth == VNC_AUTH_VENCRYPT &&
vs->subauth == VNC_AUTH_VENCRYPT_X509SASL) {
int keysize;
sasl_ssf_t ssf;
keysize = qcrypto_tls_session_get_key_size(vs->tls,
&local_err);
if (keysize < 0) {
trace_vnc_auth_fail(vs, vs->auth, "cannot TLS get cipher size",
error_get_pretty(local_err));
sasl_dispose(&vs->sasl.conn);
vs->sasl.conn = NULL;
goto authabort;
}
ssf = keysize * CHAR_BIT; /* tls key size is bytes, sasl wants bits */
err = sasl_setprop(vs->sasl.conn, SASL_SSF_EXTERNAL, &ssf);
if (err != SASL_OK) {
trace_vnc_auth_fail(vs, vs->auth, "cannot set SASL external SSF",
sasl_errstring(err, NULL, NULL));
sasl_dispose(&vs->sasl.conn);
vs->sasl.conn = NULL;
goto authabort;
}
} else {
vs->sasl.wantSSF = 1;
}
memset (&secprops, 0, sizeof secprops);
/* Inform SASL that we've got an external SSF layer from TLS.
*
* Disable SSF, if using TLS+x509+SASL only. TLS without x509
* is not sufficiently strong
*/
if (vs->vd->is_unix ||
(vs->auth == VNC_AUTH_VENCRYPT &&
vs->subauth == VNC_AUTH_VENCRYPT_X509SASL)) {
/* If we've got TLS or UNIX domain sock, we don't care about SSF */
secprops.min_ssf = 0;
secprops.max_ssf = 0;
secprops.maxbufsize = 8192;
secprops.security_flags = 0;
} else {
/* Plain TCP, better get an SSF layer */
secprops.min_ssf = 56; /* Good enough to require kerberos */
secprops.max_ssf = 100000; /* Arbitrary big number */
secprops.maxbufsize = 8192;
/* Forbid any anonymous or trivially crackable auth */
secprops.security_flags =
SASL_SEC_NOANONYMOUS | SASL_SEC_NOPLAINTEXT;
}
err = sasl_setprop(vs->sasl.conn, SASL_SEC_PROPS, &secprops);
if (err != SASL_OK) {
trace_vnc_auth_fail(vs, vs->auth, "cannot set SASL security props",
sasl_errstring(err, NULL, NULL));
sasl_dispose(&vs->sasl.conn);
vs->sasl.conn = NULL;
goto authabort;
}
err = sasl_listmech(vs->sasl.conn,
NULL, /* Don't need to set user */
"", /* Prefix */
",", /* Separator */
"", /* Suffix */
&mechlist,
NULL,
NULL);
if (err != SASL_OK) {
trace_vnc_auth_fail(vs, vs->auth, "cannot list SASL mechanisms",
sasl_errdetail(vs->sasl.conn));
sasl_dispose(&vs->sasl.conn);
vs->sasl.conn = NULL;
goto authabort;
}
trace_vnc_auth_sasl_mech_list(vs, mechlist);
vs->sasl.mechlist = g_strdup(mechlist);
mechlistlen = strlen(mechlist);
vnc_write_u32(vs, mechlistlen);
vnc_write(vs, mechlist, mechlistlen);
vnc_flush(vs);
vnc_read_when(vs, protocol_client_auth_sasl_mechname_len, 4);
return;
authabort:
error_free(local_err);
vnc_client_error(vs);
}
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