661 lines
19 KiB
C
661 lines
19 KiB
C
/*
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* QEMU VNC display driver: SASL auth protocol
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*
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* Copyright (C) 2009 Red Hat, Inc
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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#include "qemu/osdep.h"
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#include "qapi/error.h"
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#include "vnc.h"
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/* Max amount of data we send/recv for SASL steps to prevent DOS */
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#define SASL_DATA_MAX_LEN (1024 * 1024)
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void vnc_sasl_client_cleanup(VncState *vs)
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{
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if (vs->sasl.conn) {
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vs->sasl.runSSF = false;
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vs->sasl.wantSSF = false;
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vs->sasl.waitWriteSSF = 0;
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vs->sasl.encodedLength = vs->sasl.encodedOffset = 0;
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vs->sasl.encoded = NULL;
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g_free(vs->sasl.username);
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g_free(vs->sasl.mechlist);
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vs->sasl.username = vs->sasl.mechlist = NULL;
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sasl_dispose(&vs->sasl.conn);
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vs->sasl.conn = NULL;
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}
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}
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long vnc_client_write_sasl(VncState *vs)
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{
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long ret;
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VNC_DEBUG("Write SASL: Pending output %p size %zd offset %zd "
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"Encoded: %p size %d offset %d\n",
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vs->output.buffer, vs->output.capacity, vs->output.offset,
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vs->sasl.encoded, vs->sasl.encodedLength, vs->sasl.encodedOffset);
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if (!vs->sasl.encoded) {
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int err;
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err = sasl_encode(vs->sasl.conn,
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(char *)vs->output.buffer,
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vs->output.offset,
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(const char **)&vs->sasl.encoded,
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&vs->sasl.encodedLength);
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if (err != SASL_OK)
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return vnc_client_io_error(vs, -1, NULL);
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vs->sasl.encodedOffset = 0;
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}
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ret = vnc_client_write_buf(vs,
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vs->sasl.encoded + vs->sasl.encodedOffset,
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vs->sasl.encodedLength - vs->sasl.encodedOffset);
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if (!ret)
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return 0;
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vs->sasl.encodedOffset += ret;
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if (vs->sasl.encodedOffset == vs->sasl.encodedLength) {
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vs->output.offset = 0;
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vs->sasl.encoded = NULL;
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vs->sasl.encodedOffset = vs->sasl.encodedLength = 0;
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}
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/* Can't merge this block with one above, because
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* someone might have written more unencrypted
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* data in vs->output while we were processing
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* SASL encoded output
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*/
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if (vs->output.offset == 0) {
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if (vs->ioc_tag) {
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g_source_remove(vs->ioc_tag);
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}
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vs->ioc_tag = qio_channel_add_watch(
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vs->ioc, G_IO_IN, vnc_client_io, vs, NULL);
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}
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return ret;
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}
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long vnc_client_read_sasl(VncState *vs)
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{
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long ret;
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uint8_t encoded[4096];
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const char *decoded;
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unsigned int decodedLen;
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int err;
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ret = vnc_client_read_buf(vs, encoded, sizeof(encoded));
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if (!ret)
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return 0;
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err = sasl_decode(vs->sasl.conn,
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(char *)encoded, ret,
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&decoded, &decodedLen);
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if (err != SASL_OK)
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return vnc_client_io_error(vs, -1, NULL);
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VNC_DEBUG("Read SASL Encoded %p size %ld Decoded %p size %d\n",
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encoded, ret, decoded, decodedLen);
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buffer_reserve(&vs->input, decodedLen);
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buffer_append(&vs->input, decoded, decodedLen);
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return decodedLen;
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}
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static int vnc_auth_sasl_check_access(VncState *vs)
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{
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const void *val;
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int err;
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int allow;
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err = sasl_getprop(vs->sasl.conn, SASL_USERNAME, &val);
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if (err != SASL_OK) {
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VNC_DEBUG("cannot query SASL username on connection %d (%s), denying access\n",
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err, sasl_errstring(err, NULL, NULL));
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return -1;
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}
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if (val == NULL) {
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VNC_DEBUG("no client username was found, denying access\n");
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return -1;
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}
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VNC_DEBUG("SASL client username %s\n", (const char *)val);
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vs->sasl.username = g_strdup((const char*)val);
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if (vs->vd->sasl.acl == NULL) {
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VNC_DEBUG("no ACL activated, allowing access\n");
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return 0;
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}
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allow = qemu_acl_party_is_allowed(vs->vd->sasl.acl, vs->sasl.username);
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VNC_DEBUG("SASL client %s %s by ACL\n", vs->sasl.username,
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allow ? "allowed" : "denied");
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return allow ? 0 : -1;
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}
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static int vnc_auth_sasl_check_ssf(VncState *vs)
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{
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const void *val;
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int err, ssf;
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if (!vs->sasl.wantSSF)
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return 1;
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err = sasl_getprop(vs->sasl.conn, SASL_SSF, &val);
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if (err != SASL_OK)
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return 0;
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ssf = *(const int *)val;
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VNC_DEBUG("negotiated an SSF of %d\n", ssf);
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if (ssf < 56)
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return 0; /* 56 is good for Kerberos */
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/* Only setup for read initially, because we're about to send an RPC
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* reply which must be in plain text. When the next incoming RPC
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* arrives, we'll switch on writes too
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*
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* cf qemudClientReadSASL in qemud.c
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*/
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vs->sasl.runSSF = 1;
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/* We have a SSF that's good enough */
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return 1;
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}
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/*
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* Step Msg
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*
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* Input from client:
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*
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* u32 clientin-length
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* u8-array clientin-string
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*
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* Output to client:
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*
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* u32 serverout-length
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* u8-array serverout-strin
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* u8 continue
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*/
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static int protocol_client_auth_sasl_step_len(VncState *vs, uint8_t *data, size_t len);
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static int protocol_client_auth_sasl_step(VncState *vs, uint8_t *data, size_t len)
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{
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uint32_t datalen = len;
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const char *serverout;
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unsigned int serveroutlen;
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int err;
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char *clientdata = NULL;
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/* NB, distinction of NULL vs "" is *critical* in SASL */
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if (datalen) {
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clientdata = (char*)data;
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clientdata[datalen-1] = '\0'; /* Wire includes '\0', but make sure */
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datalen--; /* Don't count NULL byte when passing to _start() */
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}
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VNC_DEBUG("Step using SASL Data %p (%d bytes)\n",
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clientdata, datalen);
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err = sasl_server_step(vs->sasl.conn,
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clientdata,
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datalen,
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&serverout,
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&serveroutlen);
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if (err != SASL_OK &&
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err != SASL_CONTINUE) {
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VNC_DEBUG("sasl step failed %d (%s)\n",
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err, sasl_errdetail(vs->sasl.conn));
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sasl_dispose(&vs->sasl.conn);
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vs->sasl.conn = NULL;
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goto authabort;
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}
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if (serveroutlen > SASL_DATA_MAX_LEN) {
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VNC_DEBUG("sasl step reply data too long %d\n",
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serveroutlen);
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sasl_dispose(&vs->sasl.conn);
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vs->sasl.conn = NULL;
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goto authabort;
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}
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VNC_DEBUG("SASL return data %d bytes, nil; %d\n",
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serveroutlen, serverout ? 0 : 1);
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if (serveroutlen) {
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vnc_write_u32(vs, serveroutlen + 1);
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vnc_write(vs, serverout, serveroutlen + 1);
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} else {
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vnc_write_u32(vs, 0);
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}
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/* Whether auth is complete */
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vnc_write_u8(vs, err == SASL_CONTINUE ? 0 : 1);
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if (err == SASL_CONTINUE) {
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VNC_DEBUG("%s", "Authentication must continue\n");
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/* Wait for step length */
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vnc_read_when(vs, protocol_client_auth_sasl_step_len, 4);
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} else {
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if (!vnc_auth_sasl_check_ssf(vs)) {
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VNC_DEBUG("Authentication rejected for weak SSF %p\n", vs->ioc);
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goto authreject;
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}
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/* Check username whitelist ACL */
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if (vnc_auth_sasl_check_access(vs) < 0) {
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VNC_DEBUG("Authentication rejected for ACL %p\n", vs->ioc);
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goto authreject;
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}
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VNC_DEBUG("Authentication successful %p\n", vs->ioc);
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vnc_write_u32(vs, 0); /* Accept auth */
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/*
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* Delay writing in SSF encoded mode until pending output
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* buffer is written
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*/
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if (vs->sasl.runSSF)
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vs->sasl.waitWriteSSF = vs->output.offset;
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start_client_init(vs);
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}
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return 0;
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authreject:
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vnc_write_u32(vs, 1); /* Reject auth */
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vnc_write_u32(vs, sizeof("Authentication failed"));
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vnc_write(vs, "Authentication failed", sizeof("Authentication failed"));
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vnc_flush(vs);
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vnc_client_error(vs);
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return -1;
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authabort:
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vnc_client_error(vs);
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return -1;
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}
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static int protocol_client_auth_sasl_step_len(VncState *vs, uint8_t *data, size_t len)
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{
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uint32_t steplen = read_u32(data, 0);
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VNC_DEBUG("Got client step len %d\n", steplen);
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if (steplen > SASL_DATA_MAX_LEN) {
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VNC_DEBUG("Too much SASL data %d\n", steplen);
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vnc_client_error(vs);
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return -1;
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}
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if (steplen == 0)
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return protocol_client_auth_sasl_step(vs, NULL, 0);
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else
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vnc_read_when(vs, protocol_client_auth_sasl_step, steplen);
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return 0;
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}
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/*
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* Start Msg
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*
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* Input from client:
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*
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* u32 clientin-length
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* u8-array clientin-string
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*
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* Output to client:
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*
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* u32 serverout-length
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* u8-array serverout-strin
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* u8 continue
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*/
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#define SASL_DATA_MAX_LEN (1024 * 1024)
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static int protocol_client_auth_sasl_start(VncState *vs, uint8_t *data, size_t len)
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{
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uint32_t datalen = len;
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const char *serverout;
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unsigned int serveroutlen;
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int err;
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char *clientdata = NULL;
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/* NB, distinction of NULL vs "" is *critical* in SASL */
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if (datalen) {
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clientdata = (char*)data;
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clientdata[datalen-1] = '\0'; /* Should be on wire, but make sure */
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datalen--; /* Don't count NULL byte when passing to _start() */
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}
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VNC_DEBUG("Start SASL auth with mechanism %s. Data %p (%d bytes)\n",
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vs->sasl.mechlist, clientdata, datalen);
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err = sasl_server_start(vs->sasl.conn,
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vs->sasl.mechlist,
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clientdata,
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datalen,
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&serverout,
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&serveroutlen);
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if (err != SASL_OK &&
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err != SASL_CONTINUE) {
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VNC_DEBUG("sasl start failed %d (%s)\n",
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err, sasl_errdetail(vs->sasl.conn));
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sasl_dispose(&vs->sasl.conn);
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vs->sasl.conn = NULL;
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goto authabort;
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}
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if (serveroutlen > SASL_DATA_MAX_LEN) {
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VNC_DEBUG("sasl start reply data too long %d\n",
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serveroutlen);
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sasl_dispose(&vs->sasl.conn);
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vs->sasl.conn = NULL;
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goto authabort;
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}
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VNC_DEBUG("SASL return data %d bytes, nil; %d\n",
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serveroutlen, serverout ? 0 : 1);
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if (serveroutlen) {
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vnc_write_u32(vs, serveroutlen + 1);
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vnc_write(vs, serverout, serveroutlen + 1);
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} else {
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vnc_write_u32(vs, 0);
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}
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/* Whether auth is complete */
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vnc_write_u8(vs, err == SASL_CONTINUE ? 0 : 1);
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if (err == SASL_CONTINUE) {
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VNC_DEBUG("%s", "Authentication must continue\n");
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/* Wait for step length */
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vnc_read_when(vs, protocol_client_auth_sasl_step_len, 4);
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} else {
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if (!vnc_auth_sasl_check_ssf(vs)) {
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VNC_DEBUG("Authentication rejected for weak SSF %p\n", vs->ioc);
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goto authreject;
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}
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/* Check username whitelist ACL */
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if (vnc_auth_sasl_check_access(vs) < 0) {
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VNC_DEBUG("Authentication rejected for ACL %p\n", vs->ioc);
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goto authreject;
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}
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VNC_DEBUG("Authentication successful %p\n", vs->ioc);
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vnc_write_u32(vs, 0); /* Accept auth */
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start_client_init(vs);
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}
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return 0;
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authreject:
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vnc_write_u32(vs, 1); /* Reject auth */
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vnc_write_u32(vs, sizeof("Authentication failed"));
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vnc_write(vs, "Authentication failed", sizeof("Authentication failed"));
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vnc_flush(vs);
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vnc_client_error(vs);
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return -1;
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authabort:
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vnc_client_error(vs);
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return -1;
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}
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static int protocol_client_auth_sasl_start_len(VncState *vs, uint8_t *data, size_t len)
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{
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uint32_t startlen = read_u32(data, 0);
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VNC_DEBUG("Got client start len %d\n", startlen);
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if (startlen > SASL_DATA_MAX_LEN) {
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VNC_DEBUG("Too much SASL data %d\n", startlen);
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vnc_client_error(vs);
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return -1;
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}
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if (startlen == 0)
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return protocol_client_auth_sasl_start(vs, NULL, 0);
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vnc_read_when(vs, protocol_client_auth_sasl_start, startlen);
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return 0;
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}
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static int protocol_client_auth_sasl_mechname(VncState *vs, uint8_t *data, size_t len)
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{
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char *mechname = g_strndup((const char *) data, len);
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VNC_DEBUG("Got client mechname '%s' check against '%s'\n",
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mechname, vs->sasl.mechlist);
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if (strncmp(vs->sasl.mechlist, mechname, len) == 0) {
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if (vs->sasl.mechlist[len] != '\0' &&
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vs->sasl.mechlist[len] != ',') {
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VNC_DEBUG("One %d", vs->sasl.mechlist[len]);
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goto fail;
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}
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} else {
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char *offset = strstr(vs->sasl.mechlist, mechname);
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VNC_DEBUG("Two %p\n", offset);
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if (!offset) {
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goto fail;
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}
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VNC_DEBUG("Two '%s'\n", offset);
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if (offset[-1] != ',' ||
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(offset[len] != '\0'&&
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offset[len] != ',')) {
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goto fail;
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}
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}
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g_free(vs->sasl.mechlist);
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vs->sasl.mechlist = mechname;
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VNC_DEBUG("Validated mechname '%s'\n", mechname);
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vnc_read_when(vs, protocol_client_auth_sasl_start_len, 4);
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return 0;
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fail:
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vnc_client_error(vs);
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g_free(mechname);
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return -1;
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}
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static int protocol_client_auth_sasl_mechname_len(VncState *vs, uint8_t *data, size_t len)
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{
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uint32_t mechlen = read_u32(data, 0);
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VNC_DEBUG("Got client mechname len %d\n", mechlen);
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if (mechlen > 100) {
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VNC_DEBUG("Too long SASL mechname data %d\n", mechlen);
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vnc_client_error(vs);
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return -1;
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}
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if (mechlen < 1) {
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VNC_DEBUG("Too short SASL mechname %d\n", mechlen);
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vnc_client_error(vs);
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return -1;
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}
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vnc_read_when(vs, protocol_client_auth_sasl_mechname,mechlen);
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return 0;
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}
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static char *
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vnc_socket_ip_addr_string(QIOChannelSocket *ioc,
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bool local,
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Error **errp)
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{
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|
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_KIND_INET) {
|
|
error_setg(errp, "Not an inet socket type");
|
|
return NULL;
|
|
}
|
|
ret = g_strdup_printf("%s;%s", addr->u.inet.data->host,
|
|
addr->u.inet.data->port);
|
|
qapi_free_SocketAddress(addr);
|
|
return ret;
|
|
}
|
|
|
|
void start_auth_sasl(VncState *vs)
|
|
{
|
|
const char *mechlist = NULL;
|
|
sasl_security_properties_t secprops;
|
|
int err;
|
|
char *localAddr, *remoteAddr;
|
|
int mechlistlen;
|
|
|
|
VNC_DEBUG("Initialize SASL auth %p\n", vs->ioc);
|
|
|
|
/* Get local & remote client addresses in form IPADDR;PORT */
|
|
localAddr = vnc_socket_ip_addr_string(vs->sioc, true, NULL);
|
|
if (!localAddr) {
|
|
goto authabort;
|
|
}
|
|
|
|
remoteAddr = vnc_socket_ip_addr_string(vs->sioc, false, NULL);
|
|
if (!remoteAddr) {
|
|
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) {
|
|
VNC_DEBUG("sasl context setup failed %d (%s)",
|
|
err, 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) {
|
|
Error *local_err = NULL;
|
|
int keysize;
|
|
sasl_ssf_t ssf;
|
|
|
|
keysize = qcrypto_tls_session_get_key_size(vs->tls,
|
|
&local_err);
|
|
if (keysize < 0) {
|
|
VNC_DEBUG("cannot TLS get cipher size: %s\n",
|
|
error_get_pretty(local_err));
|
|
error_free(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) {
|
|
VNC_DEBUG("cannot set SASL external SSF %d (%s)\n",
|
|
err, 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) {
|
|
VNC_DEBUG("cannot set SASL security props %d (%s)\n",
|
|
err, 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) {
|
|
VNC_DEBUG("cannot list SASL mechanisms %d (%s)\n",
|
|
err, sasl_errdetail(vs->sasl.conn));
|
|
sasl_dispose(&vs->sasl.conn);
|
|
vs->sasl.conn = NULL;
|
|
goto authabort;
|
|
}
|
|
VNC_DEBUG("Available mechanisms for client: '%s'\n", mechlist);
|
|
|
|
vs->sasl.mechlist = g_strdup(mechlist);
|
|
mechlistlen = strlen(mechlist);
|
|
vnc_write_u32(vs, mechlistlen);
|
|
vnc_write(vs, mechlist, mechlistlen);
|
|
vnc_flush(vs);
|
|
|
|
VNC_DEBUG("Wait for client mechname length\n");
|
|
vnc_read_when(vs, protocol_client_auth_sasl_mechname_len, 4);
|
|
|
|
return;
|
|
|
|
authabort:
|
|
vnc_client_error(vs);
|
|
}
|
|
|
|
|