| /* |
| * 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 "vnc.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; |
| } |
| } |
| |
| |
| long vnc_client_write_sasl(VncState *vs) |
| { |
| long 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, EIO); |
| |
| 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) { |
| vs->output.offset = 0; |
| 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) { |
| qemu_set_fd_handler2(vs->csock, NULL, vnc_client_read, NULL, vs); |
| } |
| |
| return ret; |
| } |
| |
| |
| long vnc_client_read_sasl(VncState *vs) |
| { |
| long 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, -EIO); |
| 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 err; |
| int allow; |
| |
| err = sasl_getprop(vs->sasl.conn, SASL_USERNAME, &val); |
| if (err != SASL_OK) { |
| VNC_DEBUG("cannot query SASL username on connection %d (%s), denying access\n", |
| err, sasl_errstring(err, NULL, NULL)); |
| return -1; |
| } |
| if (val == NULL) { |
| VNC_DEBUG("no client username was found, denying access\n"); |
| return -1; |
| } |
| VNC_DEBUG("SASL client username %s\n", (const char *)val); |
| |
| vs->sasl.username = g_strdup((const char*)val); |
| |
| if (vs->vd->sasl.acl == NULL) { |
| VNC_DEBUG("no ACL activated, allowing access\n"); |
| return 0; |
| } |
| |
| allow = qemu_acl_party_is_allowed(vs->vd->sasl.acl, vs->sasl.username); |
| |
| VNC_DEBUG("SASL client %s %s by ACL\n", vs->sasl.username, |
| allow ? "allowed" : "denied"); |
| 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; |
| VNC_DEBUG("negotiated an SSF of %d\n", 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() */ |
| } |
| |
| VNC_DEBUG("Step using SASL Data %p (%d bytes)\n", |
| clientdata, datalen); |
| err = sasl_server_step(vs->sasl.conn, |
| clientdata, |
| datalen, |
| &serverout, |
| &serveroutlen); |
| if (err != SASL_OK && |
| err != SASL_CONTINUE) { |
| VNC_DEBUG("sasl step failed %d (%s)\n", |
| err, sasl_errdetail(vs->sasl.conn)); |
| sasl_dispose(&vs->sasl.conn); |
| vs->sasl.conn = NULL; |
| goto authabort; |
| } |
| |
| if (serveroutlen > SASL_DATA_MAX_LEN) { |
| VNC_DEBUG("sasl step reply data too long %d\n", |
| serveroutlen); |
| sasl_dispose(&vs->sasl.conn); |
| vs->sasl.conn = NULL; |
| goto authabort; |
| } |
| |
| VNC_DEBUG("SASL return data %d bytes, nil; %d\n", |
| serveroutlen, serverout ? 0 : 1); |
| |
| 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) { |
| VNC_DEBUG("%s", "Authentication must continue\n"); |
| /* Wait for step length */ |
| vnc_read_when(vs, protocol_client_auth_sasl_step_len, 4); |
| } else { |
| if (!vnc_auth_sasl_check_ssf(vs)) { |
| VNC_DEBUG("Authentication rejected for weak SSF %d\n", vs->csock); |
| goto authreject; |
| } |
| |
| /* Check username whitelist ACL */ |
| if (vnc_auth_sasl_check_access(vs) < 0) { |
| VNC_DEBUG("Authentication rejected for ACL %d\n", vs->csock); |
| goto authreject; |
| } |
| |
| VNC_DEBUG("Authentication successful %d\n", vs->csock); |
| 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); |
| VNC_DEBUG("Got client step len %d\n", steplen); |
| if (steplen > SASL_DATA_MAX_LEN) { |
| VNC_DEBUG("Too much SASL data %d\n", steplen); |
| 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() */ |
| } |
| |
| VNC_DEBUG("Start SASL auth with mechanism %s. Data %p (%d bytes)\n", |
| vs->sasl.mechlist, clientdata, datalen); |
| err = sasl_server_start(vs->sasl.conn, |
| vs->sasl.mechlist, |
| clientdata, |
| datalen, |
| &serverout, |
| &serveroutlen); |
| if (err != SASL_OK && |
| err != SASL_CONTINUE) { |
| VNC_DEBUG("sasl start failed %d (%s)\n", |
| err, sasl_errdetail(vs->sasl.conn)); |
| sasl_dispose(&vs->sasl.conn); |
| vs->sasl.conn = NULL; |
| goto authabort; |
| } |
| if (serveroutlen > SASL_DATA_MAX_LEN) { |
| VNC_DEBUG("sasl start reply data too long %d\n", |
| serveroutlen); |
| sasl_dispose(&vs->sasl.conn); |
| vs->sasl.conn = NULL; |
| goto authabort; |
| } |
| |
| VNC_DEBUG("SASL return data %d bytes, nil; %d\n", |
| serveroutlen, serverout ? 0 : 1); |
| |
| 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) { |
| VNC_DEBUG("%s", "Authentication must continue\n"); |
| /* Wait for step length */ |
| vnc_read_when(vs, protocol_client_auth_sasl_step_len, 4); |
| } else { |
| if (!vnc_auth_sasl_check_ssf(vs)) { |
| VNC_DEBUG("Authentication rejected for weak SSF %d\n", vs->csock); |
| goto authreject; |
| } |
| |
| /* Check username whitelist ACL */ |
| if (vnc_auth_sasl_check_access(vs) < 0) { |
| VNC_DEBUG("Authentication rejected for ACL %d\n", vs->csock); |
| goto authreject; |
| } |
| |
| VNC_DEBUG("Authentication successful %d\n", vs->csock); |
| 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); |
| VNC_DEBUG("Got client start len %d\n", startlen); |
| if (startlen > SASL_DATA_MAX_LEN) { |
| VNC_DEBUG("Too much SASL data %d\n", startlen); |
| 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_malloc(len + 1); |
| strncpy(mechname, (char*)data, len); |
| mechname[len] = '\0'; |
| VNC_DEBUG("Got client mechname '%s' check against '%s'\n", |
| mechname, vs->sasl.mechlist); |
| |
| if (strncmp(vs->sasl.mechlist, mechname, len) == 0) { |
| if (vs->sasl.mechlist[len] != '\0' && |
| vs->sasl.mechlist[len] != ',') { |
| VNC_DEBUG("One %d", vs->sasl.mechlist[len]); |
| goto fail; |
| } |
| } else { |
| char *offset = strstr(vs->sasl.mechlist, mechname); |
| VNC_DEBUG("Two %p\n", offset); |
| if (!offset) { |
| goto fail; |
| } |
| VNC_DEBUG("Two '%s'\n", offset); |
| if (offset[-1] != ',' || |
| (offset[len] != '\0'&& |
| offset[len] != ',')) { |
| goto fail; |
| } |
| } |
| |
| g_free(vs->sasl.mechlist); |
| vs->sasl.mechlist = mechname; |
| |
| VNC_DEBUG("Validated mechname '%s'\n", mechname); |
| vnc_read_when(vs, protocol_client_auth_sasl_start_len, 4); |
| return 0; |
| |
| fail: |
| 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); |
| VNC_DEBUG("Got client mechname len %d\n", mechlen); |
| if (mechlen > 100) { |
| VNC_DEBUG("Too long SASL mechname data %d\n", mechlen); |
| vnc_client_error(vs); |
| return -1; |
| } |
| if (mechlen < 1) { |
| VNC_DEBUG("Too short SASL mechname %d\n", mechlen); |
| vnc_client_error(vs); |
| return -1; |
| } |
| vnc_read_when(vs, protocol_client_auth_sasl_mechname,mechlen); |
| return 0; |
| } |
| |
| 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 %d\n", vs->csock); |
| |
| /* Get local & remote client addresses in form IPADDR;PORT */ |
| if (!(localAddr = vnc_socket_local_addr("%s;%s", vs->csock))) |
| goto authabort; |
| |
| if (!(remoteAddr = vnc_socket_remote_addr("%s;%s", vs->csock))) { |
| 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; |
| } |
| |
| #ifdef CONFIG_VNC_TLS |
| /* 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) { |
| gnutls_cipher_algorithm_t cipher; |
| sasl_ssf_t ssf; |
| |
| cipher = gnutls_cipher_get(vs->tls.session); |
| if (!(ssf = (sasl_ssf_t)gnutls_cipher_get_key_size(cipher))) { |
| VNC_DEBUG("%s", "cannot TLS get cipher size\n"); |
| sasl_dispose(&vs->sasl.conn); |
| vs->sasl.conn = NULL; |
| goto authabort; |
| } |
| ssf *= 8; /* 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 |
| #endif /* CONFIG_VNC_TLS */ |
| vs->sasl.wantSSF = 1; |
| |
| memset (&secprops, 0, sizeof secprops); |
| /* Inform SASL that we've got an external SSF layer from TLS */ |
| if (strncmp(vs->vd->display, "unix:", 5) == 0 |
| #ifdef CONFIG_VNC_TLS |
| /* Disable SSF, if using TLS+x509+SASL only. TLS without x509 |
| is not sufficiently strong */ |
| || (vs->auth == VNC_AUTH_VENCRYPT && |
| vs->subauth == VNC_AUTH_VENCRYPT_X509SASL) |
| #endif /* CONFIG_VNC_TLS */ |
| ) { |
| /* 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); |
| return; |
| } |
| |
| |
