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Diffstat (limited to 'vnc-auth-sasl.c')
-rw-r--r--vnc-auth-sasl.c626
1 files changed, 626 insertions, 0 deletions
diff --git a/vnc-auth-sasl.c b/vnc-auth-sasl.c
new file mode 100644
index 0000000000..2882a357d8
--- /dev/null
+++ b/vnc-auth-sasl.c
@@ -0,0 +1,626 @@
+/*
+ * 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 = vs->sasl.waitWriteSSF = vs->sasl.wantSSF = 0;
+ vs->sasl.encodedLength = vs->sasl.encodedOffset = 0;
+ vs->sasl.encoded = NULL;
+ free(vs->sasl.username);
+ 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 %d offset %d 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;
+
+ err = sasl_getprop(vs->sasl.conn, SASL_USERNAME, &val);
+ if (err != SASL_OK) {
+ VNC_DEBUG("cannot query SASL username on connection %d (%s)\n",
+ err, sasl_errstring(err, NULL, NULL));
+ return -1;
+ }
+ if (val == NULL) {
+ VNC_DEBUG("no client username was found\n");
+ return -1;
+ }
+ VNC_DEBUG("SASL client username %s\n", (const char *)val);
+
+ vs->sasl.username = qemu_strdup((const char*)val);
+
+ return 0;
+}
+
+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 = malloc(len + 1);
+ if (!mechname) {
+ VNC_DEBUG("Out of memory reading mechname\n");
+ vnc_client_error(vs);
+ }
+ 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]);
+ vnc_client_error(vs);
+ return -1;
+ }
+ } else {
+ char *offset = strstr(vs->sasl.mechlist, mechname);
+ VNC_DEBUG("Two %p\n", offset);
+ if (!offset) {
+ vnc_client_error(vs);
+ return -1;
+ }
+ VNC_DEBUG("Two '%s'\n", offset);
+ if (offset[-1] != ',' ||
+ (offset[len] != '\0'&&
+ offset[len] != ',')) {
+ vnc_client_error(vs);
+ return -1;
+ }
+ }
+
+ 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;
+}
+
+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;
+}
+
+#define USES_X509_AUTH(vs) \
+ ((vs)->subauth == VNC_AUTH_VENCRYPT_X509NONE || \
+ (vs)->subauth == VNC_AUTH_VENCRYPT_X509VNC || \
+ (vs)->subauth == VNC_AUTH_VENCRYPT_X509PLAIN || \
+ (vs)->subauth == VNC_AUTH_VENCRYPT_X509SASL)
+
+
+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))) {
+ 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);
+ free(localAddr);
+ 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->vd->auth == VNC_AUTH_VENCRYPT &&
+ vs->vd->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->vd->auth == VNC_AUTH_VENCRYPT &&
+ vs->vd->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);
+
+ if (!(vs->sasl.mechlist = strdup(mechlist))) {
+ VNC_DEBUG("Out of memory");
+ sasl_dispose(&vs->sasl.conn);
+ vs->sasl.conn = NULL;
+ goto authabort;
+ }
+ 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;
+}
+
+
generated by cgit v1.2.3 (git 2.26.2) at 2024-12-30 16:10:13 +0000