Merge branch 'sasl2' of git://github.com/simonwaterman/libvncserver into simonwaterman-sasl2

1 files changed, 579 insertions, 0 deletions

diff --git a/libvncclient/rfbsasl.c b/libvncclient/rfbsasl.c
new file mode 100644
index 0000000..dc7d3bc
--- /dev/null
+++ b/libvncclient/rfbsasl.c
@@ -0,0 +1,579 @@
+/*
+ * The software in this file is derived from the vncconnection.c source file
+ * from the GTK VNC Widget with modifications by S. Waterman <simon.waterman@zynstra.com>
+ * for compatibility with libvncserver.  The copyright and license
+ * statements below apply only to this source file and to no other parts of the
+ * libvncserver library.
+ *
+ * GTK VNC Widget
+ *
+ * Copyright (C) 2006  Anthony Liguori <anthony@codemonkey.ws>
+ * Copyright (C) 2009-2010 Daniel P. Berrange <dan@berrange.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.0 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301 USA
+ */
+
+/*
+ * rfbsasl.c - functions to deal with client side of the SASL protocol.
+ */
+
+#ifdef __STRICT_ANSI__
+#define _BSD_SOURCE
+#define _POSIX_SOURCE
+#define _XOPEN_SOURCE 600
+#endif
+
+#include <errno.h>
+#include <rfb/rfbclient.h>
+
+#ifdef WIN32
+#undef SOCKET
+#include <winsock2.h>
+#define EWOULDBLOCK WSAEWOULDBLOCK
+#define socklen_t int
+#define close closesocket
+#define read(sock,buf,len) recv(sock,buf,len,0)
+#define write(sock,buf,len) send(sock,buf,len,0)
+#ifdef LIBVNCSERVER_HAVE_WS2TCPIP_H
+#undef socklen_t
+#include <ws2tcpip.h>
+#endif /* LIBVNCSERVER_HAVE_WS2TCPIP_H */
+#else /* WIN32 */
+#include <arpa/inet.h>
+#endif /* WIN32 */
+
+#include "rfbsasl.h"
+
+#include "tls.h"
+
+#ifdef _MSC_VER
+#  define snprintf _snprintf /* MSVC went straight to the underscored syntax */
+#endif
+
+/*
+ * NB, keep in sync with similar method in qemud/remote.c
+ */
+static char *vnc_connection_addr_to_string(char *host, int port)
+{
+    char * buf = (char *)malloc(strlen(host) + 7);
+    sprintf(buf, "%s;%hu", host, port);
+    return buf;
+}
+
+static int log_func(void *context,
+                    int level,
+                    const char *message)
+{
+   rfbClientLog("SASL: %s\n", message);
+
+   return SASL_OK;
+}
+
+static int user_callback_adapt(void *context,
+                          int id,
+                          const char **result,
+                          unsigned *len)
+{
+   rfbClient* client = (rfbClient *)context;
+
+   if (id != SASL_CB_AUTHNAME) {
+       rfbClientLog("Unrecognized SASL callback ID %d\n", id);
+       return SASL_FAIL;
+   }
+
+   if (!client->GetUser) {
+       rfbClientLog("Client user callback not found\n");
+       return SASL_FAIL;
+   }
+
+   *result = client->GetUser(client);
+
+   if (! *result) return SASL_FAIL;
+   /**len = strlen(*result);*/
+   return SASL_OK;
+}
+
+static int password_callback_adapt(sasl_conn_t *conn,
+                                   void * context,
+                                   int id,
+                                   sasl_secret_t **secret)
+{
+   rfbClient* client = (rfbClient *)context;
+   char * password;
+
+   if (id != SASL_CB_PASS) {
+       rfbClientLog("Unrecognized SASL callback ID %d\n", id);
+       return SASL_FAIL;
+   }
+
+   if (client->saslSecret) { /* If we've already got it just return it. */
+       *secret = client->saslSecret;
+       return SASL_OK;
+   }
+
+   if (!client->GetPassword) {
+       rfbClientLog("Client password callback not found\n");
+       return SASL_FAIL;
+   }
+
+   password = client->GetPassword(client);
+
+   if (! password) return SASL_FAIL;
+
+   sasl_secret_t *lsec = (sasl_secret_t *)malloc(sizeof(sasl_secret_t) + strlen(password));
+   if (!lsec) {
+       rfbClientLog("Could not allocate sasl_secret_t\n");
+       return SASL_FAIL;
+   }
+
+   strcpy(lsec->data, password);
+   lsec->len = strlen(password);
+   client->saslSecret = lsec;
+   *secret = lsec;
+
+   /* Clear client password */
+   size_t i;
+   for (i = 0; i < lsec->len; i++) {
+        password[i] = '\0';
+   }
+   free(password);
+
+   return SASL_OK;
+}
+
+#define SASL_MAX_MECHLIST_LEN 300
+#define SASL_MAX_DATA_LEN (1024 * 1024)
+
+/* Perform the SASL authentication process
+ */
+rfbBool
+HandleSASLAuth(rfbClient *client)
+{
+    sasl_conn_t *saslconn = NULL;
+    sasl_security_properties_t secprops;
+    const char *clientout;
+    char *serverin = NULL;
+    unsigned int clientoutlen, serverinlen;
+    int err, complete = 0;
+    char *localAddr = NULL, *remoteAddr = NULL;
+    const void *val;
+    sasl_ssf_t ssf;
+    sasl_callback_t saslcb[] = {
+        {SASL_CB_LOG, (void *)log_func, NULL},
+        {SASL_CB_AUTHNAME, client->GetUser ? (void *)user_callback_adapt : NULL, client},
+        {SASL_CB_PASS, client->GetPassword ? (void *)password_callback_adapt : NULL, client},
+        { .id = 0 },
+    };
+    sasl_interact_t *interact = NULL;
+    uint32_t mechlistlen;
+    char *mechlist;
+    char *wantmech;
+    const char *mechname;
+    rfbBool ret;
+
+    client->saslconn = NULL;
+
+    /* Sets up the SASL library as a whole */
+    err = sasl_client_init(NULL);
+    rfbClientLog("Client initialize SASL authentication %d\n", err);
+    if (err != SASL_OK) {
+        rfbClientLog("failed to initialize SASL library: %d (%s)\n",
+                  err, sasl_errstring(err, NULL, NULL));
+        goto error;
+    }
+
+    /* Get local address in form  IPADDR:PORT */
+    struct sockaddr_storage localAddress;
+    socklen_t addressLength = sizeof(localAddress);
+    char buf[INET6_ADDRSTRLEN];
+    int  port;
+
+    if (getsockname(client->sock, (struct sockaddr*)&localAddress, &addressLength)) {
+        rfbClientLog("failed to get local address\n");
+        goto error;
+    }
+
+    if (localAddress.ss_family == AF_INET) {
+        struct sockaddr_in *sa_in = (struct sockaddr_in*)&localAddress;
+        inet_ntop(AF_INET, &(sa_in->sin_addr), buf, INET_ADDRSTRLEN);
+        port = ntohs(sa_in->sin_port);
+        localAddr = vnc_connection_addr_to_string(buf, port);
+    } else if (localAddress.ss_family == AF_INET6) {
+        struct sockaddr_in6 *sa_in = (struct sockaddr_in6*)&localAddress;
+        inet_ntop(AF_INET6, &(sa_in->sin6_addr), buf, INET6_ADDRSTRLEN);
+        port = ntohs(sa_in->sin6_port);
+        localAddr = vnc_connection_addr_to_string(buf, port);
+    } else {
+        rfbClientLog("failed to get local address\n");
+        goto error;
+    }
+
+    /* Get remote address in form  IPADDR:PORT */
+    remoteAddr = vnc_connection_addr_to_string(client->serverHost, client->serverPort);
+
+    rfbClientLog("Client SASL new host:'%s' local:'%s' remote:'%s'\n", client->serverHost, localAddr, remoteAddr);
+
+    /* Setup a handle for being a client */
+    err = sasl_client_new("vnc",
+                          client->serverHost,
+                          localAddr,
+                          remoteAddr,
+                          saslcb,
+                          SASL_SUCCESS_DATA,
+                          &saslconn);
+    free(localAddr);
+    free(remoteAddr);
+
+    if (err != SASL_OK) {
+        rfbClientLog("Failed to create SASL client context: %d (%s)\n",
+                  err, sasl_errstring(err, NULL, NULL));
+        goto error;
+    }
+
+    /* Initialize some connection props we care about */
+    if (client->tlsSession) {
+        if (!(ssf = (sasl_ssf_t)GetTLSCipherBits(client))) {
+            rfbClientLog("%s", "invalid cipher size for TLS session\n");
+            goto error;
+        }
+
+        rfbClientLog("Setting external SSF %d\n", ssf);
+        err = sasl_setprop(saslconn, SASL_SSF_EXTERNAL, &ssf);
+        if (err != SASL_OK) {
+            rfbClientLog("cannot set external SSF %d (%s)\n",
+                      err, sasl_errstring(err, NULL, NULL));
+            goto error;
+        }
+    }
+
+    memset (&secprops, 0, sizeof secprops);
+    /* If we've got TLS, we don't care about SSF */
+    secprops.min_ssf = client->tlsSession ? 0 : 56; /* Equiv to DES supported by all Kerberos */
+    secprops.max_ssf = client->tlsSession ? 0 : 100000; /* Very strong ! AES == 256 */
+    secprops.maxbufsize = 100000;
+    /* If we're not TLS, then forbid any anonymous or trivially crackable auth */
+    secprops.security_flags = client->tlsSession ? 0 :
+        SASL_SEC_NOANONYMOUS | SASL_SEC_NOPLAINTEXT;
+
+    err = sasl_setprop(saslconn, SASL_SEC_PROPS, &secprops);
+    if (err != SASL_OK) {
+        rfbClientLog("cannot set security props %d (%s)\n",
+                  err, sasl_errstring(err, NULL, NULL));
+        goto error;
+    }
+
+    /* Get the supported mechanisms from the server */
+    if (!ReadFromRFBServer(client, (char *)&mechlistlen, 4)) {
+        rfbClientLog("failed to read mechlistlen\n");
+        goto error;
+    }
+    mechlistlen = rfbClientSwap32IfLE(mechlistlen);
+    rfbClientLog("mechlistlen is %d\n", mechlistlen);
+    if (mechlistlen > SASL_MAX_MECHLIST_LEN) {
+        rfbClientLog("mechlistlen %d too long\n", mechlistlen);
+        goto error;
+    }
+
+    mechlist = malloc(mechlistlen+1);
+    if (!ReadFromRFBServer(client, mechlist, mechlistlen)) {
+        free(mechlist);
+        goto error;
+    }
+    mechlist[mechlistlen] = '\0';
+
+    /* Allow the client to influence the mechanism selected. */
+    if (client->GetSASLMechanism) {
+        wantmech = client->GetSASLMechanism(client, mechlist);
+        
+        if (wantmech && *wantmech != 0) {
+            if (strstr(mechlist, wantmech) == NULL) {
+                rfbClientLog("Client requested SASL mechanism %s not supported by server\n",
+                             wantmech);
+                free(mechlist);
+                free(wantmech);
+                goto error;
+            } else {
+                free(mechlist);
+                mechlist = wantmech;
+            }
+        }
+    }
+
+    rfbClientLog("Client start negotiation mechlist '%s'\n", mechlist);
+
+ restart:
+    /* Start the auth negotiation on the client end first */
+    err = sasl_client_start(saslconn,
+                            mechlist,
+                            &interact,
+                            &clientout,
+                            &clientoutlen,
+                            &mechname);
+    if (err != SASL_OK && err != SASL_CONTINUE && err != SASL_INTERACT) {
+        rfbClientLog("Failed to start SASL negotiation: %d (%s)\n",
+                  err, sasl_errdetail(saslconn));
+        free(mechlist);
+        mechlist = NULL;
+        goto error;
+    }
+
+    /* Need to gather some credentials from the client */
+    if (err == SASL_INTERACT) {
+        rfbClientLog("User interaction required but not currently supported\n");
+        goto error;
+    }
+
+    rfbClientLog("Server start negotiation with mech %s. Data %d bytes %p '%s'\n",
+              mechname, clientoutlen, clientout, clientout);
+
+    if (clientoutlen > SASL_MAX_DATA_LEN) {
+        rfbClientLog("SASL negotiation data too long: %d bytes\n",
+                  clientoutlen);
+        goto error;
+    }
+
+    /* Send back the chosen mechname */
+    uint32_t mechnamelen = rfbClientSwap32IfLE(strlen(mechname));
+    if (!WriteToRFBServer(client, (char *)&mechnamelen, 4)) goto error;
+    if (!WriteToRFBServer(client, (char *)mechname, strlen(mechname))) goto error;
+
+    /* NB, distinction of NULL vs "" is *critical* in SASL */
+    if (clientout) {
+        uint32_t colsw = rfbClientSwap32IfLE(clientoutlen + 1);
+        if (!WriteToRFBServer(client, (char *)&colsw, 4)) goto error;
+        if (!WriteToRFBServer(client, (char *)clientout, clientoutlen + 1)) goto error;
+    } else {
+        uint32_t temp = 0;
+        if (!WriteToRFBServer(client, (char *)&temp, 4)) goto error;
+    }
+
+    rfbClientLog("%s", "Getting sever start negotiation reply\n");
+    /* Read the 'START' message reply from server */
+    if (!ReadFromRFBServer(client, (char *)&serverinlen, 4)) goto error;
+    serverinlen = rfbClientSwap32IfLE(serverinlen);
+
+    if (serverinlen > SASL_MAX_DATA_LEN) {
+        rfbClientLog("SASL negotiation data too long: %d bytes\n",
+                  serverinlen);
+        goto error;
+    }
+
+    /* NB, distinction of NULL vs "" is *critical* in SASL */
+    if (serverinlen) {
+        serverin = malloc(serverinlen);
+        if (!ReadFromRFBServer(client, serverin, serverinlen)) goto error;
+        serverin[serverinlen-1] = '\0';
+        serverinlen--;
+    } else {
+        serverin = NULL;
+    }
+    if (!ReadFromRFBServer(client, (char *)&complete, 1)) goto error;
+
+    rfbClientLog("Client start result complete: %d. Data %d bytes %p '%s'\n",
+              complete, serverinlen, serverin, serverin);
+
+    /* Loop-the-loop...
+     * Even if the server has completed, the client must *always* do at least one step
+     * in this loop to verify the server isn't lying about something. Mutual auth */
+    for (;;) {
+    restep:
+        err = sasl_client_step(saslconn,
+                               serverin,
+                               serverinlen,
+                               &interact,
+                               &clientout,
+                               &clientoutlen);
+        if (err != SASL_OK && err != SASL_CONTINUE && err != SASL_INTERACT) {
+            rfbClientLog("Failed SASL step: %d (%s)\n",
+                      err, sasl_errdetail(saslconn));
+            goto error;
+        }
+
+        /* Need to gather some credentials from the client */
+        if (err == SASL_INTERACT) {
+            rfbClientLog("User interaction required but not currently supported\n");
+            goto error;
+        }
+
+        if (serverin) {
+            free(serverin);
+            serverin = NULL;
+        }
+
+        rfbClientLog("Client step result %d. Data %d bytes %p '%s'\n", err, clientoutlen, clientout, clientout);
+
+        /* Previous server call showed completion & we're now locally complete too */
+        if (complete && err == SASL_OK)
+            break;
+
+        /* Not done, prepare to talk with the server for another iteration */
+
+        /* NB, distinction of NULL vs "" is *critical* in SASL */
+        if (clientout) {
+            uint32_t colsw = rfbClientSwap32IfLE(clientoutlen + 1);
+            if (!WriteToRFBServer(client, (char *)&colsw, 4)) goto error;
+            if (!WriteToRFBServer(client, (char *)clientout, clientoutlen + 1)) goto error;
+        } else {
+            uint32_t temp = 0;
+            if (!WriteToRFBServer(client, (char *)&temp, 4)) goto error;
+        }
+
+        rfbClientLog("Server step with %d bytes %p\n", clientoutlen, clientout);
+
+        if (!ReadFromRFBServer(client, (char *)&serverinlen, 4)) goto error;
+        serverinlen = rfbClientSwap32IfLE(serverinlen);
+
+        if (serverinlen > SASL_MAX_DATA_LEN) {
+            rfbClientLog("SASL negotiation data too long: %d bytes\n",
+                      serverinlen);
+            goto error;
+        }
+
+    /* NB, distinction of NULL vs "" is *critical* in SASL */
+        if (serverinlen) {
+            serverin = malloc(serverinlen);
+            if (!ReadFromRFBServer(client, serverin, serverinlen)) goto error;
+            serverin[serverinlen-1] = '\0';
+            serverinlen--;
+        } else {
+            serverin = NULL;
+        }
+        if (!ReadFromRFBServer(client, (char *)&complete, 1)) goto error;
+
+        rfbClientLog("Client step result complete: %d. Data %d bytes %p '%s'\n",
+                  complete, serverinlen, serverin, serverin);
+
+        /* This server call shows complete, and earlier client step was OK */
+        if (complete && err == SASL_OK) {
+            free(serverin);
+            serverin = NULL;
+            break;
+        }
+    }
+
+    /* Check for suitable SSF if non-TLS */
+    if (!client->tlsSession) {
+        err = sasl_getprop(saslconn, SASL_SSF, &val);
+        if (err != SASL_OK) {
+            rfbClientLog("cannot query SASL ssf on connection %d (%s)\n",
+                      err, sasl_errstring(err, NULL, NULL));
+            goto error;
+        }
+        ssf = *(const int *)val;
+        rfbClientLog("SASL SSF value %d\n", ssf);
+        if (ssf < 56) { /* 56 == DES level, good for Kerberos */
+            rfbClientLog("negotiation SSF %d was not strong enough\n", ssf);
+            goto error;
+        }
+    }
+
+    rfbClientLog("%s", "SASL authentication complete\n");
+
+    uint32_t result;
+    if (!ReadFromRFBServer(client, (char *)&result, 4)) {
+        rfbClientLog("Failed to read authentication result\n");
+        goto error;
+    }
+    result = rfbClientSwap32IfLE(result);
+
+    if (result != 0) {
+        rfbClientLog("Authentication failure\n");
+        goto error;
+    }
+    rfbClientLog("Authentication successful - switching to SSF\n");
+
+    /* This must come *after* check-auth-result, because the former
+     * is defined to be sent unencrypted, and setting saslconn turns
+     * on the SSF layer encryption processing */
+    client->saslconn = saslconn;
+
+    /* Clear SASL secret from memory if set - it'll be free'd on dispose */
+    if (client->saslSecret) {
+        size_t i;
+        for (i = 0; i < client->saslSecret->len; i++)
+            client->saslSecret->data[i] = '\0';
+        client->saslSecret->len = 0;
+    }
+        
+    return TRUE;
+
+ error:
+    if (client->saslSecret) {
+        size_t i;
+        for (i = 0; i < client->saslSecret->len; i++)
+            client->saslSecret->data[i] = '\0';
+        client->saslSecret->len = 0;
+    }
+
+    if (saslconn)
+        sasl_dispose(&saslconn);
+    return FALSE;
+}
+
+int
+ReadFromSASL(rfbClient* client, char *out, unsigned int n)
+{
+    size_t want;
+
+    if (client->saslDecoded == NULL) {
+        char *encoded;
+        int encodedLen;
+        int err, ret;
+
+        encodedLen = 8192;
+        encoded = (char *)malloc(encodedLen);
+
+        ret = read(client->sock, encoded, encodedLen);
+        if (ret < 0) {
+            free(encoded);
+            return ret;
+        }
+        if (ret == 0) {
+            free(encoded);
+            errno = EIO;
+            return -EIO;
+        }
+
+        err = sasl_decode(client->saslconn, encoded, ret,
+                          &client->saslDecoded, &client->saslDecodedLength);
+        free(encoded);
+        if (err != SASL_OK) {
+	    rfbClientLog("Failed to decode SASL data %s\n",
+                      sasl_errstring(err, NULL, NULL));
+            return -EINVAL;
+        }
+        client->saslDecodedOffset = 0;
+    }
+
+    want = client->saslDecodedLength - client->saslDecodedOffset;
+    if (want > n)
+        want = n;
+
+    memcpy(out,
+           client->saslDecoded + client->saslDecodedOffset,
+           want);
+    client->saslDecodedOffset += want;
+    if (client->saslDecodedOffset == client->saslDecodedLength) {
+        client->saslDecodedLength = client->saslDecodedOffset = 0;
+        client->saslDecoded = NULL;
+    }
+
+    if (!want) {
+        errno = EAGAIN;
+        return -EAGAIN;
+    }
+
+    return want;
+}