source: protocols/jabber/sasl.c @ ed431c3

/***************************************************************************\
*                                                                           *
*  BitlBee - An IRC to IM gateway                                           *
*  Jabber module - SASL authentication                                      *
*                                                                           *
*  Copyright 2006-2012 Wilmer van der Gaast <wilmer@gaast.net>              *
*                                                                           *
*  This program is free software; you can redistribute it and/or modify     *
*  it under the terms of the GNU General Public License as published by     *
*  the Free Software Foundation; either version 2 of the License, or        *
*  (at your option) any later version.                                      *
*                                                                           *
*  This program 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 General Public License for more details.                             *
*                                                                           *
*  You should have received a copy of the GNU General Public License along  *
*  with this program; if not, write to the Free Software Foundation, Inc.,  *
*  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.              *
*                                                                           *
\***************************************************************************/

#include <ctype.h>

#include "jabber.h"
#include "base64.h"
#include "oauth2.h"
#include "oauth.h"

const struct oauth2_service oauth2_service_google =
{
        "https://accounts.google.com/o/oauth2/auth",
        "https://accounts.google.com/o/oauth2/token",
        "urn:ietf:wg:oauth:2.0:oob",
        "https://www.googleapis.com/auth/googletalk",
        "783993391592.apps.googleusercontent.com",
        "6C-Zgf7Tr7gEQTPlBhMUgo7R",
};

xt_status sasl_pkt_mechanisms(struct xt_node *node, gpointer data)
{
        struct im_connection *ic = data;
        struct jabber_data *jd = ic->proto_data;
        struct xt_node *c, *reply;
        char *s;
        int sup_plain = 0, sup_digest = 0, sup_gtalk = 0, sup_anonymous = 0;
        int want_oauth = FALSE, want_hipchat = FALSE, want_anonymous = FALSE;
        GString *mechs;

        if (!sasl_supported(ic)) {
                /* Should abort this now, since we should already be doing
                   IQ authentication. Strange things happen when you try
                   to do both... */
                imcb_log(ic,
                         "XMPP 1.0 non-compliant server seems to support SASL, please report this as a BitlBee bug!");
                return XT_HANDLED;
        }

        s = xt_find_attr(node, "xmlns");
        if (!s || strcmp(s, XMLNS_SASL) != 0) {
                imcb_log(ic, "Stream error while authenticating");
                imc_logout(ic, FALSE);
                return XT_ABORT;
        }

        want_anonymous = set_getbool(&ic->acc->set, "anonymous");
        want_oauth = set_getbool(&ic->acc->set, "oauth");
        want_hipchat = (jd->flags & JFLAG_HIPCHAT);

        mechs = g_string_new("");
        c = node->children;
        while ((c = xt_find_node(c, "mechanism"))) {
                if (c->text && g_strcasecmp(c->text, "PLAIN") == 0) {
                        sup_plain = 1;
                } else if (c->text && g_strcasecmp(c->text, "DIGEST-MD5") == 0) {
                        sup_digest = 1;
                } else if (c->text && g_strcasecmp(c->text, "ANONYMOUS") == 0) {
                        sup_anonymous = 1;
                } else if (c->text && g_strcasecmp(c->text, "X-OAUTH2") == 0) {
                        sup_gtalk = 1;
                }

                if (c->text) {
                        g_string_append_printf(mechs, " %s", c->text);
                }

                c = c->next;
        }

        if (!want_oauth && !sup_plain && !sup_digest) {
                if (!sup_gtalk) {
                        imcb_error(ic, "This server requires OAuth "
                                   "(supported schemes:%s)", mechs->str);
                } else {
                        imcb_error(ic, "BitlBee does not support any of the offered SASL "
                                   "authentication schemes:%s", mechs->str);
                }
                imc_logout(ic, FALSE);
                g_string_free(mechs, TRUE);
                return XT_ABORT;
        }
        g_string_free(mechs, TRUE);

        reply = xt_new_node("auth", NULL, NULL);
        if (!want_hipchat) {
                xt_add_attr(reply, "xmlns", XMLNS_SASL);
        } else {
                xt_add_attr(reply, "xmlns", XMLNS_HIPCHAT);
        }

        if (sup_gtalk && want_oauth) {
                int len;

                /* X-OAUTH2 is, not *the* standard OAuth2 SASL/XMPP implementation.
                   It's currently used by GTalk and vaguely documented on
                   http://code.google.com/apis/cloudprint/docs/rawxmpp.html . */
                xt_add_attr(reply, "mechanism", "X-OAUTH2");

                len = strlen(jd->username) + strlen(jd->oauth2_access_token) + 2;
                s = g_malloc(len + 1);
                s[0] = 0;
                strcpy(s + 1, jd->username);
                strcpy(s + 2 + strlen(jd->username), jd->oauth2_access_token);
                reply->text = base64_encode((unsigned char *) s, len);
                reply->text_len = strlen(reply->text);
                g_free(s);
        } else if (want_oauth) {
                imcb_error(ic, "OAuth requested, but not supported by server");
                imc_logout(ic, FALSE);
                xt_free_node(reply);
                return XT_ABORT;
        } else if (want_anonymous && sup_anonymous) {
                xt_add_attr(reply, "mechanism", "ANONYMOUS");

                /* Well, that was easy. */
        } else if (want_anonymous) {
                imcb_error(ic, "Anonymous login requested, but not supported by server");
                imc_logout(ic, FALSE);
                xt_free_node(reply);
                return XT_ABORT;
        } else if (sup_digest && !(jd->ssl && sup_plain)) {
                /* Only try DIGEST-MD5 if there's no SSL/TLS or if PLAIN isn't supported.
                 * Which in practice means "don't bother with DIGEST-MD5 most of the time".
                 * It's weak, pointless over TLS, and often breaks with some servers (hi openfire) */

                xt_add_attr(reply, "mechanism", "DIGEST-MD5");

                /* The rest will be done later, when we receive a <challenge/>. */
        } else if (sup_plain) {
                int len;
                GString *gs;
                char *username;

                if (!want_hipchat) {
                        xt_add_attr(reply, "mechanism", "PLAIN");
                        username = jd->username;
                } else {
                        username = jd->me;
                }

                /* set an arbitrary initial size to avoid reallocations */
                gs = g_string_sized_new(128);

                /* With SASL PLAIN in XMPP, the text should be b64(\0user\0pass) */
                g_string_append_c(gs, '\0');
                g_string_append(gs, username);
                g_string_append_c(gs, '\0');
                g_string_append(gs, ic->acc->pass);
                if (want_hipchat) {
                        /* Hipchat's variation adds \0resource at the end */
                        g_string_append_c(gs, '\0');
                        g_string_append(gs, set_getstr(&ic->acc->set, "resource"));
                }

                len = gs->len;
                s = g_string_free(gs, FALSE);

                reply->text = base64_encode((unsigned char *) s, len);
                reply->text_len = strlen(reply->text);
                g_free(s);
        }

        if (reply && !jabber_write_packet(ic, reply)) {
                xt_free_node(reply);
                return XT_ABORT;
        }
        xt_free_node(reply);

        /* To prevent classic authentication from happening. */
        jd->flags |= JFLAG_STREAM_STARTED;

        return XT_HANDLED;
}

/* Non-static function, but not mentioned in jabber.h because it's for internal
   use, just that the unittest should be able to reach it... */
char *sasl_get_part(char *data, char *field)
{
        int i, len;

        len = strlen(field);

        while (g_ascii_isspace(*data) || *data == ',') {
                data++;
        }

        if (g_strncasecmp(data, field, len) == 0 && data[len] == '=') {
                i = strlen(field) + 1;
        } else {
                for (i = 0; data[i]; i++) {
                        /* If we have a ", skip until it's closed again. */
                        if (data[i] == '"') {
                                i++;
                                while (data[i] != '"' || data[i - 1] == '\\') {
                                        i++;
                                }
                        }

                        /* If we got a comma, we got a new field. Check it,
                           find the next key after it. */
                        if (data[i] == ',') {
                                while (g_ascii_isspace(data[i]) || data[i] == ',') {
                                        i++;
                                }

                                if (g_strncasecmp(data + i, field, len) == 0 &&
                                    data[i + len] == '=') {
                                        i += len + 1;
                                        break;
                                }
                        }
                }
        }

        if (data[i] == '"') {
                int j;
                char *ret;

                i++;
                len = 0;
                while (data[i + len] != '"' || data[i + len - 1] == '\\') {
                        len++;
                }

                ret = g_strndup(data + i, len);
                for (i = j = 0; ret[i]; i++) {
                        if (ret[i] == '\\') {
                                ret[j++] = ret[++i];
                        } else {
                                ret[j++] = ret[i];
                        }
                }
                ret[j] = 0;

                return ret;
        } else if (data[i]) {
                len = 0;
                while (data[i + len] && data[i + len] != ',') {
                        len++;
                }

                return g_strndup(data + i, len);
        } else {
                return NULL;
        }
}

xt_status sasl_pkt_challenge(struct xt_node *node, gpointer data)
{
        struct im_connection *ic = data;
        struct jabber_data *jd = ic->proto_data;
        struct xt_node *reply_pkt = NULL;
        char *nonce = NULL, *realm = NULL, *cnonce = NULL;
        unsigned char cnonce_bin[30];
        char *digest_uri = NULL;
        char *dec = NULL;
        char *s = NULL, *reply = NULL;
        xt_status ret = XT_ABORT;

        if (node->text_len == 0) {
                goto error;
        }

        dec = frombase64(node->text);

        if (!(s = sasl_get_part(dec, "rspauth"))) {
                /* See RFC 2831 for for information. */
                md5_state_t A1, A2, H;
                md5_byte_t A1r[16], A2r[16], Hr[16];
                char A1h[33], A2h[33], Hh[33];
                int i;

                nonce = sasl_get_part(dec, "nonce");
                realm = sasl_get_part(dec, "realm");

                if (!nonce) {
                        goto error;
                }

                /* Jabber.Org considers the realm part optional and doesn't
                   specify one. Oh well, actually they're right, but still,
                   don't know if this is right... */
                if (!realm) {
                        realm = g_strdup(jd->server);
                }

                random_bytes(cnonce_bin, sizeof(cnonce_bin));
                cnonce = base64_encode(cnonce_bin, sizeof(cnonce_bin));
                digest_uri = g_strdup_printf("%s/%s", "xmpp", jd->server);

                /* Generate the MD5 hash of username:realm:password,
                   I decided to call it H. */
                md5_init(&H);
                s = g_strdup_printf("%s:%s:%s", jd->username, realm, ic->acc->pass);
                md5_append(&H, (unsigned char *) s, strlen(s));
                g_free(s);
                md5_finish(&H, Hr);

                /* Now generate the hex. MD5 hash of H:nonce:cnonce, called A1. */
                md5_init(&A1);
                s = g_strdup_printf(":%s:%s", nonce, cnonce);
                md5_append(&A1, Hr, 16);
                md5_append(&A1, (unsigned char *) s, strlen(s));
                g_free(s);
                md5_finish(&A1, A1r);
                for (i = 0; i < 16; i++) {
                        sprintf(A1h + i * 2, "%02x", A1r[i]);
                }

                /* A2... */
                md5_init(&A2);
                s = g_strdup_printf("%s:%s", "AUTHENTICATE", digest_uri);
                md5_append(&A2, (unsigned char *) s, strlen(s));
                g_free(s);
                md5_finish(&A2, A2r);
                for (i = 0; i < 16; i++) {
                        sprintf(A2h + i * 2, "%02x", A2r[i]);
                }

                /* Final result: A1:nonce:00000001:cnonce:auth:A2. Let's reuse H for it. */
                md5_init(&H);
                s = g_strdup_printf("%s:%s:%s:%s:%s:%s", A1h, nonce, "00000001", cnonce, "auth", A2h);
                md5_append(&H, (unsigned char *) s, strlen(s));
                g_free(s);
                md5_finish(&H, Hr);
                for (i = 0; i < 16; i++) {
                        sprintf(Hh + i * 2, "%02x", Hr[i]);
                }

                /* Now build the SASL response string: */
                reply = g_strdup_printf("username=\"%s\",realm=\"%s\",nonce=\"%s\",cnonce=\"%s\","
                                        "nc=%08x,qop=auth,digest-uri=\"%s\",response=%s,charset=%s",
                                        jd->username, realm, nonce, cnonce, 1, digest_uri, Hh, "utf-8");
        } else {
                /* We found rspauth, but don't really care... */
                g_free(s);
        }

        s = reply ? tobase64(reply) : NULL;
        reply_pkt = xt_new_node("response", s, NULL);
        xt_add_attr(reply_pkt, "xmlns", XMLNS_SASL);

        if (!jabber_write_packet(ic, reply_pkt)) {
                goto silent_error;
        }

        ret = XT_HANDLED;
        goto silent_error;

error:
        imcb_error(ic, "Incorrect SASL challenge received");
        imc_logout(ic, FALSE);

silent_error:
        g_free(digest_uri);
        g_free(cnonce);
        g_free(nonce);
        g_free(reply);
        g_free(realm);
        g_free(dec);
        g_free(s);
        xt_free_node(reply_pkt);

        return ret;
}

xt_status sasl_pkt_result(struct xt_node *node, gpointer data)
{
        struct im_connection *ic = data;
        struct jabber_data *jd = ic->proto_data;
        char *s;

        s = xt_find_attr(node, "xmlns");
        if (!s || strcmp(s, XMLNS_SASL) != 0) {
                imcb_log(ic, "Stream error while authenticating");
                imc_logout(ic, FALSE);
                return XT_ABORT;
        }

        if (strcmp(node->name, "success") == 0) {
                imcb_log(ic, "Authentication finished");
                jd->flags |= JFLAG_AUTHENTICATED | JFLAG_STREAM_RESTART;

                if (jd->flags & JFLAG_HIPCHAT) {
                        return hipchat_handle_success(ic, node);
                }
        } else if (strcmp(node->name, "failure") == 0) {
                imcb_error(ic, "Authentication failure");
                imc_logout(ic, FALSE);
                return XT_ABORT;
        }

        return XT_HANDLED;
}

/* This one is needed to judge if we'll do authentication using IQ or SASL.
   It's done by checking if the <stream:stream> from the server has a
   version attribute. I don't know if this is the right way though... */
gboolean sasl_supported(struct im_connection *ic)
{
        struct jabber_data *jd = ic->proto_data;

        return (jd->xt && jd->xt->root && xt_find_attr(jd->xt->root, "version")) != 0;
}

void sasl_oauth2_init(struct im_connection *ic)
{
        struct jabber_data *jd = ic->proto_data;
        char *msg, *url;

        imcb_log(ic, "Starting OAuth authentication");

        /* Temporary contact, just used to receive the OAuth response. */
        imcb_add_buddy(ic, JABBER_OAUTH_HANDLE, NULL);
        url = oauth2_url(jd->oauth2_service);
        msg = g_strdup_printf("Open this URL in your browser to authenticate: %s", url);
        imcb_buddy_msg(ic, JABBER_OAUTH_HANDLE, msg, 0, 0);
        imcb_buddy_msg(ic, JABBER_OAUTH_HANDLE, "Respond to this message with the returned "
                       "authorization token.", 0, 0);

        g_free(msg);
        g_free(url);
}

static gboolean sasl_oauth2_remove_contact(gpointer data, gint fd, b_input_condition cond)
{
        struct im_connection *ic = data;

        if (g_slist_find(jabber_connections, ic)) {
                imcb_remove_buddy(ic, JABBER_OAUTH_HANDLE, NULL);
        }
        return FALSE;
}

static void sasl_oauth2_got_token(gpointer data, const char *access_token, const char *refresh_token,
                                  const char *error);

int sasl_oauth2_get_refresh_token(struct im_connection *ic, const char *msg)
{
        struct jabber_data *jd = ic->proto_data;
        char *code;
        int ret;

        imcb_log(ic, "Requesting OAuth access token");

        /* Don't do it here because the caller may get confused if the contact
           we're currently sending a message to is deleted. */
        b_timeout_add(1, sasl_oauth2_remove_contact, ic);

        code = g_strdup(msg);
        g_strstrip(code);
        ret = oauth2_access_token(jd->oauth2_service, OAUTH2_AUTH_CODE,
                                  code, sasl_oauth2_got_token, ic);

        g_free(code);
        return ret;
}

int sasl_oauth2_refresh(struct im_connection *ic, const char *refresh_token)
{
        struct jabber_data *jd = ic->proto_data;

        return oauth2_access_token(jd->oauth2_service, OAUTH2_AUTH_REFRESH,
                                   refresh_token, sasl_oauth2_got_token, ic);
}

static void sasl_oauth2_got_token(gpointer data, const char *access_token, const char *refresh_token, const char *error)
{
        struct im_connection *ic = data;
        struct jabber_data *jd;
        GSList *auth = NULL;

        if (g_slist_find(jabber_connections, ic) == NULL) {
                return;
        }

        jd = ic->proto_data;

        if (access_token == NULL) {
                imcb_error(ic, "OAuth failure (%s)", error);
                imc_logout(ic, TRUE);
                return;
        }

        oauth_params_parse(&auth, ic->acc->pass);
        if (refresh_token) {
                oauth_params_set(&auth, "refresh_token", refresh_token);
        }
        if (access_token) {
                oauth_params_set(&auth, "access_token", access_token);
        }

        g_free(ic->acc->pass);
        ic->acc->pass = oauth_params_string(auth);
        oauth_params_free(&auth);

        g_free(jd->oauth2_access_token);
        jd->oauth2_access_token = g_strdup(access_token);

        jabber_connect(ic);
}