[Security Advisory] Advisory: [AD_LAB-04002]Jabberd2.x remote Buffer Overflows Authors: icbm@venustech.com.cn Class: Boundary Condition Error CVE:CAN-2004-0953 Remote: Yes, could allow remote compromise Vulnerable: Jabberd 2.* Unvulnerable: Jabberd 1.4 Vendor: http://jabberd.jabberstudio.org/ I.INFO: ------- Jabber 2 server (Jabberd), the latest release of the popular open source messaging system based on the Jabber Protocol. It has been rewritten from the ground up to be scalable, architecturally sound, and to support the latest protocol extensions coming out of the JSF. The goal of Jabber is to provide an XML protocol for synchronous and asynchronous communication for client to client, client to server, and server to server messaging, although the primary use of Jabber is instant messaging (IM). The C2S (Client to Server) component handles communication with Jabber clients: 1.Connects to Jabber clients 2.Passes packets to the SM 3.Authenticates clients 4.Registers users 5.Triggers activity with the SM The C2S component connects to the Authentication Data Package (authreg) in order to register and authenticate users. II.DESCRIPTION: ------------------------ There is a remote buffer overflow in the C2S module of Jabberd2.x which allows attackers to crash the Jabberd sever or even run an arbitrary code on it. The nature of this vulnerability lies in the fact that an attacker can bypass the length check of a username and the password and supply a very long username to the server which directly handles the long username with the database relate function like mysql_real_escape_string, PQescapeString etc. and then cause a remote buffer overflow. III.DETAILS: ----------------- In the Authreg.c(c2s) file the jabberd server cuts the length of the username with this: snprintf(username, 1024, "%.*s", NAD_CDATA_L(nad, elem), NAD_CDATA(nad, elem)); So we believe the max length of the username is 1024, so the fist problem is in the authreg_mysql.c static MYSQL_RES *_ar_mysql_get_user_tuple(authreg_t ar, char *username, char *realm) { mysqlcontext_t ctx = (mysqlcontext_t) ar->private; MYSQL *conn = ctx->conn; char euser[513], erealm[513], sql[2049]; //euser and erealm only 513 long MYSQL_RES *res; if(mysql_ping(conn) != 0) { log_write(ar->c2s->log, LOG_ERR, "mysql: connection to database lost"); return NULL; } mysql_real_escape_string(conn, euser, username, strlen(username));//Thers is the buffer overflow mysql_real_escape_string(conn, erealm, realm, strlen(realm));//and there also has one. As the user should be (strlen(username)*2)+1 long so if the username or realm is longer than 256 bytes there will be a buffer overflow. But when we patched the hole by increasing the user and realm to 2049 bytes(1024*2+1) there still was a buffer overflow. This data flow is: _sx_sasl_scod_callback(sasl.c:501) | |----->_c2s_sx_sasl_callback(main.c:264) | |----->_ar_mysql_get_password(authreg_mysql.c:92) | |----->_ar_mysql_get_user_tuple(authreg_mysql.c:42) So we find the essence of this problem: in the _c2s_sx_sasl_callback(c2s/main.c) the sever directly calls the database related function to handle the username here without any length check. BTW:In the file authreg_pgsql.c have the same problems, the code is below: char euser[513], erealm[513], sql[2049]; /* query(1024) + euser(512) + erealm(512) + \0(1) */ PGresult *res; PQescapeString(euser, username, strlen(username)); PQescapeString(erealm, realm, strlen(realm)); IV.POC&Patch: --------------------- Just a POC:) #!/usr/bin/python import xmpp name = 'a'*10240 # Born a client cl=xmpp.Client('localhost') if not cl.connect(server=('192.168.10.138',5222)): raise IOError('Can not connect to server.') if not cl.auth(name,'jabberuserpassword','optional resource name'): raise IOError('Can not auth with server.') cl.disconnect() Stephen Marquard gave a rapidly patch on this issue: diff -ru c2sorig/authreg.c c2s/authreg.c --- c2sorig/authreg.c Mon Nov 22 15:53:34 2004 +++ c2s/authreg.c Mon Nov 22 20:06:25 2004 @@ -623,7 +623,7 @@ log_write(c2s->log, LOG_NOTICE, "[%d] created user: user=%s; realm=%s", sess->s->tag, username, sess->realm); /* extract the password */ - snprintf(password, 1024, "%.*s", NAD_CDATA_L(nad, elem), NAD_CDATA(nad, elem)); + snprintf(password, 257, "%.*s", NAD_CDATA_L(nad, elem), NAD_CDATA(nad, elem)); /* change it */ if((c2s->ar->set_password)(c2s->ar, username, sess->realm, password) != 0) diff -ru c2sorig/authreg_mysql.c c2s/authreg_mysql.c --- c2sorig/authreg_mysql.c Mon Nov 22 15:53:34 2004 +++ c2s/authreg_mysql.c Mon Nov 22 16:55:37 2004 @@ -24,6 +24,10 @@ #ifdef STORAGE_MYSQL +#define MYSQL_LU 1024 /* maximum length of username - should correspond to field length */ +#define MYSQL_LR 256 /* maximum length of realm - should correspond to field length */ +#define MYSQL_LP 256 /* maximum length of password - should correspond to field length */ + #include typedef struct mysqlcontext_st { @@ -42,7 +46,8 @@ static MYSQL_RES *_ar_mysql_get_user_tuple(authreg_t ar, char *username, char *realm) { mysqlcontext_t ctx = (mysqlcontext_t) ar->private; MYSQL *conn = ctx->conn; - char euser[2049], erealm[2049], sql[5121]; /* query(1024) + euser(2048) + erealm(2048) + \0(1) */ + char iuser[MYSQL_LU+1], irealm[MYSQL_LR+1]; + char euser[MYSQL_LU*2+1], erealm[MYSQL_LR*2+1], sql[1024 + MYSQL_LU*2 + MYSQL_LR*2 + 1]; /* query(1024) + euser + erealm + \0(1) */ MYSQL_RES *res; if(mysql_ping(conn) != 0) { @@ -50,8 +55,11 @@ return NULL; } - mysql_real_escape_string(conn, euser, username, strlen(username)); - mysql_real_escape_string(conn, erealm, realm, strlen(realm)); + snprintf(iuser, MYSQL_LU+1, "%s", username); + snprintf(irealm, MYSQL_LR+1, "%s", realm); + + mysql_real_escape_string(conn, euser, iuser, strlen(iuser)); + mysql_real_escape_string(conn, erealm, irealm, strlen(irealm)); sprintf(sql, ctx->sql_select, euser, erealm); @@ -127,15 +135,21 @@ static int _ar_mysql_set_password(authreg_t ar, char *username, char *realm, char password[257]) { mysqlcontext_t ctx = (mysqlcontext_t) ar->private; MYSQL *conn = ctx->conn; - char euser[2049], erealm[2049], epass[513], sql[5633]; /* query(1024) + euser(2048) + erealm(2048) + epass(512) + \0(1) */ + char iuser[MYSQL_LU+1], irealm[MYSQL_LR+1]; + char euser[MYSQL_LU*2+1], erealm[MYSQL_LR*2+1], epass[513], sql[1024+MYSQL_LU*2+MYSQL_LR*2+512+1]; /* query(1024) + euser + erealm + epass(512) + \0(1) */ if(mysql_ping(conn) != 0) { log_write(ar->c2s->log, LOG_ERR, "mysql: connection to database lost"); return 1; } - mysql_real_escape_string(conn, euser, username, strlen(username)); - mysql_real_escape_string(conn, erealm, realm, strlen(realm)); + snprintf(iuser, MYSQL_LU+1, "%s", username); + snprintf(irealm, MYSQL_LR+1, "%s", realm); + + password[256]= '\0'; + + mysql_real_escape_string(conn, euser, iuser, strlen(iuser)); + mysql_real_escape_string(conn, erealm, irealm, strlen(irealm)); mysql_real_escape_string(conn, epass, password, strlen(password)); sprintf(sql, ctx->sql_setpassword, epass, euser, erealm); @@ -195,15 +209,19 @@ static int _ar_mysql_set_zerok(authreg_t ar, char *username, char *realm, char hash[41], char token[11], int sequence) { mysqlcontext_t ctx = (mysqlcontext_t) ar->private; MYSQL *conn = ctx->conn; - char euser[2049], erealm[2049], ehash[81], etoken[21], sql[5233]; /* query(1024) + euser(2048) + erealm(2048) + ehash(80) + etoken(20) + sequence(12) + \0(1) */ + char iuser[MYSQL_LU+1], irealm[MYSQL_LR+1]; + char euser[MYSQL_LU*2+1], erealm[MYSQL_LR*2+1], ehash[81], etoken[21], sql[1024+MYSQL_LU*2+MYSQL_LR*2+80+20+12+1]; /* query(1024) + euser + erealm + ehash(80) + etoken(20) + sequence(12) + \0(1) */ if(mysql_ping(conn) != 0) { log_write(ar->c2s->log, LOG_ERR, "mysql: connection to database lost"); return 1; } - mysql_real_escape_string(conn, euser, username, strlen(username)); - mysql_real_escape_string(conn, erealm, realm, strlen(realm)); + snprintf(iuser, MYSQL_LU+1, "%s", username); + snprintf(irealm, MYSQL_LR+1, "%s", realm); + + mysql_real_escape_string(conn, euser, iuser, strlen(iuser)); + mysql_real_escape_string(conn, erealm, irealm, strlen(irealm)); mysql_real_escape_string(conn, ehash, hash, strlen(hash)); mysql_real_escape_string(conn, etoken, token, strlen(token)); @@ -222,7 +240,8 @@ static int _ar_mysql_create_user(authreg_t ar, char *username, char *realm) { mysqlcontext_t ctx = (mysqlcontext_t) ar->private; MYSQL *conn = ctx->conn; - char euser[2049], erealm[2049], sql[5121]; /* query(1024) + euser(2048) + erealm(2048) + \0(1) */ + char iuser[MYSQL_LU+1], irealm[MYSQL_LR+1]; + char euser[MYSQL_LU*2+1], erealm[MYSQL_LR*2+1], sql[1024+MYSQL_LU*2+MYSQL_LR*2+1]; /* query(1024) + euser + erealm + \0(1) */ MYSQL_RES *res = _ar_mysql_get_user_tuple(ar, username, realm); if(res != NULL) { @@ -237,8 +256,11 @@ return 1; } - mysql_real_escape_string(conn, euser, username, strlen(username)); - mysql_real_escape_string(conn, erealm, realm, strlen(realm)); + snprintf(iuser, MYSQL_LU+1, "%s", username); + snprintf(irealm, MYSQL_LR+1, "%s", realm); + + mysql_real_escape_string(conn, euser, iuser, strlen(iuser)); + mysql_real_escape_string(conn, erealm, irealm, strlen(irealm)); sprintf(sql, ctx->sql_create, euser, erealm); @@ -255,15 +277,19 @@ static int _ar_mysql_delete_user(authreg_t ar, char *username, char *realm) { mysqlcontext_t ctx = (mysqlcontext_t) ar->private; MYSQL *conn = ctx->conn; - char euser[2049], erealm[2049], sql[5121]; /* query(1024) + euser(2048) + erealm(2048) + \0(1) */ + char iuser[MYSQL_LU+1], irealm[MYSQL_LR+1]; + char euser[MYSQL_LU*2+1], erealm[MYSQL_LR*2+1], sql[1024+MYSQL_LU*2+MYSQL_LR*2+1]; /* query(1024) + euser + erealm + \0(1) */ if(mysql_ping(conn) != 0) { log_write(ar->c2s->log, LOG_ERR, "mysql: connection to database lost"); return 1; } - mysql_real_escape_string(conn, euser, username, strlen(username)); - mysql_real_escape_string(conn, erealm, realm, strlen(realm)); + snprintf(iuser, MYSQL_LU+1, "%s", username); + snprintf(irealm, MYSQL_LR+1, "%s", realm); + + mysql_real_escape_string(conn, euser, iuser, strlen(iuser)); + mysql_real_escape_string(conn, erealm, irealm, strlen(irealm)); sprintf(sql, ctx->sql_delete, euser, erealm); diff -ru c2sorig/authreg_pgsql.c c2s/authreg_pgsql.c --- c2sorig/authreg_pgsql.c Mon Nov 22 15:53:34 2004 +++ c2s/authreg_pgsql.c Mon Nov 22 16:52:20 2004 @@ -26,6 +26,10 @@ #include +#define PGSQL_LU 1024 /* maximum length of username - should correspond to field length */ +#define PGSQL_LR 256 /* maximum length of realm - should correspond to field length */ +#define PGSQL_LP 256 /* maximum length of password - should correspond to field length */ + typedef struct pgsqlcontext_st { PGconn * conn; char * sql_create; @@ -42,11 +46,16 @@ static PGresult *_ar_pgsql_get_user_tuple(authreg_t ar, char *username, char *realm) { pgsqlcontext_t ctx = (pgsqlcontext_t) ar->private; PGconn *conn = ctx->conn; - char euser[2049], erealm[2049], sql[5121]; /* query(1024) + euser(2048) + erealm(2048) + \0(1) */ + + char iuser[PGSQL_LU+1], irealm[PGSQL_LR+1]; + char euser[PGSQL_LU*2+1], erealm[PGSQL_LR*2+1], sql[1024+PGSQL_LU*2+PGSQL_LR*2+1]; /* query(1024) + euser + erealm + \0(1) */ PGresult *res; - PQescapeString(euser, username, strlen(username)); - PQescapeString(erealm, realm, strlen(realm)); + snprintf(iuser, PGSQL_LU+1, "%s", username); + snprintf(irealm, PGSQL_LR+1, "%s", realm); + + PQescapeString(euser, iuser, strlen(iuser)); + PQescapeString(erealm, irealm, strlen(irealm)); sprintf(sql, ctx->sql_select, euser, erealm); @@ -114,11 +123,15 @@ static int _ar_pgsql_set_password(authreg_t ar, char *username, char *realm, char password[257]) { pgsqlcontext_t ctx = (pgsqlcontext_t) ar->private; PGconn *conn = ctx->conn; - char euser[2049], erealm[2049], epass[513], sql[5633]; /* query(1024) + euser(2048) + erealm(2048) + epass(512) + \0(1) */ + char iuser[PGSQL_LU+1], irealm[PGSQL_LR+1]; + char euser[PGSQL_LU*2+1], erealm[PGSQL_LR*2+1], epass[513], sql[1024+PGSQL_LU*2+PGSQL_LR*2+512+1]; /* query(1024) + euser + erealm + epass(512) + \0(1) */ PGresult *res; - PQescapeString(euser, username, strlen(username)); - PQescapeString(erealm, realm, strlen(realm)); + snprintf(iuser, PGSQL_LU+1, "%s", username); + snprintf(irealm, PGSQL_LR+1, "%s", realm); + + PQescapeString(euser, iuser, strlen(iuser)); + PQescapeString(erealm, irealm, strlen(irealm)); PQescapeString(epass, password, strlen(password)); sprintf(sql, ctx->sql_setpassword, epass, euser, erealm); @@ -177,11 +190,15 @@ static int _ar_pgsql_set_zerok(authreg_t ar, char *username, char *realm, char hash[41], char token[11], int sequence) { pgsqlcontext_t ctx = (pgsqlcontext_t) ar->private; PGconn *conn = ctx->conn; - char euser[2049], erealm[2049], ehash[81], etoken[21], sql[5233]; /* query(1024) + euser(2048) + erealm(2048) + ehash(80) + etoken(20) + sequence(12) + \0(1) */ + char iuser[PGSQL_LU+1], irealm[PGSQL_LR+1]; + char euser[PGSQL_LU*2+1], erealm[PGSQL_LR*2+1], ehash[81], etoken[21], sql[1024 + PGSQL_LU*2 + PGSQL_LR*2 + 80 + 20 + 12 + 1]; /* query(1024) + euser + erealm + ehash(80) + etoken(20) + sequence(12) + \0(1) */ PGresult *res; - PQescapeString(euser, username, strlen(username)); - PQescapeString(erealm, realm, strlen(realm)); + snprintf(iuser, PGSQL_LU+1, "%s", username); + snprintf(irealm, PGSQL_LR+1, "%s", realm); + + PQescapeString(euser, iuser, strlen(iuser)); + PQescapeString(erealm, irealm, strlen(irealm)); PQescapeString(ehash, hash, strlen(hash)); PQescapeString(etoken, token, strlen(token)); @@ -210,7 +227,8 @@ static int _ar_pgsql_create_user(authreg_t ar, char *username, char *realm) { pgsqlcontext_t ctx = (pgsqlcontext_t) ar->private; PGconn *conn = ctx->conn; - char euser[2049], erealm[2049], sql[5121]; /* query(1024) + euser(2048) + erealm(2048) + \0(1) */ + char iuser[PGSQL_LU+1], irealm[PGSQL_LR+1]; + char euser[PGSQL_LU*2+1], erealm[PGSQL_LR*2+1], sql[1024+PGSQL_LU*2+PGSQL_LR*2+1]; /* query(1024) + euser + erealm + \0(1) */ PGresult *res; res = _ar_pgsql_get_user_tuple(ar, username, realm); @@ -221,8 +239,11 @@ PQclear(res); - PQescapeString(euser, username, strlen(username)); - PQescapeString(erealm, realm, strlen(realm)); + snprintf(iuser, PGSQL_LU+1, "%s", username); + snprintf(irealm, PGSQL_LR+1, "%s", realm); + + PQescapeString(euser, iuser, strlen(iuser)); + PQescapeString(erealm, irealm, strlen(irealm)); sprintf(sql, ctx->sql_create, euser, erealm); @@ -249,11 +270,15 @@ static int _ar_pgsql_delete_user(authreg_t ar, char *username, char *realm) { pgsqlcontext_t ctx = (pgsqlcontext_t) ar->private; PGconn *conn = ctx->conn; - char euser[2049], erealm[2049], sql[5121]; /* query(1024) + euser(2048) + erealm(2048) + \0(1) */ + char iuser[PGSQL_LU+1], irealm[PGSQL_LR+1]; + char euser[PGSQL_LU*2+1], erealm[PGSQL_LR*2+1], sql[1024+PGSQL_LU*2+PGSQL_LR*2+1]; /* query(1024) + euser + erealm + \0(1) */ PGresult *res; - PQescapeString(euser, username, strlen(username)); - PQescapeString(erealm, realm, strlen(realm)); + snprintf(iuser, PGSQL_LU+1, "%s", username); + snprintf(irealm, PGSQL_LR+1, "%s", realm); + + PQescapeString(euser, iuser, strlen(iuser)); + PQescapeString(erealm, irealm, strlen(irealm)); sprintf(sql, ctx->sql_delete, euser, erealm); V.CREDIT: ---------------- Thanks to Alex, Simon and rob@cataclysm.cx help me on this and Stephen Marquard's rapidly patch. Sam, Air, Kkqq, Swan, Flashsky, S0f, Cjj and all Venustech AD-Lab guys and "Niubi" Houzi!:) And my LeiLei... VI.DISCLAIMS: ---------------------- The information in this bulletin is provided "AS IS" without warranty of any kind. In no event shall we be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages. Copyright 1996-2004 VENUSTECH. All Rights Reserved. Terms of use. VENUSTECH Security Lab VENUSTECH INFORMATION TECHNOLOGY CO.,LTD(http://www.venustech.com.cn) Security Trusted {Solution} Provider Service