Backport of upstream commit 7712455d9aa33d0db0945effaa07e900b85987b1 Author: Miroslav Lichvar Date: Wed Jul 31 15:01:15 2013 +0200 Fix buffer overflow when processing crafted command packets When the length of the REQ_SUBNETS_ACCESSED, REQ_CLIENT_ACCESSES command requests and the RPY_SUBNETS_ACCESSED, RPY_CLIENT_ACCESSES, RPY_CLIENT_ACCESSES_BY_INDEX, RPY_MANUAL_LIST command replies is calculated, the number of items stored in the packet is not validated. A crafted command request/reply can be used to crash the server/client. Only clients allowed by cmdallow (by default only localhost) can crash the server. With chrony versions 1.25 and 1.26 this bug has a smaller security impact as the server requires the clients to be authenticated in order to process the subnet and client accesses commands. In 1.27 and 1.28, however, the invalid calculated length is included also in the authentication check which may cause another crash. diff -up chrony-1.25/client.c.cve-2012-4502 chrony-1.25/client.c --- chrony-1.25/client.c.cve-2012-4502 2013-08-09 12:50:40.858855754 +0200 +++ chrony-1.25/client.c 2013-08-09 13:02:52.306179674 +0200 @@ -1374,7 +1374,8 @@ submit_request(CMD_Request *request, CMD read_length = recvfrom_status; expected_length = PKL_ReplyLength(reply); - bad_length = (read_length != expected_length); + bad_length = (read_length != expected_length || + expected_length < offsetof(CMD_Reply, data)); bad_sender = (where_from.u.sa_family != his_addr.u.sa_family || (where_from.u.sa_family == AF_INET && (where_from.in4.sin_addr.s_addr != his_addr.in4.sin_addr.s_addr || diff -up chrony-1.25/cmdmon.c.cve-2012-4502 chrony-1.25/cmdmon.c --- chrony-1.25/cmdmon.c.cve-2012-4502 2011-05-04 12:29:40.000000000 +0200 +++ chrony-1.25/cmdmon.c 2013-08-09 12:50:40.861855759 +0200 @@ -1794,29 +1794,10 @@ read_from_cmd_socket(void *anything) } read_length = status; - expected_length = PKL_CommandLength(&rx_message); - rx_command = ntohs(rx_message.command); LCL_ReadRawTime(&now); LCL_CookTime(&now, &cooked_now, NULL); - tx_message.version = PROTO_VERSION_NUMBER; - tx_message.pkt_type = PKT_TYPE_CMD_REPLY; - tx_message.res1 = 0; - tx_message.res2 = 0; - tx_message.command = rx_message.command; - tx_message.sequence = rx_message.sequence; - tx_message.reply = htons(RPY_NULL); - tx_message.number = htons(1); - tx_message.total = htons(1); - tx_message.pad1 = 0; - tx_message.utoken = htonl(utoken); - /* Set this to a default (invalid) value. This protects against the - token field being set to an arbitrary value if we reject the - message, e.g. due to the host failing the access check. */ - tx_message.token = htonl(0xffffffffUL); - memset(&tx_message.auth, 0, sizeof(tx_message.auth)); - switch (where_from.u.sa_family) { case AF_INET: remote_ip.family = IPADDR_INET4; @@ -1843,7 +1824,14 @@ read_from_cmd_socket(void *anything) allowed = ADF_IsAllowed(access_auth_table, &remote_ip) || localhost; - if (read_length < offsetof(CMD_Request, data) || + /* Message size sanity check */ + if (read_length >= offsetof(CMD_Request, data)) { + expected_length = PKL_CommandLength(&rx_message); + } else { + expected_length = 0; + } + + if (expected_length < offsetof(CMD_Request, data) || rx_message.pkt_type != PKT_TYPE_CMD_REQUEST || rx_message.res1 != 0 || rx_message.res2 != 0) { @@ -1855,6 +1843,25 @@ read_from_cmd_socket(void *anything) return; } + rx_command = ntohs(rx_message.command); + + tx_message.version = PROTO_VERSION_NUMBER; + tx_message.pkt_type = PKT_TYPE_CMD_REPLY; + tx_message.res1 = 0; + tx_message.res2 = 0; + tx_message.command = rx_message.command; + tx_message.sequence = rx_message.sequence; + tx_message.reply = htons(RPY_NULL); + tx_message.number = htons(1); + tx_message.total = htons(1); + tx_message.pad1 = 0; + tx_message.utoken = htonl(utoken); + /* Set this to a default (invalid) value. This protects against the + token field being set to an arbitrary value if we reject the + message, e.g. due to the host failing the access check. */ + tx_message.token = htonl(0xffffffffUL); + memset(&tx_message.auth, 0, sizeof(tx_message.auth)); + if (rx_message.version != PROTO_VERSION_NUMBER) { tx_message.status = htons(STT_NOHOSTACCESS); if (!LOG_RateLimited()) { diff -up chrony-1.25/pktlength.c.cve-2012-4502 chrony-1.25/pktlength.c --- chrony-1.25/pktlength.c.cve-2012-4502 2011-05-04 12:29:40.000000000 +0200 +++ chrony-1.25/pktlength.c 2013-08-09 12:50:40.863855762 +0200 @@ -125,6 +125,8 @@ PKL_CommandLength(CMD_Request *r) { unsigned long ns; ns = ntohl(r->data.subnets_accessed.n_subnets); + if (ns > MAX_SUBNETS_ACCESSED) + return 0; return (offsetof(CMD_Request, data.subnets_accessed.subnets) + ns * sizeof(REQ_SubnetsAccessed_Subnet)); } @@ -132,6 +134,8 @@ PKL_CommandLength(CMD_Request *r) { unsigned long nc; nc = ntohl(r->data.client_accesses.n_clients); + if (nc > MAX_CLIENT_ACCESSES) + return 0; return (offsetof(CMD_Request, data.client_accesses.client_ips) + nc * sizeof(unsigned long)); } @@ -195,6 +199,8 @@ PKL_ReplyLength(CMD_Reply *r) { unsigned long ns = ntohl(r->data.subnets_accessed.n_subnets); if (r->status == htons(STT_SUCCESS)) { + if (ns > MAX_SUBNETS_ACCESSED) + return 0; return (offsetof(CMD_Reply, data.subnets_accessed.subnets) + ns * sizeof(RPY_SubnetsAccessed_Subnet)); } else { @@ -205,6 +211,8 @@ PKL_ReplyLength(CMD_Reply *r) { unsigned long nc = ntohl(r->data.client_accesses.n_clients); if (r->status == htons(STT_SUCCESS)) { + if (nc > MAX_CLIENT_ACCESSES) + return 0; return (offsetof(CMD_Reply, data.client_accesses.clients) + nc * sizeof(RPY_ClientAccesses_Client)); } else { @@ -215,6 +223,8 @@ PKL_ReplyLength(CMD_Reply *r) { unsigned long nc = ntohl(r->data.client_accesses_by_index.n_clients); if (r->status == htons(STT_SUCCESS)) { + if (nc > MAX_CLIENT_ACCESSES) + return 0; return (offsetof(CMD_Reply, data.client_accesses_by_index.clients) + nc * sizeof(RPY_ClientAccesses_Client)); } else { @@ -224,6 +234,8 @@ PKL_ReplyLength(CMD_Reply *r) case RPY_MANUAL_LIST: { unsigned long ns = ntohl(r->data.manual_list.n_samples); + if (ns > MAX_MANUAL_LIST_SAMPLES) + return 0; if (r->status == htons(STT_SUCCESS)) { return (offsetof(CMD_Reply, data.manual_list.samples) + ns * sizeof(RPY_ManualListSample));