From 03345ecefeb0d82e3c3a4c28f27c3554f0611b39 Mon Sep 17 00:00:00 2001 From: Simon Kelley Date: Thu, 31 Mar 2022 21:35:20 +0100 Subject: Fix write-after-free error in DHCPv6 code. CVE-2022-0934 refers. --- CHANGELOG | 3 +++ src/rfc3315.c | 48 +++++++++++++++++++++++++++--------------------- 2 files changed, 30 insertions(+), 21 deletions(-) --- a/CHANGELOG +++ b/CHANGELOG @@ -92,6 +92,9 @@ version 2.86 of filename). Thanks to Ed Wildgoose for the initial patch and motivation for this. + Fix write-after-free error in DHCPv6 server code. + CVE-2022-0934 refers. + version 2.85 Fix problem with DNS retries in 2.83/2.84. --- a/src/rfc3315.c +++ b/src/rfc3315.c @@ -33,9 +33,9 @@ struct state { unsigned int mac_len, mac_type; }; -static int dhcp6_maybe_relay(struct state *state, void *inbuff, size_t sz, +static int dhcp6_maybe_relay(struct state *state, unsigned char *inbuff, size_t sz, struct in6_addr *client_addr, int is_unicast, time_t now); -static int dhcp6_no_relay(struct state *state, int msg_type, void *inbuff, size_t sz, int is_unicast, time_t now); +static int dhcp6_no_relay(struct state *state, int msg_type, unsigned char *inbuff, size_t sz, int is_unicast, time_t now); static void log6_opts(int nest, unsigned int xid, void *start_opts, void *end_opts); static void log6_packet(struct state *state, char *type, struct in6_addr *addr, char *string); static void log6_quiet(struct state *state, char *type, struct in6_addr *addr, char *string); @@ -104,12 +104,12 @@ unsigned short dhcp6_reply(struct dhcp_c } /* This cost me blood to write, it will probably cost you blood to understand - srk. */ -static int dhcp6_maybe_relay(struct state *state, void *inbuff, size_t sz, +static int dhcp6_maybe_relay(struct state *state, unsigned char *inbuff, size_t sz, struct in6_addr *client_addr, int is_unicast, time_t now) { void *end = inbuff + sz; void *opts = inbuff + 34; - int msg_type = *((unsigned char *)inbuff); + int msg_type = *inbuff; unsigned char *outmsgtypep; void *opt; struct dhcp_vendor *vendor; @@ -259,15 +259,15 @@ static int dhcp6_maybe_relay(struct stat return 1; } -static int dhcp6_no_relay(struct state *state, int msg_type, void *inbuff, size_t sz, int is_unicast, time_t now) +static int dhcp6_no_relay(struct state *state, int msg_type, unsigned char *inbuff, size_t sz, int is_unicast, time_t now) { void *opt; - int i, o, o1, start_opts; + int i, o, o1, start_opts, start_msg; struct dhcp_opt *opt_cfg; struct dhcp_netid *tagif; struct dhcp_config *config = NULL; struct dhcp_netid known_id, iface_id, v6_id; - unsigned char *outmsgtypep; + unsigned char outmsgtype; struct dhcp_vendor *vendor; struct dhcp_context *context_tmp; struct dhcp_mac *mac_opt; @@ -296,12 +296,13 @@ static int dhcp6_no_relay(struct state * v6_id.next = state->tags; state->tags = &v6_id; - /* copy over transaction-id, and save pointer to message type */ - if (!(outmsgtypep = put_opt6(inbuff, 4))) + start_msg = save_counter(-1); + /* copy over transaction-id */ + if (!put_opt6(inbuff, 4)) return 0; start_opts = save_counter(-1); - state->xid = outmsgtypep[3] | outmsgtypep[2] << 8 | outmsgtypep[1] << 16; - + state->xid = inbuff[3] | inbuff[2] << 8 | inbuff[1] << 16; + /* We're going to be linking tags from all context we use. mark them as unused so we don't link one twice and break the list */ for (context_tmp = state->context; context_tmp; context_tmp = context_tmp->current) @@ -347,7 +348,7 @@ static int dhcp6_no_relay(struct state * (msg_type == DHCP6REQUEST || msg_type == DHCP6RENEW || msg_type == DHCP6RELEASE || msg_type == DHCP6DECLINE)) { - *outmsgtypep = DHCP6REPLY; + outmsgtype = DHCP6REPLY; o1 = new_opt6(OPTION6_STATUS_CODE); put_opt6_short(DHCP6USEMULTI); put_opt6_string("Use multicast"); @@ -619,11 +620,11 @@ static int dhcp6_no_relay(struct state * struct dhcp_netid *solicit_tags; struct dhcp_context *c; - *outmsgtypep = DHCP6ADVERTISE; + outmsgtype = DHCP6ADVERTISE; if (opt6_find(state->packet_options, state->end, OPTION6_RAPID_COMMIT, 0)) { - *outmsgtypep = DHCP6REPLY; + outmsgtype = DHCP6REPLY; state->lease_allocate = 1; o = new_opt6(OPTION6_RAPID_COMMIT); end_opt6(o); @@ -809,7 +810,7 @@ static int dhcp6_no_relay(struct state * int start = save_counter(-1); /* set reply message type */ - *outmsgtypep = DHCP6REPLY; + outmsgtype = DHCP6REPLY; state->lease_allocate = 1; log6_quiet(state, "DHCPREQUEST", NULL, ignore ? _("ignored") : NULL); @@ -924,7 +925,7 @@ static int dhcp6_no_relay(struct state * int address_assigned = 0; /* set reply message type */ - *outmsgtypep = DHCP6REPLY; + outmsgtype = DHCP6REPLY; log6_quiet(state, msg_type == DHCP6RENEW ? "DHCPRENEW" : "DHCPREBIND", NULL, NULL); @@ -1057,7 +1058,7 @@ static int dhcp6_no_relay(struct state * int good_addr = 0; /* set reply message type */ - *outmsgtypep = DHCP6REPLY; + outmsgtype = DHCP6REPLY; log6_quiet(state, "DHCPCONFIRM", NULL, NULL); @@ -1121,7 +1122,7 @@ static int dhcp6_no_relay(struct state * log6_quiet(state, "DHCPINFORMATION-REQUEST", NULL, ignore ? _("ignored") : state->hostname); if (ignore) return 0; - *outmsgtypep = DHCP6REPLY; + outmsgtype = DHCP6REPLY; tagif = add_options(state, 1); break; } @@ -1130,7 +1131,7 @@ static int dhcp6_no_relay(struct state * case DHCP6RELEASE: { /* set reply message type */ - *outmsgtypep = DHCP6REPLY; + outmsgtype = DHCP6REPLY; log6_quiet(state, "DHCPRELEASE", NULL, NULL); @@ -1195,7 +1196,7 @@ static int dhcp6_no_relay(struct state * case DHCP6DECLINE: { /* set reply message type */ - *outmsgtypep = DHCP6REPLY; + outmsgtype = DHCP6REPLY; log6_quiet(state, "DHCPDECLINE", NULL, NULL); @@ -1275,7 +1276,12 @@ static int dhcp6_no_relay(struct state * } } - + + /* Fill in the message type. Note that we store the offset, + not a direct pointer, since the packet memory may have been + reallocated. */ + ((unsigned char *)(daemon->outpacket.iov_base))[start_msg] = outmsgtype; + log_tags(tagif, state->xid); log6_opts(0, state->xid, daemon->outpacket.iov_base + start_opts, daemon->outpacket.iov_base + save_counter(-1));