dnsmasq: Backport DHCPv6 server fix (CVE-2022-0934)
This backports a commit from upstream dnsmasq to fix CVE-2022-0934. CVE-2022-0934 description: A single-byte, non-arbitrary write/use-after-free flaw was found in dnsmasq. This flaw allows an attacker who sends a crafted packet processed by dnsmasq, potentially causing a denial of service. Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
This commit is contained in:
Hauke Mehrtens
parent
53f2e438cb
commit
002a99eccd
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@ -0,0 +1,179 @@
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From 03345ecefeb0d82e3c3a4c28f27c3554f0611b39 Mon Sep 17 00:00:00 2001
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From: Simon Kelley <simon@thekelleys.org.uk>
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Date: Thu, 31 Mar 2022 21:35:20 +0100
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Subject: Fix write-after-free error in DHCPv6 code. CVE-2022-0934 refers.
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---
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CHANGELOG | 3 +++
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src/rfc3315.c | 48 +++++++++++++++++++++++++++---------------------
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2 files changed, 30 insertions(+), 21 deletions(-)
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--- a/CHANGELOG
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+++ b/CHANGELOG
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@@ -92,6 +92,9 @@ version 2.86
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of filename). Thanks to Ed Wildgoose for the initial patch
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and motivation for this.
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+ Fix write-after-free error in DHCPv6 server code.
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+ CVE-2022-0934 refers.
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+
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version 2.85
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Fix problem with DNS retries in 2.83/2.84.
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--- a/src/rfc3315.c
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+++ b/src/rfc3315.c
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@@ -33,9 +33,9 @@ struct state {
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unsigned int mac_len, mac_type;
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};
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-static int dhcp6_maybe_relay(struct state *state, void *inbuff, size_t sz,
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+static int dhcp6_maybe_relay(struct state *state, unsigned char *inbuff, size_t sz,
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struct in6_addr *client_addr, int is_unicast, time_t now);
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-static int dhcp6_no_relay(struct state *state, int msg_type, void *inbuff, size_t sz, int is_unicast, time_t now);
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+static int dhcp6_no_relay(struct state *state, int msg_type, unsigned char *inbuff, size_t sz, int is_unicast, time_t now);
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static void log6_opts(int nest, unsigned int xid, void *start_opts, void *end_opts);
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static void log6_packet(struct state *state, char *type, struct in6_addr *addr, char *string);
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static void log6_quiet(struct state *state, char *type, struct in6_addr *addr, char *string);
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@@ -104,12 +104,12 @@ unsigned short dhcp6_reply(struct dhcp_c
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}
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/* This cost me blood to write, it will probably cost you blood to understand - srk. */
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-static int dhcp6_maybe_relay(struct state *state, void *inbuff, size_t sz,
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+static int dhcp6_maybe_relay(struct state *state, unsigned char *inbuff, size_t sz,
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struct in6_addr *client_addr, int is_unicast, time_t now)
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{
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void *end = inbuff + sz;
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void *opts = inbuff + 34;
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- int msg_type = *((unsigned char *)inbuff);
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+ int msg_type = *inbuff;
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unsigned char *outmsgtypep;
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void *opt;
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struct dhcp_vendor *vendor;
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@@ -259,15 +259,15 @@ static int dhcp6_maybe_relay(struct stat
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return 1;
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}
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-static int dhcp6_no_relay(struct state *state, int msg_type, void *inbuff, size_t sz, int is_unicast, time_t now)
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+static int dhcp6_no_relay(struct state *state, int msg_type, unsigned char *inbuff, size_t sz, int is_unicast, time_t now)
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{
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void *opt;
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- int i, o, o1, start_opts;
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+ int i, o, o1, start_opts, start_msg;
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struct dhcp_opt *opt_cfg;
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struct dhcp_netid *tagif;
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struct dhcp_config *config = NULL;
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struct dhcp_netid known_id, iface_id, v6_id;
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- unsigned char *outmsgtypep;
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+ unsigned char outmsgtype;
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struct dhcp_vendor *vendor;
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struct dhcp_context *context_tmp;
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struct dhcp_mac *mac_opt;
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@@ -296,12 +296,13 @@ static int dhcp6_no_relay(struct state *
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v6_id.next = state->tags;
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state->tags = &v6_id;
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- /* copy over transaction-id, and save pointer to message type */
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- if (!(outmsgtypep = put_opt6(inbuff, 4)))
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+ start_msg = save_counter(-1);
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+ /* copy over transaction-id */
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+ if (!put_opt6(inbuff, 4))
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return 0;
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start_opts = save_counter(-1);
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- state->xid = outmsgtypep[3] | outmsgtypep[2] << 8 | outmsgtypep[1] << 16;
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-
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+ state->xid = inbuff[3] | inbuff[2] << 8 | inbuff[1] << 16;
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+
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/* We're going to be linking tags from all context we use.
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mark them as unused so we don't link one twice and break the list */
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for (context_tmp = state->context; context_tmp; context_tmp = context_tmp->current)
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@@ -347,7 +348,7 @@ static int dhcp6_no_relay(struct state *
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(msg_type == DHCP6REQUEST || msg_type == DHCP6RENEW || msg_type == DHCP6RELEASE || msg_type == DHCP6DECLINE))
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{
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- *outmsgtypep = DHCP6REPLY;
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+ outmsgtype = DHCP6REPLY;
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o1 = new_opt6(OPTION6_STATUS_CODE);
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put_opt6_short(DHCP6USEMULTI);
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put_opt6_string("Use multicast");
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@@ -619,11 +620,11 @@ static int dhcp6_no_relay(struct state *
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struct dhcp_netid *solicit_tags;
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struct dhcp_context *c;
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- *outmsgtypep = DHCP6ADVERTISE;
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+ outmsgtype = DHCP6ADVERTISE;
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if (opt6_find(state->packet_options, state->end, OPTION6_RAPID_COMMIT, 0))
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{
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- *outmsgtypep = DHCP6REPLY;
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+ outmsgtype = DHCP6REPLY;
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state->lease_allocate = 1;
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o = new_opt6(OPTION6_RAPID_COMMIT);
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end_opt6(o);
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@@ -809,7 +810,7 @@ static int dhcp6_no_relay(struct state *
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int start = save_counter(-1);
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/* set reply message type */
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- *outmsgtypep = DHCP6REPLY;
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+ outmsgtype = DHCP6REPLY;
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state->lease_allocate = 1;
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log6_quiet(state, "DHCPREQUEST", NULL, ignore ? _("ignored") : NULL);
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@@ -924,7 +925,7 @@ static int dhcp6_no_relay(struct state *
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int address_assigned = 0;
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/* set reply message type */
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- *outmsgtypep = DHCP6REPLY;
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+ outmsgtype = DHCP6REPLY;
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log6_quiet(state, msg_type == DHCP6RENEW ? "DHCPRENEW" : "DHCPREBIND", NULL, NULL);
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@@ -1057,7 +1058,7 @@ static int dhcp6_no_relay(struct state *
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int good_addr = 0;
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/* set reply message type */
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- *outmsgtypep = DHCP6REPLY;
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+ outmsgtype = DHCP6REPLY;
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log6_quiet(state, "DHCPCONFIRM", NULL, NULL);
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@@ -1121,7 +1122,7 @@ static int dhcp6_no_relay(struct state *
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log6_quiet(state, "DHCPINFORMATION-REQUEST", NULL, ignore ? _("ignored") : state->hostname);
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if (ignore)
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return 0;
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- *outmsgtypep = DHCP6REPLY;
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+ outmsgtype = DHCP6REPLY;
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tagif = add_options(state, 1);
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break;
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}
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@@ -1130,7 +1131,7 @@ static int dhcp6_no_relay(struct state *
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case DHCP6RELEASE:
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{
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/* set reply message type */
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- *outmsgtypep = DHCP6REPLY;
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+ outmsgtype = DHCP6REPLY;
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log6_quiet(state, "DHCPRELEASE", NULL, NULL);
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@@ -1195,7 +1196,7 @@ static int dhcp6_no_relay(struct state *
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case DHCP6DECLINE:
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{
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/* set reply message type */
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- *outmsgtypep = DHCP6REPLY;
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+ outmsgtype = DHCP6REPLY;
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log6_quiet(state, "DHCPDECLINE", NULL, NULL);
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@@ -1275,7 +1276,12 @@ static int dhcp6_no_relay(struct state *
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}
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}
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-
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+
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+ /* Fill in the message type. Note that we store the offset,
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+ not a direct pointer, since the packet memory may have been
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+ reallocated. */
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+ ((unsigned char *)(daemon->outpacket.iov_base))[start_msg] = outmsgtype;
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+
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log_tags(tagif, state->xid);
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log6_opts(0, state->xid, daemon->outpacket.iov_base + start_opts, daemon->outpacket.iov_base + save_counter(-1));
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