Fix unaligned 32-bit reads from DHCP packets

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/src/dhcpv6.c b/src/dhcpv6.c
index 8a1231df1245adc1e057b5589818b93be9a9e99b..cbf6991f31a0b73f841301183104d70575e7104b 100644 (file)
--- a/src/dhcpv6.c
+++ b/src/dhcpv6.c
@@ -110,6 +110,14 @@ static uint8_t reconf_key[16];
 static unsigned int client_options = 0;
 
 
+static uint32_t ntohl_unaligned(const uint8_t *data)
+{
+       uint32_t buf;
+
+       memcpy(&buf, data, sizeof(buf));
+       return ntohl(buf);
+}
+
 int init_dhcpv6(const char *ifname, unsigned int options, int sol_timeout)
 {
        client_options = options;
@@ -806,12 +814,12 @@ static int dhcpv6_handle_advert(enum dhcpv6_msg orig, const int rc,
                } else if (otype == DHCPV6_OPT_RECONF_ACCEPT) {
                        cand.wants_reconfigure = true;
                } else if (otype == DHCPV6_OPT_SOL_MAX_RT && olen == 4) {
-                       uint32_t sol_max_rt = ntohl(*((uint32_t *)odata));
+                       uint32_t sol_max_rt = ntohl_unaligned(odata);
                        if (sol_max_rt >= DHCPV6_SOL_MAX_RT_MIN &&
                                        sol_max_rt <= DHCPV6_SOL_MAX_RT_MAX)
                                cand.sol_max_rt = sol_max_rt;
                } else if (otype == DHCPV6_OPT_INF_MAX_RT && olen == 4) {
-                       uint32_t inf_max_rt = ntohl(*((uint32_t *)odata));
+                       uint32_t inf_max_rt = ntohl_unaligned(odata);
                        if (inf_max_rt >= DHCPV6_INF_MAX_RT_MIN &&
                                        inf_max_rt <= DHCPV6_INF_MAX_RT_MAX)
                                cand.inf_max_rt = inf_max_rt;
@@ -1029,7 +1037,7 @@ static int dhcpv6_handle_reply(enum dhcpv6_msg orig, _unused const int rc,
                        } else if (otype == DHCPV6_OPT_SIP_SERVER_D) {
                                odhcp6c_add_state(STATE_SIP_FQDN, odata, olen);
                        } else if (otype == DHCPV6_OPT_INFO_REFRESH && olen >= 4) {
-                               refresh = ntohl(*((uint32_t*)odata));
+                               refresh = ntohl_unaligned(odata);
                                passthru = false;
                        } else if (otype == DHCPV6_OPT_AUTH) {
                                if (olen == -4 + sizeof(struct dhcpv6_auth_reconfigure)) {
@@ -1046,13 +1054,13 @@ static int dhcpv6_handle_reply(enum dhcpv6_msg orig, _unused const int rc,
                                        odhcp6c_add_state(STATE_AFTR_NAME, odata, olen);
                                passthru = false;
                        } else if (otype == DHCPV6_OPT_SOL_MAX_RT && olen == 4) {
-                               uint32_t sol_max_rt = ntohl(*((uint32_t *)odata));
+                               uint32_t sol_max_rt = ntohl_unaligned(odata);
                                if (sol_max_rt >= DHCPV6_SOL_MAX_RT_MIN &&
                                                sol_max_rt <= DHCPV6_SOL_MAX_RT_MAX)
                                        dhcpv6_retx[DHCPV6_MSG_SOLICIT].max_timeo = sol_max_rt;
                                passthru = false;
                        } else if (otype == DHCPV6_OPT_INF_MAX_RT && olen == 4) {
-                               uint32_t inf_max_rt = ntohl(*((uint32_t *)odata));
+                               uint32_t inf_max_rt = ntohl_unaligned(odata);
                                if (inf_max_rt >= DHCPV6_INF_MAX_RT_MIN &&
                                                inf_max_rt <= DHCPV6_INF_MAX_RT_MAX)
                                        dhcpv6_retx[DHCPV6_MSG_INFO_REQ].max_timeo = inf_max_rt;