Fix possible stack buffer overflow in s46_to_env when copying IPv6 prefixes
authorBen Hutchings <ben@decadent.org.uk>
Thu, 28 Jan 2016 00:49:22 +0000 (00:49 +0000)
committerBen Hutchings <ben@decadent.org.uk>
Thu, 28 Jan 2016 13:30:29 +0000 (13:30 +0000)
An 8-bit prefix-length field can be as large as 255, but values larger
than 128 will result in a buffer overflow when copying to in6.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
src/script.c

index 89cb0d6..3579331 100644 (file)
@@ -282,7 +282,8 @@ static void s46_to_env(enum odhcp6c_state state, const uint8_t *data, size_t len
                        size_t prefix6len = rule->prefix6_len;
                        prefix6len = (prefix6len % 8 == 0) ? prefix6len / 8 : prefix6len / 8 + 1;
 
-                       if (olen < sizeof(struct dhcpv6_s46_rule) + prefix6len)
+                       if (prefix6len > sizeof(in6) ||
+                           olen < sizeof(struct dhcpv6_s46_rule) + prefix6len)
                                continue;
 
                        memcpy(&in6, rule->ipv6_prefix, prefix6len);
@@ -311,7 +312,8 @@ static void s46_to_env(enum odhcp6c_state state, const uint8_t *data, size_t len
                                        size_t prefix6len = dmr->dmr_prefix6_len;
                                        prefix6len = (prefix6len % 8 == 0) ? prefix6len / 8 : prefix6len / 8 + 1;
 
-                                       if (olen < sizeof(struct dhcpv6_s46_dmr) + prefix6len)
+                                       if (prefix6len > sizeof(in6) ||
+                                           olen < sizeof(struct dhcpv6_s46_dmr) + prefix6len)
                                                continue;
 
                                        memcpy(&in6, dmr->dmr_ipv6_prefix, prefix6len);
@@ -330,7 +332,8 @@ static void s46_to_env(enum odhcp6c_state state, const uint8_t *data, size_t len
                        size_t prefix6len = bind->bindprefix6_len;
                        prefix6len = (prefix6len % 8 == 0) ? prefix6len / 8 : prefix6len / 8 + 1;
 
-                       if (olen < sizeof(struct dhcpv6_s46_v4v6bind) + prefix6len)
+                       if (prefix6len > sizeof(in6) ||
+                           olen < sizeof(struct dhcpv6_s46_v4v6bind) + prefix6len)
                                continue;
 
                        memcpy(&in6, bind->bind_ipv6_prefix, prefix6len);