diff options
authorRich Felker <>2017-10-18 18:50:03 (GMT)
committerRich Felker <>2017-10-18 18:50:03 (GMT)
commit45ca5d3fcb6f874bf5ba55d0e9651cef68515395 (patch)
parent5b5eb527c5ed5ca2786bf82892a04ca3bdf33d31 (diff)
in dns parsing callback, enforce MAXADDRS to preclude overflow
MAXADDRS was chosen not to need enforcement, but the logic used to compute it assumes the answers received match the RR types of the queries. specifically, it assumes that only one replu contains A record answers. if the replies to both the A and the AAAA query have their answer sections filled with A records, MAXADDRS can be exceeded and clobber the stack of the calling function. this bug was found and reported by Felix Wilhelm.
1 files changed, 1 insertions, 0 deletions
diff --git a/src/network/lookup_name.c b/src/network/lookup_name.c
index 066be4d..209c20f 100644
--- a/src/network/lookup_name.c
+++ b/src/network/lookup_name.c
@@ -111,6 +111,7 @@ static int dns_parse_callback(void *c, int rr, const void *data, int len, const
char tmp[256];
struct dpc_ctx *ctx = c;
+ if (ctx->cnt >= MAXADDRS) return -1;
switch (rr) {
case RR_A:
if (len != 4) return -1;