Attention is currently required from: fixeria, n0k0.

Hello Jenkins Builder, fixeria,

I'd like you to reexamine a change. Please visit

https://gerrit.osmocom.org/c/osmo-hlr/+/42888?usp=email

to look at the new patch set (#4).

The following approvals got outdated and were removed: Code-Review+1 by fixeria, Verified+1 by Jenkins Builder

Change subject: mslookup: fix size_t underflow in mDNS decode ......................................................................

mslookup: fix size_t underflow in mDNS decode

osmo_mdns_rfc_record_decode() computes the strnlen() scan bound as 'data_len - 10' where data_len is a size_t. osmo_mdns_msg_answer_decode() loops "while (data_len)" with no minimum-length guard, so it can call record_decode() with data_len in 1..9. 'data_len - 10' then underflows to ~SIZE_MAX and strnlen() scans far past the receive buffer until it finds a NUL, and data[name_len] reads further still, before the trailing "name_len + 10 + rdlength > data_len" check ever runs.

A record must contain at least one name byte plus the 10 fixed trailing bytes (type, class, ttl, rdlength); reject anything shorter so the subtraction cannot underflow.

Additionally, an unterminated name still let the fixed-field loads read one byte past the buffer: strnlen() can return its bound, making name_len equal to data_len - 9, so osmo_load16be(data + name_len + 8) touched data[data_len] before the trailing length check ran. Require room for the name plus the 10 fixed trailing bytes before reading any of them.

Change-Id: I1bf5bade953217b1a998f91679711a6170a886a8 --- M src/mslookup/mdns_rfc.c 1 file changed, 13 insertions(+), 0 deletions(-)

git pull ssh://gerrit.osmocom.org:29418/osmo-hlr refs/changes/88/42888/4