dhcp-identifier: always use a fixed machine-id while fuzzing

It's a follow-up to https://github.com/systemd/systemd/pull/10200 where
that fuzzer was introduced. At the time it was run regularly on machines
where machine-id wasn't present so it was kind of reproducible. Now
it's run on CIFuzz and CFLite using GHActions with the public OSS-Fuzz
corpora (based on that particular machine-id) so to fully utilize
those corpora it's necessary to use it always. Other than that
it makes it possible for fuzzers targeting outgoing packets
based on incoming packets like https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1795921
to get past client_parse_message on my machine :-)

1 files changed, 5 insertions, 7 deletions

diff --git a/src/libsystemd-network/dhcp-identifier.c b/src/libsystemd-network/dhcp-identifier.c
index 3ea6c7ce24..4f02022cd3 100644
--- a/src/libsystemd-network/dhcp-identifier.c
+++ b/src/libsystemd-network/dhcp-identifier.c
@@ -110,19 +110,17 @@ int dhcp_identifier_set_duid_ll(struct duid *duid, const uint8_t *addr, size_t a
 int dhcp_identifier_set_duid_en(struct duid *duid, size_t *len) {
         sd_id128_t machine_id;
         uint64_t hash;
-        int r;
 
         assert(duid);
         assert(len);
 
-        r = sd_id128_get_machine(&machine_id);
-        if (r < 0) {
-#ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
-                machine_id = SD_ID128_MAKE(01, 02, 03, 04, 05, 06, 07, 08, 09, 0a, 0b, 0c, 0d, 0e, 0f, 10);
-#else
+#ifndef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
+        int r = sd_id128_get_machine(&machine_id);
+        if (r < 0)
                 return r;
+#else
+        machine_id = SD_ID128_MAKE(01, 02, 03, 04, 05, 06, 07, 08, 09, 0a, 0b, 0c, 0d, 0e, 0f, 10);
 #endif
-        }
 
         unaligned_write_be16(&duid->type, DUID_TYPE_EN);
         unaligned_write_be32(&duid->en.pen, SYSTEMD_PEN);