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authorMark Haines <mjark@negativecurvature.net>2016-05-25 15:00:05 +0100
committerMark Haines <mjark@negativecurvature.net>2016-05-25 15:00:05 +0100
commit19a7fb5df5ec3445201ce5fbe475a08faf6319fc (patch)
treee9f9ac72d035106a42260e792cdc0bad6c72fc4e
parent01ea3d4b9a3c6f3e0303c2d421a248715a96af99 (diff)
Fix an integer wrap around bug and add a couple more tests
-rw-r--r--src/megolm.c6
-rw-r--r--tests/test_megolm.cpp33
2 files changed, 38 insertions, 1 deletions
diff --git a/src/megolm.c b/src/megolm.c
index a969b36..affd3cb 100644
--- a/src/megolm.c
+++ b/src/megolm.c
@@ -116,7 +116,11 @@ void megolm_advance_to(Megolm *megolm, uint32_t advance_to) {
((advance_to >> shift) - (megolm->counter >> shift)) & 0xff;
if (steps == 0) {
- continue;
+ if (advance_to < megolm->counter) {
+ steps = 0x100;
+ } else {
+ continue;
+ }
}
/* for all but the last step, we can just bump R(j) without regard
diff --git a/tests/test_megolm.cpp b/tests/test_megolm.cpp
index bf53346..3048fa3 100644
--- a/tests/test_megolm.cpp
+++ b/tests/test_megolm.cpp
@@ -98,4 +98,37 @@ std::uint8_t random_bytes[] =
assert_equals(megolm_get_data(&mr2), megolm_get_data(&mr1), MEGOLM_RATCHET_LENGTH);
}
+{
+ TestCase test_case("Megolm::advance overflow by one");
+
+ Megolm mr1, mr2;
+
+ megolm_init(&mr1, random_bytes, 0xffffffffUL);
+ megolm_advance_to(&mr1, 0x0);
+ assert_equals(0x0U, mr1.counter);
+
+ megolm_init(&mr2, random_bytes, 0xffffffffUL);
+ megolm_advance(&mr2);
+ assert_equals(0x0U, mr2.counter);
+
+ assert_equals(megolm_get_data(&mr2), megolm_get_data(&mr1), MEGOLM_RATCHET_LENGTH);
+}
+
+{
+ TestCase test_case("Megolm::advance overflow");
+
+ Megolm mr1, mr2;
+
+ megolm_init(&mr1, random_bytes, 0x1UL);
+ megolm_advance_to(&mr1, 0x80000000UL);
+ megolm_advance_to(&mr1, 0x0);
+ assert_equals(0x0U, mr1.counter);
+
+ megolm_init(&mr2, random_bytes, 0x1UL);
+ megolm_advance_to(&mr2, 0x0UL);
+ assert_equals(0x0U, mr2.counter);
+
+ assert_equals(megolm_get_data(&mr2), megolm_get_data(&mr1), MEGOLM_RATCHET_LENGTH);
+}
+
}