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Empty stacks are vacuously sorted

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In the X.509 policy rewrite, I'll be using sorted stacks to keep the
overall algorithm subquadratic. Fix up sk_FOO_is_sorted in these edge
cases so the asserts work more smoothly.

Change-Id: I369f53543f0c2219df6f62a81aead630a9dbcd8d
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/56031
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: Bob Beck <bbe@google.com>
This commit is contained in:
David Benjamin
2023-01-17 17:02:21 +00:00
committed by Boringssl LUCI CQ
parent 49e07914b3
commit ff23b7cb2c
3 changed files with 49 additions and 3 deletions
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crypto/stack/stack.c
+2 -1
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@@ -415,7 +415,8 @@ int sk_is_sorted(const _STACK *sk) {
if (!sk) {
return 1;
}
return sk->sorted;
// Zero- and one-element lists are always sorted.
return sk->sorted || (sk->comp != NULL && sk->num < 2);
}
OPENSSL_sk_cmp_func sk_set_cmp_func(_STACK *sk, OPENSSL_sk_cmp_func comp) {
crypto/stack/stack_test.cc
+44
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@@ -434,3 +434,47 @@ TEST(StackTest, DeleteIf) {
ExpectStackEquals(sk.get(), {});
EXPECT_TRUE(sk_TEST_INT_is_sorted(sk.get()));
}
TEST(StackTest, IsSorted) {
bssl::UniquePtr<STACK_OF(TEST_INT)> sk(sk_TEST_INT_new_null());
ASSERT_TRUE(sk);
EXPECT_FALSE(sk_TEST_INT_is_sorted(sk.get()));
// Empty lists are always known to be sorted.
sk_TEST_INT_set_cmp_func(sk.get(), compare);
EXPECT_TRUE(sk_TEST_INT_is_sorted(sk.get()));
// As are one-element lists.
auto value = TEST_INT_new(2);
ASSERT_TRUE(value);
ASSERT_TRUE(bssl::PushToStack(sk.get(), std::move(value)));
EXPECT_TRUE(sk_TEST_INT_is_sorted(sk.get()));
// Two-element lists require an explicit sort.
value = TEST_INT_new(1);
ASSERT_TRUE(value);
ASSERT_TRUE(bssl::PushToStack(sk.get(), std::move(value)));
EXPECT_FALSE(sk_TEST_INT_is_sorted(sk.get()));
// The list is now sorted.
sk_TEST_INT_sort(sk.get());
EXPECT_TRUE(sk_TEST_INT_is_sorted(sk.get()));
// After changing the comparison function, it no longer is sorted.
sk_TEST_INT_set_cmp_func(sk.get(), compare_reverse);
EXPECT_FALSE(sk_TEST_INT_is_sorted(sk.get()));
sk_TEST_INT_sort(sk.get());
EXPECT_TRUE(sk_TEST_INT_is_sorted(sk.get()));
// But, starting from one element, switching the comparison function preserves
// the sorted bit.
TEST_INT_free(sk_TEST_INT_pop(sk.get()));
EXPECT_TRUE(sk_TEST_INT_is_sorted(sk.get()));
sk_TEST_INT_set_cmp_func(sk.get(), compare);
EXPECT_TRUE(sk_TEST_INT_is_sorted(sk.get()));
// Without a comparison function, the list cannot be sorted.
sk_TEST_INT_set_cmp_func(sk.get(), nullptr);
EXPECT_FALSE(sk_TEST_INT_is_sorted(sk.get()));
}
include/openssl/stack.h
+3 -2
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@@ -267,8 +267,9 @@ typedef void *(*OPENSSL_sk_copy_func)(void *ptr);
// Note its actual type is |int (*)(const T **a, const T **b)|. Low-level |sk_*|
// functions will be passed a type-specific wrapper to call it correctly.
//
// TODO(davidben): This type should be |const T *const *|. It is already fixed
// in OpenSSL 1.1.1, so hopefully we can fix this compatibly.
// TODO(https://crbug.com/boringssl/498): This type should be
// |const T *const *|. It is already fixed in OpenSSL 1.1.1, so hopefully we can
// fix this compatibly.
typedef int (*OPENSSL_sk_cmp_func)(const void **a, const void **b);
// OPENSSL_sk_delete_if_func is the generic version of