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fuzz: don't fail when fuzzer generates valid MAC

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The cryptofuzz target was based on a false premise: that it is
impossible for any fuzzer to generate a valid ciphertext+MAC for the
decrypt function. Niklas Gogge proved this premise incorrect using AFL++
with the CMPLOG feature, which enabled AFL++ to generate such valid
messages.

We remove the assertions requiring decryption to fail and add the inputs
AFL++ found to the corpus.
This commit is contained in:
Matt Morehouse
2025-04-14 12:02:26 -05:00
committed by Rusty Russell
parent 9da6487246
commit 2b5140fbcd
3 changed files with 6 additions and 4 deletions
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1
tests/fuzz/corpora/fuzz-cryptomsg/solution-91d462b6755f937129fcab6715327f0e0f2e8c1e Normal file
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@@ -0,0 +1 @@
CBBp摺0hﾕu霽 ﾎｨﾟﾔﾓｾ

1
tests/fuzz/corpora/fuzz-cryptomsg/solution-d5a84620e070d142563b0e6e5dd934c85242f3aa Normal file
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@@ -0,0 +1 @@
CB^~õ˜ï½kcȦO†¥zfB

8
tests/fuzz/fuzz-cryptomsg.c
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@@ -78,7 +78,7 @@ static void test_encrypt_decrypt_equality(const u8 *msg)
assert(tal_arr_eq(dec, msg));
}
/* Test header decryption of arbitrary bytes (should always fail). */
/* Test header decryption of arbitrary bytes. */
static void test_decrypt_header(const u8 *buf)
{
struct crypto_state cs_in = init_cs_in;
@@ -87,15 +87,15 @@ static void test_decrypt_header(const u8 *buf)
if (tal_bytelen(buf) < CRYPTOMSG_HDR_SIZE)
return;
assert(!cryptomsg_decrypt_header(&cs_in, buf, &len));
cryptomsg_decrypt_header(&cs_in, buf, &len);
}
/* Test body decryption of arbitrary bytes (should always fail). */
/* Test body decryption of arbitrary bytes. */
static void test_decrypt_body(const u8 *buf)
{
struct crypto_state cs_in = init_cs_in;
assert(cryptomsg_decrypt_body(buf, &cs_in, buf) == NULL);
cryptomsg_decrypt_body(buf, &cs_in, buf);
}
void run(const u8 *data, size_t size)