Merge bitcoin/bitcoin#22331: crypto: Fix K1/K2 use in ChaCha20-Poly1305 AEAD

cd37356 [crypto] Fix K1/K2 use in ChaCha20-Poly1305 AEAD (Dhruv Mehta)

Pull request description:

  BIP324 mentions K1 is used for the associated data and K2 is used for the payload. The code does the opposite. This is not a security problem but will be a problem across implementations based on the HKDF key derivations.

  BIP324 author Jonas Schnelli thinks a [code update will be better](bitcoin/bitcoin#15649 (comment)) than a BIP update.

  If this PR is merged:

  - [ ] We need to update the test vector 3 in BIP324

ACKs for top commit:
  jonasschnelli:
    utACK cd37356

Tree-SHA512: e2165117bfbf7a031060e7376912f9af1c1bfc57916383799a0fa2c040e2caaab0d6aafc3425c083a233b96c84fafec75c938e00ceb6bd7d52607d58607cb145

Author: fanquake

src/crypto/chacha_poly_aead.cpp

@@ -31,8 +31,9 @@ ChaCha20Poly1305AEAD::ChaCha20Poly1305AEAD(const unsigned char* K_1, size_t K_1_
 {
     assert(K_1_len == CHACHA20_POLY1305_AEAD_KEY_LEN);
     assert(K_2_len == CHACHA20_POLY1305_AEAD_KEY_LEN);
-    m_chacha_main.SetKey(K_1, CHACHA20_POLY1305_AEAD_KEY_LEN);
-    m_chacha_header.SetKey(K_2, CHACHA20_POLY1305_AEAD_KEY_LEN);
+
+    m_chacha_header.SetKey(K_1, CHACHA20_POLY1305_AEAD_KEY_LEN);
+    m_chacha_main.SetKey(K_2, CHACHA20_POLY1305_AEAD_KEY_LEN);
 
     // set the cached sequence number to uint64 max which hints for an unset cache.
     // we can't hit uint64 max since the rekey rule (which resets the sequence number) is 1GB

src/test/crypto_tests.cpp

@@ -617,7 +617,7 @@ static void TestChaCha20Poly1305AEAD(bool must_succeed, unsigned int expected_aa
     ChaCha20Poly1305AEAD aead(aead_K_1.data(), aead_K_1.size(), aead_K_2.data(), aead_K_2.size());
 
     // create a chacha20 instance to compare against
-    ChaCha20 cmp_ctx(aead_K_2.data(), 32);
+    ChaCha20 cmp_ctx(aead_K_1.data(), 32);
 
     // encipher
     bool res = aead.Crypt(seqnr_payload, seqnr_aad, aad_pos, ciphertext_buf.data(), ciphertext_buf.size(), plaintext_buf.data(), plaintext_buf.size(), true);
@@ -708,8 +708,8 @@ BOOST_AUTO_TEST_CASE(chacha20_poly1305_aead_testvector)
         "b1a03d5bd2855d60699e7d3a3133fa47be740fe4e4c1f967555e2d9271f31c3a8bd94d54b5ecabbc41ffbb0c90924080");
     TestChaCha20Poly1305AEAD(true, 255,
         "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",
-        "000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f",
         "ff0102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f",
+        "000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f",
         "c640c1711e3ee904ac35c57ab9791c8a1c408603a90b77a83b54f6c844cb4b06d94e7fc6c800e165acd66147e80ec45a567f6ce66d05ec0cae679dceeb890017",
         "3940c1e92da4582ff6f92a776aeb14d014d384eeb30f660dacf70a14a23fd31e91212701334e2ce1acf5199dc84f4d61ddbe6571bca5af874b4c9226c26e650995d157644e1848b96ed6c2102d5489a050e71d29a5a66ece11de5fb5c9558d54da28fe45b0bc4db4e5b88030bfc4a352b4b7068eccf656bae7ad6a35615315fc7c49d4200388d5eca67c2e822e069336c69b40db67e0f3c81209c50f3216a4b89fb3ae1b984b7851a2ec6f68ab12b101ab120e1ea7313bb93b5a0f71185c7fea017ddb92769861c29dba4fbc432280d5dff21b36d1c4c790128b22699950bb18bf74c448cdfe547d8ed4f657d8005fdc0cd7a050c2d46050a44c4376355858981fbe8b184288276e7a93eabc899c4a",
         "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");