Provide EVP_chacha20_poly1305()

EVP_chacha20_poly1305() is an EVP_CIPHER implementation of the
ChaCha20-Poly1305 AEAD. This is potentially used to provide encryption for
the QUIC transport layer.

Where possible, this should be avoided in favour of the significantly saner
EVP_AEAD interface.

ok tb@

2 files changed, 260 insertions, 7 deletions

diff --git a/src/lib/libcrypto/evp/e_chacha20poly1305.c b/src/lib/libcrypto/evp/e_chacha20poly1305.c
index 3b29364586..129adb9ef9 100644
--- a/src/lib/libcrypto/evp/e_chacha20poly1305.c
+++ b/src/lib/libcrypto/evp/e_chacha20poly1305.c
@@ -1,6 +1,7 @@
-/* $OpenBSD: e_chacha20poly1305.c,v 1.22 2022/08/20 18:51:09 jsing Exp $ */
+/* $OpenBSD: e_chacha20poly1305.c,v 1.23 2022/08/20 19:22:28 jsing Exp $ */
 
 /*
+ * Copyright (c) 2022 Joel Sing <jsing@openbsd.org>
  * Copyright (c) 2015 Reyk Floter <reyk@openbsd.org>
  * Copyright (c) 2014, Google Inc.
  *
@@ -29,6 +30,7 @@
 #include <openssl/chacha.h>
 #include <openssl/poly1305.h>
 
+#include "bytestring.h"
 #include "evp_locl.h"
 
 #define POLY1305_TAG_LEN 16
@@ -99,14 +101,11 @@ poly1305_update_with_length(poly1305_state *poly1305,
 }
 
 static void
-poly1305_update_with_pad16(poly1305_state *poly1305,
-    const unsigned char *data, size_t data_len)
+poly1305_pad16(poly1305_state *poly1305, size_t data_len)
 {
         static const unsigned char zero_pad16[16];
         size_t pad_len;
 
-        CRYPTO_poly1305_update(poly1305, data, data_len);
-
         /* pad16() is defined in RFC 7539 2.8.1. */
         if ((pad_len = data_len % 16) == 0)
                 return;
@@ -114,6 +113,14 @@ poly1305_update_with_pad16(poly1305_state *poly1305,
         CRYPTO_poly1305_update(poly1305, zero_pad16, 16 - pad_len);
 }
 
+static void
+poly1305_update_with_pad16(poly1305_state *poly1305,
+    const unsigned char *data, size_t data_len)
+{
+        CRYPTO_poly1305_update(poly1305, data, data_len);
+        poly1305_pad16(poly1305, data_len);
+}
+
 static int
 aead_chacha20_poly1305_seal(const EVP_AEAD_CTX *ctx, unsigned char *out,
     size_t *out_len, size_t max_out_len, const unsigned char *nonce,
@@ -360,4 +367,244 @@ EVP_aead_xchacha20_poly1305()
         return &aead_xchacha20_poly1305;
 }
 
+struct chacha20_poly1305_ctx {
+        ChaCha_ctx chacha;
+        poly1305_state poly1305;
+
+        unsigned char key[32];
+        unsigned char nonce[CHACHA20_NONCE_LEN];
+        size_t nonce_len;
+        unsigned char tag[POLY1305_TAG_LEN];
+        size_t tag_len;
+
+        size_t ad_len;
+        size_t in_len;
+
+        int in_ad;
+        int started;
+};
+
+static int
+chacha20_poly1305_init(EVP_CIPHER_CTX *ctx, const unsigned char *key,
+    const unsigned char *iv, int encrypt)
+{
+        struct chacha20_poly1305_ctx *cpx = ctx->cipher_data;
+        uint8_t *data;
+        CBB cbb;
+        int ret = 0;
+
+        memset(&cbb, 0, sizeof(cbb));
+
+        if (key == NULL && iv == NULL)
+                goto done;
+
+        cpx->started = 0;
+
+        if (key != NULL)
+                memcpy(cpx->key, key, sizeof(cpx->key));
+
+        if (iv != NULL) {
+                /*
+                 * Left zero pad if configured nonce length is less than ChaCha
+                 * nonce length.
+                 */
+                if (!CBB_init_fixed(&cbb, cpx->nonce, sizeof(cpx->nonce)))
+                        goto err;
+                if (!CBB_add_space(&cbb, &data, sizeof(cpx->nonce) - cpx->nonce_len))
+                        goto err;
+                if (!CBB_add_bytes(&cbb, iv, cpx->nonce_len))
+                        goto err;
+                if (!CBB_finish(&cbb, NULL, NULL))
+                        goto err;
+        }
+
+ done:
+        ret = 1;
+
+ err:
+        CBB_cleanup(&cbb);
+
+        return ret;
+}
+
+static int
+chacha20_poly1305_cipher(EVP_CIPHER_CTX *ctx, unsigned char *out,
+    const unsigned char *in, size_t len)
+{
+        struct chacha20_poly1305_ctx *cpx = ctx->cipher_data;
+
+        /*
+         * Since we're making AEAD work within the constraints of EVP_CIPHER...
+         * If in is non-NULL then this is an update, while if in is NULL then
+         * this is a final. If in is non-NULL but out is NULL, then the input
+         * being provided is associated data. Plus we have to handle encryption
+         * (sealing) and decryption (opening) in the same function.
+         */
+
+        if (!cpx->started) {
+                unsigned char poly1305_key[32];
+                const unsigned char *iv;
+                uint64_t ctr;
+
+                ctr = (uint64_t)((uint32_t)(cpx->nonce[0]) |
+                    (uint32_t)(cpx->nonce[1]) << 8 |
+                    (uint32_t)(cpx->nonce[2]) << 16 |
+                    (uint32_t)(cpx->nonce[3]) << 24) << 32;
+                iv = cpx->nonce + CHACHA20_CONSTANT_LEN;
+
+                ChaCha_set_key(&cpx->chacha, cpx->key, 8 * sizeof(cpx->key));
+                ChaCha_set_iv(&cpx->chacha, iv, NULL);
+
+                /* See chacha.c for details re handling of counter. */
+                cpx->chacha.input[12] = (uint32_t)ctr;
+                cpx->chacha.input[13] = (uint32_t)(ctr >> 32);
+
+                memset(poly1305_key, 0, sizeof(poly1305_key));
+                ChaCha(&cpx->chacha, poly1305_key, poly1305_key,
+                   sizeof(poly1305_key));
+                CRYPTO_poly1305_init(&cpx->poly1305, poly1305_key);
+
+                /* Mark remaining key block as used. */
+                cpx->chacha.unused = 0;
+
+                cpx->ad_len = 0;
+                cpx->in_len = 0;
+                cpx->in_ad = 0;
+
+                cpx->started = 1;
+        }
+
+        if (len > SIZE_MAX - cpx->in_len) {
+                EVPerror(EVP_R_TOO_LARGE);
+                return 0;
+        }
+
+        /* Disallow authenticated data after plaintext/ciphertext. */
+        if (cpx->in_len > 0 && in != NULL && out == NULL)
+                return -1;
+
+        if (cpx->in_ad && (in == NULL || out != NULL)) {
+                poly1305_pad16(&cpx->poly1305, cpx->ad_len);
+                cpx->in_ad = 0;
+        }
+
+        /* Update with AD or plaintext/ciphertext. */
+        if (in != NULL) {
+                if (out == NULL) {
+                        cpx->ad_len += len;
+                        cpx->in_ad = 1;
+                } else {
+                        ChaCha(&cpx->chacha, out, in, len);
+                        cpx->in_len += len;
+                }
+                if (ctx->encrypt && out != NULL)
+                        CRYPTO_poly1305_update(&cpx->poly1305, out, len);
+                else 
+                        CRYPTO_poly1305_update(&cpx->poly1305, in, len);
+
+                return len;
+        }
+
+        /* Final. */
+        poly1305_pad16(&cpx->poly1305, cpx->in_len);
+        poly1305_update_with_length(&cpx->poly1305, NULL, cpx->ad_len);
+        poly1305_update_with_length(&cpx->poly1305, NULL, cpx->in_len);
+
+        if (ctx->encrypt) {
+                CRYPTO_poly1305_finish(&cpx->poly1305, cpx->tag);
+                cpx->tag_len = sizeof(cpx->tag);
+        } else {
+                unsigned char tag[POLY1305_TAG_LEN];
+
+                /* Ensure that a tag has been provided. */
+                if (cpx->tag_len <= 0)
+                        return -1;
+
+                CRYPTO_poly1305_finish(&cpx->poly1305, tag);
+                if (timingsafe_memcmp(tag, cpx->tag, cpx->tag_len) != 0)
+                        return -1;
+        }
+
+        cpx->started = 0;
+
+        return len;
+}
+
+static int
+chacha20_poly1305_cleanup(EVP_CIPHER_CTX *ctx)
+{
+        struct chacha20_poly1305_ctx *cpx = ctx->cipher_data;
+
+        explicit_bzero(cpx, sizeof(*cpx));
+
+        return 0;
+}
+
+static int
+chacha20_poly1305_ctrl(EVP_CIPHER_CTX *ctx, int type, int arg, void *ptr)
+{
+        struct chacha20_poly1305_ctx *cpx = ctx->cipher_data;
+
+        switch (type) {
+        case EVP_CTRL_INIT:
+                memset(cpx, 0, sizeof(*cpx));
+                cpx->nonce_len = sizeof(cpx->nonce);
+                return 1;
+
+        case EVP_CTRL_AEAD_SET_IVLEN:
+                if (arg <= 0 || arg > sizeof(cpx->nonce))
+                        return 0;
+                cpx->nonce_len = arg;
+                return 1;
+
+        case EVP_CTRL_AEAD_SET_TAG:
+                if (ctx->encrypt)
+                        return 0;
+                if (arg <= 0 || arg > sizeof(cpx->tag))
+                        return 0;
+                if (ptr != NULL) {
+                        memcpy(cpx->tag, ptr, arg);
+                        cpx->tag_len = arg;
+                }
+                return 1;
+
+        case EVP_CTRL_AEAD_GET_TAG:
+                if (!ctx->encrypt)
+                        return 0;
+                if (arg <= 0 || arg > cpx->tag_len)
+                        return 0;
+                memcpy(ptr, cpx->tag, arg);
+                return 1;
+
+        case EVP_CTRL_AEAD_SET_IV_FIXED:
+                if (arg != sizeof(cpx->nonce))
+                        return 0;
+                memcpy(cpx->nonce, ptr, arg);
+                return 1;
+        }
+
+        return 0;
+}
+
+static const EVP_CIPHER cipher_chacha20_poly1305 = {
+        .nid = NID_chacha20_poly1305,
+        .block_size = 1,
+        .key_len = 32,
+        .iv_len = 12,
+        .flags = EVP_CIPH_ALWAYS_CALL_INIT | EVP_CIPH_CTRL_INIT |
+            EVP_CIPH_CUSTOM_IV | EVP_CIPH_FLAG_AEAD_CIPHER |
+            EVP_CIPH_FLAG_CUSTOM_CIPHER | EVP_CIPH_FLAG_DEFAULT_ASN1,
+        .init = chacha20_poly1305_init,
+        .do_cipher = chacha20_poly1305_cipher,
+        .cleanup = chacha20_poly1305_cleanup,
+        .ctx_size = sizeof(struct chacha20_poly1305_ctx),
+        .ctrl = chacha20_poly1305_ctrl,
+};
+
+const EVP_CIPHER *
+EVP_chacha20_poly1305(void)
+{
+        return &cipher_chacha20_poly1305;
+}
+
 #endif  /* !OPENSSL_NO_CHACHA && !OPENSSL_NO_POLY1305 */
diff --git a/src/lib/libcrypto/evp/evp.h b/src/lib/libcrypto/evp/evp.h
index f016b6377c..0b7fc08fc8 100644
--- a/src/lib/libcrypto/evp/evp.h
+++ b/src/lib/libcrypto/evp/evp.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: evp.h,v 1.103 2022/07/12 14:42:49 kn Exp $ */
+/* $OpenBSD: evp.h,v 1.104 2022/08/20 19:22:28 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -251,10 +251,11 @@ extern "C" {
 #define         EVP_CTRL_AEAD_SET_IVLEN         0x9
 #define         EVP_CTRL_AEAD_GET_TAG           0x10
 #define         EVP_CTRL_AEAD_SET_TAG           0x11
+#define         EVP_CTRL_AEAD_SET_IV_FIXED      0x12
 #define         EVP_CTRL_GCM_SET_IVLEN          EVP_CTRL_AEAD_SET_IVLEN
 #define         EVP_CTRL_GCM_GET_TAG            EVP_CTRL_AEAD_GET_TAG
 #define         EVP_CTRL_GCM_SET_TAG            EVP_CTRL_AEAD_SET_TAG
-#define         EVP_CTRL_GCM_SET_IV_FIXED       0x12
+#define         EVP_CTRL_GCM_SET_IV_FIXED       EVP_CTRL_AEAD_SET_IV_FIXED
 #define         EVP_CTRL_GCM_IV_GEN             0x13
 #define         EVP_CTRL_CCM_SET_IVLEN          EVP_CTRL_AEAD_SET_IVLEN
 #define         EVP_CTRL_CCM_GET_TAG            EVP_CTRL_AEAD_GET_TAG
@@ -680,6 +681,11 @@ const EVP_CIPHER *EVP_aes_256_ccm(void);
 const EVP_CIPHER *EVP_aes_256_gcm(void);
 const EVP_CIPHER *EVP_aes_256_wrap(void);
 const EVP_CIPHER *EVP_aes_256_xts(void);
+#if defined(LIBRESSL_NEXT_API) || defined(LIBRESSL_INTERNAL)
+#if !defined(OPENSSL_NO_CHACHA) && !defined(OPENSSL_NO_POLY1305)
+const EVP_CIPHER *EVP_chacha20_poly1305(void);
+#endif
+#endif
 #if !defined(OPENSSL_NO_SHA) && !defined(OPENSSL_NO_SHA1)
 const EVP_CIPHER *EVP_aes_128_cbc_hmac_sha1(void);
 const EVP_CIPHER *EVP_aes_256_cbc_hmac_sha1(void);