openssl: add openssl_hmac_many()

Add function to perform HMAC on multiple buffers.

Also update test-openssl with associated testing, and replace some memcmp()
with memcmp_nn().

src/shared/openssl-util.c

@@ -139,6 +139,103 @@ int openssl_digest_many(
         return 0;
 }
 
+/* Calculate the HMAC digest hash value for the provided data, using the provided key and specified digest
+ * algorithm. Returns 0 on success, -EOPNOTSUPP if the digest algorithm is not supported, or < 0 for any
+ * other error. */
+int openssl_hmac_many(
+                const char *digest_alg,
+                const void *key,
+                size_t key_size,
+                const struct iovec data[],
+                size_t n_data,
+                void **ret_digest,
+                size_t *ret_digest_size) {
+
+        assert(digest_alg);
+        assert(key);
+        assert(data || n_data == 0);
+        assert(ret_digest);
+        /* ret_digest_size is optional, as caller may already know the digest size */
+
+#if OPENSSL_VERSION_MAJOR >= 3
+        _cleanup_(EVP_MD_freep) EVP_MD *md = EVP_MD_fetch(NULL, digest_alg, NULL);
+#else
+        const EVP_MD *md = EVP_get_digestbyname(digest_alg);
+#endif
+        if (!md)
+                return log_debug_errno(SYNTHETIC_ERRNO(EOPNOTSUPP),
+                                       "Digest algorithm '%s' not supported.", digest_alg);
+
+#if OPENSSL_VERSION_MAJOR >= 3
+        _cleanup_(EVP_MAC_freep) EVP_MAC *mac = EVP_MAC_fetch(NULL, "HMAC", NULL);
+        if (!mac)
+                return log_openssl_errors("Failed to create new EVP_MAC");
+
+        _cleanup_(EVP_MAC_CTX_freep) EVP_MAC_CTX *ctx = EVP_MAC_CTX_new(mac);
+        if (!ctx)
+                return log_openssl_errors("Failed to create new EVP_MAC_CTX");
+
+        _cleanup_(OSSL_PARAM_BLD_freep) OSSL_PARAM_BLD *bld = OSSL_PARAM_BLD_new();
+        if (!bld)
+                return log_openssl_errors("Failed to create new OSSL_PARAM_BLD");
+
+        if (!OSSL_PARAM_BLD_push_utf8_string(bld, OSSL_MAC_PARAM_DIGEST, (char*) digest_alg, 0))
+                return log_openssl_errors("Failed to set HMAC OSSL_MAC_PARAM_DIGEST");
+
+        _cleanup_(OSSL_PARAM_freep) OSSL_PARAM *params = OSSL_PARAM_BLD_to_param(bld);
+        if (!params)
+                return log_openssl_errors("Failed to build HMAC OSSL_PARAM");
+
+        if (!EVP_MAC_init(ctx, key, key_size, params))
+                return log_openssl_errors("Failed to initializate EVP_MAC_CTX");
+#else
+        _cleanup_(HMAC_CTX_freep) HMAC_CTX *ctx = HMAC_CTX_new();
+        if (!ctx)
+                return log_openssl_errors("Failed to create new HMAC_CTX");
+
+        if (!HMAC_Init_ex(ctx, key, key_size, md, NULL))
+                return log_openssl_errors("Failed to initialize HMAC_CTX");
+#endif
+
+        for (size_t i = 0; i < n_data; i++)
+#if OPENSSL_VERSION_MAJOR >= 3
+                if (!EVP_MAC_update(ctx, data[i].iov_base, data[i].iov_len))
+#else
+                if (!HMAC_Update(ctx, data[i].iov_base, data[i].iov_len))
+#endif
+                        return log_openssl_errors("Failed to update HMAC");
+
+        size_t digest_size;
+#if OPENSSL_VERSION_MAJOR >= 3
+        digest_size = EVP_MAC_CTX_get_mac_size(ctx);
+#else
+        digest_size = HMAC_size(ctx);
+#endif
+        if (digest_size == 0)
+                return log_openssl_errors("Failed to get HMAC digest size");
+
+        _cleanup_free_ void *buf = malloc(digest_size);
+        if (!buf)
+                return log_oom_debug();
+
+#if OPENSSL_VERSION_MAJOR >= 3
+        size_t size;
+        if (!EVP_MAC_final(ctx, buf, &size, digest_size))
+#else
+        unsigned int size;
+        if (!HMAC_Final(ctx, buf, &size))
+#endif
+                return log_openssl_errors("Failed to finalize HMAC");
+
+        assert(size == digest_size);
+
+        *ret_digest = TAKE_PTR(buf);
+        if (ret_digest_size)
+                *ret_digest_size = size;
+
+        return 0;
+}
+
 int rsa_encrypt_bytes(
                 EVP_PKEY *pkey,
                 const void *decrypted_key,

src/shared/openssl-util.h

@@ -40,11 +40,14 @@ DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(SSL*, SSL_free, NULL);
 DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(BIO*, BIO_free, NULL);
 DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(EVP_MD_CTX*, EVP_MD_CTX_free, NULL);
 #if OPENSSL_VERSION_MAJOR >= 3
+DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(EVP_MAC*, EVP_MAC_free, NULL);
+DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(EVP_MAC_CTX*, EVP_MAC_CTX_free, NULL);
 DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(EVP_MD*, EVP_MD_free, NULL);
 DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(OSSL_PARAM*, OSSL_PARAM_free, NULL);
 DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(OSSL_PARAM_BLD*, OSSL_PARAM_BLD_free, NULL);
 #else
 DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(EC_KEY*, EC_KEY_free, NULL);
+DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(HMAC_CTX*, HMAC_CTX_free, NULL);
 DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(RSA*, RSA_free, NULL);
 #endif
 
@@ -65,6 +68,12 @@ static inline int openssl_digest(const char *digest_alg, const void *buf, size_t
         return openssl_digest_many(digest_alg, &IOVEC_MAKE((void*) buf, len), 1, ret_digest, ret_digest_size);
 }
 
+int openssl_hmac_many(const char *digest_alg, const void *key, size_t key_size, const struct iovec data[], size_t n_data, void **ret_digest, size_t *ret_digest_size);
+
+static inline int openssl_hmac(const char *digest_alg, const void *key, size_t key_size, const void *buf, size_t len, void **ret_digest, size_t *ret_digest_size) {
+        return openssl_hmac_many(digest_alg, key, key_size, &IOVEC_MAKE((void*) buf, len), 1, ret_digest, ret_digest_size);
+}
+
 int rsa_encrypt_bytes(EVP_PKEY *pkey, const void *decrypted_key, size_t decrypted_key_size, void **ret_encrypt_key, size_t *ret_encrypt_key_size);
 
 int rsa_pkey_to_suitable_key_size(EVP_PKEY *pkey, size_t *ret_suitable_key_size);