1 files changed, 134 insertions, 0 deletions
diff --git a/include/olm/cipher.h b/include/olm/cipher.h
new file mode 100644
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--- /dev/null
+++ b/include/olm/cipher.h
@@ -0,0 +1,134 @@
+/* Copyright 2015 OpenMarket Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef OLM_CIPHER_H_
+#define OLM_CIPHER_H_
+
+#include <stdint.h>
+#include <stdlib.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+struct olm_cipher;
+
+struct cipher_ops {
+    /**
+     * Returns the length of the message authentication code that will be
+     * appended to the output.
+     */
+    size_t (*mac_length)(const struct olm_cipher *cipher);
+
+    /**
+     * Returns the length of cipher-text for a given length of plain-text.
+     */
+    size_t (*encrypt_ciphertext_length)(const struct olm_cipher *cipher,
+                                        size_t plaintext_length);
+
+    /*
+     * Encrypts the plain-text into the output buffer and authenticates the
+     * contents of the output buffer covering both cipher-text and any other
+     * associated data in the output buffer.
+     *
+     *  |---------------------------------------output_length-->|
+     *  output  |--ciphertext_length-->|       |---mac_length-->|
+     *          ciphertext
+     *
+     * The plain-text pointers and cipher-text pointers may be the same.
+     *
+     * Returns size_t(-1) if the length of the cipher-text or the output
+     * buffer is too small. Otherwise returns the length of the output buffer.
+     */
+    size_t (*encrypt)(
+        const struct olm_cipher *cipher,
+        uint8_t const * key, size_t key_length,
+        uint8_t const * plaintext, size_t plaintext_length,
+        uint8_t * ciphertext, size_t ciphertext_length,
+        uint8_t * output, size_t output_length
+    );
+
+    /**
+     * Returns the maximum length of plain-text that a given length of
+     * cipher-text can contain.
+     */
+    size_t (*decrypt_max_plaintext_length)(
+        const struct olm_cipher *cipher,
+        size_t ciphertext_length
+    );
+
+    /**
+     * Authenticates the input and decrypts the cipher-text into the plain-text
+     * buffer.
+     *
+     *  |----------------------------------------input_length-->|
+     *  input   |--ciphertext_length-->|       |---mac_length-->|
+     *          ciphertext
+     *
+     * The plain-text pointers and cipher-text pointers may be the same.
+     *
+     *  Returns size_t(-1) if the length of the plain-text buffer is too
+     *  small or if the authentication check fails. Otherwise returns the length
+     *  of the plain text.
+     */
+    size_t (*decrypt)(
+        const struct olm_cipher *cipher,
+        uint8_t const * key, size_t key_length,
+        uint8_t const * input, size_t input_length,
+        uint8_t const * ciphertext, size_t ciphertext_length,
+        uint8_t * plaintext, size_t max_plaintext_length
+    );
+
+    /** destroy any private data associated with this cipher */
+    void (*destruct)(struct olm_cipher *cipher);
+};
+
+struct olm_cipher {
+    const struct cipher_ops *ops;
+    /* cipher-specific fields follow */
+};
+
+struct olm_cipher_aes_sha_256 {
+    struct olm_cipher base_cipher;
+
+    uint8_t const * kdf_info;
+    size_t kdf_info_length;
+};
+
+
+/**
+ * initialises a cipher type which uses AES256 for encryption and SHA256 for
+ * authentication.
+ *
+ * cipher: structure to be initialised
+ *
+ * kdf_info: context string for the HKDF used for deriving the AES256 key, HMAC
+ * key, and AES IV, from the key material passed to encrypt/decrypt. Note that
+ * this is NOT copied so must have a lifetime at least as long as the cipher
+ * instance.
+ *
+ * kdf_info_length: length of context string kdf_info
+ */
+struct olm_cipher *olm_cipher_aes_sha_256_init(
+    struct olm_cipher_aes_sha_256 *cipher,
+    uint8_t const * kdf_info,
+    size_t kdf_info_length);
+
+
+#ifdef __cplusplus
+} /* extern "C" */
+#endif
+
+#endif /* OLM_CIPHER_H_ */