Prepare DM media as authenticated records using target key

src/dm/dm_crypto.c

@@ -147,3 +147,90 @@ int dm_decrypt(const uint8_t key[DM_CONTENT_KEY_SIZE], const uint8_t nonce[DM_NO
                const uint8_t* ct, size_t ct_len, uint8_t* out, size_t* out_len) {
     return dm_ccm_crypt(key, nonce, ct, ct_len, out, out_len, 0, NULL);
 }
+
+/* Каждая порция имеет собственный nonce, ciphertext неизменен для всех сетевых повторов. */
+int dm_media_encrypt_stream(const uint8_t key[DM_CONTENT_KEY_SIZE], uint64_t author, const uint8_t media_id[16],
+                            FILE* src, FILE* dst, uint64_t* plain_size, uint8_t ciphertext_hash[32]) {
+    if (!key || !author || !media_id || !src || !dst || src == dst || !plain_size || !ciphertext_hash) {
+        DEBUG_ERROR(DEBUG_CATEGORY_DM, "%s: invalid media encryption arguments", DM_ID);
+        return -1;
+    }
+    *plain_size = 0;
+    memset(ciphertext_hash, 0, 32);
+    uint8_t plain[DM_MEDIA_PLAIN_SIZE], cipher[DM_MEDIA_PLAIN_SIZE + DM_TAG_SIZE], nonce[DM_NONCE_SIZE];
+    uint64_t part = 0, total = 0;
+    SHA256_CTX hash;
+    SHA256_Init(&hash);
+    for (;;) {
+        size_t n = fread(plain, 1, sizeof(plain), src);
+        if (ferror(src)) {
+            DEBUG_ERROR(DEBUG_CATEGORY_DM, "%s: media source read failed part=%llu", DM_ID, (unsigned long long)part);
+            return -1;
+        }
+        if (!n && part) break;
+        size_t clen = 0;
+        dm_build_media_nonce(author, media_id, part, nonce);
+        if (dm_encrypt(key, nonce, plain, n, cipher, &clen) != 0) return -1;
+        if (fwrite(cipher, 1, clen, dst) != clen) {
+            DEBUG_ERROR(DEBUG_CATEGORY_DM, "%s: media ciphertext write failed part=%llu", DM_ID, (unsigned long long)part);
+            return -1;
+        }
+        SHA256_Update(&hash, cipher, clen);
+        total += n;
+        part++;
+        if (n < sizeof(plain)) break;
+    }
+    if (fflush(dst) != 0) {
+        DEBUG_ERROR(DEBUG_CATEGORY_DM, "%s: media ciphertext flush failed", DM_ID);
+        return -1;
+    }
+    SHA256_Final(ciphertext_hash, &hash);
+    *plain_size = total;
+    DEBUG_DEBUG(DEBUG_CATEGORY_DM, "%s: media encrypted author=%llu plain=%llu records=%llu", DM_ID,
+                (unsigned long long)author, (unsigned long long)total, (unsigned long long)part);
+    return 0;
+}
+
+/* Размер и хеш берутся из подписанного manifest; никакого size-only принятия файла. */
+int dm_media_decrypt_stream(const uint8_t key[DM_CONTENT_KEY_SIZE], uint64_t author, const uint8_t media_id[16],
+                            uint64_t plain_size, const uint8_t ciphertext_hash[32], FILE* src, FILE* dst) {
+    if (!key || !author || !media_id || !ciphertext_hash || !src || !dst || src == dst) {
+        DEBUG_ERROR(DEBUG_CATEGORY_DM, "%s: invalid media decryption arguments", DM_ID);
+        return -1;
+    }
+    uint8_t plain[DM_MEDIA_PLAIN_SIZE], cipher[DM_MEDIA_PLAIN_SIZE + DM_TAG_SIZE], nonce[DM_NONCE_SIZE];
+    uint64_t remaining = plain_size, part = 0;
+    SHA256_CTX hash;
+    SHA256_Init(&hash);
+    do {
+        size_t n = remaining > DM_MEDIA_PLAIN_SIZE ? DM_MEDIA_PLAIN_SIZE : (size_t)remaining;
+        size_t clen = n + DM_TAG_SIZE, plen = 0;
+        if (fread(cipher, 1, clen, src) != clen) {
+            DEBUG_ERROR(DEBUG_CATEGORY_DM, "%s: media ciphertext short/read failure part=%llu expected=%zu", DM_ID,
+                        (unsigned long long)part, clen);
+            return -1;
+        }
+        SHA256_Update(&hash, cipher, clen);
+        dm_build_media_nonce(author, media_id, part, nonce);
+        if (dm_decrypt(key, nonce, cipher, clen, plain, &plen) != 0) return -1;
+        if (plen != n || fwrite(plain, 1, plen, dst) != plen) {
+            DEBUG_ERROR(DEBUG_CATEGORY_DM, "%s: media plaintext write/length failure part=%llu", DM_ID, (unsigned long long)part);
+            return -1;
+        }
+        remaining -= n;
+        part++;
+    } while (remaining);
+    uint8_t actual_hash[32];
+    SHA256_Final(actual_hash, &hash);
+    if (fgetc(src) != EOF || ferror(src) || memcmp(actual_hash, ciphertext_hash, 32)) {
+        DEBUG_ERROR(DEBUG_CATEGORY_DM, "%s: media ciphertext size/hash mismatch plain=%llu", DM_ID, (unsigned long long)plain_size);
+        return -1;
+    }
+    if (fflush(dst) != 0) {
+        DEBUG_ERROR(DEBUG_CATEGORY_DM, "%s: media plaintext flush failed", DM_ID);
+        return -1;
+    }
+    DEBUG_DEBUG(DEBUG_CATEGORY_DM, "%s: media verified author=%llu plain=%llu records=%llu", DM_ID,
+                (unsigned long long)author, (unsigned long long)plain_size, (unsigned long long)part);
+    return 0;
+}