add encrypting for save files

add libhydrogen for encrypting and decrypting #9
2026-04-03 14:59:37 +02:00
parent abb6556fd4
commit c277ab10d9
68 changed files with 5737 additions and 74 deletions
@@ -0,0 +1,44 @@
+#include <mbedtls/ctr_drbg.h>
+#include <mbedtls/entropy.h>
+
+#if defined(MBEDTLS_ENTROPY_C)
+
+static int
+hydro_random_init(void)
+{
+    mbedtls_entropy_context entropy;
+    uint16_t                pos = 0;
+
+    mbedtls_entropy_init(&entropy);
+
+    // Pull data directly out of the entropy pool for the state, as it's small enough.
+    if (mbedtls_entropy_func(&entropy, (uint8_t *) &hydro_random_context.counter,
+                             sizeof hydro_random_context.counter) != 0) {
+        return -1;
+    }
+    // mbedtls_entropy_func can't provide more than MBEDTLS_ENTROPY_BLOCK_SIZE in one go.
+    // This constant depends of mbedTLS configuration (whether the PRNG is backed by SHA256/SHA512
+    // at this time) Therefore, if necessary, we get entropy multiple times.
+
+    do {
+        const uint8_t dataLeftToConsume = gimli_BLOCKBYTES - pos;
+        const uint8_t currentChunkSize  = (dataLeftToConsume > MBEDTLS_ENTROPY_BLOCK_SIZE)
+                                              ? MBEDTLS_ENTROPY_BLOCK_SIZE
+                                              : dataLeftToConsume;
+
+        // Forces mbedTLS to fetch fresh entropy, then get some to feed libhydrogen.
+        if (mbedtls_entropy_gather(&entropy) != 0 ||
+            mbedtls_entropy_func(&entropy, &hydro_random_context.state[pos], currentChunkSize) !=
+                0) {
+            return -1;
+        }
+        pos += MBEDTLS_ENTROPY_BLOCK_SIZE;
+    } while (pos < gimli_BLOCKBYTES);
+
+    mbedtls_entropy_free(&entropy);
+
+    return 0;
+}
+#else
+#    error Need an entropy source
+#endif