grasshopper: Fix streaming for CTR mode

Previously CTR did not continue unfinished block on the next cipher
iteration.

(cherry picked from commit cf2ab51a449ce3d92163217c8078f0f625aac7ae)

diff --git a/gost_grasshopper_cipher.c b/gost_grasshopper_cipher.c
index c797fe1ca042d364767ba8f5e14a8d32cd9c1dfa..2cdf57eba611a5df84bae8e5f6e9f1899220baa4 100644 (file)
--- a/gost_grasshopper_cipher.c
+++ b/gost_grasshopper_cipher.c
@@ -208,6 +208,7 @@ GRASSHOPPER_INLINE int gost_grasshopper_cipher_init_ctr(EVP_CIPHER_CTX* ctx, con
     gost_grasshopper_cipher_ctx_ctr* c = EVP_CIPHER_CTX_get_cipher_data(ctx);
 
     c->c.type = GRASSHOPPER_CIPHER_CTR;
+    EVP_CIPHER_CTX_set_num(ctx, 0);
 
     grasshopper_zero128(&c->iv_buffer);
     grasshopper_zero128(&c->partial_buffer);
@@ -300,12 +301,20 @@ int gost_grasshopper_cipher_do_ctr(EVP_CIPHER_CTX* ctx, unsigned char* out,
     unsigned char* iv = EVP_CIPHER_CTX_iv_noconst(ctx);
     const unsigned char* current_in = in;
     unsigned char* current_out = out;
-    size_t blocks = inl / GRASSHOPPER_BLOCK_SIZE;
     grasshopper_w128_t* currentInputBlock;
     grasshopper_w128_t* currentOutputBlock;
+    unsigned int n = EVP_CIPHER_CTX_num(ctx);
     size_t lasted;
     size_t i;
 
+    while (n && inl) {
+       *(current_out++) = *(current_in++) ^ c->partial_buffer.b[n];
+       --inl;
+       n = (n + 1) % GRASSHOPPER_BLOCK_SIZE;
+    }
+    EVP_CIPHER_CTX_set_num(ctx, n);
+    size_t blocks = inl / GRASSHOPPER_BLOCK_SIZE;
+
     memcpy(&c->iv_buffer, iv, 8);
 
     // full parts
@@ -328,6 +337,7 @@ int gost_grasshopper_cipher_do_ctr(EVP_CIPHER_CTX* ctx, unsigned char* out,
         for (i = 0; i < lasted; i++) {
             currentOutputBlock->b[i] = c->partial_buffer.b[i] ^ currentInputBlock->b[i];
         }
+       EVP_CIPHER_CTX_set_num(ctx, i);
         ctr128_inc(c->iv_buffer.b);
     }