From 32902e6eae89af32a406a68f4a7c8dbf318305a0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Manuel=20P=C3=A9gouri=C3=A9-Gonnard?=
 <manuel.pegourie-gonnard@arm.com>
Date: Thu, 10 May 2018 12:30:19 +0200
Subject: [PATCH] cipher: handle ChaCha20 as a stream cipher

That's what it is. So we shouldn't set a block size != 1.

While at it, move call to chachapoly_update() closer to the one for GCM, as
they are similar (AEAD).
---
 include/mbedtls/cipher.h |  2 +-
 library/cipher.c         | 34 +++++++++-------------------------
 library/cipher_wrap.c    | 21 +++++++++++++++++----
 3 files changed, 27 insertions(+), 30 deletions(-)

diff --git a/include/mbedtls/cipher.h b/include/mbedtls/cipher.h
index 591aa79aa..1ae847d20 100644
--- a/include/mbedtls/cipher.h
+++ b/include/mbedtls/cipher.h
@@ -193,7 +193,7 @@ enum {
 /** Maximum length of any IV, in Bytes. */
 #define MBEDTLS_MAX_IV_LENGTH      16
 /** Maximum block size of any cipher, in Bytes. */
-#define MBEDTLS_MAX_BLOCK_LENGTH   64
+#define MBEDTLS_MAX_BLOCK_LENGTH   16
 
 /**
  * Base cipher information (opaque struct).
diff --git a/library/cipher.c b/library/cipher.c
index 2463a6148..cf10094f6 100644
--- a/library/cipher.c
+++ b/library/cipher.c
@@ -367,6 +367,15 @@ int mbedtls_cipher_update( mbedtls_cipher_context_t *ctx, const unsigned char *i
     }
 #endif
 
+#if defined(MBEDTLS_CHACHAPOLY_C)
+    if ( ctx->cipher_info->type == MBEDTLS_CIPHER_CHACHA20_POLY1305 )
+    {
+        *olen = ilen;
+        return mbedtls_chachapoly_update( (mbedtls_chachapoly_context*) ctx->cipher_ctx,
+                                                      ilen, input, output );
+    }
+#endif
+
     if ( 0 == block_size )
     {
         return MBEDTLS_ERR_CIPHER_INVALID_CONTEXT;
@@ -378,31 +387,6 @@ int mbedtls_cipher_update( mbedtls_cipher_context_t *ctx, const unsigned char *i
         return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
     }
 
-
-#if defined(MBEDTLS_CHACHA20_C)
-    if ( ctx->cipher_info->type == MBEDTLS_CIPHER_CHACHA20 )
-    {
-        *olen = ilen;
-        return mbedtls_chacha20_update( (mbedtls_chacha20_context*) ctx->cipher_ctx,
-                                         ilen, input, output );
-    }
-#endif
-
-    if( input == output &&
-       ( ctx->unprocessed_len != 0 || ilen % mbedtls_cipher_get_block_size( ctx ) ) )
-    {
-        return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
-    }
-
-#if defined(MBEDTLS_CHACHAPOLY_C)
-    if ( ctx->cipher_info->type == MBEDTLS_CIPHER_CHACHA20_POLY1305 )
-    {
-        *olen = ilen;
-        return mbedtls_chachapoly_update( (mbedtls_chachapoly_context*) ctx->cipher_ctx,
-                                                      ilen, input, output );
-    }
-#endif
-
 #if defined(MBEDTLS_CIPHER_MODE_CBC)
     if( ctx->cipher_info->mode == MBEDTLS_MODE_CBC )
     {
diff --git a/library/cipher_wrap.c b/library/cipher_wrap.c
index 5c8082850..9110b968c 100644
--- a/library/cipher_wrap.c
+++ b/library/cipher_wrap.c
@@ -1305,6 +1305,19 @@ static int chacha20_setkey_wrap( void *ctx, const unsigned char *key,
     return( 0 );
 }
 
+static int chacha20_stream_wrap( void *ctx,  size_t length,
+                                 const unsigned char *input,
+                                 unsigned char *output )
+{
+    int ret;
+
+    ret = mbedtls_chacha20_update( ctx, length, input, output );
+    if( ret == MBEDTLS_ERR_CHACHA20_BAD_INPUT_DATA )
+        return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
+
+    return( ret );
+}
+
 static void * chacha20_ctx_alloc( void )
 {
     mbedtls_chacha20_context *ctx;
@@ -1337,7 +1350,7 @@ static const mbedtls_cipher_base_t chacha20_base_info = {
     NULL,
 #endif
 #if defined(MBEDTLS_CIPHER_MODE_STREAM)
-    NULL,
+    chacha20_stream_wrap,
 #endif
     chacha20_setkey_wrap,
     chacha20_setkey_wrap,
@@ -1346,12 +1359,12 @@ static const mbedtls_cipher_base_t chacha20_base_info = {
 };
 static const mbedtls_cipher_info_t chacha20_info = {
     MBEDTLS_CIPHER_CHACHA20,
-    MBEDTLS_MODE_NONE,
+    MBEDTLS_MODE_STREAM,
     256,
     "CHACHA20",
     12,
     0,
-    64,
+    1,
     &chacha20_base_info
 };
 #endif /* MBEDTLS_CHACHA20_C */
@@ -1417,7 +1430,7 @@ static const mbedtls_cipher_info_t chachapoly_info = {
     "CHACHA20-POLY1305",
     12,
     0,
-    64,
+    1,
     &chachapoly_base_info
 };
 #endif /* MBEDTLS_CHACHAPOLY_C */