From ac56a1aec430ab48ae4f7c5cc1d2735cbc93f2e7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Manuel=20P=C3=A9gouri=C3=A9-Gonnard?= <mpg@elzevir.fr>
Date: Thu, 25 Jul 2013 12:31:10 +0200
Subject: [PATCH] Make cipher_set_padding() actually work

(Only one padding mode recognized yet.)
---
 include/polarssl/cipher.h |  4 ++++
 library/cipher.c          | 44 +++++++++++++++++++++++++--------------
 2 files changed, 32 insertions(+), 16 deletions(-)

diff --git a/include/polarssl/cipher.h b/include/polarssl/cipher.h
index 48fe97dab..aa0c42a65 100644
--- a/include/polarssl/cipher.h
+++ b/include/polarssl/cipher.h
@@ -202,6 +202,10 @@ typedef struct {
     /** Operation that the context's key has been initialised for */
     operation_t operation;
 
+    /** Padding functions to use, if relevant for cipher mode */
+    void (*add_padding)( unsigned char *output, size_t olen, size_t data_len );
+    int (*get_padding)( unsigned char *input, size_t ilen, size_t *data_len );
+
     /** Buffer for data that hasn't been encrypted yet */
     unsigned char unprocessed_data[POLARSSL_MAX_IV_LENGTH];
 
diff --git a/library/cipher.c b/library/cipher.c
index d2c8ab373..d0000b271 100644
--- a/library/cipher.c
+++ b/library/cipher.c
@@ -323,6 +323,11 @@ int cipher_init_ctx( cipher_context_t *ctx, const cipher_info_t *cipher_info )
 
     ctx->cipher_info = cipher_info;
 
+    /*
+     * Ignore possible errors caused by a cipher mode that doesn't use padding
+     */
+    (void) cipher_set_padding_mode( ctx, POLARSSL_PADDING_PKCS7 );
+
     return 0;
 }
 
@@ -368,18 +373,6 @@ int cipher_setkey( cipher_context_t *ctx, const unsigned char *key,
     return POLARSSL_ERR_CIPHER_BAD_INPUT_DATA;
 }
 
-int cipher_set_padding_mode( cipher_context_t *ctx, cipher_padding_t mode )
-{
-    if( NULL == ctx ||
-        POLARSSL_MODE_CBC != ctx->cipher_info->mode ||
-        POLARSSL_PADDING_PKCS7 != mode )
-    {
-        return POLARSSL_ERR_CIPHER_BAD_INPUT_DATA;
-    }
-
-    return 0;
-}
-
 int cipher_reset( cipher_context_t *ctx, const unsigned char *iv )
 {
     if( NULL == ctx || NULL == ctx->cipher_info || NULL == iv )
@@ -543,8 +536,8 @@ static void add_pkcs_padding( unsigned char *output, size_t output_len,
         output[data_len + i] = (unsigned char) padding_len;
 }
 
-static int get_pkcs_padding( unsigned char *input, unsigned int input_len,
-        size_t *data_len)
+static int get_pkcs_padding( unsigned char *input, size_t input_len,
+        size_t *data_len )
 {
     unsigned int i, padding_len = 0;
 
@@ -585,7 +578,7 @@ int cipher_finish( cipher_context_t *ctx, unsigned char *output, size_t *olen)
     {
         if( POLARSSL_ENCRYPT == ctx->operation )
         {
-            add_pkcs_padding( ctx->unprocessed_data, cipher_get_iv_size( ctx ),
+            ctx->add_padding( ctx->unprocessed_data, cipher_get_iv_size( ctx ),
                     ctx->unprocessed_len );
         }
         else if ( cipher_get_block_size( ctx ) != ctx->unprocessed_len )
@@ -604,7 +597,8 @@ int cipher_finish( cipher_context_t *ctx, unsigned char *output, size_t *olen)
 
         /* Set output size for decryption */
         if( POLARSSL_DECRYPT == ctx->operation )
-            return get_pkcs_padding( output, cipher_get_block_size( ctx ), olen );
+            return ctx->get_padding( output, cipher_get_block_size( ctx ),
+                                     olen );
 
         /* Set output size for encryption */
         *olen = cipher_get_block_size( ctx );
@@ -614,6 +608,24 @@ int cipher_finish( cipher_context_t *ctx, unsigned char *output, size_t *olen)
     return POLARSSL_ERR_CIPHER_FEATURE_UNAVAILABLE;
 }
 
+int cipher_set_padding_mode( cipher_context_t *ctx, cipher_padding_t mode )
+{
+    if( NULL == ctx ||
+        POLARSSL_MODE_CBC != ctx->cipher_info->mode )
+    {
+        return POLARSSL_ERR_CIPHER_BAD_INPUT_DATA;
+    }
+
+    if( POLARSSL_PADDING_PKCS7 == mode )
+    {
+        ctx->add_padding = add_pkcs_padding;
+        ctx->get_padding = get_pkcs_padding;
+        return 0;
+    }
+
+    return POLARSSL_ERR_CIPHER_BAD_INPUT_DATA;
+}
+
 #if defined(POLARSSL_SELF_TEST)
 
 #include <stdio.h>