RFC 5649 support.

Add support for RFC5649 key wrapping with padding.

Add RFC5649 tests to evptests.txt

Based on PR#3434 contribution by Petr Spacek <pspacek@redhat.com>.

EVP support and minor changes added by Stephen Henson.

Doxygen comment block updates by Tim Hudson.

Reviewed-by: Tim Hudson <tjh@openssl.org>

crypto/evp/c_allc.c

@@ -175,6 +175,7 @@ void OpenSSL_add_all_ciphers(void)
 	EVP_add_cipher(EVP_aes_128_xts());
 	EVP_add_cipher(EVP_aes_128_ccm());
 	EVP_add_cipher(EVP_aes_128_wrap());
+	EVP_add_cipher(EVP_aes_128_wrap_pad());
 	EVP_add_cipher_alias(SN_aes_128_cbc,"AES128");
 	EVP_add_cipher_alias(SN_aes_128_cbc,"aes128");
 	EVP_add_cipher(EVP_aes_192_ecb());
@@ -187,6 +188,7 @@ void OpenSSL_add_all_ciphers(void)
 	EVP_add_cipher(EVP_aes_192_gcm());
 	EVP_add_cipher(EVP_aes_192_ccm());
 	EVP_add_cipher(EVP_aes_192_wrap());
+	EVP_add_cipher(EVP_aes_192_wrap_pad());
 	EVP_add_cipher_alias(SN_aes_192_cbc,"AES192");
 	EVP_add_cipher_alias(SN_aes_192_cbc,"aes192");
 	EVP_add_cipher(EVP_aes_256_ecb());
@@ -200,6 +202,7 @@ void OpenSSL_add_all_ciphers(void)
 	EVP_add_cipher(EVP_aes_256_xts());
 	EVP_add_cipher(EVP_aes_256_ccm());
 	EVP_add_cipher(EVP_aes_256_wrap());
+	EVP_add_cipher(EVP_aes_256_wrap_pad());
 	EVP_add_cipher_alias(SN_aes_256_cbc,"AES256");
 	EVP_add_cipher_alias(SN_aes_256_cbc,"aes256");
 #if !defined(OPENSSL_NO_SHA) && !defined(OPENSSL_NO_SHA1)

crypto/evp/e_aes.c

@@ -1,5 +1,5 @@
 /* ====================================================================
- * Copyright (c) 2001-2011 The OpenSSL Project.  All rights reserved.
+ * Copyright (c) 2001-2014 The OpenSSL Project.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -2086,7 +2086,7 @@ static int aes_wrap_init_key(EVP_CIPHER_CTX *ctx, const unsigned char *key,
 		}
 	if (iv)
 		{
-		memcpy(ctx->iv, iv, 8);
+		memcpy(ctx->iv, iv, EVP_CIPHER_CTX_iv_length(ctx));
 		wctx->iv = ctx->iv;
 		}
 	return 1;
@@ -2097,27 +2097,62 @@ static int aes_wrap_cipher(EVP_CIPHER_CTX *ctx, unsigned char *out,
 	{
 	EVP_AES_WRAP_CTX *wctx = ctx->cipher_data;
 	size_t rv;
+	/* AES wrap with padding has IV length of 4, without padding 8 */
+	int pad = EVP_CIPHER_CTX_iv_length(ctx) == 4;
+	/* No final operation so always return zero length */
 	if (!in)
 		return 0;
-	if (inlen % 8)
+	/* Input length must always be non-zero */
+	if (!inlen)
 		return -1;
-	if (ctx->encrypt && inlen < 8)
+	/* If decrypting need at least 16 bytes and multiple of 8 */
+	if (!ctx->encrypt && (inlen < 16 || inlen & 0x7))
 		return -1;
-	if (!ctx->encrypt && inlen < 16)
+	/* If not padding input must be multiple of 8 */
+	if (!pad && inlen & 0x7)
 		return -1;
 	if (!out)
 		{
 		if (ctx->encrypt)
+			{
+			/* If padding round up to multiple of 8 */
+			if (pad)
+				inlen = (inlen + 7)/8 * 8;
+			/* 8 byte prefix */
 			return inlen + 8;
+			}
 		else
+			{
+			/* If not padding output will be exactly 8 bytes
+			 * smaller than input. If padding it will be at
+			 * least 8 bytes smaller but we don't know how
+			 * much.
+			 */
 			return inlen - 8;
+			}
 		}
-	if (ctx->encrypt)
+	if (pad)
-		rv = CRYPTO_128_wrap(&wctx->ks.ks, wctx->iv, out, in, inlen,
+		{
+		if (ctx->encrypt)
+			rv = CRYPTO_128_wrap_pad(&wctx->ks.ks, wctx->iv,
+						out, in, inlen,
 						(block128_f)AES_encrypt);
-	else
+		else
-		rv = CRYPTO_128_unwrap(&wctx->ks.ks, wctx->iv, out, in, inlen,
+			rv = CRYPTO_128_unwrap_pad(&wctx->ks.ks, wctx->iv,
+						out, in, inlen,
 						(block128_f)AES_decrypt);
+		}
+	else
+		{
+		if (ctx->encrypt)
+			rv = CRYPTO_128_wrap(&wctx->ks.ks, wctx->iv,
+						out, in, inlen,
+						(block128_f)AES_encrypt);
+		else
+			rv = CRYPTO_128_unwrap(&wctx->ks.ks, wctx->iv,
+						out, in, inlen,
+						(block128_f)AES_decrypt);
+		}
 	return rv ? (int)rv : -1;
 	}
 
@@ -2129,7 +2164,7 @@ static const EVP_CIPHER aes_128_wrap = {
 	NID_id_aes128_wrap,
 	8, 16, 8, WRAP_FLAGS,
 	aes_wrap_init_key, aes_wrap_cipher,
-	NULL,	
+	NULL,
 	sizeof(EVP_AES_WRAP_CTX),
 	NULL,NULL,NULL,NULL };
 
@@ -2142,7 +2177,7 @@ static const EVP_CIPHER aes_192_wrap = {
 	NID_id_aes192_wrap,
 	8, 24, 8, WRAP_FLAGS,
 	aes_wrap_init_key, aes_wrap_cipher,
-	NULL,	
+	NULL,
 	sizeof(EVP_AES_WRAP_CTX),
 	NULL,NULL,NULL,NULL };
 
@@ -2155,7 +2190,7 @@ static const EVP_CIPHER aes_256_wrap = {
 	NID_id_aes256_wrap,
 	8, 32, 8, WRAP_FLAGS,
 	aes_wrap_init_key, aes_wrap_cipher,
-	NULL,	
+	NULL,
 	sizeof(EVP_AES_WRAP_CTX),
 	NULL,NULL,NULL,NULL };
 
@@ -2164,4 +2199,43 @@ const EVP_CIPHER *EVP_aes_256_wrap(void)
 	return &aes_256_wrap;
 	}
 
+static const EVP_CIPHER aes_128_wrap_pad = {
+	NID_id_aes128_wrap_pad,
+	8, 16, 4, WRAP_FLAGS,
+	aes_wrap_init_key, aes_wrap_cipher,
+	NULL,
+	sizeof(EVP_AES_WRAP_CTX),
+	NULL,NULL,NULL,NULL };
+
+const EVP_CIPHER *EVP_aes_128_wrap_pad(void)
+	{
+	return &aes_128_wrap_pad;
+	}
+
+static const EVP_CIPHER aes_192_wrap_pad = {
+	NID_id_aes192_wrap_pad,
+	8, 24, 4, WRAP_FLAGS,
+	aes_wrap_init_key, aes_wrap_cipher,
+	NULL,
+	sizeof(EVP_AES_WRAP_CTX),
+	NULL,NULL,NULL,NULL };
+
+const EVP_CIPHER *EVP_aes_192_wrap_pad(void)
+	{
+	return &aes_192_wrap_pad;
+	}
+
+static const EVP_CIPHER aes_256_wrap_pad = {
+	NID_id_aes256_wrap_pad,
+	8, 32, 4, WRAP_FLAGS,
+	aes_wrap_init_key, aes_wrap_cipher,
+	NULL,
+	sizeof(EVP_AES_WRAP_CTX),
+	NULL,NULL,NULL,NULL };
+
+const EVP_CIPHER *EVP_aes_256_wrap_pad(void)
+	{
+	return &aes_256_wrap_pad;
+	}
+
 #endif

crypto/evp/evp.h

@@ -849,6 +849,7 @@ const EVP_CIPHER *EVP_aes_128_ccm(void);
 const EVP_CIPHER *EVP_aes_128_gcm(void);
 const EVP_CIPHER *EVP_aes_128_xts(void);
 const EVP_CIPHER *EVP_aes_128_wrap(void);
+const EVP_CIPHER *EVP_aes_128_wrap_pad(void);
 const EVP_CIPHER *EVP_aes_192_ecb(void);
 const EVP_CIPHER *EVP_aes_192_cbc(void);
 const EVP_CIPHER *EVP_aes_192_cfb1(void);
@@ -860,6 +861,7 @@ const EVP_CIPHER *EVP_aes_192_ctr(void);
 const EVP_CIPHER *EVP_aes_192_ccm(void);
 const EVP_CIPHER *EVP_aes_192_gcm(void);
 const EVP_CIPHER *EVP_aes_192_wrap(void);
+const EVP_CIPHER *EVP_aes_192_wrap_pad(void);
 const EVP_CIPHER *EVP_aes_256_ecb(void);
 const EVP_CIPHER *EVP_aes_256_cbc(void);
 const EVP_CIPHER *EVP_aes_256_cfb1(void);
@@ -872,6 +874,7 @@ const EVP_CIPHER *EVP_aes_256_ccm(void);
 const EVP_CIPHER *EVP_aes_256_gcm(void);
 const EVP_CIPHER *EVP_aes_256_xts(void);
 const EVP_CIPHER *EVP_aes_256_wrap(void);
+const EVP_CIPHER *EVP_aes_256_wrap_pad(void);
 # if !defined(OPENSSL_NO_SHA) && !defined(OPENSSL_NO_SHA1)
 const EVP_CIPHER *EVP_aes_128_cbc_hmac_sha1(void);
 const EVP_CIPHER *EVP_aes_256_cbc_hmac_sha1(void);

crypto/evp/evptests.txt

@@ -401,3 +401,7 @@ id-aes256-wrap:000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F:
 id-aes192-wrap:000102030405060708090A0B0C0D0E0F1011121314151617::00112233445566778899AABBCCDDEEFF0001020304050607:031D33264E15D33268F24EC260743EDCE1C6C7DDEE725A936BA814915C6762D2
 id-aes256-wrap:000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F::00112233445566778899AABBCCDDEEFF0001020304050607:A8F9BC1612C68B3FF6E6F4FBE30E71E4769C8B80A32CB8958CD5D17D6B254DA1
 id-aes256-wrap:000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F::00112233445566778899AABBCCDDEEFF000102030405060708090A0B0C0D0E0F:28C9F404C4B810F4CBCCB35CFB87F8263F5786E2D80ED326CBC7F0E71A99F43BFB988B9B7A02DD21
+# AES wrap tests from RFC5649
+id-aes192-wrap-pad:5840df6e29b02af1ab493b705bf16ea1ae8338f4dcc176a8::c37b7e6492584340bed12207808941155068f738:138bdeaa9b8fa7fc61f97742e72248ee5ae6ae5360d1ae6a5f54f373fa543b6a
+id-aes192-wrap-pad:5840df6e29b02af1ab493b705bf16ea1ae8338f4dcc176a8::466f7250617369:afbeb0f07dfbf5419200f2ccb50bb24f
+

crypto/modes/modes.h

@@ -141,3 +141,9 @@ size_t CRYPTO_128_wrap(void *key, const unsigned char *iv,
 size_t CRYPTO_128_unwrap(void *key, const unsigned char *iv,
 		unsigned char *out,
 		const unsigned char *in, size_t inlen, block128_f block);
+size_t CRYPTO_128_wrap_pad(void *key, const unsigned char *icv,
+		unsigned char *out,
+		const unsigned char *in, size_t inlen, block128_f block);
+size_t CRYPTO_128_unwrap_pad(void *key, const unsigned char *icv,
+		unsigned char *out,
+		const unsigned char *in, size_t inlen, block128_f block);

crypto/modes/wrap128.c

@@ -1,6 +1,7 @@
 /* crypto/modes/wrap128.c */
 /* Written by Dr Stephen N Henson (steve@openssl.org) for the OpenSSL
  * project.
+ * Mode with padding contributed by Petr Spacek (pspacek@redhat.com).
  */
 /* ====================================================================
  * Copyright (c) 2013 The OpenSSL Project.  All rights reserved.
@@ -51,28 +52,55 @@
  * ====================================================================
  */
 
+/**  Beware!
+ *
+ *  Following wrapping modes were designed for AES but this implementation
+ *  allows you to use them for any 128 bit block cipher.
+ */
+
 #include "cryptlib.h"
 #include <openssl/modes.h>
 
+/** RFC 3394 section 2.2.3.1 Default Initial Value */
 static const unsigned char default_iv[] = {
   0xA6, 0xA6, 0xA6, 0xA6, 0xA6, 0xA6, 0xA6, 0xA6,
 };
-/* Input size limit: lower than maximum of standards but far larger than
+
- * anything that will be used in practice.
+/** RFC 5649 section 3 Alternative Initial Value 32-bit constant */
+static const unsigned char default_aiv[] = {
+  0xA6, 0x59, 0x59, 0xA6
+};
+
+/** Input size limit: lower than maximum of standards but far larger than
+ *  anything that will be used in practice.
  */
 #define CRYPTO128_WRAP_MAX (1UL << 31)
 
+/** Wrapping according to RFC 3394 section 2.2.1.
+ *
+ *  @param[in]  key    Key value. 
+ *  @param[in]  iv     IV value. Length = 8 bytes. NULL = use default_iv.
+ *  @param[in]  in     Plain text as n 64-bit blocks, n >= 2.
+ *  @param[in]  inlen  Length of in.
+ *  @param[out] out    Cipher text. Minimal buffer length = (inlen + 8) bytes.
+ *                     Input and output buffers can overlap if block function
+ *                     supports that.
+ *  @param[in]  block  Block processing function.
+ *  @return            0 if inlen does not consist of n 64-bit blocks, n >= 2.
+ *                     or if inlen > CRYPTO128_WRAP_MAX.
+ *                     Output length if wrapping succeeded.
+ */
 size_t CRYPTO_128_wrap(void *key, const unsigned char *iv,
 		unsigned char *out,
 		const unsigned char *in, size_t inlen, block128_f block)
 	{
 	unsigned char *A, B[16], *R;
 	size_t i, j, t;
-	if ((inlen & 0x7) || (inlen < 8) || (inlen > CRYPTO128_WRAP_MAX))
+	if ((inlen & 0x7) || (inlen < 16) || (inlen > CRYPTO128_WRAP_MAX))
 		return 0;
 	A = B;
 	t = 1;
-	memcpy(out + 8, in, inlen);
+	memmove(out + 8, in, inlen);
 	if (!iv)
 		iv = default_iv;
 
@@ -99,9 +127,26 @@ size_t CRYPTO_128_wrap(void *key, const unsigned char *iv,
 	return inlen + 8;
 	}
 
-size_t CRYPTO_128_unwrap(void *key, const unsigned char *iv,
+
-		unsigned char *out,
+/** Unwrapping according to RFC 3394 section 2.2.2 steps 1-2.
-		const unsigned char *in, size_t inlen, block128_f block)
+ *  IV check (step 3) is responsibility of the caller.
+ *
+ *  @param[in]  key    Key value. 
+ *  @param[out] iv     Unchecked IV value. Minimal buffer length = 8 bytes.
+ *  @param[out] out    Plain text without IV.
+ *                     Minimal buffer length = (inlen - 8) bytes.
+ *                     Input and output buffers can overlap if block function
+ *                     supports that.
+ *  @param[in]  in     Ciphertext text as n 64-bit blocks
+ *  @param[in]  inlen  Length of in.
+ *  @param[in]  block  Block processing function.
+ *  @return            0 if inlen is out of range [24, CRYPTO128_WRAP_MAX]
+ *                     or if inlen is not multiply of 8.
+ *                     Output length otherwise.
+ */
+static size_t crypto_128_unwrap_raw(void *key, unsigned char *iv,
+		unsigned char *out, const unsigned char *in,
+		size_t inlen, block128_f block)
 	{
 	unsigned char *A, B[16], *R;
 	size_t i, j, t;
@@ -111,7 +156,7 @@ size_t CRYPTO_128_unwrap(void *key, const unsigned char *iv,
 	A = B;
 	t =  6 * (inlen >> 3);
 	memcpy(A, in, 8);
-	memcpy(out, in + 8, inlen);
+	memmove(out, in + 8, inlen);
 	for (j = 0; j < 6; j++)
 		{
 		R = out + inlen - 8;
@@ -129,12 +174,199 @@ size_t CRYPTO_128_unwrap(void *key, const unsigned char *iv,
 			memcpy(R, B + 8, 8);
 			}
 		}
+	memcpy(iv, A, 8);
+	return inlen;
+	}
+
+/** Unwrapping according to RFC 3394 section 2.2.2 including IV check.
+ *  First block of plain text have to match supplied IV otherwise an error is
+ *  returned.
+ *
+ *  @param[in]  key    Key value. 
+ *  @param[out] iv     Unchecked IV value. Minimal buffer length = 8 bytes.
+ *  @param[out] out    Plain text without IV.
+ *                     Minimal buffer length = (inlen - 8) bytes.
+ *                     Input and output buffers can overlap if block function
+ *                     supports that.
+ *  @param[in]  in     Ciphertext text as n 64-bit blocks
+ *  @param[in]  inlen  Length of in.
+ *  @param[in]  block  Block processing function.
+ *  @return            0 if inlen is out of range [24, CRYPTO128_WRAP_MAX]
+ *                     or if inlen is not multiply of 8
+ *                     or if IV doesn't match expected value.
+ *                     Output length otherwise.
+ */
+size_t CRYPTO_128_unwrap(void *key, const unsigned char *iv,
+		unsigned char *out, const unsigned char *in, size_t inlen,
+		block128_f block)
+	{
+	size_t ret;
+	unsigned char got_iv[8];
+
+	ret = crypto_128_unwrap_raw(key, got_iv, out, in, inlen, block);
+	if (ret != inlen)
+		return ret;
+
 	if (!iv)
 		iv = default_iv;
-	if (memcmp(A, iv, 8))
+	if (CRYPTO_memcmp(out, iv, 8))
 		{
 		OPENSSL_cleanse(out, inlen);
 		return 0;
 		}
 	return inlen;
 	}
+
+/** Wrapping according to RFC 5649 section 4.1.
+ *
+ *  @param[in]  key    Key value. 
+ *  @param[in]  icv    (Non-standard) IV, 4 bytes. NULL = use default_aiv.
+ *  @param[out] out    Cipher text. Minimal buffer length = (inlen + 15) bytes.
+ *                     Input and output buffers can overlap if block function
+ *                     supports that.
+ *  @param[in]  in     Plain text as n 64-bit blocks, n >= 2.
+ *  @param[in]  inlen  Length of in.
+ *  @param[in]  block  Block processing function.
+ *  @return            0 if inlen is out of range [1, CRYPTO128_WRAP_MAX].
+ *                     Output length if wrapping succeeded.
+ */
+size_t CRYPTO_128_wrap_pad(void *key, const unsigned char *icv,
+		unsigned char *out,
+		const unsigned char *in, size_t inlen, block128_f block)
+	{
+	/* n: number of 64-bit blocks in the padded key data */
+	const size_t blocks_padded = (inlen + 8) / 8;
+	const size_t padded_len = blocks_padded * 8;
+	const size_t padding_len = padded_len - inlen;
+	/* RFC 5649 section 3: Alternative Initial Value */
+	unsigned char aiv[8];
+	int ret;
+
+	/* Section 1: use 32-bit fixed field for plaintext octet length */
+	if (inlen == 0 || inlen >= CRYPTO128_WRAP_MAX)
+		return 0;
+
+	/* Section 3: Alternative Initial Value */
+	if (!icv)
+		memcpy(aiv, default_aiv, 4);
+	else
+		memcpy(aiv, icv, 4); /* Standard doesn't mention this. */
+
+	aiv[4] = (inlen >> 24) & 0xFF;
+	aiv[5] = (inlen >> 16) & 0xFF;
+	aiv[6] = (inlen >> 8) & 0xFF;
+	aiv[7] = inlen & 0xFF;
+
+	if (padded_len == 8)
+		{
+		/* Section 4.1 - special case in step 2:
+		 * If the padded plaintext contains exactly eight octets, then
+		 * prepend the AIV and encrypt the resulting 128-bit block
+		 * using AES in ECB mode. */
+		memmove(out + 8, in, inlen);
+		memcpy(out, aiv, 8);
+		memset(out + 8 + inlen, 0, padding_len);
+		block(out, out, key);
+		ret = 16; /* AIV + padded input */
+		}
+		else
+		{
+		memmove(out, in, inlen);
+		memset(out + inlen, 0, padding_len); /* Section 4.1 step 1 */
+		ret = CRYPTO_128_wrap(key, aiv, out, out, padded_len, block);
+		}
+
+	return ret;
+	}
+
+/** Unwrapping according to RFC 5649 section 4.2.
+ *
+ *  @param[in]  key    Key value. 
+ *  @param[in]  icv    (Non-standard) IV, 4 bytes. NULL = use default_aiv.
+ *  @param[out] out    Plain text. Minimal buffer length = inlen bytes.
+ *                     Input and output buffers can overlap if block function
+ *                     supports that.
+ *  @param[in]  in     Ciphertext text as n 64-bit blocks
+ *  @param[in]  inlen  Length of in.
+ *  @param[in]  block  Block processing function.
+ *  @return            0 if inlen is out of range [16, CRYPTO128_WRAP_MAX],
+ *                     or if inlen is not multiply of 8
+ *                     or if IV and message length indicator doesn't match.
+ *                     Output length if unwrapping succeeded and IV matches.
+ */
+size_t CRYPTO_128_unwrap_pad(void *key, const unsigned char *icv,
+		unsigned char *out,
+		const unsigned char *in, size_t inlen, block128_f block)
+	{
+	/* n: number of 64-bit blocks in the padded key data */
+	size_t n = inlen / 8 - 1;
+	size_t padded_len;
+	size_t padding_len;
+	size_t ptext_len;
+	/* RFC 5649 section 3: Alternative Initial Value */
+	unsigned char aiv[8];
+	static unsigned char zeros[8] = {0x0};
+	size_t ret;
+
+	/* Section 4.2: Cipher text length has to be (n+1) 64-bit blocks. */
+	if ((inlen & 0x7) != 0 || inlen < 16 || inlen >= CRYPTO128_WRAP_MAX)
+		return 0;
+
+	memmove(out, in, inlen);
+	if (inlen == 16)
+		{
+		/* Section 4.2 - special case in step 1:
+		 * When n=1, the ciphertext contains exactly two 64-bit
+		 * blocks and they are decrypted as a single AES
+		 * block using AES in ECB mode:
+		 * AIV | P[1] = DEC(K, C[0] | C[1])
+		 */
+		block(out, out, key);
+		memcpy(aiv, out, 8);
+		/* Remove AIV */
+		memmove(out, out + 8, 8);
+		padded_len = 8;
+		}
+		else
+		{
+		padded_len = inlen - 8;
+		ret = crypto_128_unwrap_raw(key, aiv, out, out, inlen, block);
+		if (padded_len != ret)
+			{
+			OPENSSL_cleanse(out, inlen);
+			return 0;
+			}
+		}
+
+	/* Section 3: AIV checks: Check that MSB(32,A) = A65959A6.
+	 * Optionally a user-supplied value can be used
+	 * (even if standard doesn't mention this). */
+	if ((!icv && CRYPTO_memcmp(aiv, default_aiv, 4))
+		|| (icv && CRYPTO_memcmp(aiv, icv, 4)))
+		{
+		OPENSSL_cleanse(out, inlen);
+		return 0;
+		}
+
+	/* Check that 8*(n-1) < LSB(32,AIV) <= 8*n.
+	 * If so, let ptext_len = LSB(32,AIV). */
+
+	ptext_len = (aiv[4] << 24) | (aiv[5] << 16) | (aiv[6] << 8) | aiv[7];
+	if (8*(n-1) >= ptext_len || ptext_len > 8*n)
+		{
+		OPENSSL_cleanse(out, inlen);
+		return 0;
+		}
+
+	/* Check that the rightmost padding_len octets of the output data
+	 * are zero. */
+	padding_len = padded_len - ptext_len;
+	if (CRYPTO_memcmp(out + ptext_len, zeros, padding_len) != 0)
+		{
+		OPENSSL_cleanse(out, inlen);
+		return 0;
+		}
+
+	/* Section 4.2 step 3: Remove padding */
+	return ptext_len;
+	}