--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libtomcrypt/src/pk/pkcs1/pkcs_1_v1_5_decode.c	Sat Feb 03 08:20:30 2007 +0000
@@ -0,0 +1,110 @@
+/* LibTomCrypt, modular cryptographic library -- Tom St Denis
+ *
+ * LibTomCrypt is a library that provides various cryptographic
+ * algorithms in a highly modular and flexible manner.
+ *
+ * The library is free for all purposes without any express
+ * guarantee it works.
+ *
+ * Tom St Denis, [email protected], http://libtomcrypt.com
+ */
+#include "tomcrypt.h"
+
+/** @file pkcs_1_v1_5_decode.c
+ *
+ *  PKCS #1 v1.5 Padding. (Andreas Lange)
+ */
+
+#ifdef PKCS_1
+
+/** @brief PKCS #1 v1.5 decode.
+ *
+ *  @param msg              The encoded data to decode
+ *  @param msglen           The length of the encoded data (octets)
+ *  @param block_type       Block type to use in padding (\sa ltc_pkcs_1_v1_5_blocks)
+ *  @param modulus_bitlen   The bit length of the RSA modulus
+ *  @param out              [out] Destination of decoding
+ *  @param outlen           [in/out] The max size and resulting size of the decoding
+ *  @param is_valid         [out] Boolean whether the padding was valid
+ *
+ *  @return CRYPT_OK if successful (even if invalid)
+ */
+int pkcs_1_v1_5_decode(const unsigned char *msg, 
+                             unsigned long  msglen,
+                                       int  block_type,
+                             unsigned long  modulus_bitlen,
+                             unsigned char *out, 
+                             unsigned long *outlen,
+                                       int *is_valid)
+{
+  unsigned long modulus_len, ps_len, i;
+  int result;
+
+  /* default to invalid packet */
+  *is_valid = 0;
+
+  modulus_len = (modulus_bitlen >> 3) + (modulus_bitlen & 7 ? 1 : 0);
+
+  /* test message size */
+
+  if ((msglen > modulus_len) || (modulus_len < 11)) {
+    return CRYPT_PK_INVALID_SIZE;
+  }
+
+  /* separate encoded message */
+
+  if ((msg[0] != 0x00) || (msg[1] != (unsigned char)block_type)) {
+    result = CRYPT_INVALID_PACKET;
+    goto bail;
+  }
+
+  if (block_type == LTC_PKCS_1_EME) {
+    for (i = 2; i < modulus_len; i++) {
+      /* separator */
+      if (msg[i] == 0x00) { break; }
+    }
+    ps_len = i++ - 2;
+
+    if ((i >= modulus_len) || (ps_len < 8)) {
+      /* There was no octet with hexadecimal value 0x00 to separate ps from m,
+       * or the length of ps is less than 8 octets.
+       */
+      result = CRYPT_INVALID_PACKET;
+      goto bail;
+    }
+  } else {
+    for (i = 2; i < modulus_len - 1; i++) {
+       if (msg[i] != 0xFF) { break; }
+    }
+
+    /* separator check */
+    if (msg[i] != 0) {
+      /* There was no octet with hexadecimal value 0x00 to separate ps from m. */
+      result = CRYPT_INVALID_PACKET;
+      goto bail;
+    }
+
+    ps_len = i - 2;
+  }
+
+  if (*outlen < (msglen - (2 + ps_len + 1))) {
+    *outlen = msglen - (2 + ps_len + 1);
+    result = CRYPT_BUFFER_OVERFLOW;
+    goto bail;
+  }
+
+  *outlen = (msglen - (2 + ps_len + 1));
+  XMEMCPY(out, &msg[2 + ps_len + 1], *outlen);
+
+  /* valid packet */
+  *is_valid = 1;
+  result    = CRYPT_OK;
+bail:
+  return result;
+} /* pkcs_1_v1_5_decode */
+
+#endif /* #ifdef PKCS_1 */
+
+/* $Source: /cvs/libtom/libtomcrypt/src/pk/pkcs1/pkcs_1_v1_5_decode.c,v $ */
+/* $Revision: 1.5 $ */
+/* $Date: 2006/12/16 17:41:21 $ */