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thirdparty/libtomcrypt/pk/pkcs1/pkcs_1_v1_5_decode.c

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+/* 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.
+ */
+#include "tomcrypt.h"
+
+/** @file pkcs_1_v1_5_decode.c
+ *
+ *  PKCS #1 v1.5 Padding. (Andreas Lange)
+ */
+
+#ifdef LTC_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
+ */
+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;
+  }
+
+  result = CRYPT_OK;
+
+  /* separate encoded message */
+
+  if ((msg[0] != 0x00) || (msg[1] != (unsigned char)block_type)) {
+    result = CRYPT_INVALID_PACKET;
+  }
+
+  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) {
+      /* There was no octet with hexadecimal value 0x00 to separate ps from m.
+       */
+      result = CRYPT_INVALID_PACKET;
+    }
+  } 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;
+    }
+
+    ps_len = i - 2;
+  }
+
+  if (ps_len < 8)
+  {
+    /* The length of ps is less than 8 octets.
+     */
+    result = CRYPT_INVALID_PACKET;
+  }
+
+  if (*outlen < (msglen - (2 + ps_len + 1))) {
+    result = CRYPT_INVALID_PACKET;
+  }
+
+  if (result == CRYPT_OK) {
+     *outlen = (msglen - (2 + ps_len + 1));
+     XMEMCPY(out, &msg[2 + ps_len + 1], *outlen);
+
+     /* valid packet */
+     *is_valid = 1;
+  }
+
+  return result;
+} /* pkcs_1_v1_5_decode */
+
+#endif /* #ifdef LTC_PKCS_1 */
+
+/* ref:         HEAD -> master, tag: v1.18.2 */
+/* git commit:  7e7eb695d581782f04b24dc444cbfde86af59853 */
+/* commit time: 2018-07-01 22:49:01 +0200 */