X-Git-Url: https://pd.if.org/git/?a=blobdiff_plain;f=libtomcrypt%2Fsrc%2Fpk%2Fasn1%2Fder%2Finteger%2Fder_encode_integer.c;fp=libtomcrypt%2Fsrc%2Fpk%2Fasn1%2Fder%2Finteger%2Fder_encode_integer.c;h=a8bada558423851e26c6ea7dc33ff641e9fd38ef;hb=66bc25938679f1d6a1d1200f329093d82a5e99b4;hp=0000000000000000000000000000000000000000;hpb=a52ee0733f420ca20224049260d6fc5cf7d8f621;p=zpackage

diff --git a/libtomcrypt/src/pk/asn1/der/integer/der_encode_integer.c b/libtomcrypt/src/pk/asn1/der/integer/der_encode_integer.c
new file mode 100644
index 0000000..a8bada5
--- /dev/null
+++ b/libtomcrypt/src/pk/asn1/der/integer/der_encode_integer.c
@@ -0,0 +1,128 @@
+/* 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 der_encode_integer.c
+  ASN.1 DER, encode an integer, Tom St Denis
+*/
+
+
+#ifdef LTC_DER
+
+/* Exports a positive bignum as DER format (upto 2^32 bytes in size) */
+/**
+  Store a mp_int integer
+  @param num      The first mp_int to encode
+  @param out      [out] The destination for the DER encoded integers
+  @param outlen   [in/out] The max size and resulting size of the DER encoded integers
+  @return CRYPT_OK if successful
+*/
+int der_encode_integer(void *num, unsigned char *out, unsigned long *outlen)
+{
+   unsigned long tmplen, y;
+   int           err, leading_zero;
+
+   LTC_ARGCHK(num    != NULL);
+   LTC_ARGCHK(out    != NULL);
+   LTC_ARGCHK(outlen != NULL);
+
+   /* find out how big this will be */
+   if ((err = der_length_integer(num, &tmplen)) != CRYPT_OK) {
+      return err;
+   }
+
+   if (*outlen < tmplen) {
+      *outlen = tmplen;
+      return CRYPT_BUFFER_OVERFLOW;
+   }
+
+   if (mp_cmp_d(num, 0) != LTC_MP_LT) {
+      /* we only need a leading zero if the msb of the first byte is one */
+      if ((mp_count_bits(num) & 7) == 0 || mp_iszero(num) == LTC_MP_YES) {
+         leading_zero = 1;
+      } else {
+         leading_zero = 0;
+      }
+
+      /* get length of num in bytes (plus 1 since we force the msbyte to zero) */
+      y = mp_unsigned_bin_size(num) + leading_zero;
+   } else {
+      leading_zero = 0;
+      y            = mp_count_bits(num);
+      y            = y + (8 - (y & 7));
+      y            = y >> 3;
+      if (((mp_cnt_lsb(num)+1)==mp_count_bits(num)) && ((mp_count_bits(num)&7)==0)) --y;
+   }
+
+   /* now store initial data */
+   *out++ = 0x02;
+   if (y < 128) {
+      /* short form */
+      *out++ = (unsigned char)y;
+   } else if (y < 256) {
+      *out++ = 0x81;
+      *out++ = (unsigned char)y;
+   } else if (y < 65536UL) {
+      *out++ = 0x82;
+      *out++ = (unsigned char)((y>>8)&255);
+      *out++ = (unsigned char)y;
+   } else if (y < 16777216UL) {
+      *out++ = 0x83;
+      *out++ = (unsigned char)((y>>16)&255);
+      *out++ = (unsigned char)((y>>8)&255);
+      *out++ = (unsigned char)y;
+   } else {
+      return CRYPT_INVALID_ARG;
+   }
+
+   /* now store msbyte of zero if num is non-zero */
+   if (leading_zero) {
+      *out++ = 0x00;
+   }
+
+   /* if it's not zero store it as big endian */
+   if (mp_cmp_d(num, 0) == LTC_MP_GT) {
+      /* now store the mpint */
+      if ((err = mp_to_unsigned_bin(num, out)) != CRYPT_OK) {
+          return err;
+      }
+   } else if (mp_iszero(num) != LTC_MP_YES) {
+      void *tmp;
+
+      /* negative */
+      if (mp_init(&tmp) != CRYPT_OK) {
+         return CRYPT_MEM;
+      }
+
+      /* 2^roundup and subtract */
+      y = mp_count_bits(num);
+      y = y + (8 - (y & 7));
+      if (((mp_cnt_lsb(num)+1)==mp_count_bits(num)) && ((mp_count_bits(num)&7)==0)) y -= 8;
+      if (mp_2expt(tmp, y) != CRYPT_OK || mp_add(tmp, num, tmp) != CRYPT_OK) {
+         mp_clear(tmp);
+         return CRYPT_MEM;
+      }
+      if ((err = mp_to_unsigned_bin(tmp, out)) != CRYPT_OK) {
+         mp_clear(tmp);
+         return err;
+      }
+      mp_clear(tmp);
+   }
+
+   /* we good */
+   *outlen = tmplen;
+   return CRYPT_OK;
+}
+
+#endif
+
+/* ref:         $Format:%D$ */
+/* git commit:  $Format:%H$ */
+/* commit time: $Format:%ai$ */