Mercurial > dropbear
view libtomcrypt/src/pk/asn1/der/short_integer/der_encode_short_integer.c @ 791:0bf76f54de6f
Limit decompressed size
author | Matt Johnston <matt@ucc.asn.au> |
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date | Wed, 08 May 2013 23:23:14 +0800 |
parents | 0cbe8f6dbf9e |
children | f849a5ca2efc |
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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. * * Tom St Denis, [email protected], http://libtomcrypt.com */ #include "tomcrypt.h" /** @file der_encode_short_integer.c ASN.1 DER, encode an integer, Tom St Denis */ #ifdef LTC_DER /** Store a short integer in the range (0,2^32-1) @param num The integer 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_short_integer(unsigned long num, unsigned char *out, unsigned long *outlen) { unsigned long len, x, y, z; int err; LTC_ARGCHK(out != NULL); LTC_ARGCHK(outlen != NULL); /* force to 32 bits */ num &= 0xFFFFFFFFUL; /* find out how big this will be */ if ((err = der_length_short_integer(num, &len)) != CRYPT_OK) { return err; } if (*outlen < len) { *outlen = len; return CRYPT_BUFFER_OVERFLOW; } /* get len of output */ z = 0; y = num; while (y) { ++z; y >>= 8; } /* handle zero */ if (z == 0) { z = 1; } /* see if msb is set */ z += (num&(1UL<<((z<<3) - 1))) ? 1 : 0; /* adjust the number so the msB is non-zero */ for (x = 0; (z <= 4) && (x < (4 - z)); x++) { num <<= 8; } /* store header */ x = 0; out[x++] = 0x02; out[x++] = (unsigned char)z; /* if 31st bit is set output a leading zero and decrement count */ if (z == 5) { out[x++] = 0; --z; } /* store values */ for (y = 0; y < z; y++) { out[x++] = (unsigned char)((num >> 24) & 0xFF); num <<= 8; } /* we good */ *outlen = x; return CRYPT_OK; } #endif /* $Source: /cvs/libtom/libtomcrypt/src/pk/asn1/der/short_integer/der_encode_short_integer.c,v $ */ /* $Revision: 1.7 $ */ /* $Date: 2006/12/04 21:34:03 $ */