Mercurial > dropbear

annotate libtomcrypt/src/pk/asn1/der/integer/der_decode_integer.c @ 672:6c35ff40e496

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Ignore -q if SCP_PROGRESS isn't set
author Matt Johnston <matt@ucc.asn.au>
date Tue, 24 Apr 2012 22:05:55 +0800
parents 0cbe8f6dbf9e
children f849a5ca2efc
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1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis
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2 *
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3 * LibTomCrypt is a library that provides various cryptographic
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4 * algorithms in a highly modular and flexible manner.
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5 *
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6 * The library is free for all purposes without any express
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7 * guarantee it works.
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8 *
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9 * Tom St Denis, [email protected], http://libtomcrypt.com
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10 */
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11 #include "tomcrypt.h"
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12
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13 /**
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14 @file der_decode_integer.c
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15 ASN.1 DER, decode an integer, Tom St Denis
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16 */
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18
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19 #ifdef LTC_DER
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20
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21 /**
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22 Read a mp_int integer
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23 @param in The DER encoded data
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24 @param inlen Size of DER encoded data
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25 @param num The first mp_int to decode
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26 @return CRYPT_OK if successful
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27 */
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28 int der_decode_integer(const unsigned char *in, unsigned long inlen, void *num)
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29 {
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30 unsigned long x, y, z;
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31 int err;
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33 LTC_ARGCHK(num != NULL);
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34 LTC_ARGCHK(in != NULL);
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36 /* min DER INTEGER is 0x02 01 00 == 0 */
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37 if (inlen < (1 + 1 + 1)) {
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38 return CRYPT_INVALID_PACKET;
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39 }
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41 /* ok expect 0x02 when we AND with 0001 1111 [1F] */
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42 x = 0;
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43 if ((in[x++] & 0x1F) != 0x02) {
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44 return CRYPT_INVALID_PACKET;
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45 }
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47 /* now decode the len stuff */
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48 z = in[x++];
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49
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50 if ((z & 0x80) == 0x00) {
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51 /* short form */
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52
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53 /* will it overflow? */
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54 if (x + z > inlen) {
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55 return CRYPT_INVALID_PACKET;
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56 }
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57
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58 /* no so read it */
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59 if ((err = mp_read_unsigned_bin(num, (unsigned char *)in + x, z)) != CRYPT_OK) {
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60 return err;
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61 }
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62 } else {
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63 /* long form */
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64 z &= 0x7F;
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65
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66 /* will number of length bytes overflow? (or > 4) */
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67 if (((x + z) > inlen) || (z > 4) || (z == 0)) {
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68 return CRYPT_INVALID_PACKET;
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69 }