Mercurial > dropbear
annotate libtomcrypt/src/pk/dh/dh_shared_secret.c @ 1652:d2753238f35f
Added signature for changeset ebcdb893992d
author | Matt Johnston <matt@ucc.asn.au> |
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date | Wed, 27 Mar 2019 22:15:23 +0800 |
parents | 6dba84798cd5 |
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Update to libtomcrypt 1.18.1, merged with Dropbear changes
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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 |
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10 #include "tomcrypt.h" |
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11 |
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12 #ifdef LTC_MDH |
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13 |
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14 /** |
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15 Create a DH shared secret. |
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16 @param private_key The private DH key in the pair |
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17 @param public_key The public DH key in the pair |
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18 @param out [out] The destination of the shared data |
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19 @param outlen [in/out] The max size and resulting size of the shared data. |
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20 @return CRYPT_OK if successful |
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21 */ |
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22 int dh_shared_secret(dh_key *private_key, dh_key *public_key, |
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23 unsigned char *out, unsigned long *outlen) |
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24 { |
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25 void *tmp; |
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26 unsigned long x; |
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27 int err; |
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28 |
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29 LTC_ARGCHK(private_key != NULL); |
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30 LTC_ARGCHK(public_key != NULL); |
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31 LTC_ARGCHK(out != NULL); |
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32 LTC_ARGCHK(outlen != NULL); |
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33 |
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34 /* types valid? */ |
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35 if (private_key->type != PK_PRIVATE) { |
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36 return CRYPT_PK_NOT_PRIVATE; |
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37 } |
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38 |
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39 /* same DH group? */ |
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40 if (mp_cmp(private_key->prime, public_key->prime) != LTC_MP_EQ) { return CRYPT_PK_TYPE_MISMATCH; } |
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41 if (mp_cmp(private_key->base, public_key->base) != LTC_MP_EQ) { return CRYPT_PK_TYPE_MISMATCH; } |
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42 |
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43 /* init big numbers */ |
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44 if ((err = mp_init(&tmp)) != CRYPT_OK) { |
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45 return err; |
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46 } |
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47 |
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48 /* check public key */ |
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49 if ((err = dh_check_pubkey(public_key)) != CRYPT_OK) { |
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50 goto error; |
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51 } |
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52 |
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53 /* compute tmp = y^x mod p */ |
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54 if ((err = mp_exptmod(public_key->y, private_key->x, private_key->prime, tmp)) != CRYPT_OK) { |
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55 goto error; |
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56 } |
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57 |
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58 /* enough space for output? */ |
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59 x = (unsigned long)mp_unsigned_bin_size(tmp); |
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60 if (*outlen < x) { |
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61 *outlen = x; |
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62 err = CRYPT_BUFFER_OVERFLOW; |
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63 goto error; |
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64 } |
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65 if ((err = mp_to_unsigned_bin(tmp, out)) != CRYPT_OK) { |
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66 goto error; |
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67 } |
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68 *outlen = x; |
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69 err = CRYPT_OK; |
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70 |
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71 error: |
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72 mp_clear(tmp); |
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73 return err; |
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74 } |
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75 |
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76 #endif /* LTC_MDH */ |
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77 |
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78 /* ref: $Format:%D$ */ |
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79 /* git commit: $Format:%H$ */ |
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80 /* commit time: $Format:%ai$ */ |