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annotate libtomcrypt/src/encauth/chachapoly/chacha20poly1305_decrypt.c @ 1820:e9854650d45b

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Clarify help text for dropbear -e environment option
author Matt Johnston <matt@ucc.asn.au>
date Thu, 19 Aug 2021 23:17:34 +0800
parents 6dba84798cd5
children
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1471
6dba84798cd5 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_CHACHA20POLY1305_MODE
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13
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14 /**
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15 Decrypt bytes of ciphertext with ChaCha20Poly1305
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16 @param st The ChaCha20Poly1305 state
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17 @param in The ciphertext
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18 @param inlen The length of the input (octets)
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19 @param out [out] The plaintext (length inlen)
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20 @return CRYPT_OK if successful
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21 */
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22 int chacha20poly1305_decrypt(chacha20poly1305_state *st, const unsigned char *in, unsigned long inlen, unsigned char *out)
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23 {
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24 unsigned char padzero[16] = { 0 };
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25 unsigned long padlen;
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26 int err;
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27
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28 if (inlen == 0) return CRYPT_OK; /* nothing to do */
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29 LTC_ARGCHK(st != NULL);
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30
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31 if (st->aadflg) {
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32 padlen = 16 - (unsigned long)(st->aadlen % 16);
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33 if (padlen < 16) {
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34 if ((err = poly1305_process(&st->poly, padzero, padlen)) != CRYPT_OK) return err;
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35 }
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36 st->aadflg = 0; /* no more AAD */
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37 }
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38 if (st->aadflg) st->aadflg = 0; /* no more AAD */
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39 if ((err = poly1305_process(&st->poly, in, inlen)) != CRYPT_OK) return err;
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40 if ((err = chacha_crypt(&st->chacha, in, inlen, out)) != CRYPT_OK) return err;
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41 st->ctlen += (ulong64)inlen;
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42 return CRYPT_OK;
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43 }
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44
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45 #endif
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46
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47 /* ref: $Format:%D$ */
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48 /* git commit: $Format:%H$ */
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49 /* commit time: $Format:%ai$ */