50 lines
1.1 KiB
C
50 lines
1.1 KiB
C
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#include <string.h>
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#include "crypto_sign.h"
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#include "crypto_verify_32.h"
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#include "crypto_hash_sha512.h"
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#include "ge25519.h"
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int crypto_sign_open(
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unsigned char *m,unsigned long long *mlen,
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const unsigned char *sm,unsigned long long smlen,
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const unsigned char *pk
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)
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{
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unsigned char pkcopy[32];
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unsigned char rcopy[32];
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unsigned char hram[64];
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unsigned char rcheck[32];
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ge25519 get1, get2;
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sc25519 schram, scs;
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if (smlen < 64) goto badsig;
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if (sm[63] & 224) goto badsig;
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if (ge25519_unpackneg_vartime(&get1,pk)) goto badsig;
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memmove(pkcopy,pk,32);
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memmove(rcopy,sm,32);
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sc25519_from32bytes(&scs, sm+32);
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memmove(m,sm,smlen);
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memmove(m + 32,pkcopy,32);
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crypto_hash_sha512(hram,m,smlen);
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sc25519_from64bytes(&schram, hram);
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ge25519_double_scalarmult_vartime(&get2, &get1, &schram, &scs);
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ge25519_pack(rcheck, &get2);
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if (crypto_verify_32(rcopy,rcheck) == 0) {
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memmove(m,m + 64,smlen - 64);
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memset(m + smlen - 64,0,64);
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*mlen = smlen - 64;
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return 0;
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}
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badsig:
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*mlen = (unsigned long long) -1;
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memset(m,0,smlen);
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return -1;
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}
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