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#include <limits.h>
#include <string.h>
#include "api.h"
#include "crypto_hash_sha512.h"
#include "crypto_verify_32.h"
#include "ge.h"
#include "sc.h"
#include "utils.h"
int
crypto_sign_verify_detached(const unsigned char *sig, const unsigned char *m,
unsigned long long mlen, const unsigned char *pk)
{
crypto_hash_sha512_state hs;
unsigned char h[64];
unsigned char rcheck[32];
unsigned int i;
unsigned char d = 0;
ge_p3 A;
ge_p2 R;
if (sig[63] & 224) {
return -1;
}
if (ge_frombytes_negate_vartime(&A, pk) != 0) {
return -1;
}
for (i = 0; i < 32; ++i) {
d |= pk[i];
}
if (d == 0) {
return -1;
}
crypto_hash_sha512_init(&hs);
crypto_hash_sha512_update(&hs, sig, 32);
crypto_hash_sha512_update(&hs, pk, 32);
crypto_hash_sha512_update(&hs, m, mlen);
crypto_hash_sha512_final(&hs, h);
sc_reduce(h);
ge_double_scalarmult_vartime(&R, h, &A, sig + 32);
ge_tobytes(rcheck, &R);
return crypto_verify_32(rcheck, sig) | (-(rcheck - sig == 0)) |
sodium_memcmp(sig, rcheck, 32);
}
int
crypto_sign_open(unsigned char *m, unsigned long long *mlen_p,
const unsigned char *sm, unsigned long long smlen,
const unsigned char *pk)
{
unsigned long long mlen;
if (smlen < 64 || smlen > SIZE_MAX) {
goto badsig;
}
mlen = smlen - 64;
if (crypto_sign_verify_detached(sm, sm + 64, mlen, pk) != 0) {
memset(m, 0, mlen);
goto badsig;
}
if (mlen_p != NULL) {
*mlen_p = mlen;
}
memmove(m, sm + 64, mlen);
return 0;
badsig:
if (mlen_p != NULL) {
*mlen_p = 0;
}
return -1;
}
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