xmss-KAT-generator/ui/sign.c

#include <stdio.h>

#include "../params.h"
#include "../xmss.h"

#ifdef XMSSMT
    #define XMSS_PARSE_OID xmssmt_parse_oid
    #define XMSS_SIGN xmssmt_sign
#else
    #define XMSS_PARSE_OID xmss_parse_oid
    #define XMSS_SIGN xmss_sign
#endif

int main(int argc, char **argv) {
    FILE *keypair_file;
    FILE *m_file;

    xmss_params params;
    uint32_t oid_pk;
    uint32_t oid_sk;

    unsigned long long mlen;

    if (argc != 3) {
        fprintf(stderr, "Expected keypair and message filenames as two "
                        "parameters.\n"
                        "The keypair is updated with the changed state, "
                        "and the message + signature is output via stdout.\n");
        return -1;
    }

    keypair_file = fopen(argv[1], "r+b");
    if (keypair_file == NULL) {
        fprintf(stderr, "Could not open keypair file.\n");
        return -1;
    }

    m_file = fopen(argv[2], "rb");
    if (m_file == NULL) {
        fprintf(stderr, "Could not open message file.\n");
        return -1;
    }

    /* Find out the message length. */
    fseek(m_file, 0, SEEK_END);
    mlen = ftell(m_file);

    /* Read the OID from the public key, as we need its length to seek past it */
    fread(&oid_pk, 1, XMSS_OID_LEN, keypair_file);
    XMSS_PARSE_OID(&params, oid_pk);

    /* fseek past the public key */
    fseek(keypair_file, params.pk_bytes, SEEK_CUR);
    /* This is the OID we're actually going to use. Likely the same, but still. */
    fread(&oid_sk, 1, XMSS_OID_LEN, keypair_file);
    XMSS_PARSE_OID(&params, oid_sk);

    unsigned char sk[XMSS_OID_LEN + params.sk_bytes];
    unsigned char m[mlen];
    unsigned char sm[params.sig_bytes + mlen];
    unsigned long long smlen;

    /* fseek back to start of sk. */
    fseek(keypair_file, -((long int)XMSS_OID_LEN), SEEK_CUR);
    fseek(m_file, 0, SEEK_SET);
    fread(sk, 1, XMSS_OID_LEN + params.sk_bytes, keypair_file);
    fread(m, 1, mlen, m_file);

    XMSS_SIGN(sk, sm, &smlen, m, mlen);

    fseek(keypair_file, -((long int)params.sk_bytes), SEEK_CUR);
    fwrite(sk + XMSS_OID_LEN, 1, params.sk_bytes, keypair_file);
    fwrite(sm, 1, smlen, stdout);

    fclose(keypair_file);
    fclose(m_file);
}