/* Targeted runtime checks for the vendored libssh2 security backports.
 * SPDX-License-Identifier: MIT
 * This program deliberately supplies boundary lengths, without any network.
 */
#include <limits.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include <openssl/evp.h>
#include "libssh2.h"

/* Internal function from the statically linked, patched OpenSSL backend. */
extern int _libssh2_cipher_crypt(EVP_CIPHER_CTX **ctx,
                               const EVP_CIPHER *(*algo)(void),
                               int encrypt, unsigned char *block,
                               size_t blocksize, int firstlast);

static int check_crypto_bounds(void)
{
    unsigned char buffer[EVP_MAX_BLOCK_LENGTH + 32];
    unsigned char original[sizeof(buffer)];
    size_t length;
    memset(buffer, 0xa5, sizeof(buffer));
    memcpy(original, buffer, sizeof(buffer));

    /* A complete AES-GCM block requires 4 bytes of AAD plus a 16-byte tag.
     * A null context makes an accidental call into OpenSSL fail immediately;
     * a correct bounds check rejects these inputs before touching it. */
    for(length = 0; length < 20; length++) {
        if(_libssh2_cipher_crypt(NULL, EVP_aes_128_gcm, 0, buffer,
                                 length, 3) != 1)
            return 1;
    }
    if(_libssh2_cipher_crypt(NULL, EVP_aes_128_gcm, 0, buffer,
                             sizeof(buffer), 3) != 1)
        return 1;
    if(_libssh2_cipher_crypt(NULL, EVP_aes_128_gcm, 0, buffer,
                             SIZE_MAX, 3) != 1)
        return 1;
    return memcmp(buffer, original, sizeof(buffer)) != 0;
}

static int check_username_bounds(void)
{
    LIBSSH2_SESSION *session = libssh2_session_init();
    int failure = 0;
    if(!session)
        return 1;
    if(libssh2_userauth_list(session, "x", UINT_MAX) != NULL ||
       libssh2_session_last_errno(session) != LIBSSH2_ERROR_PROTO)
        failure = 1;
    if(libssh2_userauth_password_ex(session, "x", UINT_MAX, "p", 1,
                                   NULL) != LIBSSH2_ERROR_PROTO)
        failure = 1;
    libssh2_session_free(session);
    return failure;
}

int main(void)
{
    int failure;
    if(libssh2_init(0) != 0)
        return 1;
    failure = check_crypto_bounds() | check_username_bounds();
    libssh2_exit();
    if(failure) {
        fputs("libssh2 security boundary regression failed\n", stderr);
        return 1;
    }
    puts("libssh2 security boundaries: AES-GCM short/oversized blocks and overflowing username lengths PASS");
    return 0;
}