/*      $OpenBSD: fuzz.c,v 1.3 2025/05/22 04:34:18 bluhm Exp $  */
/*
 * Copyright (c) 2011 Damien Miller <djm@mindrot.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

/* Utility functions/framework for fuzz tests */

#include <sys/types.h>

#include <assert.h>
#include <ctype.h>
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>

#include "test_helper.h"

/* #define FUZZ_DEBUG */

#ifdef FUZZ_DEBUG
# define FUZZ_DBG(x) do { \
                printf("%s:%d %s: ", __FILE__, __LINE__, __func__); \
                printf x; \
                printf("\n"); \
                fflush(stdout); \
        } while (0)
#else
# define FUZZ_DBG(x)
#endif

/* For brevity later */
typedef unsigned long long fuzz_ullong;

/* For base-64 fuzzing */
static const char fuzz_b64chars[] =
    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

struct fuzz {
        /* Fuzz method currently in use */
        int strategy;

        /* Fuzz methods remaining */
        int strategies;

        /* Original seed data blob */
        void *seed;
        size_t slen;

        /* Current working copy of seed with fuzz mutations applied */
        u_char *fuzzed;

        /* Used by fuzz methods */
        size_t o1, o2;
};

static const char *
fuzz_ntop(u_int n)
{
        switch (n) {
        case 0:
                return "NONE";
        case FUZZ_1_BIT_FLIP:
                return "FUZZ_1_BIT_FLIP";
        case FUZZ_2_BIT_FLIP:
                return "FUZZ_2_BIT_FLIP";
        case FUZZ_1_BYTE_FLIP:
                return "FUZZ_1_BYTE_FLIP";
        case FUZZ_2_BYTE_FLIP:
                return "FUZZ_2_BYTE_FLIP";
        case FUZZ_TRUNCATE_START:
                return "FUZZ_TRUNCATE_START";
        case FUZZ_TRUNCATE_END:
                return "FUZZ_TRUNCATE_END";
        case FUZZ_BASE64:
                return "FUZZ_BASE64";
        default:
                abort();
        }
}

void
fuzz_dump(struct fuzz *fuzz)
{
        u_char *p = fuzz_ptr(fuzz);
        size_t i, j, len = fuzz_len(fuzz);

        switch (fuzz->strategy) {
        case FUZZ_1_BIT_FLIP:
                fprintf(stderr, "%s case %zu of %zu (bit: %zu)\n",
                    fuzz_ntop(fuzz->strategy),
                    fuzz->o1, fuzz->slen * 8, fuzz->o1);
                break;
        case FUZZ_2_BIT_FLIP:
                fprintf(stderr, "%s case %llu of %llu (bits: %zu, %zu)\n",
                    fuzz_ntop(fuzz->strategy),
                    (((fuzz_ullong)fuzz->o2) * fuzz->slen * 8) + fuzz->o1,
                    ((fuzz_ullong)fuzz->slen * 8) * fuzz->slen * 8,
                    fuzz->o1, fuzz->o2);
                break;
        case FUZZ_1_BYTE_FLIP:
                fprintf(stderr, "%s case %zu of %zu (byte: %zu)\n",
                    fuzz_ntop(fuzz->strategy),
                    fuzz->o1, fuzz->slen, fuzz->o1);
                break;
        case FUZZ_2_BYTE_FLIP:
                fprintf(stderr, "%s case %llu of %llu (bytes: %zu, %zu)\n",
                    fuzz_ntop(fuzz->strategy),
                    (((fuzz_ullong)fuzz->o2) * fuzz->slen) + fuzz->o1,
                    ((fuzz_ullong)fuzz->slen) * fuzz->slen,
                    fuzz->o1, fuzz->o2);
                break;
        case FUZZ_TRUNCATE_START:
                fprintf(stderr, "%s case %zu of %zu (offset: %zu)\n",
                    fuzz_ntop(fuzz->strategy),
                    fuzz->o1, fuzz->slen, fuzz->o1);
                break;
        case FUZZ_TRUNCATE_END:
                fprintf(stderr, "%s case %zu of %zu (offset: %zu)\n",
                    fuzz_ntop(fuzz->strategy),
                    fuzz->o1, fuzz->slen, fuzz->o1);
                break;
        case FUZZ_BASE64:
                assert(fuzz->o2 < sizeof(fuzz_b64chars) - 1);
                fprintf(stderr, "%s case %llu of %llu (offset: %zu char: %c)\n",
                    fuzz_ntop(fuzz->strategy),
                    (fuzz->o1 * (fuzz_ullong)64) + fuzz->o2,
                    fuzz->slen * (fuzz_ullong)64, fuzz->o1,
                    fuzz_b64chars[fuzz->o2]);
                break;
        default:
                abort();
        }

        fprintf(stderr, "fuzz context %p len = %zu\n", fuzz, len);
        for (i = 0; i < len; i += 16) {
                fprintf(stderr, "%.4zd: ", i);
                for (j = i; j < i + 16; j++) {
                        if (j < len)
                                fprintf(stderr, "%02x ", p[j]);
                        else
                                fprintf(stderr, "   ");
                }
                fprintf(stderr, " ");
                for (j = i; j < i + 16; j++) {
                        if (j < len) {
                                if  (isascii(p[j]) && isprint(p[j]))
                                        fprintf(stderr, "%c", p[j]);
                                else
                                        fprintf(stderr, ".");
                        }
                }
                fprintf(stderr, "\n");
        }
}

struct fuzz *
fuzz_begin(u_int strategies, void *p, size_t l)
{
        struct fuzz *ret = calloc(sizeof(*ret), 1);

        assert(p != NULL);
        assert(ret != NULL);
        ret->seed = malloc(l);
        assert(ret->seed != NULL);
        memcpy(ret->seed, p, l);
        ret->slen = l;
        ret->strategies = strategies;

        assert(ret->slen < SIZE_MAX / 8);
        assert(ret->strategies <= (FUZZ_MAX|(FUZZ_MAX-1)));

        FUZZ_DBG(("begin, ret = %p", ret));

        fuzz_next(ret);
        return ret;
}

void
fuzz_cleanup(struct fuzz *fuzz)
{
        FUZZ_DBG(("cleanup, fuzz = %p", fuzz));
        assert(fuzz != NULL);
        assert(fuzz->seed != NULL);
        assert(fuzz->fuzzed != NULL);
        free(fuzz->seed);
        free(fuzz->fuzzed);
        free(fuzz);
}

static int
fuzz_strategy_done(struct fuzz *fuzz)
{
        FUZZ_DBG(("fuzz = %p, strategy = %s, o1 = %zu, o2 = %zu, slen = %zu",
            fuzz, fuzz_ntop(fuzz->strategy), fuzz->o1, fuzz->o2, fuzz->slen));

        switch (fuzz->strategy) {
        case FUZZ_1_BIT_FLIP:
                return fuzz->o1 >= fuzz->slen * 8;
        case FUZZ_2_BIT_FLIP:
                return fuzz->o2 >= fuzz->slen * 8;
        case FUZZ_2_BYTE_FLIP:
                return fuzz->o2 >= fuzz->slen;
        case FUZZ_1_BYTE_FLIP:
        case FUZZ_TRUNCATE_START:
        case FUZZ_TRUNCATE_END:
        case FUZZ_BASE64:
                return fuzz->o1 >= fuzz->slen;
        default:
                abort();
        }
}

void
fuzz_next(struct fuzz *fuzz)
{
        u_int i;

        FUZZ_DBG(("start, fuzz = %p, strategy = %s, strategies = 0x%lx, "
            "o1 = %zu, o2 = %zu, slen = %zu", fuzz, fuzz_ntop(fuzz->strategy),
            (u_long)fuzz->strategies, fuzz->o1, fuzz->o2, fuzz->slen));

        if (fuzz->strategy == 0 || fuzz_strategy_done(fuzz)) {
                /* If we are just starting out, we need to allocate too */
                if (fuzz->fuzzed == NULL) {
                        FUZZ_DBG(("alloc"));
                        fuzz->fuzzed = calloc(fuzz->slen, 1);
                }
                /* Pick next strategy */
                FUZZ_DBG(("advance"));
                for (i = 1; i <= FUZZ_MAX; i <<= 1) {
                        if ((fuzz->strategies & i) != 0) {
                                fuzz->strategy = i;
                                break;
                        }
                }
                FUZZ_DBG(("selected = %u", fuzz->strategy));
                if (fuzz->strategy == 0) {
                        FUZZ_DBG(("done, no more strategies"));
                        return;
                }
                fuzz->strategies &= ~(fuzz->strategy);
                fuzz->o1 = fuzz->o2 = 0;
        }

        assert(fuzz->fuzzed != NULL);

        switch (fuzz->strategy) {
        case FUZZ_1_BIT_FLIP:
                assert(fuzz->o1 / 8 < fuzz->slen);
                memcpy(fuzz->fuzzed, fuzz->seed, fuzz->slen);
                fuzz->fuzzed[fuzz->o1 / 8] ^= 1 << (fuzz->o1 % 8);
                fuzz->o1++;
                break;
        case FUZZ_2_BIT_FLIP:
                assert(fuzz->o1 / 8 < fuzz->slen);
                assert(fuzz->o2 / 8 < fuzz->slen);
                memcpy(fuzz->fuzzed, fuzz->seed, fuzz->slen);
                fuzz->fuzzed[fuzz->o1 / 8] ^= 1 << (fuzz->o1 % 8);
                fuzz->fuzzed[fuzz->o2 / 8] ^= 1 << (fuzz->o2 % 8);
                fuzz->o1++;
                if (fuzz->o1 >= fuzz->slen * 8) {
                        fuzz->o1 = 0;
                        fuzz->o2++;
                }
                break;
        case FUZZ_1_BYTE_FLIP:
                assert(fuzz->o1 < fuzz->slen);
                memcpy(fuzz->fuzzed, fuzz->seed, fuzz->slen);
                fuzz->fuzzed[fuzz->o1] ^= 0xff;
                fuzz->o1++;
                break;
        case FUZZ_2_BYTE_FLIP:
                assert(fuzz->o1 < fuzz->slen);
                assert(fuzz->o2 < fuzz->slen);
                memcpy(fuzz->fuzzed, fuzz->seed, fuzz->slen);
                fuzz->fuzzed[fuzz->o1] ^= 0xff;
                fuzz->fuzzed[fuzz->o2] ^= 0xff;
                fuzz->o1++;
                if (fuzz->o1 >= fuzz->slen) {
                        fuzz->o1 = 0;
                        fuzz->o2++;
                }
                break;
        case FUZZ_TRUNCATE_START:
        case FUZZ_TRUNCATE_END:
                assert(fuzz->o1 < fuzz->slen);
                memcpy(fuzz->fuzzed, fuzz->seed, fuzz->slen);
                fuzz->o1++;
                break;
        case FUZZ_BASE64:
                assert(fuzz->o1 < fuzz->slen);
                assert(fuzz->o2 < sizeof(fuzz_b64chars) - 1);
                memcpy(fuzz->fuzzed, fuzz->seed, fuzz->slen);
                fuzz->fuzzed[fuzz->o1] = fuzz_b64chars[fuzz->o2];
                fuzz->o2++;
                if (fuzz->o2 >= sizeof(fuzz_b64chars) - 1) {
                        fuzz->o2 = 0;
                        fuzz->o1++;
                }
                break;
        default:
                abort();
        }

        FUZZ_DBG(("done, fuzz = %p, strategy = %s, strategies = 0x%lx, "
            "o1 = %zu, o2 = %zu, slen = %zu", fuzz, fuzz_ntop(fuzz->strategy),
            (u_long)fuzz->strategies, fuzz->o1, fuzz->o2, fuzz->slen));
}

int
fuzz_done(struct fuzz *fuzz)
{
        FUZZ_DBG(("fuzz = %p, strategies = 0x%lx", fuzz,
            (u_long)fuzz->strategies));

        return fuzz_strategy_done(fuzz) && fuzz->strategies == 0;
}

size_t
fuzz_len(struct fuzz *fuzz)
{
        assert(fuzz->fuzzed != NULL);
        switch (fuzz->strategy) {
        case FUZZ_1_BIT_FLIP:
        case FUZZ_2_BIT_FLIP:
        case FUZZ_1_BYTE_FLIP:
        case FUZZ_2_BYTE_FLIP:
        case FUZZ_BASE64:
                return fuzz->slen;
        case FUZZ_TRUNCATE_START:
        case FUZZ_TRUNCATE_END:
                assert(fuzz->o1 <= fuzz->slen);
                return fuzz->slen - fuzz->o1;
        default:
                abort();
        }
}

u_char *
fuzz_ptr(struct fuzz *fuzz)
{
        assert(fuzz->fuzzed != NULL);
        switch (fuzz->strategy) {
        case FUZZ_1_BIT_FLIP:
        case FUZZ_2_BIT_FLIP:
        case FUZZ_1_BYTE_FLIP:
        case FUZZ_2_BYTE_FLIP:
        case FUZZ_BASE64:
                return fuzz->fuzzed;
        case FUZZ_TRUNCATE_START:
                assert(fuzz->o1 <= fuzz->slen);
                return fuzz->fuzzed + fuzz->o1;
        case FUZZ_TRUNCATE_END:
                assert(fuzz->o1 <= fuzz->slen);
                return fuzz->fuzzed;
        default:
                abort();
        }
}