Re: [FFmpeg-devel] [PATCH v2] tools: add target_enc_fuzzer.c

[James Almer <jamrial@gmail.com>]

On 4/21/2024 2:05 PM, Michael Niedermayer wrote:
> Sponsored-by: Sovereign Tech Fund
> Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> ---
>   Makefile                  |   3 +
>   tools/Makefile            |   3 +
>   tools/target_enc_fuzzer.c | 201 ++++++++++++++++++++++++++++++++++++++
>   3 files changed, 207 insertions(+)
>   create mode 100644 tools/target_enc_fuzzer.c
> 
> diff --git a/Makefile b/Makefile
> index b309dbc4db9..de727cbe00e 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -52,6 +52,9 @@ $(TOOLS): %$(EXESUF): %.o
>   target_dec_%_fuzzer$(EXESUF): target_dec_%_fuzzer.o $(FF_DEP_LIBS)
>   	$(LD) $(LDFLAGS) $(LDEXEFLAGS) $(LD_O) $^ $(ELIBS) $(FF_EXTRALIBS) $(LIBFUZZER_PATH)
>   
> +target_enc_%_fuzzer$(EXESUF): target_enc_%_fuzzer.o $(FF_DEP_LIBS)
> +	$(LD) $(LDFLAGS) $(LDEXEFLAGS) $(LD_O) $^ $(ELIBS) $(FF_EXTRALIBS) $(LIBFUZZER_PATH)
> +
>   tools/target_bsf_%_fuzzer$(EXESUF): tools/target_bsf_%_fuzzer.o $(FF_DEP_LIBS)
>   	$(LD) $(LDFLAGS) $(LDEXEFLAGS) $(LD_O) $^ $(ELIBS) $(FF_EXTRALIBS) $(LIBFUZZER_PATH)
>   
> diff --git a/tools/Makefile b/tools/Makefile
> index 72e8e709a8d..2a11fa0ae62 100644
> --- a/tools/Makefile
> +++ b/tools/Makefile
> @@ -5,6 +5,9 @@ TOOLS-$(CONFIG_ZLIB) += cws2fws
>   tools/target_dec_%_fuzzer.o: tools/target_dec_fuzzer.c
>   	$(COMPILE_C) -DFFMPEG_DECODER=$*
>   
> +tools/target_enc_%_fuzzer.o: tools/target_enc_fuzzer.c
> +	$(COMPILE_C) -DFFMPEG_ENCODER=$*
> +
>   tools/target_bsf_%_fuzzer.o: tools/target_bsf_fuzzer.c
>   	$(COMPILE_C) -DFFMPEG_BSF=$*
>   
> diff --git a/tools/target_enc_fuzzer.c b/tools/target_enc_fuzzer.c
> new file mode 100644
> index 00000000000..43f5c4c133c
> --- /dev/null
> +++ b/tools/target_enc_fuzzer.c
> @@ -0,0 +1,201 @@
> +/*
> + * Copyright (c) 2024 Michael Niedermayer <michael-ffmpeg@niedermayer.cc>
> + *
> + * This file is part of FFmpeg.
> + *
> + * FFmpeg is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2.1 of the License, or (at your option) any later version.
> + *
> + * FFmpeg is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with FFmpeg; if not, write to the Free Software
> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
> + *
> + * Based on target_dec_fuzzer
> + */
> +
> +#include "config.h"
> +#include "libavutil/avassert.h"
> +#include "libavutil/avstring.h"
> +#include "libavutil/cpu.h"
> +#include "libavutil/imgutils.h"
> +#include "libavutil/intreadwrite.h"
> +#include "libavutil/mem.h"
> +
> +#include "libavcodec/avcodec.h"
> +#include "libavcodec/bytestream.h"
> +#include "libavcodec/codec_internal.h"
> +#include "libavformat/avformat.h"
> +
> +int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size);
> +
> +extern const FFCodec * codec_list[];
> +
> +static void error(const char *err)
> +{
> +    fprintf(stderr, "%s", err);
> +    exit(1);
> +}
> +
> +static const FFCodec *c = NULL;
> +
> +// Ensure we don't loop forever
> +const uint32_t maxiteration = 8096;
> +
> +
> +static int encode(AVCodecContext *enc_ctx, AVFrame *frame, AVPacket *pkt)
> +{
> +    int ret;
> +
> +    ret = avcodec_send_frame(enc_ctx, frame);
> +    if (ret < 0)
> +        return ret;
> +
> +    while (ret >= 0) {
> +        ret = avcodec_receive_packet(enc_ctx, pkt);
> +        if (ret == AVERROR(EAGAIN)) {
> +            return 0;
> +        } else if (ret < 0) {
> +            return ret;
> +        }
> +
> +        av_packet_unref(pkt);
> +    }
> +    av_assert0(0);
> +}
> +
> +int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
> +    uint64_t maxpixels_per_frame = 512 * 512;
> +    uint64_t maxpixels;
> +
> +    const uint8_t *end = data + size;
> +    uint32_t it = 0;
> +    uint64_t nb_samples = 0;
> +    AVDictionary *opts = NULL;
> +
> +    if (!c) {
> +#define ENCODER_SYMBOL0(CODEC) ff_##CODEC##_encoder
> +#define ENCODER_SYMBOL(CODEC) ENCODER_SYMBOL0(CODEC)
> +        extern FFCodec ENCODER_SYMBOL(FFMPEG_ENCODER);
> +        codec_list[0] = &ENCODER_SYMBOL(FFMPEG_ENCODER);
> +
> +        c = &ENCODER_SYMBOL(FFMPEG_ENCODER);
> +        av_log_set_level(AV_LOG_PANIC);
> +    }
> +
> +    av_assert0(c->p.type == AVMEDIA_TYPE_VIDEO);
> +
> +    maxpixels = maxpixels_per_frame * maxiteration;
> +
> +    maxpixels_per_frame  = FFMIN(maxpixels_per_frame , maxpixels);
> +
> +    AVCodecContext* ctx = avcodec_alloc_context3(&c->p);
> +    if (!ctx)
> +        error("Failed memory allocation");
> +
> +    if (ctx->max_pixels == 0 || ctx->max_pixels > maxpixels_per_frame)
> +        ctx->max_pixels = maxpixels_per_frame; //To reduce false positive OOM and hangs
> +
> +    ctx->pix_fmt = AV_PIX_FMT_YUV420P;
> +    if (size > 1024) {
> +        GetByteContext gbc;
> +        int flags;
> +        int64_t flags64;
> +
> +        size -= 1024;
> +        bytestream2_init(&gbc, data + size, 1024);
> +        ctx->width                              = bytestream2_get_le32(&gbc) & 0xFFFF;
> +        ctx->height                             = bytestream2_get_le32(&gbc) & 0xFFFF;
> +        ctx->bit_rate                           = bytestream2_get_le64(&gbc);
> +        ctx->gop_size                           = bytestream2_get_le32(&gbc) & 0x7FFFFFFF;
> +        ctx->max_b_frames                       = bytestream2_get_le32(&gbc) & 0x7FFFFFFF;
> +        ctx->time_base.num                      = bytestream2_get_le32(&gbc) & 0x7FFFFFFF;
> +        ctx->time_base.den                      = bytestream2_get_le32(&gbc) & 0x7FFFFFFF;
> +        ctx->framerate.num                      = bytestream2_get_le32(&gbc) & 0x7FFFFFFF;
> +        ctx->framerate.den                      = bytestream2_get_le32(&gbc) & 0x7FFFFFFF;
> +
> +        flags = bytestream2_get_byte(&gbc);
> +        if (flags & 2)
> +            ctx->strict_std_compliance = FF_COMPLIANCE_EXPERIMENTAL;
> +
> +        if (flags & 0x40)
> +            av_force_cpu_flags(0);
> +
> +        flags64 = bytestream2_get_le64(&gbc);
> +
> +        int npixfmts = 0;
> +        while (c->p.pix_fmts[npixfmts++] != AV_PIX_FMT_NONE)
> +            ;
> +        ctx->pix_fmt = c->p.pix_fmts[bytestream2_get_byte(&gbc) % npixfmts];
> +
> +        switch (c->p.id) {
> +        case AV_CODEC_ID_FFV1:{
> +            int coder = bytestream2_get_byte(&gbc)&3;
> +            if (coder == 3) coder = -2;
> +            av_dict_set_int(&opts, "coder", coder, 0);
> +            av_dict_set_int(&opts, "context", bytestream2_get_byte(&gbc)&1, 0);
> +            av_dict_set_int(&opts, "slicecrc", bytestream2_get_byte(&gbc)&1, 0);
> +            break;}
> +        }
> +    }
> +    if (ctx->width == 0 || av_image_check_size(ctx->width, ctx->height, 0, ctx))
> +        ctx->width = ctx->height = 64;
> +
> +    int res = avcodec_open2(ctx, &c->p, &opts);
> +    if (res < 0) {
> +        avcodec_free_context(&ctx);
> +        av_dict_free(&opts);
> +        return 0; // Failure of avcodec_open2() does not imply that a issue was found
> +    }
> +
> +
> +    AVFrame *frame = av_frame_alloc();
> +    AVPacket *avpkt = av_packet_alloc();
> +    if (!frame || !avpkt)
> +        error("Failed memory allocation");
> +
> +    frame->format = ctx->pix_fmt;
> +    frame->width  = ctx->width;
> +    frame->height = ctx->height;
> +
> +    while (data < end && it < maxiteration) {
> +        res = av_frame_get_buffer(frame, 0);
> +        if (res < 0)
> +            error("Failed av_frame_get_buffer");
> +        int frame_size = frame->buf[0]->size;
> +
> +        int buf_size = FFMIN(end-data, frame_size);
> +        memcpy(frame->buf[0]->data, data, buf_size);
> +        if (frame_size - buf_size)
> +            memset(frame->buf[0]->data + buf_size, 0, frame_size - buf_size);

This assumes av_frame_get_buffer() allocates a single buffer, which is 
not documented. Better do this in a loop for all potential buffers, like 
you're doing when freeing them below.

> +        data += buf_size;
> +
> +        frame->pts = nb_samples;
> +
> +        res = encode(ctx, frame, avpkt);
> +        if (res < 0)
> +            break;
> +        it++;
> +        for (int i=0; i<FF_ARRAY_ELEMS(frame->buf); i++)
> +            av_buffer_unref(&frame->buf[i]);
> +
> +        av_packet_unref(avpkt);
> +    }
> +
> +    encode(ctx, NULL, avpkt);
> +    av_packet_unref(avpkt);
> +
> +//     fprintf(stderr, "frames encoded: %"PRId64",  iterations: %d\n", nb_samples  , it);
> +
> +    av_frame_free(&frame);
> +    avcodec_free_context(&ctx);
> +    av_packet_free(&avpkt);
> +    av_dict_free(&opts);
> +    return 0;
> +}
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