ios-kernel-patch/make_kernel_patchfile.c

#include <data/common.h>
#include <data/find.h>
#include <data/binary.h>
#include <data/link.h>
#include "lambda.h"

extern unsigned char sandbox_o[];
extern unsigned int sandbox_o_len;

int patchfd;

static inline void patch_with_range(const char *name, addr_t addr, prange_t pr) {
    uint32_t len = strlen(name);
    write(patchfd, &len, sizeof(len));
    write(patchfd, name, len);
    write(patchfd, &addr, sizeof(addr));
    uint32_t size = pr.size; // size_t no good
    write(patchfd, &size, sizeof(size));
    write(patchfd, pr.start, pr.size);
}

#define patch(name, addr, typeof_to, to...) \
    ({ typeof_to to_[] = to; \
       patch_with_range(name, addr, (prange_t) {&to_[0], sizeof(to_)}); })

uint32_t find_dvp_struct_offset(struct binary *binary) {
    bool is_armv7 = binary->actual_cpusubtype == 9;
    range_t range = b_macho_segrange(binary, "__PRELINK_TEXT");
    addr_t derive_vnode_path = find_bof(range, find_int32(range, find_string(range, "path", 0, true), true), is_armv7);
    uint8_t byte = b_read8(binary, find_data((range_t){binary, derive_vnode_path, 1024}, !is_armv7 ? "00 00 50 e3 02 30 a0 11 - .. 00 94 e5" : "- .. 69 6a 46", 0, true));
    if(is_armv7) {
        return (4 | (byte >> 6)) << 2;
    } else {
        return byte;
    }
}

addr_t find_sysctl(struct binary *binary, const char *name) {
    addr_t cs = find_string(b_macho_segrange(binary, "__TEXT"), name, 0, true);
    addr_t csref = find_int32(b_macho_segrange(binary, "__DATA"), cs, true);
    return b_read32(binary, csref - 8);
}

void do_kernel(struct binary *binary, struct binary *sandbox) {
    //printf("%x\n", find_dvp_struct_offset(binary));

    bool is_armv7 = binary->actual_cpusubtype == 9;

    addr_t _kernel_pmap, _PE_i_can_has_debugger, _vn_getpath, _memcmp;
    bool four_dot_three;
    if(0) {
        _kernel_pmap = 0x8027e2dc;
        _PE_i_can_has_debugger = 0x80203f75;
        _vn_getpath = 0x8008d7bd;
        _memcmp = 0x8006558d;
        four_dot_three = true;
    } else {
        _kernel_pmap = b_sym(binary, "_kernel_pmap", false, true);
        _PE_i_can_has_debugger = b_sym(binary, "_PE_i_can_has_debugger", true, true);
        _vn_getpath = b_sym(binary, "_vn_getpath", true, true);
        _memcmp = b_sym(binary, "_memcmp", true, true);
        // a new symbol
        four_dot_three = b_sym(binary, "_vfs_getattr", false, false);
    }

    struct findmany *text = findmany_init(b_macho_segrange(binary, "__TEXT"));
#define spec2(armv7, armv6) (is_armv7 ? (armv7) : (armv6))
#define spec3(four_three, armv7, armv6) (four_dot_three ? (four_three) : spec2(armv7, armv6))

    addr_t nxei; findmany_add(&nxei, text, spec3("23 68 - c3 f8 24 84", "03 68 - c3 f8 20 24", "84 23 db 00 - d5 50 22 68"));
    addr_t vme; findmany_add(&vme, text, spec2("- 02 0f .. .. 63 08 03 f0 01 05 e3 0a 13 f0 01 03", "- .. .. .. .. .. 08 1e 1c .. 0a 01 22 .. 1c 16 40 .. 40"));
    addr_t vmp; findmany_add(&vmp, text, spec2("- 25 f0 04 05 .. e7 92 45 98 bf 02 99 .. d8", "?"));
    addr_t mystery = find_data(b_macho_segrange(binary, "__PRELINK_TEXT"), spec3("- f0 b5 03 af 4d f8 04 8d .. .. 03 78 80 46", "- 90 b5 01 af 14 29 .. .. .. .. 90 f8 00 c0", "???"), 0, true);
    addr_t dei; findmany_add(&dei, text, spec2("04 22 01 92 00 98 .. 49 -", "?"));
    addr_t tfp0; findmany_add(&tfp0, text, spec2("85 68 00 23 .. 93 .. 93 - 5c b9 02 a8 29 46 04 22", "85 68 .. 93 .. 93 - 00 2c 0b d1"));
    addr_t csedp; findmany_add(&csedp, text, spec3("1d ee 90 3f d3 f8 80 33 93 f8 94 30 1b 09 03 f0 01 02 + .. .. .. ..", "1d ee 90 3f d3 f8 4c 33 d3 f8 9c 20 + .. .. .. .. 19 68 00 29", "9c 22 03 59 99 58 + .. .. 1a 68 00 2a"));

    findmany_go(text);


    patch("-kernel_pmap.nx_enabled initializer", nxei, uint32_t, {spec3(0x6424f8c3, 0xc420f8c3, 0x682250d0)});
    // vm_map_enter (patch1) - allow RWX pages
    patch("vm_map_enter", vme, uint32_t, {spec2(0x46c00f02, 0x46c046c0)});
    // vm_map_protect - allow vm_protect etc. to create RWX pages
    patch("vm_map_protect", vmp, uint32_t, {spec2(0x0500f025, 42)});
    // AMFI (patch3) - disable the predefined list of executable stuff
    patch("AMFI", mystery, uint32_t, {spec2(0x47702001, 0xe3a00001)});
    // PE_i_can_has_debugger (patch4) - so AMFI allows non-ldid'd binaries (and some other stuff is allowed)
    // switching to patching the actual thing, and the startup code
    // why? debug_enabled is used directly in kdp, and I was not emulating PE_i_can_has's behavior correctly anyway
    patch("+debug_enabled", resolve_ldr(binary, _PE_i_can_has_debugger + 2), uint32_t, {1});
    patch("-debug_enabled initializer", dei, uint32_t, {spec2(0x60082001, 42)});
    // task_for_pid 0
    // this is necessary so a reboot isn't required after using the screwed up version
    patch("task_for_pid 0", tfp0, uint32_t, {spec2(0xa802e00b, 0xe00b2c00)});
    patch("cs_enforcement_disable", resolve_ldr(binary, csedp), uint32_t, {1});

    addr_t scratch = resolve_ldr(binary, is_armv7 ? (mystery + 9) : 42);



    // patches
    patch("+kernel_pmap.nx_enabled",
          b_read32(binary, _kernel_pmap) + 0x420,
          uint32_t, {0});

    patch("-lunchd",
          find_string(b_macho_segrange(binary, "__DATA"), "/sbin/launchd", 0, true),
          char, "/sbin/lunchd");

    patch("proc_enforce",
          find_sysctl(binary, "proc_enforce"),
          uint32_t, {0});
    
    // sandbox
    range_t range = b_macho_segrange(binary, "__PRELINK_TEXT");
    addr_t sb_evaluate = find_bof(range, find_int32(range, find_string(range, "bad opcode", false, true), true), is_armv7);
    
   
    DECL_LAMBDA(l, uint32_t, (const char *name), {
        if(!strcmp(name, "c_sb_evaluate_orig1")) return b_read32(binary, sb_evaluate);
        if(!strcmp(name, "c_sb_evaluate_orig2")) return b_read32(binary, sb_evaluate + 4);
        if(!strcmp(name, "c_sb_evaluate_jumpto")) return sb_evaluate + (is_armv7 ? 9 : 8);
        if(!strcmp(name, "c_memcmp")) return _memcmp;
        if(!strcmp(name, "c_vn_getpath")) return _vn_getpath;
        if(!strcmp(name, "c_dvp_struct_offset")) return spec3(0xde, 0xad, 0xbe);
        if(!strcmp(name, "c_is_armv7")) return is_armv7;
        die("? %s", name);
    })
    b_relocate(sandbox, (void *) l.arg, (void *) l.func, 0);
    prange_t sandbox_pr = rangeconv(b_nth_segment(sandbox, 0));
    patch_with_range("sb_evaluate hook",
                     scratch,
                     sandbox_pr);
    
    patch("sb_evaluate",
          sb_evaluate,
          uint32_t, {(is_armv7 ? 0xf000f8df : 0xe51ff004), scratch | 1});

    // "note"
    patch("scratch", 0, uint32_t, {(scratch + sandbox_pr.size + 0xfff) & ~0xfff});
}


int main(int argc, char **argv) {
    (void) argc;
    struct binary kernel, sandbox;
    b_init(&kernel);
    b_init(&sandbox);
    b_load_macho(&kernel, argv[1], false);
    b_prange_load_macho(&sandbox, (prange_t) {&sandbox_o, sandbox_o_len}, "sandbox.o");

    patchfd = open(argv[2], O_WRONLY | O_CREAT | O_TRUNC, 0644);
    if(patchfd == -1) {
        edie("could not open patchfd");
    }

    do_kernel(&kernel, &sandbox);

    close(patchfd);
    return 0;
}