merdian/Meridian/amfid/ent_patching.m

#include <stdlib.h>
#include <stddef.h>
#include <Foundation/Foundation.h>
#include "cs_dingling.h"
#include "helpers/kexecute.h"
#include "helpers/kmem.h"
#include "helpers/osobject.h"
#include "helpers/patchfinder64.h"
#include "ubc_headers.h"
#include "kern_utils.h"

uint64_t get_vfs_context() {
    // vfs_context_t vfs_context_current(void)
    uint64_t vfs_context = kexecute(offset_vfs_context_current, 1, 0, 0, 0, 0, 0, 0);
    vfs_context = zm_fix_addr(vfs_context);
    return vfs_context;
}

int get_vnode_fromfd(uint64_t vfs_context, int fd, uint64_t *vpp) {
    uint64_t vnode = kalloc(sizeof(vnode_t *));
    
    // int vnode_getfromfd(vfs_context_t cfx, int fd, vnode_t vpp)
    int ret = kexecute(offset_vnode_getfromfd, vfs_context, fd, vnode, 0, 0, 0, 0);
    if (ret != 0) {
        return -1;
    }
    
    *vpp = vnode;
    return 0;
}

int check_vtype(uint64_t vnode) {
    /*
         struct vnode { // `vnode`
            ...
            uint16_t `v_type`;
     */
    uint16_t v_type = rk64(vnode + offsetof(struct vnode, v_type));
    return (v_type == VREG) ? 0 : 1;
}

uint64_t get_vu_ubcinfo(uint64_t vnode) {
    /*
         struct vnode { // `vnode`
            ...
            union {
                struct ubc_info *vu_ubcinfo;
            } v_un;
     */
    return rk64(vnode + offsetof(struct vnode, v_un));
}

uint64_t get_csblobs(uint64_t vu_ubcinfo) {
    /*
         struct ubc_info { // `vu_ubcinfo`
            ....
            struct cs_blob *cs_blobs;
     */
    return rk64(vu_ubcinfo + offsetof(struct ubc_info, cs_blobs));
}

void csblob_ent_dict_set(uint64_t cs_blobs, uint64_t dict) {
    // void csblob_entitlements_dictionary_set(struct cs_blob *csblob, void *entitlements)
    kexecute(offset_csblob_ent_dict_set, cs_blobs, dict, 0, 0, 0, 0, 0);
}

void csblob_update_csflags(uint64_t cs_blobs, uint64_t flags_to_add) {
    uint64_t csflags = rk64(cs_blobs + offsetof(struct cs_blob, csb_flags));
    csflags |= flags_to_add;
    wk64(cs_blobs + offsetof(struct cs_blob, csb_flags), csflags);
}

int set_memory_object_code_signed(uint64_t vu_ubcinfo) {
    uint64_t ui_control = rk64(vu_ubcinfo + offsetof(struct ubc_info, ui_control));
    if (ui_control == 0) {
        NSLog(@"failed to get ui_control");
        return 1;
    }
    
    uint64_t moc_object = rk64(ui_control + 0x8); // offsetof(struct memory_object_control, moc_object)
    if (moc_object == 0) {
        NSLog(@"failed to get moc_object");
        return 1;
    }
    
    uint64_t code_signed_addr = moc_object + 0xb8;
    
    uint32_t curr_code_signed = rk32(code_signed_addr);
    
    // `code_signed` is only 1 bit
    curr_code_signed |= 0x100;
    wk32(code_signed_addr, curr_code_signed);
    
    return 0;
}

uint64_t cs_hash_ptr = 0;
uint64_t find_csb_hashtype(uint32_t hashType) {
    // We're keeping hold of this just incase the patchfind for `cs_find_md` fails
    if (cs_hash_ptr == 0) {
        const struct cs_hash hash = {
            .cs_type = CS_HASHTYPE_SHA1,
            .cs_size = CS_SHA1_LEN,
            .cs_init = offset_sha1_init,
            .cs_update = offset_sha1_update,
            .cs_final = offset_sha1_final
        };
        cs_hash_ptr = kalloc(sizeof(hash));
        kwrite(cs_hash_ptr, &hash, sizeof(hash));
    }
    
    uint64_t cs_find_md = find_cs_find_md();
    if (cs_find_md == 0) {
        // Dammit :( If the hash isn't SHA1 it now won't run,
        // but if we return 0 it will just KP. I'd rather a Killed: 9
        NSLog(@"FATAL ERROR! Unable to find 'cs_find_md'!!");
        return cs_hash_ptr;
    }
    
    return rk64(cs_find_md + ((hashType - 1) * 0x8));
}

uint64_t construct_cs_blob(const void *cs,
                           uint32_t cs_length,
                           uint8_t cd_hash[20],
                           uint32_t chosen_off,
                           uint64_t macho_offset) {
    uint64_t entire_csdir = kalloc(cs_length);
    kwrite(entire_csdir, cs, cs_length);
    
    const CS_CodeDirectory *blob = (const CS_CodeDirectory *)((uintptr_t)cs + chosen_off);
    
    uint64_t cs_blob = kalloc(sizeof(struct cs_blob));
    wk64(cs_blob + offsetof(struct cs_blob, csb_next), 0);
    wk32(cs_blob + offsetof(struct cs_blob, csb_cpu_type), -1); // kern will update this for us :-)
    
    uint32_t csb_flags = (ntohl(blob->flags) & CS_ALLOWED_MACHO) | CS_VALID | CS_SIGNED;
    wk32(cs_blob + offsetof(struct cs_blob, csb_flags), csb_flags);

    wk64(cs_blob + offsetof(struct cs_blob, csb_base_offset), macho_offset);
    wk64(cs_blob + offsetof(struct cs_blob, csb_start_offset), 0);
    if (ntohl(blob->version) >= CS_SUPPORTSSCATTER && (ntohl(blob->scatterOffset))) {
        const SC_Scatter *scatter = (const SC_Scatter *)((const char *)blob + ntohl(blob->scatterOffset));
        wk64(cs_blob + offsetof(struct cs_blob, csb_start_offset), ((off_t)ntohl(scatter->base)) * (1U << blob->pageSize));
    }
    wk64(cs_blob + offsetof(struct cs_blob, csb_end_offset), ((vm_offset_t)ntohl(blob->codeLimit) +
                                                              ((1U << blob->pageSize) - 1) &
                                                                ~((vm_offset_t)((1U << blob->pageSize) - 1))));
    
    wk64(cs_blob + offsetof(struct cs_blob, csb_mem_size), cs_length);
    wk64(cs_blob + offsetof(struct cs_blob, csb_mem_offset), 0);
    wk64(cs_blob + offsetof(struct cs_blob, csb_mem_kaddr), entire_csdir);
    
    kwrite(cs_blob + offsetof(struct cs_blob, csb_cdhash), cd_hash, CS_CDHASH_LEN);
    wk64(cs_blob + offsetof(struct cs_blob, csb_hashtype), find_csb_hashtype(blob->hashType));
    
    wk64(cs_blob + offsetof(struct cs_blob, csb_hash_pagesize), (1U << blob->pageSize));
    wk64(cs_blob + offsetof(struct cs_blob, csb_hash_pagemask), (1U << blob->pageSize) - 1);
    wk64(cs_blob + offsetof(struct cs_blob, csb_hash_pageshift), blob->pageSize);
    wk64(cs_blob + offsetof(struct cs_blob, csb_hash_firstlevel_pagesize), 0);
    wk64(cs_blob + offsetof(struct cs_blob, csb_cd), entire_csdir + chosen_off);
    
    wk64(cs_blob + offsetof(struct cs_blob, csb_teamid), 0);
    wk64(cs_blob + offsetof(struct cs_blob, csb_entitlements_blob), 0);
    wk64(cs_blob + offsetof(struct cs_blob, csb_entitlements), 0); /* we'll update this later */
    wk32(cs_blob + offsetof(struct cs_blob, csb_platform_binary), 0);
    wk32(cs_blob + offsetof(struct cs_blob, csb_platform_path), 0);
    
    if (csb_flags & CS_PLATFORM_BINARY) {
        wk64(cs_blob + offsetof(struct cs_blob, csb_platform_binary), 1);
        wk64(cs_blob + offsetof(struct cs_blob, csb_platform_path), !!(csb_flags & CS_PLATFORM_PATH));
    } else if ((ntohl(blob->version) >= CS_SUPPORTSTEAMID) &&
               (blob->teamOffset > 0)) {
        const char *name = ((const char *)blob) + ntohl(blob->teamOffset);
        uint64_t teamid_addr = kalloc(strlen(name));
        kwrite(teamid_addr, name, strlen(name));
        wk64(cs_blob + offsetof(struct cs_blob, csb_teamid), teamid_addr);
    }
    
    return cs_blob;
}

int fixup_platform_application(const char *path,
                               uint64_t macho_offset,
                               const void *blob,
                               uint32_t cs_length,
                               uint8_t cd_hash[20],
                               uint32_t csdir_offset,
                               const CS_GenericBlob *entitlements) {
    int ret;
    
    uint64_t vfs_context = get_vfs_context();
    if (vfs_context == 0) {
        ret = -1;
        goto out;
    }
    
    int fd = open(path, O_RDONLY);
    if (fd < 0) {
        ret = -2;
        goto out;
    }
    
    uint64_t *vpp = malloc(sizeof(vnode_t *));
    ret = get_vnode_fromfd(vfs_context, fd, vpp);
    if (ret != 0) {
        ret = -3;
        goto out;
    }
    
    uint64_t vnode = rk64(*vpp);
    if (vnode == 0) {
        ret = -4;
        goto out;
    }
    
    ret = check_vtype(vnode);
    if (ret != 0) {
        ret = -5;
        goto out;
    }
    
    uint64_t vu_ubcinfo = get_vu_ubcinfo(vnode);
    if (vu_ubcinfo == 0) {
        ret = -6;
        goto out;
    }
    
    uint64_t cs_blobs = get_csblobs(vu_ubcinfo);
    if (cs_blobs == 0) {
        uint64_t new_cs_blob = construct_cs_blob(blob,
                                                 cs_length,
                                                 cd_hash,
                                                 csdir_offset,
                                                 macho_offset);
        if (new_cs_blob < 1) {
            NSLog(@"failed to construct csblob");
            ret = -7;
            goto out;
        }
        
        wk64(vu_ubcinfo + offsetof(struct ubc_info, cs_blobs), new_cs_blob);
        cs_blobs = rk64(vu_ubcinfo + offsetof(struct ubc_info, cs_blobs));
        
        // we now need to update a few other bits and bobs
        
        // memory_object_signed
        // uip->ui_control->moc_object->code_signed = 1
        ret = set_memory_object_code_signed(vu_ubcinfo);
        if (ret != 0) {
            ret = -8;
            goto out;
        }
        
        // disabled for now... causes panics on 2nd run of the binary
        // something to do with a mutex lock.. i don't care to figure out what
        // set generation count
//        wk64(vu_ubcinfo + offsetof(struct ubc_info, cs_add_gen), 1);
//        NSLog(@"cs_add_gen: %llx", rk64(vu_ubcinfo + offsetof(struct ubc_info, cs_add_gen)));

        // record_mtime
        uint64_t vnode_attr = kalloc(sizeof(struct vnode_attr));
        wk64(vnode_attr + offsetof(struct vnode_attr, va_supported), 0);
        wk64(vnode_attr + offsetof(struct vnode_attr, va_active), 1LL << 14);
        wk64(vnode_attr + offsetof(struct vnode_attr, va_vaflags), 0);
        // vnode_getattr
        ret = kexecute(offset_vnode_getattr, vnode, vnode_attr, vfs_context, 0, 0, 0, 0);
        if (ret != 0) {
            NSLog(@"vnode_attr failed - ret value: %d", ret);
        } else {
            uint64_t mtime = rk64(vnode_attr + offsetof(struct vnode_attr, va_modify_time));
            if (mtime == 0) {
                NSLog(@"mtime is 0!");
            } else {
                NSLog(@"got mtime: %llx", mtime);
                wk64(vu_ubcinfo + offsetof(struct ubc_info, cs_mtime), mtime);
            }
        }
    }
    
    if (entitlements == NULL) {
        // generate some new entitlements
        // this is all we're here to do, really :-)
        const char *cstring = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>"
                              "<!DOCTYPE plist PUBLIC \"-//Apple//DTD PLIST 1.0//EN\" \"http://www.apple.com/DTDs/PropertyList-1.0.dtd\">"
                              "<plist version=\"1.0\">"
                              "<dict>"
                                  "<key>platform-application</key>"                         // escape container restriction
                                  "<true/>"
                                  "<key>com.apple.private.security.no-container</key>"      // no container
                                  "<true/>"
                                  "<key>get-task-allow</key>"                               // task_for_pid
                                  "<true/>"
                                  "<key>com.apple.private.skip-library-validation</key>"    // allow invalid libs
                                  "<true/>"
                              "</dict>"
                              "</plist>";
        
        uint64_t dict = OSUnserializeXML(cstring);
        csblob_ent_dict_set(cs_blobs, dict);
        csblob_update_csflags(dict, CS_GET_TASK_ALLOW);
        
        // Update csb_entitlements_blob
        int size = 8 + strlen(cstring);
        CS_GenericBlob *entitlements_blob = (CS_GenericBlob *)malloc(size);
        entitlements_blob->magic = CSMAGIC_EMBEDDED_ENTITLEMENTS;
        entitlements_blob->length = 8 + strlen(cstring);
        stpcpy(entitlements_blob->data, cstring);
        
        // Copy the data into kernel, and write to the csb_entitlements_blob field
        uint64_t entptr = kalloc(size);
        kwrite(entptr, entitlements_blob, size);
        wk64(cs_blobs + offsetof(struct cs_blob, csb_entitlements_blob), entptr);
        
        free(entitlements_blob);
    } else {
        // there are some entitlements, let's parse them, update the osdict w/
        // platform-application (true), and write them into kern
        uint64_t dict = OSUnserializeXML(entitlements->data);

        // gotta check for get-task-allow as it sets another csflag
        // remember: csflags have to be *perfect* otherwise the trick won't work
        // the reason this is *before* we add it manually is because the kernel won't
        // know about the manually added entitlement, and therefore this flag won't be set
        // (assuming it wasn't already in the existing entitlements)
        ret = OSDictionary_GetItem(dict, "get-task-allow");
        if (ret != 0) {
            csblob_update_csflags(cs_blobs, CS_GET_TASK_ALLOW);
        }
        
        OSDictionary_SetItem(dict, "platform-application", find_OSBoolean_True());
        OSDictionary_SetItem(dict, "com.apple.private.security.no-container", find_OSBoolean_True());
        OSDictionary_SetItem(dict, "get-task-allow", find_OSBoolean_True());
        OSDictionary_SetItem(dict, "com.apple.private.skip-library-validation", find_OSBoolean_True());

        csblob_ent_dict_set(cs_blobs, dict);
        
        // map the genblob up to csb_entitlements_blob
        // idk if we necessarily need to do this but w/e
        // TODO: fix this so it uses the *new* entitlements, not the original ones (duh)
        // Note to self: this field seems to be checked in the case of things like uicache, which requires
        // the 'com.apple.lsapplicationworkspace.rebuildappdatabases' entitlement. I suspect this field is
        // designed to be 'userland-viewable'
        int size = ntohl(entitlements->length);
        uint64_t entptr = kalloc(size);
        kwrite(entptr, entitlements, size);
        wk64(cs_blobs + offsetof(struct cs_blob, csb_entitlements_blob), entptr);
    }
    
    ret = 0;
    
out:
    if (fd >= 0)
        close(fd);
    return ret;
}