mirror of
https://github.com/AuxXxilium/arc.git
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492 lines
15 KiB
C
492 lines
15 KiB
C
/*
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* Copyright (c) 2022 Fabio Belavenuto <belavenuto@gmail.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*
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*/
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/**
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* Converted from php code by Fabio Belavenuto <belavenuto@gmail.com>
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*
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* A quick tool for patching the boot_params check in the DSM kernel image
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* This lets you tinker with the initial ramdisk contents without disabling mount() features and modules loading
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*
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* The overall pattern we need to find is:
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* - an CDECL function
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* - does "LOCK OR [const-ptr],n" 4x
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* - values of ORs are 1/2/4/8 respectively
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* - [const-ptr] is always the same
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*
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* Added patch for CMOS_WRITE by Fabio Belavenuto
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*
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <string.h>
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#include <getopt.h>
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#include <errno.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <stdarg.h>
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#include <gelf.h>
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const int DIR_FWD = 1;
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const int DIR_RWD = -1;
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/* Variables */
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int fd, verbose = 1, read_only = 0;
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Elf *elfHandle;
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GElf_Ehdr elfExecHeader;
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uint64_t orPos[4], fileSize, rodataAddr, rodataOffs, initTextOffs;
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unsigned char *fileData;
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/*****************************************************************************/
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void errorMsg(char *fmt, ...)
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{
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va_list args;
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va_start(args, fmt);
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vfprintf(stderr, fmt, args);
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va_end(args);
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fprintf(stderr, "\n");
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exit(1);
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}
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/*****************************************************************************/
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void errorNum()
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{
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char str[100] = {0};
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perror(str);
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exit(2);
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}
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/*****************************************************************************/
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void elfErrno()
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{
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int err;
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if ((err = elf_errno()) != 0)
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{
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fprintf(stderr, "%s\n", elf_errmsg(err));
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exit(3);
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}
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}
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/*****************************************************************************/
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// Finding a function boundary is non-trivial really as patters can vary, we can have multiple exit points, and in CISC
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// there are many things which may match e.g. "PUSH EBP". Implementing even a rough disassembler is pointless.
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// However, we can certainly cheat here as we know with CDECL a non-empty function will always contain one or more
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// PUSH (0x41) R12-R15 (0x54-57) sequences. Then we can search like a 1K forward for these characteristic LOCK OR.
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uint64_t findPUSH_R12_R15_SEQ(uint64_t start)
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{
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uint64_t i;
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for (i = start; i < fileSize; i++)
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{
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if (fileData[i] == 0x41 && (fileData[i + 1] >= 0x54 && fileData[i + 1] <= 0x57))
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{
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return i;
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}
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}
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return -1;
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}
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/*****************************************************************************/
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//[0xF0, 0x80, null, null, null, null, null, 0xXX],
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uint64_t findORs(uint64_t start, uint32_t maxCheck)
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{
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uint64_t i;
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int c = 0;
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uint8_t lb = 0x01;
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for (i = start; i < fileSize; i++)
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{
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if (fileData[i] == 0xF0 && fileData[i + 1] == 0x80 && fileData[i + 7] == lb)
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{
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orPos[c++] = i;
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i += 7;
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lb <<= 1;
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}
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if (c == 4)
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{
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break;
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}
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if (--maxCheck == 0)
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{
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break;
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}
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}
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return c;
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}
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/*****************************************************************************/
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void patchBootParams()
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{
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uint64_t addr, pos;
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uint64_t newPtrOffset, ptrOffset;
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int n;
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printf("Patching boot params.\n");
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// The function will reside in init code part. We don't care we may potentially search beyond as we expect it to be found
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while (initTextOffs < fileSize)
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{
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addr = findPUSH_R12_R15_SEQ(initTextOffs);
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if (addr == -1)
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break; // no more "functions" left
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printf("\rAnalyzing f() candidate @ %lX, PUSH @ %lX", initTextOffs, addr);
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// we found something looking like PUSH R12-R15, now find the ORs
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n = findORs(initTextOffs, 1024);
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if (n != 4)
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{
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// We can always move forward by the function token length (obvious) but if we couldn't find any LOCK-OR tokens
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// we can skip the whole look ahead distance. We CANNOT do that if we found even a single token because the next one
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// might have been just after the look ahead distance
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initTextOffs += 2;
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if (n == 0)
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{
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initTextOffs += 1024;
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}
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continue; // Continue the main search loop to find next function candidate
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}
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// We found LOCK(); OR ptr sequences so we can print some logs and collect ptrs (as this is quite expensive)
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printf("\n[?] Found possible f() @ %lX\n", initTextOffs);
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ptrOffset = 0;
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int ec = 0;
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for (n = 0; n < 4; n++)
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{
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// data will have the following bytes:
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// [0-LOCK()] [1-OR()] [2-BYTE-PTR] [3-OFFS-b3] [4-OFFS-b2] [5-OFFS-b1] [6-OFFS-b1] [7-NUMBER]
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pos = orPos[n];
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// how far it "jumps"
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newPtrOffset = pos + (fileData[pos + 6] << 24 | fileData[pos + 5] << 16 | fileData[pos + 4] << 8 | fileData[pos + 3]);
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if (ptrOffset == 0)
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{
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ptrOffset = newPtrOffset;
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++ec;
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}
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else if (ptrOffset == newPtrOffset)
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{
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++ec;
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}
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printf("\t[+] Found LOCK-OR#%d sequence @ %lX => %02X %02X %02X %02X %02X %02X %02X %02X [RIP+%lX]\n",
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n, pos, fileData[pos], fileData[pos + 1], fileData[pos + 2], fileData[pos + 3], fileData[pos + 4],
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fileData[pos + 5], fileData[pos + 6], fileData[pos + 7], newPtrOffset);
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}
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if (ec != 4)
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{
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printf("\t[-] LOCK-OR PTR offset mismatch - %d/4 matched\n", ec);
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// If the pointer checking failed we can at least move beyond the last LOCK-OR found as we know there's no valid
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// sequence of LOCK-ORs there
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initTextOffs = orPos[3];
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continue;
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}
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printf("\t[+] All %d LOCK-OR PTR offsets equal - match found!\n", ec);
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break;
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}
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if (addr == -1)
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{
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errorMsg("\nFailed to find matching sequences\n");
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}
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else
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{
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// Patch offsets
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for (n = 0; n < 4; n++)
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{
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// The offset will point at LOCK(), we need to change the OR (0x80 0x0d) to AND (0x80 0x25) so the two bytes after
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pos = orPos[n] + 2;
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printf("Patching OR to AND @ %lX\n", pos);
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fileData[pos] = 0x25;
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}
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}
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}
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/*****************************************************************************/
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uint32_t changeEndian(uint32_t num)
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{
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return ((num >> 24) & 0xff) | // move byte 3 to byte 0
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((num << 8) & 0xff0000) | // move byte 1 to byte 2
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((num >> 8) & 0xff00) | // move byte 2 to byte 1
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((num << 24) & 0xff000000); // move byte 0 to byte 3
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}
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/*****************************************************************************/
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uint64_t findSeq(const char *seq, int len, uint32_t pos, int dir, uint64_t max)
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{
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uint64_t i = pos;
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do
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{
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if (memcmp((const char *)fileData + i, seq, len) == 0)
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{
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return i;
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}
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i += dir;
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--max;
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} while (i > 0 && i < fileSize && max > 0);
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return -1;
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}
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/*****************************************************************************/
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void patchRamdiskCheck()
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{
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uint64_t pos, errPrintAddr;
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uint64_t printkPos, testPos, jzPos;
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const char str[] = "3ramdisk corrupt";
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printf("Patching ramdisk check.\n");
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for (pos = rodataOffs; pos < fileSize; pos++)
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{
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if (memcmp(str, (const char *)(fileData + pos), 16) == 0)
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{
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pos -= rodataOffs;
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break;
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}
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}
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errPrintAddr = rodataAddr + pos - 1;
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printf("LE arg addr: %08lX\n", errPrintAddr);
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printkPos = findSeq((const char *)&errPrintAddr, 4, 0, DIR_FWD, -1);
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if (printkPos == -1)
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{
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errorMsg("printk pos not found!\n");
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}
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// double check if it's a MOV reg,VAL (where reg is EAX/ECX/EDX/EBX/ESP/EBP/ESI/EDI)
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printkPos -= 3;
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if (memcmp((const char *)fileData + printkPos, "\x48\xc7", 2) != 0)
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{
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errorMsg("Expected MOV=>reg before printk error, got %02X %02X\n", fileData[printkPos], fileData[printkPos + 1]);
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}
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if (fileData[printkPos + 2] < 0xC0 || fileData[printkPos + 2] > 0xC7)
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{
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errorMsg("Expected MOV w/reg operand [C0-C7], got %02X\n", fileData[printkPos + 2]);
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}
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printf("Found printk MOV @ %08lX\n", printkPos);
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// now we should seek a reasonable amount (say, up to 32 bytes) for a sequence of CALL x => TEST EAX,EAX => JZ
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testPos = findSeq("\x85\xc0", 2, printkPos, DIR_RWD, 32);
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if (testPos == -1)
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{
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errorMsg("Failed to find TEST eax,eax\n");
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}
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printf("Found TEST eax,eax @ %08lX\n", testPos);
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jzPos = testPos + 2;
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if (fileData[jzPos] != 0x74)
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{
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errorMsg("Failed to find JZ\n");
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}
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printf("OK - patching %02X%02X (JZ) to %02X%02X (JMP) @ %08lX\n",
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fileData[jzPos], fileData[jzPos + 1], 0xEB, fileData[jzPos + 1], jzPos);
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fileData[jzPos] = 0xEB;
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}
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/*****************************************************************************/
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void patchCmosWrite()
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{
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uint64_t pos, errPrintAddr;
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uint64_t pr_errPos, testPos, callPos;
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const char str[] = "3smpboot: %s: this boot have memory training";
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printf("Patching call to rtc_cmos_write.\n");
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for (pos = rodataOffs; pos < fileSize; pos++)
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{
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if (memcmp(str, (const char *)(fileData + pos), 16) == 0)
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{
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pos -= rodataOffs;
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break;
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}
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}
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errPrintAddr = rodataAddr + pos - 1;
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printf("LE arg addr: %08lX\n", errPrintAddr);
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pr_errPos = findSeq((const char *)&errPrintAddr, 4, 0, DIR_FWD, -1);
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if (pr_errPos == -1)
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{
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printf("pr_err pos not found - ignoring.\n"); // Some kernels do not have the call, exit without error
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return;
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}
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// double check if it's a MOV reg,VAL (where reg is EAX/ECX/EDX/EBX/ESP/EBP/ESI/EDI)
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pr_errPos -= 3;
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if (memcmp((const char *)fileData + pr_errPos, "\x48\xc7", 2) != 0)
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{
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errorMsg("Expected MOV=>reg before pr_err error, got %02X %02X\n", fileData[pr_errPos], fileData[pr_errPos + 1]);
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}
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if (fileData[pr_errPos + 2] < 0xC0 || fileData[pr_errPos + 2] > 0xC7)
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{
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errorMsg("Expected MOV w/reg operand [C0-C7], got %02X\n", fileData[pr_errPos + 2]);
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}
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printf("Found pr_err MOV @ %08lX\n", pr_errPos);
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// now we should seek a reasonable amount (say, up to 64 bytes) for a sequence of
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// MOV ESI, 0x48 => MOV EDI, 0xFF => MOV EBX, EAX
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testPos = findSeq("\xBE\x48\x00\x00\x00\xBF\xFF\x00\x00\x00\x89\xC3", 12, pr_errPos, DIR_RWD, 64);
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if (testPos == -1)
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{
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printf("Failed to find MOV ESI, 0x48 => MOV EDI, 0xFF => MOV EBX, EAX\n");
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return;
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}
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printf("Found MOV ESI, 0x48 => MOV EDI, 0xFF => MOV EBX, EAX @ %08lX\n", testPos);
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callPos = testPos + 12;
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if (fileData[callPos] != 0xE8)
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{
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errorMsg("Failed to find CALL\n");
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}
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printf("OK - patching %02X (CALL) to 0x90.. (NOPs) @ %08lX\n",
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fileData[callPos], callPos);
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for (uint64_t i = 0; i < 5; i++)
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fileData[callPos + i] = 0x90;
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}
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/*****************************************************************************/
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int main(int argc, char *argv[])
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{
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struct stat fileInf;
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Elf_Scn *section;
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GElf_Shdr sectionHeader;
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char *sectionName;
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char *fileIn = NULL, *fileOut = NULL;
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int onlyBoot = 0, onlyRD = 0, onlyCMOS = 0, c;
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if (argc < 3)
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{
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errorMsg("Use: kpatch (option) <vmlinux> <output>\nOptions:\n -b Only bootparams\n -r Only ramdisk\n -c Only CMOS");
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}
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c = 1;
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while (c < argc)
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{
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if (strcmp(argv[c], "-b") == 0)
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{
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onlyBoot = 1;
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}
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else if (strcmp(argv[c], "-r") == 0)
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{
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onlyRD = 1;
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}
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else if (strcmp(argv[c], "-c") == 0)
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{
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onlyCMOS = 1;
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}
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else if (fileIn == NULL)
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{
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fileIn = argv[c];
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}
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else
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{
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fileOut = argv[c];
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break;
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}
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++c;
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}
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if (NULL == fileIn)
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{
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errorMsg("Please give a input filename");
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}
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if (NULL == fileOut)
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{
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errorMsg("Please give a output filename");
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}
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if (elf_version(EV_CURRENT) == EV_NONE)
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elfErrno();
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if ((fd = open(fileIn, O_RDONLY)) == -1)
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errorNum();
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if ((elfHandle = elf_begin(fd, ELF_C_READ, NULL)) == NULL)
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elfErrno();
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if (gelf_getehdr(elfHandle, &elfExecHeader) == NULL)
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elfErrno();
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switch (elf_kind(elfHandle))
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{
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case ELF_K_NUM:
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case ELF_K_NONE:
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errorMsg("file type unknown\n");
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break;
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case ELF_K_COFF:
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errorMsg("COFF binaries not supported\n");
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break;
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case ELF_K_AR:
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errorMsg("AR archives not supported\n");
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break;
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case ELF_K_ELF:
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break;
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}
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section = NULL;
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while ((section = elf_nextscn(elfHandle, section)) != NULL)
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{
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if (gelf_getshdr(section, §ionHeader) != §ionHeader)
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elfErrno();
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if ((sectionName = elf_strptr(elfHandle, elfExecHeader.e_shstrndx, sectionHeader.sh_name)) == NULL)
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elfErrno();
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if (strcmp(sectionName, ".init.text") == 0)
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{
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initTextOffs = sectionHeader.sh_offset;
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}
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else if (strcmp(sectionName, ".rodata") == 0)
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{
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rodataAddr = sectionHeader.sh_addr & 0xFFFFFFFF;
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rodataOffs = sectionHeader.sh_offset;
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}
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}
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elfErrno(); /* If there isn't elf_errno set, nothing will happend. */
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elf_end(elfHandle);
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if (fstat(fd, &fileInf) == -1)
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errorNum();
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fileSize = fileInf.st_size;
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fileData = malloc(fileSize);
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if (fileSize != read(fd, fileData, fileSize))
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{
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errorNum();
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}
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close(fd);
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printf("Found .init.text offset @ %lX\n", initTextOffs);
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printf("Found .rodata address @ %lX\n", rodataAddr);
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printf("Found .rodata offset @ %lX\n", rodataOffs);
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if (onlyBoot == 0 && onlyCMOS == 0 && onlyRD == 0)
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{
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patchBootParams();
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patchRamdiskCheck();
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patchCmosWrite();
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}
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else
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{
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if (onlyBoot == 1)
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{
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patchBootParams();
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}
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if (onlyRD == 1)
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{
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patchRamdiskCheck();
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}
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if (onlyCMOS == 1)
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{
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patchCmosWrite();
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}
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}
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if ((fd = open(fileOut, O_WRONLY | O_CREAT, 0644)) == -1)
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{
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errorNum();
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}
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if (fileSize != write(fd, fileData, fileSize))
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{
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errorNum();
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}
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close(fd);
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printf("Finish!\n");
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return 0;
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} |