解密 AES 加密文件，导致崩溃的函数
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【中文标题】解密 AES 加密文件，导致崩溃的函数【英文标题】：Decrypt AES-encrypted file, function causing a crash 【发布时间】：2015-01-12 00:10:12 【问题描述】：我正在尝试编写一个 C++ 程序来加密和解密某些文件。加密工作正常，但是当我来解密该函数时似乎导致程序崩溃。
这是我用来解密的函数：
CString DecryptFile(CString csSourceFile)
CString csDecryptedFile = csSourceFile;
CRijndael aesEncryption;
int nPos = csDecryptedFile.ReverseFind('.');
if(nPos == -1)
//Log("ERROR:: file name not proper");
return CString("");
csDecryptedFile = csDecryptedFile.Left(nPos);
csDecryptedFile += ".wav";
FILE *fIn = fopen(csSourceFile.GetBuffer(0),"rb");
FILE *fOut = fopen(csDecryptedFile.GetBuffer(0),"wb");
if(!fIn || !fOut)
//Log("ERROR:: failed to Open File for encryption");
return CString("");
int nlen = -1;
aesEncryption.MakeKey(AM_ENC_KEY,AM_NULL_KEY,BLOCK_SIZE,BLOCK_SIZE);
int nRead = 0;
while (true)
char szBlockIn[EBLOCK_SIZE+1] = 0;
char szBlockOut[BLOCK_SIZE+1] = 0;
char szBlockDec[BLOCK_SIZE+1] = 0;
memset(szBlockIn,0,sizeof(char)*(EBLOCK_SIZE+1));
memset(szBlockOut,0,sizeof(char)*(BLOCK_SIZE+1));
memset(szBlockDec,0,sizeof(char)*(BLOCK_SIZE+1));
int nRead = fread(szBlockIn,sizeof(char),EBLOCK_SIZE, fIn);
if(nRead <= 0)
break;
nlen = EBLOCK_SIZE;
Decode(szBlockIn,szBlockOut,nlen);
aesEncryption.DecryptBlock((char *)szBlockOut,szBlockDec);
fwrite(szBlockDec,sizeof(char),BLOCK_SIZE,fOut);
fclose(fIn);
fclose(fOut);
RemoveEndTag(csDecryptedFile.GetBuffer(0));
AfxMessageBox(csDecryptedFile);
AfxMessageBox(_T("returning"));
return csDecryptedFile;
这是调用函数的代码sn-p：
CString strTest = DecryptFile(m_DecompressedTempFile);
AfxMessageBox(strTest);
奇怪的是解密执行得非常好 - 如果我到达文件位置，我可以看到解密的文件并访问它。不幸的是，该程序必须做更多的事情，并且该程序只是紧随其后而挂起。特别奇怪的是，如您所见，我在函数结束之前调用了AfxMessageBox(_T("returning"));：这会产生一个消息框。但是当我从运行该函数的代码中调用AfxMessageBox(strTest); 时，不会生成任何消息框。
通过调试，问题似乎以某种方式在我用于加密文件的while循环中路由，所以我想知道我是否没有关闭我应该关闭的东西或其他东西？虽然不太确定从哪里开始，所以任何可以提供任何帮助的人都会很棒！？！
提前致谢。
我忘了提到这已经工作多年了——最近唯一的变化是我们现在在 Windows 7 上编译代码，而之前是在 Windows XP 上。这会对函数中的任何内容产生影响吗？
更新： 值得注意的是，如果我删除 while 循环并只运行一次循环的内容，就会出现同样的问题。如果我删除aesEncryption.DecryptBlock((char *)szBlockOut,szBlockDec);，那么问题就会消失，但显然我需要那条线。所以问题是我认为的那个功能。虽然这个函数存在于库中，但我将它包含在下面：
//Decrypt exactly one block of ciphertext.
// in - The ciphertext.
// result - The plaintext generated from a ciphertext using the session key.
void CRijndael::DecryptBlock(char const* in, char* result)
if(false==m_bKeyInit)
throw exception(sm_szErrorMsg1);
if(DEFAULT_BLOCK_SIZE == m_blockSize)
DefDecryptBlock(in, result);
return;
int BC = m_blockSize / 4;
int SC = BC == 4 ? 0 : (BC == 6 ? 1 : 2);
int s1 = sm_shifts[SC][1][1];
int s2 = sm_shifts[SC][2][1];
int s3 = sm_shifts[SC][3][1];
//Temporary Work Arrays
int i;
int tt;
int* pi = t;
for(i=0; i<BC; i++)
*pi = ((unsigned char)*(in++) << 24);
*pi |= ((unsigned char)*(in++) << 16);
*pi |= ((unsigned char)*(in++) << 8);
(*(pi++) |= (unsigned char)*(in++)) ^= m_Kd[0][i];
//Apply Round Transforms
for(int r=1; r<m_iROUNDS; r++)
for(i=0; i<BC; i++)
a[i] = (sm_T5[(t[i] >> 24) & 0xFF] ^
sm_T6[(t[(i + s1) % BC] >> 16) & 0xFF] ^
sm_T7[(t[(i + s2) % BC] >> 8) & 0xFF] ^
sm_T8[ t[(i + s3) % BC] & 0xFF]) ^ m_Kd[r][i];
memcpy(t, a, 4*BC);
int j;
//Last Round is Special
for(i=0,j=0; i<BC; i++)
tt = m_Kd[m_iROUNDS][i];
result[j++] = sm_Si[(t[i] >> 24) & 0xFF] ^ (tt >> 24);
result[j++] = sm_Si[(t[(i + s1) % BC] >> 16) & 0xFF] ^ (tt >> 16);
result[j++] = sm_Si[(t[(i + s2) % BC] >> 8) & 0xFF] ^ (tt >> 8);
result[j++] = sm_Si[ t[(i + s3) % BC] & 0xFF] ^ tt;
【问题讨论】：
是GetBuffer(0) 打来的电话吗？ msdn.microsoft.com/en-us/library/aa314880%28v=vs.60%29.aspx 由于 CString 是引用计数字符串，您可能需要调用 ReleaseBuffer
谢谢你，ReleaseBuffer 肯定应该在那里。不幸的是，这对悬挂问题没有帮助:(
也许你应该使用另一个 AES 库，因为你使用的那个似乎没有经过很多同行评审：codeproject.com/Articles/1380/…
我忘了提到这已经工作了好几年了——最近唯一的变化是我们现在在 Windows 7 上编译代码，而之前是在 Windows XP 上。这会对函数中的任何内容产生影响吗？
有加密++。 cryptopp.com 只需确保您采用现有示例并根据您的需要对其进行定制。该库是稳定的，但往往难以使用（我的看法）。
【参考方案1】：
不清楚您是否只需要 C++ 解决方案；如果您对 Python 解决方案没问题，请尝试 PyCrypto 模块。这是我用来压缩当前目录的内容，除了一些忽略模式，并在 ./bin 下加密 .zip（其中大部分是从 SO 上其他地方复制的代码）：
import sys
import os
import zipfile
import getpass
from contextlib import contextmanager
from hashlib import md5
from Crypto.Cipher import AES
from Crypto import Random
def derive_key_and_iv(password, salt, key_length, iv_length):
d = d_i = ''
while len(d) < key_length + iv_length:
d_i = md5(d_i + password + salt).digest()
d += d_i
return d[:key_length], d[key_length:key_length+iv_length]
def encrypt(in_file, out_file, password, key_length=32):
bs = AES.block_size
salt = Random.new().read(bs - len('Salted__'))
key, iv = derive_key_and_iv(password, salt, key_length, bs)
cipher = AES.new(key, AES.MODE_CBC, iv)
out_file.write('Salted__' + salt)
finished = False
while not finished:
chunk = in_file.read(1024 * bs)
if len(chunk) == 0 or len(chunk) % bs != 0:
padding_length = (bs - len(chunk) % bs) or bs
chunk += padding_length * chr(padding_length)
finished = True
out_file.write(cipher.encrypt(chunk))
def decrypt(in_file, out_file, password, key_length=32):
bs = AES.block_size
salt = in_file.read(bs)[len('Salted__'):]
key, iv = derive_key_and_iv(password, salt, key_length, bs)
cipher = AES.new(key, AES.MODE_CBC, iv)
next_chunk = ''
finished = False
while not finished:
chunk, next_chunk = next_chunk, cipher.decrypt(in_file.read(1024 * bs))
if len(next_chunk) == 0:
padding_length = ord(chunk[-1])
chunk = chunk[:-padding_length]
finished = True
out_file.write(chunk)
def query_yes_no(question, default="yes", quiet=False):
"""Ask a yes/no question via raw_input() and return their answer.
"question" is a string that is presented to the user.
"default" is the presumed answer if the user just hits <Enter>.
It must be "yes" (the default), "no" or None (meaning
an answer is required of the user).
The "answer" return value is True for "yes" or False for "no".
"""
valid = "yes": True, "y": True, "ye": True,
"no": False, "n": False
if default is None:
prompt = " [y/n] "
elif default == "yes":
prompt = " [Y/n] "
elif default == "no":
prompt = " [y/N] "
else:
raise ValueError("invalid default answer: '%s'" % default)
while True:
if not quiet:
sys.stdout.write(question + prompt)
if quiet and default is not None:
choice=default
else:
choice = raw_input().lower()
if default is not None and choice == '':
return valid[default]
elif choice in valid:
return valid[choice]
else:
sys.stdout.write("Please respond with 'yes' or 'no' "
"(or 'y' or 'n')\n")
dircurr=os.path.abspath('.').replace('\\','/')
dirwithenc=dircurr+'/bin'
if os.path.isfile(dirwithenc+'/bak.enc'):
if query_yes_no("\nDo you want to decrypt '"+dirwithenc+"/bak.enc'?",'no'):
password=getpass.getpass('\nDecryption password: ')
with open(dirwithenc+'/bak.enc', 'rb') as in_file, open(dircurr+'/bak.zip', 'wb') as out_file:
decrypt(in_file,out_file,password)
print("\nFile '"+dircurr+"/bak.enc' decrypted to '"+dircurr+"/bak.zip'")
raw_input("""
***DONE***
Press Enter...""")
exit(0)
else:
print("\nAnswered 'no'")
print("\nEncrypting files will overwrite any preexisting file '"+dirwithenc+"/bak.enc'")
password=getpass.getpass('\nSet an encryption password (will not be saved): ')
print('\nZipping files, excepting certain ignore patterns...')
zf = zipfile.ZipFile(dircurr+'/bak.zip', 'w')
for dirname, subdirs, files in os.walk(os.path.abspath('.')):
#Do not archive system files beginning with period
for filename in files:
if filename[:1]=='.':
files.remove(filename)
#Do not archive the binaries directory, it should just be delivered as is
if 'bin' in subdirs:
subdirs.remove('bin')
#Do not archive any previous archives, or you will just make a giant snowball
if 'bak.zip' in files:
files.remove('bak.zip')
if 'bak.enc' in files:
files.remove('bak.enc')
zf.write(dirname)
for filename in files:
zf.write(os.path.join(dirname, filename))
#If there was a folder 'dat' under the binaries folder, then archive it too,
#so that you have everything you need to rebuild the project
print("Including files under 'bin/dat'")
if os.path.isdir(dircurr+'/bin/dat'):
for dirname, subdirs, files in os.walk(dircurr+'/bin/dat'):
if 'bin' in subdirs:
subdirs.remove('bin')
zf.write(dirname)
for filename in files:
zf.write(os.path.join(dirname, filename))
#If there were any files '*.ico' under the binaries folder, then archive them too,
#so that you have everything you need to rebuild the project
print("Including .ico files under 'bin'")
for dirname, subdirs, files in os.walk(dircurr+'/bin'):
for filename in files:
if filename[-4:]=='.ico':
zf.write(os.path.join(dirname, filename))
zf.close()
print("\nZipped to '"+dircurr+"/bak.zip'")
print("\nEncrypting zipped file and removing unencrypted zipped file...")
with open(dircurr+'/bak.zip', 'rb') as in_file, open(dirwithenc+'/bak.enc', 'wb') as out_file:
encrypt(in_file, out_file, password)
os.remove(dircurr+'/bak.zip')
print("\nEncrypted to '"+dirwithenc+"/bak.enc'")
raw_input("""
***DONE***
Press Enter...""")
exit(0)
【讨论】：
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