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Make QTemporaryDir file name more random

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qrand() returns a number between 0 and RAND_MAX, which is only
guaranteed to be bigger than 32767. Dividing it repeatedly means
that the last bytes are always 0.

[ChangeLog][QtCore][QTemporaryDir] Fixed bug in QTemporaryDir name generator that dramatically
reduced randomness of the name.

Change-Id: I90613a652e6384296aed827e2714fe63cd8797ee
Reviewed-by: Rafael Roquetto <rafael.roquetto@kdab.com>
Reviewed-by: Tim Jenssen <tim.jenssen@digia.com>
This commit is contained in:
Kai Koehne 2013-12-11 13:14:18 +01:00 committed by The Qt Project
parent 4d8a12904a
commit 70c70aef7e
1 changed files with 25 additions and 14 deletions
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39
src/corelib/io/qtemporarydir.cpp
View File

@ -94,9 +94,19 @@ static QString defaultTemplateName()
return QDir::tempPath() + QLatin1Char('/') + baseName + QLatin1String("-XXXXXX");
}
#if defined(Q_OS_QNX ) || defined(Q_OS_WIN) || defined(Q_OS_ANDROID)
static int nextRand(int &v)
{
int r = v % 62;
v /= 62;
if (v < 62)
v = qrand();
return r;
}
static char *q_mkdtemp(char *templateName)
{
#if defined(Q_OS_QNX ) || defined(Q_OS_WIN) || defined(Q_OS_ANDROID)
static const char letters[] = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
const size_t length = strlen(templateName);
@ -110,16 +120,11 @@ static char *q_mkdtemp(char *templateName)
int v = qrand();
/* Fill in the random bits. */
XXXXXX[0] = letters[v % 62];
v /= 62;
XXXXXX[1] = letters[v % 62];
v /= 62;
XXXXXX[2] = letters[v % 62];
v /= 62;
XXXXXX[3] = letters[v % 62];
v /= 62;
XXXXXX[4] = letters[v % 62];
v /= 62;
XXXXXX[0] = letters[nextRand(v)];
XXXXXX[1] = letters[nextRand(v)];
XXXXXX[2] = letters[nextRand(v)];
XXXXXX[3] = letters[nextRand(v)];
XXXXXX[4] = letters[nextRand(v)];
XXXXXX[5] = letters[v % 62];
QString templateNameStr = QFile::decodeName(templateName);
@ -137,11 +142,17 @@ static char *q_mkdtemp(char *templateName)
}
}
return 0;
#else
return mkdtemp(templateName);
#endif
}
#else // defined(Q_OS_QNX ) || defined(Q_OS_WIN) || defined(Q_OS_ANDROID)
static char *q_mkdtemp(char *templateName)
{
return mkdtemp(templateName);
}
#endif
void QTemporaryDirPrivate::create(const QString &templateName)
{
QByteArray buffer = QFile::encodeName(templateName);