Differential D6829 Diff 17203 src/ioslaves/file/file_unix.cpp

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src/ioslaves/file/file_unix.cpp

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34#include <QDebug> 34​#include <QDebug>
35#include <kconfiggroup.h> 35​#include <kconfiggroup.h>
36#include <klocalizedstring.h> 36​#include <klocalizedstring.h>
37#include <kmountpoint.h> 37​#include <kmountpoint.h>
38 38​
39#include <errno.h> 39​#include <errno.h>
40#include <utime.h> 40​#include <utime.h>
41 41​
42​#include <KAuth>
43​
42//sendfile has different semantics in different platforms 44​//sendfile has different semantics in different platforms
43#if defined HAVE_SENDFILE && defined Q_OS_LINUX 45​#if defined HAVE_SENDFILE && defined Q_OS_LINUX
44#define USE_SENDFILE 1 46​#define USE_SENDFILE 1
45#endif 47​#endif
46 48​
47#ifdef USE_SENDFILE 49​#ifdef USE_SENDFILE
48#include <sys/sendfile.h> 50​#include <sys/sendfile.h>
49#endif 51​#endif
▲ Show 20 Lines • Show All 595 Lines • ▼ Show 20 Line(s)646 for (; it1 != mOutgoingMetaData.end(); it1++) {
645 // qDebug() << it1.key() << " = " << it1.data(); 647​ // qDebug() << it1.key() << " = " << it1.data();
646 } 648​ }
647///////// 649​/////////
648#endif 650​#endif
649 statEntry(entry); 651​ statEntry(entry);
650 652​
651 finished(); 653​ finished();
652} 654​}
655​
656​bool FileProtocol::execWithElevatedPrivilege(int error, ActionType action, const QVariant &arg1,
657​ const QVariant &arg2, const QVariant &arg3)
658​{
659​ if (error != EACCES || !isPrivilegeOperationAllowed()) {
dfaureUnsubmitted
Not Done

with EPERM we should try as root too, no?

(e.g. for unlink, rename, chown...)

dfaure: with EPERM we should try as root too, no? (e.g. for unlink, rename, chown...)
660​ return false;
661​ }
662​
663​ QByteArray helperArgs;
664​ QDataStream out(&helperArgs, QIODevice::WriteOnly);
665​ out << action << arg1 << arg2 << arg3;
666​
dfaureUnsubmitted
Not Done

Who's going to read that value? The caller? Abusing errno to ship a return value via global state reads horrible to me.... we're not a libc function....

dfaure: Who's going to read that value? The caller? Abusing errno to ship a return value via global…
dfaureUnsubmitted
Not Done

No chance to return an enum instead of a bool here, to avoid modifying state?

The problem with mUserCanceled is that it's easy to get it wrong. Like in this patch, which never resets it to false for the next operation after one canceled operation. It's just cleaner to return an enum instead of modifying a member variable temporarily, although the question is, in both cases, what the caller code will look like...

My fear with a member var is that too many callers will forget to check it.
Let's approach this from the viewpoint of the calling code.

Before:

if (!dir.rmdir(itemPath)) {
    error(KIO::ERR_CANNOT_DELETE, itemPath);
    return false;
}

After:

if (!dir.rmdir(itemPath)) {
    if (auto ret = execWithElevatedPrivilege(RMDIR, itemPath)) { // for this to work, success must be 0 (or the returned type can be a class with operator bool()...)
        if (ret == KIO::OperationCanceled) { // or a different enum
            error(KIO::ERR_USER_CANCELED, itemPath);
        } else {
            error(KIO::ERR_CANNOT_DELETE, itemPath);
        }
        return false;
    }
}

Alternatively, since we know cancelling will always need to error(KIO::ERR_USER_CANCELED) (and the QString argument doesn't matter), we could call error from within execWithElevatedPrivilege. But we still need the enum ret val:

if (!dir.rmdir(itemPath)) {
    if (auto ret = execWithElevatedPrivilege(RMDIR, itemPath)) { // see above
        if (ret != KIO::OperationCanceled) { // or a different enum
            error(KIO::ERR_CANNOT_DELETE, itemPath);
        }
        return false;
    }
}

I actually like the idea of returning a small class. Then it could even have a wasCanceled() method... we don't need an enum, we need a value that can convert to bool (for the if) and additionally let us know if cancelation happened. But all this in a temporary value, not in a member var of slavebase.

To flesh it out in more details:

class ExecWithElevatedPrivilegeReturnValue
{
public:
    static ExecWithElevatedPrivilegeReturnValue success() { return ExecWithElevatedPrivilegeReturnValue{true, false}; }
    static ExecWithElevatedPrivilegeReturnValue failure() { return ExecWithElevatedPrivilegeReturnValue{true, false}; }
    static ExecWithElevatedPrivilegeReturnValue canceled() { return ExecWithElevatedPrivilegeReturnValue{true, true}; }
    operator bool() const { return m_success; }
    bool wasCanceled() const { return m_canceled; }
private:
    ExecWithElevatedPrivilegeReturnValue(bool success, bool canceled) : m_success(success), m_canceled(canceled) {}
    const bool m_success;
    const bool m_canceled;
};

(no setters, all of the slave code shouldn't be able to change this object, it's created immediately with the right values)

With this, the calling code can be simply

if (!dir.rmdir(itemPath)) {
    if (auto ret = execWithElevatedPrivilege(RMDIR, itemPath)) {
        if (!ret.wasCanceled()) {
            error(KIO::ERR_CANNOT_DELETE, itemPath);
        }
        return false;
    }
}

and the code in this review (execWithElevatedPrivilege) can do things like return ExecWithElevatedPrivilegeReturnValue::canceled(); etc.

How does that sound?

dfaure: No chance to return an enum instead of a bool here, to avoid modifying state? The problem with…
667​ QVariantMap argv;
668​ argv.insert(QStringLiteral("arguments"), helperArgs);
669​
670​ KAuth::Action execAction(QStringLiteral("org.kde.kio.file.exec"));
dfaureUnsubmitted
Done

Wait, why the two step roundtrip here?
Instead of "can you become root?" / "yes I can" / "ok please ask the user" / "OK, the user said yes", the protocol here could really be simplified to
"request to elevate privilege" "OK (it's enabled, and the user said yes)".

Which even removes the need for any enum, it's really just one request and one reply which is true or false.

dfaure: Wait, why the two step roundtrip here? Instead of "can you become root?" / "yes I can" / "ok…
671​ execAction.setHelperId(QStringLiteral("org.kde.kio.file"));
672​ execAction.setArguments(argv);
673​
674​ // if we are unit testing let's pretend to execute the action.
675​ if (metaData(QStringLiteral("UnitTesting")) == QLatin1String("true")) {
676​ const QString metaData = execAction.name() + ","
677​ + QString::number(execAction.isValid()) + ","
dfaureUnsubmitted
Not Done

single-quotes for the commas (','), like in my earlier recommendation.

dfaure: single-quotes for the commas (','), like in my earlier recommendation.
678​ + execAction.helperId() + ","
679​ + QString::number(execAction.status()) + ",";
680​ setMetaData(QStringLiteral("TestData"), metaData);
681​ return true;
682​ }
683​
684​ auto reply = execAction.execute();
685​ if (reply->exec()) {
686​ return true;
687​ }
688​
689​ return false;
690​}
dfaureUnsubmitted
Done

use C++11 initializer to avoid reallocations, i.e. QStringList testData{execAction.name(), ..., ..., ...};

Ah but then you just use a join(","), so the most efficient thing to do here would be to drop the QStringList and do

const QString metaData = execAction.name() + ',' + QString::number... + ',' + etc.
dfaure: use C++11 initializer to avoid reallocations, i.e. `QStringList testData{execAction.name(), ...