Replace rtc::CryptString with std::string

Replace rtc::CryptString with std::string

CryptString is intended for secret data, such as passwords, and the
memory is cleared on deallocation. However, where it is used in
libjingle_xmpp, the password is copied to other objects without any
magic clearing, so the security benefit is questionable.

In addition, CryptString is yet another string class, it's unused
within webrtc, and essentially unmaintained. If we can replace its use
in Chrome, it will be deleted.

BUG=webrtc:6424
Review-Url: https://codereview.chromium.org/2738973004
Cr-Commit-Position: refs/heads/master@{#456021}
Committed: https://chromium.googlesource.com/chromium/src/+/871bffc2d8203073da09b7ac16eec2e8a589725a

[nisse-chromium (ooo August 14), 2017-03-09 12:51:21]

The CQ bit was checked by nisse@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-03-09 12:51:35]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[nisse-chromium (ooo August 14), 2017-03-09 13:01:56]

nisse@chromium.org changed reviewers:
+ palmer@chromium.org, sergeyu@chromium.org

[nisse-chromium (ooo August 14), 2017-03-09 13:01:57]

PTAL. 

palmer@, can you review random security-related changes like this one? I'm
mainly working with webrtc, and I don't know how password strings are handled
elsewhere in Chrome.

For background, I tried to delete cryptstring.{h,cc} in webrtc (cl
https://codereview.webrtc.org/2740633003/), but had to revert due to this use in
Chrome. 

And all code in the libjingle_xmpp directory were recently moved over from
webrtc to Chrome, since there were no other uses of it.

https://codereview.chromium.org/2738973004/diff/1/third_party/libjingle_xmpp/...
File third_party/libjingle_xmpp/xmpp/saslplainmechanism.h (right):

https://codereview.chromium.org/2738973004/diff/1/third_party/libjingle_xmpp/...
third_party/libjingle_xmpp/xmpp/saslplainmechanism.h:36:
el->AddText(Base64EncodeFromArray(ss.str().data(), ss.str().length()));
I think this is where the password is ultimately used. It's copied into the
XmlElement object, which, as far as I'm aware, doesn't overwrite it before
deallocation.

[commit-bot: I haz the power, 2017-03-09 14:08:29]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2017-03-09 14:08:30]

Dry run: This issue passed the CQ dry run.

[Sergey Ulanov, 2017-03-09 18:25:25]

lgtm

[palmer, 2017-03-10 02:59:45]

LGTM.

[nisse-chromium (ooo August 14), 2017-03-10 07:58:36]

The CQ bit was checked by nisse@chromium.org

[commit-bot: I haz the power, 2017-03-10 07:58:44]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-03-10 08:03:14]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1489132716368840, "parent_rev":
"33aee2483346831a1881aeedc837cb5bc6cbe97c", "commit_rev":
"871bffc2d8203073da09b7ac16eec2e8a589725a"}

[commit-bot: I haz the power, 2017-03-10 08:03:51]

Description was changed from

==========
Replace rtc::CryptString with std::string

CryptString is intended for secret data, such as passwords, and the
memory is cleared on deallocation. However, where it is used in
libjingle_xmpp, the password is copied to other objects without any
magic clearing, so the security benefit is questionable.

In addition, CryptString is yet another string class, it's unused
within webrtc, and essentially unmaintained. If we can replace its use
in Chrome, it will be deleted.

BUG=webrtc:6424
==========

to

==========
Replace rtc::CryptString with std::string

CryptString is intended for secret data, such as passwords, and the
memory is cleared on deallocation. However, where it is used in
libjingle_xmpp, the password is copied to other objects without any
magic clearing, so the security benefit is questionable.

In addition, CryptString is yet another string class, it's unused
within webrtc, and essentially unmaintained. If we can replace its use
in Chrome, it will be deleted.

BUG=webrtc:6424

Review-Url: https://codereview.chromium.org/2738973004
Cr-Commit-Position: refs/heads/master@{#456021}
Committed:
https://chromium.googlesource.com/chromium/src/+/871bffc2d8203073da09b7ac16ee...
==========

[commit-bot: I haz the power, 2017-03-10 08:03:52]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/chromium/src/+/871bffc2d8203073da09b7ac16ee...

[RE66, 2017-03-10 11:17:56]

On 2017/03/10 08:03:52, commit-bot: I haz the power wrote:
> Committed patchset #1 (id:1) as
>
https://chromium.googlesource.com/chromium/src/+/871bffc2d8203073da09b7ac16ee...

Bad patch , unneeded security path
what is needed is to ask libjingle to support encrypted strings