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Escape rather than remove any printable characters in UAs #10731

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@luke-jr @jgarzik @MarcoFalke @promag @laanwj @gmaxwell @jonasschnelli @TheBlueMatt @ryanofsky
@luke-jr
Member

luke-jr commented Jul 3, 2017 •
Edited 1 time

Current Core strips out the !, + and = characters used by the UASF client and Knots to indicate whether BIP148 enforcement is enabled. This expands the allowed characters to all printable ASCII characters for the GUI, and escapes the disallowed-from-log ones in %XX format when printing to the log.
@jgarzik
Contributor

jgarzik commented Jul 3, 2017

It seems risky to put quote chars in there.
@luke-jr
Member

luke-jr commented Jul 3, 2017

Hmm, you mean in case someone is reading the log and inserting it into a SQL database or something?
@jgarzik
Contributor

jgarzik commented Jul 3, 2017

@luke-jr Yep. Or it makes its way to the command line, and someone is lazy and fails to quote. We've seen this movie before :)

@jonasschnelli jonasschnelli added the P2P label Jul 3, 2017

@luke-jr luke-jr changed the title from net_processing: Avoid filtering any printable characters from UAs in the log to SanitizeString: Expand upon allowed characters in logging to include "!#%&*+=^{}~" Jul 3, 2017

@luke-jr
Member

luke-jr commented Jul 3, 2017

Reduced the subset to avoid quotes and other possibly dangerous characters, and just made it the default (which is only used for logging).
@gmaxwell

gmaxwell reviewed Jul 4, 2017
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NAK.

! can divert shell processing (past event references), % and & can divert URIs and HTML contexts (by constructing other prohibited characters).

Do we really need to do things like this? Reviewing these sorts of things take time an effort that could better be spent elsewhere.

@luke-jr
Member

luke-jr commented Jul 4, 2017

I can remove % and & (although IMO this is a bit too much nannying), but ! is needed to properly log existing UAs...
@MarcoFalke
Member

MarcoFalke commented Jul 4, 2017 •
Edited 1 time

Concept NACK per @gmaxwell. The existing safe chars should be enough to generate any ua comment that might render useful.
@luke-jr
Member

luke-jr commented Jul 4, 2017

@MarcoFalke I'm not talking about a speculative scenario. UAs using !, +, and = are already live on the network. This only fixes the display and logging of these.

And the existing safe chars uses the same limits for both -uacomment options as well as the log filtering. That particular combination makes it impossible to have code-only UA comments, hence why the usage of !, +, and = were necessary.
@luke-jr
Member

luke-jr commented Jul 4, 2017

(Also, the super-nanny approach of not allowing any possible "needs escaping" characters already sailed a long time ago: ; is one of the most dangerous such characters, and has been allowed from the start.)
@promag
Contributor

promag commented Jul 4, 2017

; is one of the most dangerous such characters, and has been allowed from the start.)

@luke-jr that doesn't sound a good argument 😄.
@laanwj
Owner

laanwj commented Jul 6, 2017

Do we really need to do things like this? Reviewing these sorts of things take time an effort that could better be spent elsewhere.

I agree, I'd rather not make this change.
@luke-jr
Member

luke-jr commented Jul 6, 2017

@laanwj You yourself added shell characters in #4983 ...

How do we get this fixed? Would it help to reduce it to just !, +, and = so it only addresses the real-world issue?
@gmaxwell
Member

gmaxwell commented Jul 6, 2017

! is shell problematic
@jonasschnelli
Member

jonasschnelli commented Jul 13, 2017

Closing because seems not something we should do.

@jonasschnelli jonasschnelli closed this Jul 13, 2017

@luke-jr
Member

luke-jr commented Jul 13, 2017

Please reopen. This is a bug fix for a present issue, for which no alternate solutions have been proposed.

We already use/allow "shell-problematic" characters (such as parenthesis and semicolon), and worrying about them in log files is pretty absurd anyway. My bitcoin logs already have ! from other sources anyway.
@jonasschnelli
Member

jonasschnelli commented Jul 13, 2017

But @luke-jr: your changing the default charset for the general function SanitizeString() where you break the assumption that this function produces a sanitized/safe string?
If you wan't to fix a bug, I think you should find a ways that doesn't break that – reasonable – assumption.
Example: there are open pull requests who want to use SanitizeString for user feedback (via CLI, RPC). Not sure if this is a good idea or not but it clearly shows that SanitizeString() should include shell/pipe safety.
@jonasschnelli
Member

jonasschnelli commented Jul 13, 2017

reopening

@jonasschnelli jonasschnelli reopened this Jul 13, 2017

@luke-jr luke-jr changed the title from SanitizeString: Expand upon allowed characters in logging to include "!#%&*+=^{}~" to Escape rather than remove any printable characters in UAs Jul 13, 2017

@luke-jr
Member

luke-jr commented Jul 13, 2017

Rewrote this to only allow the full set of printable characters in the GUI where it should be harmless, and to escape them in %XX format when printing to the log.
src/utilstrencodings.cpp
strResult.push_back(str[i]);
+ } else if (escape) {
+ strResult += strprintf("%02x", str[i]);
@ryanofsky

ryanofsky Jul 13, 2017 •
Edited 1 time

Contributor

This isn't really escaping, because the output is ambiguous (there no way to detect escape sequences and recover the original string). Probably would be better to change to something like strprintf("%%%02X", str[i]) or strprintf("\\x%02X", str[i]) to use a more standard url-style or c-style escape format.

Also, if you do url-style or c-style escaping you should make sure the % or \ escape character is itself escaped by tweaking the SAFE_CHARS.find condition or just not including the character in SAFE_CHAR lists.

@luke-jr

luke-jr Jul 13, 2017

Member

Indeed, it was supposed to be %%%02x

Fixed

src/utilstrencodings.cpp
strResult.push_back(str[i]);
+ } else if (escape) {
+ strResult += strprintf("%%%02x", str[i]);
@ryanofsky

ryanofsky Jul 13, 2017

Contributor

You will also want to remove the % character from SAFE_CHARS_PRINTABLE so it will be escaped itself, or alternately add a && (!escape || str[i] != '%') clause to the find check above.

@ryanofsky

ryanofsky Jul 13, 2017 •
Edited 1 time

Contributor

Maybe use %02X instead of %02x since it helps escape sequences stand out a little more, and is the more common way you see percent encoding done.

@luke-jr

luke-jr Jul 17, 2017

Member

Done

@TheBlueMatt
Contributor

TheBlueMatt commented Jul 14, 2017

Can we instead remove exposing of subver entirely? I'm really tired of people "voting" by spinning up sybil attacks, its just not in any way useful.
@luke-jr
Member

luke-jr commented Jul 17, 2017

@TheBlueMatt Whether we do or don't, it's outside the scope of this PR.
@luke-jr
Member

luke-jr commented Jul 27, 2017

@ryanofsky (addressed your nits btw)

@laanwj laanwj added the Docs and Output label Sep 6, 2017

@MarcoFalke
Member

MarcoFalke commented Sep 7, 2017

There seems to be no conceptual acknowledgment to do this. Closing for now.

@MarcoFalke MarcoFalke closed this Sep 7, 2017

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