threads / patch / 22560
Subject: [PATCH 0/2] gitweb: Improve escaping
Jakub NarebskiThose two patches are dependent on each other only because of single
change in second patch, showcasing the feature.
---
Jakub Narebski (2):
gitweb: esc_html (short) error message in die_error
gitweb: Protect escaping functions against calling on undefgitweb/gitweb.perl | 11 +++++++++-- 1 files changed, 9 insertions(+), 2 deletions(-)
-- Jakub Narebski ShadeHawk on #git Poland
Jakub Narebski[PATCH 1/2] gitweb: esc_html (short) error message in die_error
The error message (second argument to die_error) is meant to be short, one-line text description of given error. A few callers call die_error with error message containing unescaped user supplied data ($hash, $file_name). Instead of forcing callers to escape data, simply call esc_html on the parameter.
Note that optional third parameter, which contains detailed error description, is meant to be HTML formatted, and therefore should be not escaped.
While at it update esc_html synopsis/usage, and bring default error description to read 'Internal Server Error' (titlecased).
Signed-off-by: Jakub Narebski <jnareb@gmail.com> --- Alternate solution would be to do escaping in call sites for die_error.
But in error messages shown on 'die' via CGI::Carp qw(fatalsToBrowser) the error message is HTML escaped, so in fact we are following here this "calling convention".
Note that for any patch relied on 'Internal server error' as error message, it must be changed to not fail wrongly.
gitweb/gitweb.perl | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/gitweb/gitweb.perl b/gitweb/gitweb.perl index a5bc359..e393f65 100755 --- a/gitweb/gitweb.perl +++ b/gitweb/gitweb.perl @@ -3374,7 +3374,7 @@ sub git_footer_html { "</html>"; } -# die_error(<http_status_code>, <error_message>) +# die_error(<http_status_code>, <error_message>[, <detailed_html_description>]) # Example: die_error(404, 'Hash not found') # By convention, use the following status codes (as defined in RFC 2616): # 400: Invalid or missing CGI parameters, or @@ -3389,7 +3389,7 @@ sub git_footer_html { # or down for maintenance). Generally, this is a temporary state. sub die_error { my $status = shift || 500; - my $error = shift || "Internal server error"; + my $error = esc_html(shift || "Internal Server Error"); my $extra = shift; my %http_responses = (
Jakub NarebskiRe: [PATCH 1/2] gitweb: esc_html (short) error message in die_error
On Sun, 7 Feb 2010, Jakub Narebski wrote:
> The error message (second argument to die_error) is meant to be short, > one-line text description of given error. A few callers call > die_error with error message containing unescaped user supplied data > ($hash, $file_name). Instead of forcing callers to escape data, > simply call esc_html on the parameter. > > Note that optional third parameter, which contains detailed error > description, is meant to be HTML formatted, and therefore should be > not escaped. > > While at it update esc_html synopsis/usage, and bring default error > description to read 'Internal Server Error' (titlecased). > > Signed-off-by: Jakub Narebski <jnareb@gmail.com> > --- > Alternate solution would be to do escaping in call sites for die_error. > > But in error messages shown on 'die' via CGI::Carp qw(fatalsToBrowser) > the error message is HTML escaped, so in fact we are following here > this "calling convention". > > Note that for any patch relied on 'Internal server error' as error > message, it must be changed to not fail wrongly.
Ping!
On one hand it introduces different treatment for second parameter to die_error (error message), which is now being HTML-escaped, and optional third parameter to die_error (detailed description), which is taken as formatted and not escaped. On the other hand this is simple solution not requiring changes in callsites, and allowing easy extending error messages with relevant information.
Another related issue is how detailed should be our one-line error messages, and what data should they include. User provided input ($file_name, $hash, etc.) should be safe if HTML-escaped. But what about adding errno message: "$!"? It can help in debugging the problem, but theoretically it exposes information to a possible attacker...
What do you think about it?
-- Jakub Narebski Poland
Jakub Narebski[PATCH 2/2] gitweb: Protect escaping functions against calling on undef
This is a bit of future-proofing esc_html and friends: when called with undefined value they would now would return undef... which would probably mean that error would still occur, but closer to the source of problem.
This means that we can safely use esc_html(shift) || "Internal Server Error" in die_error() instead of esc_html(shift || "Internal Server Error")
Signed-off-by: Jakub Narebski <jnareb@gmail.com> --- Without the second part (i.e. the change in die_error) those two patches would be totally independent.
gitweb/gitweb.perl | 9 ++++++++- 1 files changed, 8 insertions(+), 1 deletions(-)
diff --git a/gitweb/gitweb.perl b/gitweb/gitweb.perl index e393f65..c10967c 100755 --- a/gitweb/gitweb.perl +++ b/gitweb/gitweb.perl @@ -1145,6 +1145,7 @@ sub validate_refname { # in utf-8 thanks to "binmode STDOUT, ':utf8'" at beginning sub to_utf8 { my $str = shift; + return undef unless defined $str; if (utf8::valid($str)) { utf8::decode($str); return $str; @@ -1157,6 +1158,7 @@ sub to_utf8 { # correct, but quoted slashes look too horrible in bookmarks sub esc_param { my $str = shift; + return undef unless defined $str; $str =~ s/([^A-Za-z0-9\-_.~()\/:@ ]+)/CGI::escape($1)/eg; $str =~ s/ /\+/g; return $str; @@ -1165,6 +1167,7 @@ sub esc_param { # quote unsafe chars in whole URL, so some charactrs cannot be quoted sub esc_url { my $str = shift; + return undef unless defined $str; $str =~ s/([^A-Za-z0-9\-_.~();\/;?:@&=])/sprintf("%%%02X", ord($1))/eg; $str =~ s/\+/%2B/g; $str =~ s/ /\+/g; @@ -1176,6 +1179,8 @@ sub esc_html { my $str = shift; my %opts = @_; + return undef unless defined $str; + $str = to_utf8($str); $str = $cgi->escapeHTML($str); if ($opts{'-nbsp'}) { @@ -1190,6 +1195,8 @@ sub esc_path { my $str = shift; my %opts = @_; + return undef unless defined $str; + $str = to_utf8($str); $str = $cgi->escapeHTML($str); if ($opts{'-nbsp'}) { @@ -3389,7 +3396,7 @@ sub git_footer_html { # or down for maintenance). Generally, this is a temporary state. sub die_error { my $status = shift || 500; - my $error = esc_html(shift || "Internal Server Error"); + my $error = esc_html(shift) || "Internal Server Error"; my $extra = shift; my %http_responses = (
Jakub NarebskiRe: [PATCH 2/2] gitweb: Protect escaping functions against calling on undef
On Sun, 7 Feb 2010, Jakub Narebski wrote:
> This is a bit of future-proofing esc_html and friends: when called > with undefined value they would now would return undef... which would > probably mean that error would still occur, but closer to the source > of problem. > > This means that we can safely use > esc_html(shift) || "Internal Server Error" > in die_error() instead of > esc_html(shift || "Internal Server Error") > > Signed-off-by: Jakub Narebski <jnareb@gmail.com> > --- > Without the second part (i.e. the change in die_error) those two > patches would be totally independent.
Ping!
All but last chunk (last chunk depends on PATCH 1/2) are a bit of hardening / defensive programming... although currently not necessary (gitweb doesn't pass undef to its escaping subroutines... I think).
-- Jakub Narebski Poland