commit f1657a9decc820f748fa3aff68168d3145258031
Author: Christos Tsantilas <christos@chtsanti.net>
Date:   2018-10-17 15:14:07 +0000

    Certificate fields injection via %D in ERR_SECURE_CONNECT_FAIL (#306)
    
    %ssl_subject, %ssl_ca_name, and %ssl_cn values were not properly escaped when %D code was expanded in HTML context of the ERR_SECURE_CONNECT_FAIL template. This bug affects all
    ERR_SECURE_CONNECT_FAIL page templates containing %D, including the default template.
    
    Other error pages are not vulnerable because Squid does not populate %D with certificate details in other contexts (yet).
    
    Thanks to Nikolas Lohmann [eBlocker] for identifying the problem.
    
    TODO: If those certificate details become needed for ACL checks or other non-HTML purposes, make their HTML-escaping conditional.
    
    This is a Measurement Factory project.

diff --git a/src/ssl/ErrorDetail.cc b/src/ssl/ErrorDetail.cc
index b5030e3..314e998 100644
--- a/src/ssl/ErrorDetail.cc
+++ b/src/ssl/ErrorDetail.cc
@@ -8,6 +8,8 @@
 
 #include "squid.h"
 #include "errorpage.h"
+#include "fatal.h"
+#include "html_quote.h"
 #include "ssl/ErrorDetail.h"
 
 #include <climits>
@@ -432,8 +434,11 @@ const char  *Ssl::ErrorDetail::subject() const
 {
     if (broken_cert.get()) {
         static char tmpBuffer[256]; // A temporary buffer
-        if (X509_NAME_oneline(X509_get_subject_name(broken_cert.get()), tmpBuffer, sizeof(tmpBuffer)))
-            return tmpBuffer;
+        if (X509_NAME_oneline(X509_get_subject_name(broken_cert.get()), tmpBuffer, sizeof(tmpBuffer))) {
+            // quote to avoid possible html code injection through
+            // certificate subject
+            return html_quote(tmpBuffer);
+        }
     }
     return "[Not available]";
 }
@@ -461,8 +466,11 @@ const char *Ssl::ErrorDetail::cn() const
         static String tmpStr;  ///< A temporary string buffer
         tmpStr.clean();
         Ssl::matchX509CommonNames(broken_cert.get(), &tmpStr, copy_cn);
-        if (tmpStr.size())
-            return tmpStr.termedBuf();
+        if (tmpStr.size()) {
+            // quote to avoid possible html code injection through
+            // certificate subject
+            return html_quote(tmpStr.termedBuf());
+        }
     }
     return "[Not available]";
 }
@@ -474,8 +482,11 @@ const char *Ssl::ErrorDetail::ca_name() const
 {
     if (broken_cert.get()) {
         static char tmpBuffer[256]; // A temporary buffer
-        if (X509_NAME_oneline(X509_get_issuer_name(broken_cert.get()), tmpBuffer, sizeof(tmpBuffer)))
-            return tmpBuffer;
+        if (X509_NAME_oneline(X509_get_issuer_name(broken_cert.get()), tmpBuffer, sizeof(tmpBuffer))) {
+            // quote to avoid possible html code injection through
+            // certificate issuer subject
+            return html_quote(tmpBuffer);
+        }
     }
     return "[Not available]";
 }