From: Alex Rousskov <rousskov@measurement-factory.com>
Date: Mon, 26 Nov 2012 18:54:43 +0000 (-0700)
Subject: Make it possible to match empty header field values using req_header and rep_header.
X-Git-Tag: SQUID_3_4_0_1~473
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=b2c447187eb0087fc63bfe5bd3b32d858ac3337f;p=thirdparty%2Fsquid.git

Make it possible to match empty header field values using req_header and rep_header.

Warning: Some req_header and rep_header ACLs that were [accidentally] not
matching empty headers (e.g., "^$" or ".*") will now start matching them.


A new HttpHeader::getByNameIfPresent() method is added to be able to detect
presence of empty header fields while ACLHTTPHeaderData::match() is adjusted
to convert undefined String values into empty c-strings ("") for
ACLRegexData::match() to work.

Prior to these changes, when trying to match an empty header value with a
regex like "^$", ACLHTTPHeaderData::match() would return false because:

  * HttpHeader::getStrOrList() and getByName() return an undefined String.
  * String::termedBuf() returns NULL for undefined Strings; and
  * ACLRegexData::match() always fails on NULL c-strings.
---

diff --git a/src/HttpHeader.cc b/src/HttpHeader.cc
index 1333cf5ccb..4515303804 100644
--- a/src/HttpHeader.cc
+++ b/src/HttpHeader.cc
@@ -1020,10 +1020,19 @@ HttpHeader::getStrOrList(http_hdr_type id) const
 }
 
 /*
- * Returns the value of the specified header.
+ * Returns the value of the specified header and/or an undefined String.
  */
 String
 HttpHeader::getByName(const char *name) const
+{
+    String result;
+    // ignore presence: return undefined string if an empty header is present
+    (void)getByNameIfPresent(name, result);
+    return result;
+}
+
+bool
+HttpHeader::getByNameIfPresent(const char *name, String &result) const
 {
     http_hdr_type id;
     HttpHeaderPos pos = HttpHeaderInitPos;
@@ -1034,19 +1043,23 @@ HttpHeader::getByName(const char *name) const
     /* First try the quick path */
     id = httpHeaderIdByNameDef(name, strlen(name));
 
-    if (id != -1)
-        return getStrOrList(id);
-
-    String result;
+    if (id != -1) {
+        if (!has(id))
+            return false;
+        result = getStrOrList(id);
+        return true;
+    }
 
     /* Sorry, an unknown header name. Do linear search */
+    bool found = false;
     while ((e = getEntry(&pos))) {
         if (e->id == HDR_OTHER && e->name.caseCmp(name) == 0) {
+            found = true;
             strListAdd(&result, e->value.termedBuf(), ',');
         }
     }
 
-    return result;
+    return found;
 }
 
 /*
diff --git a/src/HttpHeader.h b/src/HttpHeader.h
index 4def174193..e93cf95d67 100644
--- a/src/HttpHeader.h
+++ b/src/HttpHeader.h
@@ -247,6 +247,8 @@ public:
     bool getList(http_hdr_type id, String *s) const;
     String getStrOrList(http_hdr_type id) const;
     String getByName(const char *name) const;
+    /// sets value and returns true iff a [possibly empty] named field is there
+    bool getByNameIfPresent(const char *name, String &value) const;
     String getByNameListMember(const char *name, const char *member, const char separator) const;
     String getListMember(http_hdr_type id, const char *member, const char separator) const;
     int has(http_hdr_type id) const;
diff --git a/src/acl/HttpHeaderData.cc b/src/acl/HttpHeaderData.cc
index 7ba80d9086..d84633df05 100644
--- a/src/acl/HttpHeaderData.cc
+++ b/src/acl/HttpHeaderData.cc
@@ -65,9 +65,23 @@ ACLHTTPHeaderData::match(HttpHeader* hdr)
 
     debugs(28, 3, "aclHeaderData::match: checking '" << hdrName << "'");
 
-    String value = hdrId != HDR_BAD_HDR ? hdr->getStrOrList(hdrId) : hdr->getByName(hdrName.termedBuf());
+    String value;
+    if (hdrId != HDR_BAD_HDR) {
+        if (!hdr->has(hdrId))
+            return false;
+        value = hdr->getStrOrList(hdrId);
+    } else {
+        if (!hdr->getByNameIfPresent(hdrName.termedBuf(), value))
+            return false;
+    }
 
-    return regex_rule->match(value.termedBuf());
+    // By now, we know the header is present, but:
+    // HttpHeader::get*() return an undefined String for empty header values;
+    // String::termedBuf() returns NULL for undefined Strings; and
+    // ACLRegexData::match() always fails on NULL strings.
+    // This makes it possible to detect an empty header value using regex:
+    const char *cvalue = value.defined() ? value.termedBuf() : "";
+    return regex_rule->match(cvalue);
 }
 
 wordlist *