core: Make sure and check that LimitXMLRequestBody fits in system memory.

LimitXMLRequestBody can not exceed the size needed to ap_escape_html2() the
body without failing to allocate memory, so enforce this at load time based
on APR_SIZE_MAX, and make sure that ap_escape_html2() is within the bounds.

Document the limits for LimitXMLRequestBody in our docs.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1898686 13f79535-47bb-0310-9956-ffa450edef68

diff --git a/changes-entries/AP_MAX_LIMIT_XML_BODY.diff b/changes-entries/AP_MAX_LIMIT_XML_BODY.diff
new file mode 100644 (file)
index 0000000..07fef3c
--- /dev/null
+++ b/changes-entries/AP_MAX_LIMIT_XML_BODY.diff
@@ -0,0 +1,2 @@
+  *) core: Make sure and check that LimitXMLRequestBody fits in system memory.
+     [Ruediger Pluem, Yann Ylavic]
\ No newline at end of file

diff --git a/docs/manual/mod/core.xml b/docs/manual/mod/core.xml
index e22545e8cfe8f5cc9532ade0011e3ea6c17af8cb..bb493d8fc4152ff6c5c058ae16ec08e7c3bce093 100644 (file)
--- a/docs/manual/mod/core.xml
+++ b/docs/manual/mod/core.xml
@@ -3044,13 +3044,19 @@ LimitRequestLine 4094
 <override>All</override>
 
 <usage>
-    <p>Limit (in bytes) on maximum size of an XML-based request
-    body. A value of <code>0</code> will disable any checking.</p>
+    <p>Limit (in bytes) on the maximum size of an XML-based request
+    body. A value of <code>0</code> will apply a hard limit (depending on
+    32bit vs 64bit system) allowing for XML escaping within the bounds of
+    the system addressable memory, but it exists for compatibility only
+    and is not recommended since it does not account for memory consumed
+    elsewhere or concurrent requests, which might result in an overall
+    system out-of-memory.
 
     <p>Example:</p>
 
     <highlight language="config">
-LimitXMLRequestBody 0
+# Limit of 1 MiB
+LimitXMLRequestBody 1073741824
     </highlight>
 
 </usage>

diff --git a/server/core.c b/server/core.c
index 67c36f8134d26c0d0223bce6628c1138fdf11fd8..1730ceee44bbc1aa99dcdc54022782d062028caf 100644 (file)
--- a/server/core.c
+++ b/server/core.c
@@ -73,6 +73,8 @@
 /* LimitXMLRequestBody handling */
 #define AP_LIMIT_UNSET                  ((long) -1)
 #define AP_DEFAULT_LIMIT_XML_BODY       ((apr_size_t)1000000)
+/* Hard limit for ap_escape_html2() */
+#define AP_MAX_LIMIT_XML_BODY           ((apr_size_t)(APR_SIZE_MAX / 6 - 1))
 
 #define AP_MIN_SENDFILE_BYTES           (256)
 
@@ -3888,6 +3890,11 @@ static const char *set_limit_xml_req_body(cmd_parms *cmd, void *conf_,
     if (conf->limit_xml_body < 0)
         return "LimitXMLRequestBody requires a non-negative integer.";
 
+    /* zero is AP_MAX_LIMIT_XML_BODY (implicitly) */
+    if ((apr_size_t)conf->limit_xml_body > AP_MAX_LIMIT_XML_BODY)
+        return apr_psprintf(cmd->pool, "LimitXMLRequestBody must not exceed "
+                            "%" APR_SIZE_T_FMT, AP_MAX_LIMIT_XML_BODY);
+
     return NULL;
 }
 
@@ -3976,6 +3983,8 @@ AP_DECLARE(apr_size_t) ap_get_limit_xml_body(const request_rec *r)
     conf = ap_get_core_module_config(r->per_dir_config);
     if (conf->limit_xml_body == AP_LIMIT_UNSET)
         return AP_DEFAULT_LIMIT_XML_BODY;
+    if (conf->limit_xml_body == 0)
+        return AP_MAX_LIMIT_XML_BODY;
 
     return (apr_size_t)conf->limit_xml_body;
 }

diff --git a/server/util.c b/server/util.c
index 2018396e5a2f6dac23e7e85ae8fd58a1cdfe5b6b..771ba7b16f3047c1d5eb1f15e95492f0a442b08d 100644 (file)
--- a/server/util.c
+++ b/server/util.c
@@ -2152,11 +2152,14 @@ AP_DECLARE(char *) ap_escape_urlencoded(apr_pool_t *p, const char *buffer)
 
 AP_DECLARE(char *) ap_escape_html2(apr_pool_t *p, const char *s, int toasc)
 {
-    int i, j;
+    apr_size_t i, j;
     char *x;
 
     /* first, count the number of extra characters */
-    for (i = 0, j = 0; s[i] != '\0'; i++)
+    for (i = 0, j = 0; s[i] != '\0'; i++) {
+        if (i + j > APR_SIZE_MAX - 6) {
+            abort();
+        }
         if (s[i] == '<' || s[i] == '>')
             j += 3;
         else if (s[i] == '&')
@@ -2165,6 +2168,7 @@ AP_DECLARE(char *) ap_escape_html2(apr_pool_t *p, const char *s, int toasc)
             j += 5;
         else if (toasc && !apr_isascii(s[i]))
             j += 5;
+    }
 
     if (j == 0)
         return apr_pstrmemdup(p, s, i);

diff --git a/server/util_xml.c b/server/util_xml.c
index 4845194656ef935029705f68fc649d954090c314..22806fa8a40a1eee11a05e3861d4ae3cab435113 100644 (file)
--- a/server/util_xml.c
+++ b/server/util_xml.c
@@ -85,7 +85,7 @@ AP_DECLARE(int) ap_xml_parse_input(request_rec * r, apr_xml_doc **pdoc)
             }
 
             total_read += len;
-            if (limit_xml_body && total_read > limit_xml_body) {
+            if (total_read > limit_xml_body) {
                 ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r, APLOGNO(00539)
                               "XML request body is larger than the configured "
                               "limit of %lu", (unsigned long)limit_xml_body);