htdocs/archive: improved xml validation

htdocs/archive/validatexml.c

@@ -0,0 +1,95 @@
+
+#include "validatexml.h"
+#include <string.h>
+#include <stdio.h>
+#include <ctype.h>
+
+void skipspaces(const char xmldata[], int *pos, int *linenr)
+{
+    const char *p = &xmldata[*pos];
+    while (isspace(*p) || *p == '\r' || *p == '\n') {
+        if (strncmp(p,"\r\n",2)==0)
+            ++p;
+        if (*p == '\r' || *p == '\n')
+            ++(*linenr);
+        ++p;
+    }
+    *pos = p - xmldata;
+}
+
+int validatexml(const char xmldata[])
+{
+    if (strncmp(xmldata,"<?xml version=\"1.0\"?>",21)!=0)
+        return 1;
+    int linenr = 1;
+    char elementNames[10][64];  // only 10 element levels handled
+    int level = 0;
+    for (int pos = 21; xmldata[pos]; pos++) {
+        if (strncmp(&xmldata[pos], "\r\n", 2)==0) {
+            ++linenr;
+            ++pos;
+        } else if (xmldata[pos]=='\r' || xmldata[pos]=='\n') {
+            ++linenr;
+        } else if (xmldata[pos] == '<') {
+            ++pos;
+            skipspaces(xmldata,&pos,&linenr);
+            if (xmldata[pos] == '/') {
+                if (level <= 0) {
+                    return linenr;
+                }
+                --level;
+                int len = strlen(elementNames[level]);
+                if (strncmp(&xmldata[pos+1],elementNames[level],len)!=0 || xmldata[pos+1+len]!='>')
+                    return linenr;
+                pos += 1 + len;
+            } else {
+                if (level > 8)
+                    return linenr;
+                if (!isalpha(xmldata[pos]))
+                    return linenr;
+                memset(elementNames[level], 0, 64);
+                for (int i = 0; i < 64; i++) {
+                    if ((xmldata[pos+i]>='a' && xmldata[pos+i]<='z') || xmldata[pos+i] == '-')
+                        elementNames[level][i] = xmldata[pos+i];
+                    else {
+                        pos += i;
+                        break;
+                    }
+                }
+
+                if (!strchr("> \r\n", xmldata[pos]))
+                    return linenr;
+
+                level++;
+
+                while (xmldata[pos] != '>') {
+                    skipspaces(xmldata,&pos,&linenr);
+                    if ((xmldata[pos] >= 'a') && xmldata[pos] <= 'z') {
+                        while (((xmldata[pos] >= 'a') && xmldata[pos] <= 'z') || xmldata[pos] == '-')
+                            ++pos;
+                        if (xmldata[pos++] != '=')
+                            return linenr;
+                        if (xmldata[pos++] != '\"')
+                            return linenr;
+                        while (isalnum(xmldata[pos]) || strchr(":-.,",xmldata[pos]))
+                            ++pos;
+                        if (xmldata[pos++] != '\"')
+                            return linenr;
+                        if (!strchr("> \r\n", xmldata[pos]))
+                            return linenr;
+                    } else if (xmldata[pos] != '>') {
+                        return linenr;
+                    }
+                }
+            }
+        } else if (xmldata[pos] == '>') {
+            return linenr;
+        }
+    }
+
+    if (level != 0)
+        return linenr;
+    
+    return -1;
+}
+

htdocs/archive/validatexml.h

@@ -0,0 +1,7 @@
+#ifndef VALIDATEXMLH
+#define VALIDATEXMLH
+
+/** validate xml data */
+int validatexml(const char xmldata[]);
+
+#endif

htdocs/archive/webarchive.h

@@ -1,3 +1,4 @@
+#include "validatexml.h"
 #include <string.h>
 #include <ctype.h>
 #include <stdio.h>
@@ -174,42 +175,17 @@ const char *validate_name_version_data(const char *data)
     i += 6;
 
     // validate xml
-    char xml[strlen(data+i)];
-    memset(xml, 0, strlen(data+i));
-    unencode(data+i, xml);
-
-    if (strncmp(xml,"<?xml version=\"1.0\"?>",21)!=0)
-        return "invalid query string: XML must start with '&lt;?xml version=\"1.0\"?&gt;'";
-    int linenr = 1;
-    enum {TEXT,ELEMENT} state = TEXT;
-    for (int pos = 21; xml[pos]; pos++) {
-        if (strncmp(&xml[pos], "\r\n", 2)==0) {
-            ++linenr;
-            ++pos;
-        } else if (xml[pos]=='\r' || xml[pos]=='\n') {
-            ++linenr;
-        } else if (xml[pos] == '<') {
-            if (state != TEXT) {
-                static char errmsg[256];
-                sprintf(errmsg, "invalid query string: Invalid XML at line %i", linenr);
-                return errmsg;
-            }
-            state = ELEMENT;
-        } else if (xml[pos] == '>') {
-            if (state != ELEMENT) {
-                static char errmsg[256];
-                sprintf(errmsg, "invalid query string: Invalid XML at line %i", linenr);
-                return errmsg;
-            }
-            state = TEXT;
-        }
-    }
-    if (state != TEXT) {
-        static char errmsg[256];
-        sprintf(errmsg, "invalid query string: Invalid XML at line %i", linenr);
-        return errmsg;
+    char xmldata[strlen(data+i)];
+    memset(xmldata, 0, strlen(data+i));
+    unencode(data+i, xmldata);
+    const int badline = validatexml(xmldata);
+    if (badline >= 1) {
+        static char buf[256];
+        sprintf(buf, "Invalid query: Invalid XML at line %i\n", badline);
+        return buf;
     }
 
+    // No error
     return NULL;
 }