[Libguestfs] [PATCH] hivexml

[Alex Nelson]

I will try to test this by tomorrow afternoon and let you know how well it works compared to what I tried previously.

--Alex


On Feb 1, 2012, at 13:08 , Todd Mummert wrote:

> I changed the name of the function to is_valid_xml_string() to avoid
> camel-case.   I also briefly commented the function itself, since it
> does expect its input to be valid UTF-8.   Also, the patch was missing
> an end-attribute call, which apparently didn't matter in this case
> since the element was being ended subsequently anyway -- but it
> missing was an oversight, not intentional.
> 
> The updated patch to handle illegal XML characters that appear in
> registry values is below:
> 
> [todd at tm-nc hivex]# cat hivexml.patch
> diff -urNp hivex-1.3.3-orig/xml/hivexml.c hivex-1.3.3-new/xml/hivexml.c
> --- hivex-1.3.3-orig/xml/hivexml.c      2011-09-22 09:17:09.000000000 -0400
> +++ hivex-1.3.3-new/xml/hivexml.c       2012-02-01 15:51:06.481728986 -0500
> @@ -33,6 +33,7 @@
> #endif
> 
> #include <libxml/xmlwriter.h>
> +#include <libxml/chvalid.h>
> 
> #include "hivex.h"
> 
> @@ -208,6 +209,26 @@ filetime_to_8601 (int64_t windows_ticks)
>   return ret;
> }
> 
> +/*
> + * Check that a UTF-8 string contains only valid XML characters.
> + * There is an assumption that the input string is valid UTF-8.
> + */
> +static int
> +is_valid_xml_string(const char *string)
> +{
> +  int c;
> +  int pos = 0;
> +  int len = strlen(string);
> +  int charlen = len;
> +  while ((c = xmlGetUTF8Char(string+pos, &charlen)) >= 0) {
> +    if (xmlIsCharQ(c) == 0)
> +      return 0;
> +    pos += charlen;
> +    charlen = len - pos;
> +  }
> +  return 1;
> +}
> +
> static int
> node_start (hive_h *h, void *writer_v, hive_node_h node, const char *name)
> {
> @@ -265,6 +286,20 @@ end_value (xmlTextWriterPtr writer)
>   XML_CHECK (xmlTextWriterEndElement, (writer));
> }
> 
> +static void
> +start_string(xmlTextWriterPtr writer, const char *encoding)
> +{
> +  XML_CHECK (xmlTextWriterStartElement, (writer, BAD_CAST "string"));
> +  if (encoding)
> +    XML_CHECK (xmlTextWriterWriteAttribute, (writer, BAD_CAST
> "encoding", BAD_CAST encoding));
> +}
> +
> +static void
> +end_string(xmlTextWriterPtr writer)
> +{
> +  XML_CHECK (xmlTextWriterEndElement, (writer));
> +}
> +
> static int
> value_string (hive_h *h, void *writer_v, hive_node_h node, hive_value_h value,
>               hive_type t, size_t len, const char *key, const char *str)
> @@ -292,9 +327,14 @@ value_string (hive_h *h, void *writer_v,
>     type = "unknown";
>   }
> 
> -  start_value (writer, key, type, NULL);
> +  int validXML = is_valid_xml_string(str);
> +  start_value (writer, key, type, validXML ? NULL : "base64");
>   XML_CHECK (xmlTextWriterStartAttribute, (writer, BAD_CAST "value"));
> -  XML_CHECK (xmlTextWriterWriteString, (writer, BAD_CAST str));
> +  if (validXML)
> +    XML_CHECK (xmlTextWriterWriteString, (writer, BAD_CAST str));
> +  else
> +    XML_CHECK (xmlTextWriterWriteBase64, (writer, str, 0, strlen(str)));
> +
>   XML_CHECK (xmlTextWriterEndAttribute, (writer));
>   end_value (writer);
>   return 0;
> @@ -310,9 +350,15 @@ value_multiple_strings (hive_h *h, void
> 
>   size_t i;
>   for (i = 0; argv[i] != NULL; ++i) {
> -    XML_CHECK (xmlTextWriterStartElement, (writer, BAD_CAST "string"));
> -    XML_CHECK (xmlTextWriterWriteString, (writer, BAD_CAST argv[i]));
> -    XML_CHECK (xmlTextWriterEndElement, (writer));
> +    int validXML = is_valid_xml_string(argv[i]);
> +    start_string(writer, validXML ? NULL : "base64");
> +    XML_CHECK (xmlTextWriterStartAttribute, (writer, BAD_CAST "value"));
> +    if (validXML)
> +      XML_CHECK (xmlTextWriterWriteString, (writer, BAD_CAST argv[i]));
> +    else
> +      XML_CHECK (xmlTextWriterWriteBase64, (writer, argv[i], 0,
> strlen(argv[i])));
> +    XML_CHECK (xmlTextWriterEndAttribute, (writer));
> +    end_string(writer);
>   }
> 
>   end_value (writer);
> [todd at tm-nc hivex]#
> 
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