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gthreadedresolver: Add error checking to all record parsing

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This should catch all kinds of invalid records, and correctly report
them as errors.

Heavily based on work by Patrick Griffis in !2134.

Signed-off-by: Philip Withnall <pwithnall@endlessos.org>
This commit is contained in:
Philip Withnall 2022-03-18 15:53:18 +00:00
parent 81193c5aac
commit 023fab80f9
1 changed files with 110 additions and 21 deletions
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131
gio/gthreadedresolver.c
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@ -529,18 +529,56 @@ typedef enum __ns_type {
#endif /* __BIONIC__ */
/* Wrapper around dn_expand() which does associated length checks and returns
* errors as #GError. */
static gboolean
expand_name (const gchar *rrname,
const guint8 *answer,
const guint8 *end,
const guint8 **p,
gchar *namebuf,
gsize namebuf_len,
GError **error)
{
int expand_result;
expand_result = dn_expand (answer, end, *p, namebuf, namebuf_len);
if (expand_result < 0 || end - *p < expand_result)
{
g_set_error (error, G_RESOLVER_ERROR, G_RESOLVER_ERROR_INTERNAL,
/* Translators: the placeholder is a DNS record type, such as ‘MX’ or ‘SRV’ */
_("Error parsing DNS %s record: malformed DNS packet"), rrname);
return FALSE;
}
*p += expand_result;
return TRUE;
}
static GVariant *
parse_res_srv (const guint8 *answer,
const guint8 *end,
const guint8 **p)
const guint8 **p,
GError **error)
{
gchar namebuf[1024];
guint16 priority, weight, port;
if (end - *p < 6)
{
g_set_error (error, G_RESOLVER_ERROR, G_RESOLVER_ERROR_INTERNAL,
/* Translators: the placeholder is a DNS record type, such as ‘MX’ or ‘SRV’ */
_("Error parsing DNS %s record: malformed DNS packet"), "SRV");
return NULL;
}
GETSHORT (priority, *p);
GETSHORT (weight, *p);
GETSHORT (port, *p);
*p += dn_expand (answer, end, *p, namebuf, sizeof (namebuf));
if (!expand_name ("SRV", answer, end, p, namebuf, sizeof (namebuf), error))
return NULL;
return g_variant_new ("(qqqs)",
priority,
@ -552,14 +590,26 @@ parse_res_srv (const guint8 *answer,
static GVariant *
parse_res_soa (const guint8 *answer,
const guint8 *end,
const guint8 **p)
const guint8 **p,
GError **error)
{
gchar mnamebuf[1024];
gchar rnamebuf[1024];
guint32 serial, refresh, retry, expire, ttl;
*p += dn_expand (answer, end, *p, mnamebuf, sizeof (mnamebuf));
*p += dn_expand (answer, end, *p, rnamebuf, sizeof (rnamebuf));
if (!expand_name ("SOA", answer, end, p, mnamebuf, sizeof (mnamebuf), error))
return NULL;
if (!expand_name ("SOA", answer, end, p, rnamebuf, sizeof (rnamebuf), error))
return NULL;
if (end - *p < 20)
{
g_set_error (error, G_RESOLVER_ERROR, G_RESOLVER_ERROR_INTERNAL,
/* Translators: the placeholder is a DNS record type, such as ‘MX’ or ‘SRV’ */
_("Error parsing DNS %s record: malformed DNS packet"), "SOA");
return NULL;
}
GETLONG (serial, *p);
GETLONG (refresh, *p);
@ -580,11 +630,13 @@ parse_res_soa (const guint8 *answer,
static GVariant *
parse_res_ns (const guint8 *answer,
const guint8 *end,
const guint8 **p)
const guint8 **p,
GError **error)
{
gchar namebuf[1024];
*p += dn_expand (answer, end, *p, namebuf, sizeof (namebuf));
if (!expand_name ("NS", answer, end, p, namebuf, sizeof (namebuf), error))
return NULL;
return g_variant_new ("(s)", namebuf);
}
@ -592,14 +644,24 @@ parse_res_ns (const guint8 *answer,
static GVariant *
parse_res_mx (const guint8 *answer,
const guint8 *end,
const guint8 **p)
const guint8 **p,
GError **error)
{
gchar namebuf[1024];
guint16 preference;
if (end - *p < 2)
{
g_set_error (error, G_RESOLVER_ERROR, G_RESOLVER_ERROR_INTERNAL,
/* Translators: the placeholder is a DNS record type, such as ‘MX’ or ‘SRV’ */
_("Error parsing DNS %s record: malformed DNS packet"), "MX");
return NULL;
}
GETSHORT (preference, *p);
*p += dn_expand (answer, end, *p, namebuf, sizeof (namebuf));
if (!expand_name ("MX", answer, end, p, namebuf, sizeof (namebuf), error))
return NULL;
return g_variant_new ("(qs)",
preference,
@ -609,19 +671,35 @@ parse_res_mx (const guint8 *answer,
static GVariant *
parse_res_txt (const guint8 *answer,
const guint8 *end,
const guint8 **p)
const guint8 **p,
GError **error)
{
GVariant *record;
GPtrArray *array;
const guint8 *at = *p;
gsize len;
if (end - *p == 0)
{
g_set_error (error, G_RESOLVER_ERROR, G_RESOLVER_ERROR_INTERNAL,
/* Translators: the placeholder is a DNS record type, such as ‘MX’ or ‘SRV’ */
_("Error parsing DNS %s record: malformed DNS packet"), "TXT");
return NULL;
}
array = g_ptr_array_new_with_free_func (g_free);
while (at < end)
{
len = *(at++);
if (len > (gsize) (end - at))
break;
{
g_set_error (error, G_RESOLVER_ERROR, G_RESOLVER_ERROR_INTERNAL,
/* Translators: the placeholder is a DNS record type, such as ‘MX’ or ‘SRV’ */
_("Error parsing DNS %s record: malformed DNS packet"), "TXT");
g_ptr_array_free (array, TRUE);
return NULL;
}
g_ptr_array_add (array, g_strndup ((gchar *)at, len));
at += len;
}
@ -668,6 +746,7 @@ g_resolver_records_from_res_query (const gchar *rrname,
GList *records;
GVariant *record;
gsize len_unsigned;
GError *parsing_error = NULL;
if (len <= 0)
{
@ -744,10 +823,11 @@ g_resolver_records_from_res_query (const gchar *rrname,
{
/* Not possible to recover parsing as the length of the rest of the
* record is unknown or is too short. */
g_set_error (error, G_RESOLVER_ERROR, G_RESOLVER_ERROR_INTERNAL,
_("Error resolving “%s”"), rrname);
g_list_free_full (records, (GDestroyNotify) g_variant_unref);
return NULL;
g_set_error (&parsing_error, G_RESOLVER_ERROR, G_RESOLVER_ERROR_INTERNAL,
/* Translators: the first placeholder is a domain name, the
* second is an error message */
_("Error resolving “%s”: %s"), rrname, _("Malformed DNS packet"));
break;
}
p += expand_result;
@ -765,19 +845,19 @@ g_resolver_records_from_res_query (const gchar *rrname,
switch (rrtype)
{
case T_SRV:
record = parse_res_srv (answer, end, &p);
record = parse_res_srv (answer, end, &p, &parsing_error);
break;
case T_MX:
record = parse_res_mx (answer, end, &p);
record = parse_res_mx (answer, end, &p, &parsing_error);
break;
case T_SOA:
record = parse_res_soa (answer, end, &p);
record = parse_res_soa (answer, end, &p, &parsing_error);
break;
case T_NS:
record = parse_res_ns (answer, end, &p);
record = parse_res_ns (answer, end, &p, &parsing_error);
break;
case T_TXT:
record = parse_res_txt (answer, p + rdlength, &p);
record = parse_res_txt (answer, p + rdlength, &p, &parsing_error);
break;
default:
g_debug ("Unrecognised DNS record type %u", rrtype);
@ -787,9 +867,18 @@ g_resolver_records_from_res_query (const gchar *rrname,
if (record != NULL)
records = g_list_prepend (records, record);
if (parsing_error != NULL)
break;
}
if (records == NULL)
if (parsing_error != NULL)
{
g_propagate_prefixed_error (error, parsing_error, _("Failed to parse DNS response for “%s”: "), rrname);
g_list_free_full (records, (GDestroyNotify)g_variant_unref);
return NULL;
}
else if (records == NULL)
{
g_set_error (error, G_RESOLVER_ERROR, G_RESOLVER_ERROR_NOT_FOUND,
_("No DNS record of the requested type for “%s”"), rrname);