Changeset 98cf33f in mod_gnutls

Timestamp:

Sep 17, 2017, 1:01:23 PM (18 months ago)

Author:

Thomas Klute <thomas2.klute@…>

Branches:

debian/master, debian/stretch-backports, master, upstream

Children:

2ae1c3c

Parents:

017ef2d

git-author:

Thomas Klute <thomas2.klute@…> (09/17/17 12:52:37)

git-committer:

Thomas Klute <thomas2.klute@…> (09/17/17 13:01:23)

Message:

Rewrite SNI handler to accept long names and ignore unknown name types

Names longer than the default buffer require a dynamic buffer
allocation of the size reported by GnuTLS. DNS is the only type
currently known to GnuTLS, but mod_gnutls should be able to handle any
future extension gracefully.

Location:

src

Files:

• gnutls_hooks.c (modified) (3 diffs)
• gnutls_io.c (modified) (1 diff)

src/gnutls_hooks.c

@@ -4 +4 @@
  *  Copyright 2011 Dash Shendy
  *  Copyright 2013-2014 Daniel Kahn Gillmor
- *  Copyright 2015-2016 Thomas Klute
+ *  Copyright 2015-2017 Thomas Klute
  *
  *  Licensed under the Apache License, Version 2.0 (the "License");
@@ -741 +741 @@
 }
 
-#define MAX_HOST_LEN 255
+/**
+ * Default buffer size for SNI data, including the terminating NULL
+ * byte. The size matches what gnutls-cli uses initially.
+ */
+#define DEFAULT_SNI_HOST_LEN 256
 
 typedef struct {
@@ -834 +838 @@
 }
 
+/**
+ * Get SNI data from GnuTLS (if any) and search for a matching virtual
+ * host configuration. This method is called from the post client
+ * hello function.
+ *
+ * @param session the GnuTLS session
+ *
+ * @return either the matching mod_gnutls server config, or `NULL`
+ */
 mgs_srvconf_rec *mgs_find_sni_server(gnutls_session_t session)
 {
+    mgs_handle_t *ctxt = gnutls_session_get_ptr(session);
+
+    char *sni_name = apr_palloc(ctxt->c->pool, DEFAULT_SNI_HOST_LEN);
+    size_t sni_len = DEFAULT_SNI_HOST_LEN;
     unsigned int sni_type;
-    size_t data_len = MAX_HOST_LEN;
-    char sni_name[MAX_HOST_LEN];
-
-    if (session == NULL)
-        return NULL;
-
-    mgs_handle_t *ctxt = gnutls_session_get_ptr(session);
-    int rv = gnutls_server_name_get(session, sni_name,
-                                    &data_len, &sni_type, 0);
-
-
-    if (rv != 0) {
-        ap_log_cerror(APLOG_MARK, APLOG_TRACE1, APR_EGENERAL, ctxt->c,
-                      "%s: no SNI data found: %s (%d)",
+
+    /* Search for a DNS SNI element. Note that RFC 6066 prohibits more
+     * than one server name per type. */
+    int sni_index = -1;
+    int rv = 0;
+    do {
+        /* The sni_index is incremented before each use, so if the
+         * loop terminates with a type match we will have the right
+         * one stored. */
+        rv = gnutls_server_name_get(session, sni_name,
+                                    &sni_len, &sni_type, ++sni_index);
+        if (rv == GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE)
+        {
+            ap_log_cerror(APLOG_MARK, APLOG_TRACE1, APR_EGENERAL, ctxt->c,
+                          "%s: no DNS SNI found (last index: %d).",
+                          __func__, sni_index);
+            return NULL;
+        }
+    } while (sni_type != GNUTLS_NAME_DNS);
+    /* The (rv == GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE) path inside
+     * the loop above returns, so if we reach this point we have a DNS
+     * SNI at the current index. */
+
+    if (rv == GNUTLS_E_SHORT_MEMORY_BUFFER)
+    {
+        /* Allocate a new buffer of the right size and retry */
+        sni_name = apr_palloc(ctxt->c->pool, sni_len);
+        ap_log_cerror(APLOG_MARK, APLOG_TRACE1, APR_SUCCESS, ctxt->c,
+                      "%s: reallocated SNI data buffer for %" APR_SIZE_T_FMT
+                      " bytes.", __func__, sni_len);
+        rv = gnutls_server_name_get(session, sni_name,
+                                    &sni_len, &sni_type, sni_index);
+    }
+
+    /* Unless there's a bug in the GnuTLS API only GNUTLS_E_IDNA_ERROR
+     * can occur here, but a catch all is safer and no more
+     * complicated. */
+    if (rv != GNUTLS_E_SUCCESS)
+    {
+        ap_log_cerror(APLOG_MARK, APLOG_INFO, APR_EGENERAL, ctxt->c,
+                      "%s: error while getting SNI DNS data: '%s' (%d).",
                       __func__, gnutls_strerror(rv), rv);
         return NULL;
     }
 
-    if (sni_type != GNUTLS_NAME_DNS) {
-        ap_log_cerror(APLOG_MARK, APLOG_CRIT, 0, ctxt->c,
-                      "GnuTLS: Unknown type '%d' for SNI: '%s'",
-                      sni_type, sni_name);
-        return NULL;
-    }
-
-    ap_log_cerror(APLOG_MARK, APLOG_TRACE1, 0, ctxt->c,
+    ap_log_cerror(APLOG_MARK, APLOG_TRACE1, APR_SUCCESS, ctxt->c,
                   "%s: client requested server '%s'.",
                   __func__, sni_name);

src/gnutls_io.c

@@ -3 +3 @@
  *  Copyright 2008 Nikos Mavrogiannopoulos
  *  Copyright 2011 Dash Shendy
- *  Copyright 2015-2016 Thomas Klute
+ *  Copyright 2015-2017 Thomas Klute
  *
  *  Licensed under the Apache License, Version 2.0 (the "License");