Resolve crashes due to large stack allocations when using TCP

Asterisk had several places where messages received over various network
transports may be copied in a single stack allocation. In the case of TCP,
since multiple packets in a stream may be concatenated together, this can
lead to large allocations that overflow the stack.

This patch modifies those portions of Asterisk using TCP to either
favor heap allocations or use an upper bound to ensure that the stack will not
overflow:
 * For HTTP, the allocation is now a heap allocation instead of a stack
   allocation
 * For XMPP (in res_jabber), the allocation has been eliminated since it was
   unnecesary.

Note that the HTTP portion of this issue was independently found by Brandon
Edwards of Exodus Intelligence.

(issue ASTERISK-20658)
Reported by: wdoekes, Brandon Edwards
Tested by: mmichelson, wdoekes
patches:
  ASTERISK-20658_res_jabber.c.patch uploaded by mmichelson (license 5049)
  issueA20658_http_postvars_use_malloc2.patch uploaded by wdoekes (license 5674)
........

Merged revisions 378269 from http://svn.asterisk.org/svn/asterisk/branches/1.8

git-svn-id: https://origsvn.digium.com/svn/asterisk/certified/branches/1.8.11@378289 65c4cc65-6c06-0410-ace0-fbb531ad65f3

diff --git a/main/http.c b/main/http.c
index 88e36c7a1f1791a6c27015e799cecc955f60e645..67c4b81352f7ca1345eea21cd3c20dd0014d835c 100644 (file)
--- a/main/http.c
+++ b/main/http.c
@@ -622,6 +622,7 @@ struct ast_variable *ast_http_get_post_vars(
        int content_length = 0;
        struct ast_variable *v, *post_vars=NULL, *prev = NULL;
        char *buf, *var, *val;
+       int res;
 
        for (v = headers; v; v = v->next) {
                if (!strcasecmp(v->name, "Content-Type")) {
@@ -634,21 +635,27 @@ struct ast_variable *ast_http_get_post_vars(
 
        for (v = headers; v; v = v->next) {
                if (!strcasecmp(v->name, "Content-Length")) {
-                       content_length = atoi(v->value) + 1;
+                       content_length = atoi(v->value);
                        break;
                }
        }
 
-       if (!content_length) {
+       if (content_length <= 0) {
                return NULL;
        }
 
-       if (!(buf = alloca(content_length))) {
+       buf = ast_malloc(content_length + 1);
+       if (!buf) {
                return NULL;
        }
-       if (!fgets(buf, content_length, ser->f)) {
-               return NULL;
+
+       res = fread(buf, 1, content_length, ser->f);
+       if (res < content_length) {
+               /* Error, distinguishable by ferror() or feof(), but neither
+                * is good. */
+               goto done;
        }
+       buf[content_length] = '\0';
 
        while ((val = strsep(&buf, "&"))) {
                var = strsep(&val, "=");
@@ -667,6 +674,9 @@ struct ast_variable *ast_http_get_post_vars(
                        prev = v;
                }
        }
+       
+done:
+       ast_free(buf);
        return post_vars;
 }
 

diff --git a/res/res_jabber.c b/res/res_jabber.c
index 69b1c6f5517f63a7d99821bec10a8bc9565363bb..4bb97486d4018734cd7e47cbdccca7ae5455e356 100644 (file)
--- a/res/res_jabber.c
+++ b/res/res_jabber.c
@@ -777,7 +777,7 @@ static struct ast_custom_function jabberstatus_function = {
  */
 static int acf_jabberreceive_read(struct ast_channel *chan, const char *name, char *data, char *buf, size_t buflen)
 {
-       char *aux = NULL, *parse = NULL;
+       char *parse = NULL;
        int timeout;
        int jidlen, resourcelen;
        struct timeval start;
@@ -894,7 +894,7 @@ static int acf_jabberreceive_read(struct ast_channel *chan, const char *name, ch
                                continue;
                        }
                        found = 1;
-                       aux = ast_strdupa(tmp->message);
+                       ast_copy_string(buf, tmp->message, buflen);
                        AST_LIST_REMOVE_CURRENT(list);
                        aji_message_destroy(tmp);
                        break;
@@ -919,7 +919,6 @@ static int acf_jabberreceive_read(struct ast_channel *chan, const char *name, ch
                ast_log(LOG_NOTICE, "Timed out : no message received from %s\n", args.jid);
                return -1;
        }
-       ast_copy_string(buf, aux, buflen);
 
        return 0;
 }