Fix a rare edge case in the rlm_rest POST encoder

If there are additional attributes to encode, and there is exactly one byte free in the output buffer, then we lose the value of the previously encoded attribute.
FreeRADIUS · Jan 12, 2021 · 3dd36aa · 3dd36aa
1 parent b2adf9c
commit 3dd36aa
Showing 1 changed file with 10 additions and 1 deletion.
diff --git a/src/modules/rlm_rest/rest.c b/src/modules/rlm_rest/rest.c
@@ -652,10 +652,19 @@ static size_t rest_encode_post(void *out, size_t size, size_t nmemb, void *userd
 		/*
 		 *  there are more attributes, insert a separator
 		 */
-		if (fr_cursor_next(&ctx->cursor)) {
+		if (fr_cursor_next_peek(&ctx->cursor)) {
 			if (freespace < 1) goto no_space;
 			*p++ = '&';
 			freespace--;
+			/*
+			 *	Only advance once we have a separator
+			 *	really we should have an additional
+			 *	state for encoding the separator,
+			 *	but, we don't, and v3.0.x is stable
+			 *	so let's do the easiest fix with the
+			 *	lowest risk.
+			 */
+			fr_cursor_next(&ctx->cursor);
 		}
 
 		/*