1 files changed, 63 insertions, 1 deletions

diff --git a/kex.c b/kex.c
index af2a41cca..5100c661d 100644
--- a/kex.c
+++ b/kex.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: kex.c,v 1.108 2015/07/29 08:34:54 djm Exp $ */
+/* $OpenBSD: kex.c,v 1.109 2015/07/30 00:01:34 djm Exp $ */
 /*
  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
  *
@@ -155,6 +155,68 @@ kex_names_valid(const char *names)
         return 1;
 }
 
+/*
+ * Concatenate algorithm names, avoiding duplicates in the process.
+ * Caller must free returned string.
+ */
+char *
+kex_names_cat(const char *a, const char *b)
+{
+        char *ret = NULL, *tmp = NULL, *cp, *p;
+        size_t len;
+
+        if (a == NULL || *a == '\0')
+                return NULL;
+        if (b == NULL || *b == '\0')
+                return strdup(a);
+        if (strlen(b) > 1024*1024)
+                return NULL;
+        len = strlen(a) + strlen(b) + 2;
+        if ((tmp = cp = strdup(b)) == NULL ||
+            (ret = calloc(1, len)) == NULL) {
+                free(tmp);
+                return NULL;
+        }
+        strlcpy(ret, a, len);
+        for ((p = strsep(&cp, ",")); p && *p != '\0'; (p = strsep(&cp, ","))) {
+                if (match_list(ret, p, NULL) != NULL)
+                        continue; /* Algorithm already present */
+                if (strlcat(ret, ",", len) >= len ||
+                    strlcat(ret, p, len) >= len) {
+                        free(tmp);
+                        free(ret);
+                        return NULL; /* Shouldn't happen */
+                }
+        }
+        free(tmp);
+        return ret;
+}
+
+/*
+ * Assemble a list of algorithms from a default list and a string from a
+ * configuration file. The user-provided string may begin with '+' to
+ * indicate that it should be appended to the default.
+ */
+int
+kex_assemble_names(const char *def, char **list)
+{
+        char *ret;
+
+        if (list == NULL || *list == NULL || **list == '\0') {
+                *list = strdup(def);
+                return 0;
+        }
+        if (**list != '+') {
+                return 0;
+        }
+
+        if ((ret = kex_names_cat(def, *list + 1)) == NULL)
+                return SSH_ERR_ALLOC_FAIL;
+        free(*list);
+        *list = ret;
+        return 0;
+}
+
 /* put algorithm proposal into buffer */
 int
 kex_prop2buf(struct sshbuf *b, char *proposal[PROPOSAL_MAX])