Fix out-of-bounds memory accesses with virtual_root=""

The CGit configuration variable virtual_root is normalized so that it
does not have a trailing '/' character, but it is allowed to be empty
(the empty string and NULL have different meanings here) and there is
code that is insufficiently cautious when checking if it ends in a '/':

	if (virtual_root[strlen(virtual_root) - 1] != '/')

Clearly this check is redundant, but rather than simply removing it we
get a slight efficiency improvement by switching the normalization so
that the virtual_root variable always ends in '/'.  Do this with a new
"ensure_end" helper.

Signed-off-by: John Keeping <john@keeping.me.uk>

1 files changed, 5 insertions, 9 deletions

diff --git a/ui-shared.c b/ui-shared.c
index 945d560..c1f3c20 100644
--- a/ui-shared.c
+++ b/ui-shared.c
@@ -57,7 +57,7 @@ const char *cgit_hosturl()
 const char *cgit_rooturl()
 {
         if (ctx.cfg.virtual_root)
-                return fmt("%s/", ctx.cfg.virtual_root);
+                return ctx.cfg.virtual_root;
         else
                 return ctx.cfg.script_name;
 }
@@ -65,7 +65,7 @@ const char *cgit_rooturl()
 char *cgit_repourl(const char *reponame)
 {
         if (ctx.cfg.virtual_root) {
-                return fmt("%s/%s/", ctx.cfg.virtual_root, reponame);
+                return fmt("%s%s/", ctx.cfg.virtual_root, reponame);
         } else {
                 return fmt("?r=%s", reponame);
         }
@@ -78,7 +78,7 @@ char *cgit_fileurl(const char *reponame, const char *pagename,
         char *delim;
 
         if (ctx.cfg.virtual_root) {
-                tmp = fmt("%s/%s/%s/%s", ctx.cfg.virtual_root, reponame,
+                tmp = fmt("%s%s/%s/%s", ctx.cfg.virtual_root, reponame,
                           pagename, (filename ? filename:""));
                 delim = "?";
         } else {
@@ -126,11 +126,9 @@ static void site_url(const char *page, const char *search, const char *sort, int
 {
         char *delim = "?";
 
-        if (ctx.cfg.virtual_root) {
+        if (ctx.cfg.virtual_root)
                 html_attr(ctx.cfg.virtual_root);
-                if (ctx.cfg.virtual_root[strlen(ctx.cfg.virtual_root) - 1] != '/')
-                        html("/");
-        } else
+        else
                 html(ctx.cfg.script_name);
 
         if (page) {
@@ -201,8 +199,6 @@ static char *repolink(const char *title, const char *class, const char *page,
         html(" href='");
         if (ctx.cfg.virtual_root) {
                 html_url_path(ctx.cfg.virtual_root);
-                if (ctx.cfg.virtual_root[strlen(ctx.cfg.virtual_root) - 1] != '/')
-                        html("/");
                 html_url_path(ctx.repo->url);
                 if (ctx.repo->url[strlen(ctx.repo->url) - 1] != '/')
                         html("/");