[hackers] [quark] Fix normabspath() to handle consecutive '..'s properly || Laslo Hunhold

[git]

commit bd2e9e66ffda25e583b2978d1f84163b15f301db
Author:     Laslo Hunhold <d...@frign.de>
AuthorDate: Wed Jun 21 11:02:35 2017 +0200
Commit:     Laslo Hunhold <d...@frign.de>
CommitDate: Wed Jun 21 11:02:35 2017 +0200

    Fix normabspath() to handle consecutive '..'s properly
    
    The approach with lastp only works if we only go back one dir at a time.
    Of course, this cannot be assumed, so we traverse the path backwards
    looking for the previous /.

diff --git a/quark.c b/quark.c
index 4d056d3..de41214 100644
--- a/quark.c
+++ b/quark.c
@@ -460,8 +460,8 @@ static int
 normabspath(char *path)
 {
        size_t len;
-       int done = 0;
-       char *p, *q, *lastp;
+       int last = 0;
+       char *p, *q;
 
        /* require and skip first slash */
        if (path[0] != '/') {
@@ -472,25 +472,37 @@ normabspath(char *path)
        /* get length of path */
        len = strlen(p);
 
-       for (lastp = p; !done; ) {
+       for (; !last; ) {
                /* bound path component within (p,q) */
                if (!(q = strchr(p, '/'))) {
                        q = strchr(p, '\0');
-                       done = 1;
+                       last = 1;
                }
 
                if (p == q || (q - p == 1 && p[0] == '.')) {
                        /* "/" or "./" */
-                       memcpy(p, q + 1, len - ((q + 1) - path) + 2);
-                       len -= (q + 1) - p;
+                       goto squash;
                } else if (q - p == 2 && p[0] == '.' && p[1] == '.') {
                        /* "../" */
-                       memcpy(lastp, q + 1, len - ((q + 1) - path) + 2);
-                       len -= (q + 1) - lastp;
-                       p = lastp;
+                       if (p != path + 1) {
+                               /* place p right after the previous / */
+                               for (p -= 2; p > path && *p != '/'; p--);
+                               p++;
+                       }
+                       goto squash;
                } else {
-                       lastp = p;
+                       /* move on */
                        p = q + 1;
+                       continue;
+               }
+squash:
+               /* squash (p,q) into void */
+               if (last) {
+                       *p = '\0';
+                       len = p - path;
+               } else {
+                       memcpy(p, q + 1, len - ((q + 1) - path) + 2);
+                       len -= (q + 1) - p;
                }
        }