[hackers] [sbase] tar: Don't assume that name, linkname and prefix are null-terminated || sin

[git]

commit fde9e29d05d754aeb133af0d58802494b591bc1c
Author: sin <s...@2f30.org>
Date:   Tue Apr 21 15:05:51 2015 +0100

    tar: Don't assume that name, linkname and prefix are null-terminated

diff --git a/tar.c b/tar.c
index 0f82f15..44523ff 100644
--- a/tar.c
+++ b/tar.c
@@ -203,7 +203,8 @@ unarchive(char *fname, ssize_t l, char b[BLKSIZ])
                break;
        case HARDLINK:
        case SYMLINK:
-               estrlcpy(lname, h->link, sizeof(lname));
+               snprintf(lname, sizeof(lname), "%.*s", (int)sizeof(h->link),
+                        h->link);
                if (((h->type == HARDLINK) ? link : symlink)(lname, fname) < 0)
                        eprintf("%s %s -> %s:",
                                (h->type == HARDLINK) ? "link" : "symlink",
@@ -314,20 +315,21 @@ sanitize(struct header *h)
 static void
 xt(int (*fn)(char *, ssize_t, char[BLKSIZ]))
 {
+       char b[BLKSIZ], fname[256 + 1], *p;
        struct header *h;
        long size;
-       char b[BLKSIZ], fname[256 + 1], *p;
+       int n;
 
        h = (void *)b;
 
        while (fread(b, BLKSIZ, 1, tarfile) == 1 && *(h->name)) {
                sanitize(h);
-               fname[0] = '\0';
-               if (*(h->prefix)) {
-                       estrlcat(fname, h->prefix, sizeof(fname));
-                       estrlcat(fname, "/", sizeof(fname));
-               }
-               estrlcat(fname, h->name, sizeof(fname));
+               n = 0;
+               if (h->prefix[0])
+                       n = snprintf(fname, sizeof(fname), "%.*s/",
+                                    (int)sizeof(h->prefix), h->prefix);
+               snprintf(fname + n, sizeof(fname) - n, "%.*s",
+                        (int)sizeof(h->name), h->name);
                if ((size = strtol(h->size, &p, 8)) < 0 || *p != '\0')
                        eprintf("strtol %s: invalid number\n", h->size);