pkgs/sandbox: Handle store paths that are symlinks

For example the store path of libGL-1.0.0 is a symlink pointing to
libglvnd-1.0.0 right now on my machine.

If we have such a symlink the sandbox would just silently skip it and
only mount the *resolved* path instead of creating the symlink leading
to the target.

Now whenever bind_mount() with the resolve argument being true is used,
we create all the symlinks leading to the target path determined by
realpath().

Signed-off-by: aszlig <aszlig@nix.build>

1 files changed, 63 insertions, 0 deletions

diff --git a/pkgs/build-support/build-sandbox/src/setup.c b/pkgs/build-support/build-sandbox/src/setup.c
index a23983c8..da6c65c7 100644
--- a/pkgs/build-support/build-sandbox/src/setup.c
+++ b/pkgs/build-support/build-sandbox/src/setup.c
@@ -189,6 +189,62 @@ static bool bind_file(const char *path)
     return true;
 }
 
+static bool makelinks(const char *from, const char *to)
+{
+    char linktarget[PATH_MAX];
+    char *target, *tmp;
+    ssize_t linksize;
+    bool result;
+
+    if (strcmp(from, to) == 0)
+        return true;
+
+    if ((linksize = readlink(from, linktarget, PATH_MAX)) == -1) {
+        if (errno == EINVAL)
+            // Not a symbolic link
+            return true;
+
+        fprintf(stderr, "reading link %s: %s\n", from, strerror(errno));
+        return false;
+    }
+
+    linktarget[linksize] = '\0';
+
+    if ((target = get_mount_target(from)) == NULL)
+        return false;
+
+    if ((tmp = strdup(target)) == NULL) {
+        fprintf(stderr, "strdup of %s: %s\n", target, strerror(errno));
+        free(target);
+        return false;
+    }
+
+    if (!makedirs(dirname(tmp), true)) {
+        free(target);
+        free(tmp);
+        return false;
+    }
+
+    free(tmp);
+
+    if (cache_path(cached_paths, target)) {
+        if (symlink(linktarget, target) == -1) {
+            if (errno == EEXIST)
+                goto recurse;
+
+            fprintf(stderr, "creating symlink from %s to %s: %s\n",
+                    target, linktarget, strerror(errno));
+            free(target);
+            return false;
+        }
+    }
+
+recurse:
+    result = makelinks(linktarget, to);
+    free(target);
+    return result;
+}
+
 bool bind_mount(const char *path, bool restricted, bool resolve)
 {
     int mflags = MS_BIND | MS_REC;
@@ -207,6 +263,13 @@ bool bind_mount(const char *path, bool restricted, bool resolve)
     if ((target = get_mount_target(resolve ? src : path)) == NULL)
         return false;
 
+    if (resolve) {
+        if (!makelinks(path, src)) {
+            free(target);
+            return false;
+        }
+    }
+
     if (!makedirs(target, false)) {
         free(target);
         return false;