From d3d1f33470d3ae79b2bbc43e2e4e93dd5c4a54c1 Mon Sep 17 00:00:00 2001
From: Simon Farnsworth <simonfar@fb.com>
Date: Wed, 2 Feb 2022 14:16:31 -0800
Subject: [PATCH] Special-case linkfile src="."

Summary:
I am making it impossible to put "." or ".." as a path element in Mononoke's `MPath` abstraction, since Mononoke does not do path traversal, and canonicalization is a minefield.

However, `linkfile src="."` occurs in https://fburl.com/code/evq63pto as a special case. Treat it specially in our code, so that I can forbid path traversal type elements in an `MPath`.

Reviewed By: mojsarn

Differential Revision: D33952767

fbshipit-source-id: 0c4ce68014fb6877163035d1c7eb813616748dd2
---
 eden/mononoke/megarepo_api/src/common.rs | 31 +++++++++++++++++++++---
 1 file changed, 27 insertions(+), 4 deletions(-)

diff --git a/eden/mononoke/megarepo_api/src/common.rs b/eden/mononoke/megarepo_api/src/common.rs
index f5f21f79e1..6e1cc506ee 100644
--- a/eden/mononoke/megarepo_api/src/common.rs
+++ b/eden/mononoke/megarepo_api/src/common.rs
@@ -562,7 +562,7 @@ pub trait MegarepoOp {
                     )
                     .map_err(MegarepoError::request)?;
 
-                    let linkfiles = self.prepare_linkfiles(&source_config, &mover)?;
+                    let linkfiles = self.prepare_linkfiles(&source_config, &directory_mover)?;
                     let linkfiles = self.upload_linkfiles(ctx, linkfiles, repo).await?;
                     // TODO(stash): it assumes that commit is present in target
                     let moved = self
@@ -695,12 +695,16 @@ pub trait MegarepoOp {
     fn prepare_linkfiles(
         &self,
         source_config: &Source,
-        mover: &MultiMover,
+        mover: &DirectoryMultiMover,
     ) -> Result<BTreeMap<MPath, Bytes>, MegarepoError> {
         let mut links = BTreeMap::new();
         for (dst, src) in &source_config.mapping.linkfiles {
             // src is a file inside a given source, so mover needs to be applied to it
-            let src = MPath::new(src).map_err(MegarepoError::request)?;
+            let src = if src == "." {
+                None
+            } else {
+                MPath::new_opt(src).map_err(MegarepoError::request)?
+            };
             let dst = MPath::new(dst).map_err(MegarepoError::request)?;
             let moved_srcs = mover(&src).map_err(MegarepoError::request)?;
 
@@ -708,6 +712,10 @@ pub trait MegarepoOp {
             let moved_src = match (iter.next(), iter.next()) {
                 (Some(moved_src), None) => moved_src,
                 (None, None) => {
+                    let src = match src {
+                        None => ".".to_string(),
+                        Some(path) => path.to_string(),
+                    };
                     return Err(MegarepoError::request(anyhow!(
                         "linkfile source {} does not map to any file inside source {}",
                         src,
@@ -715,13 +723,28 @@ pub trait MegarepoOp {
                     )));
                 }
                 _ => {
+                    let src = match src {
+                        None => ".".to_string(),
+                        Some(path) => path.to_string(),
+                    };
                     return Err(MegarepoError::request(anyhow!(
                         "linkfile source {} maps to too many files inside source {}",
                         src,
                         source_config.name
                     )));
                 }
-            };
+            }
+            .ok_or_else(|| {
+                let src = match src {
+                    None => ".".to_string(),
+                    Some(path) => path.to_string(),
+                };
+                MegarepoError::request(anyhow!(
+                    "linkfile source {} does not map to any file inside the destination from source {}",
+                    src,
+                    source_config.name
+                ))
+            })?;
 
             let content = create_relative_symlink(&moved_src, &dst)?;
             links.insert(dst, content);