SourcePath::resolveSymlinks(): Fix handling of symlinks that start wi…

…th '..' Fixes #8437.
NixOS · Jun 5, 2023 · 6731850 · 6731850
1 parent 9c6ede8
commit 6731850
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Showing 4 changed files with 48 additions and 6 deletions.
diff --git a/src/libfetchers/input-accessor.cc b/src/libfetchers/input-accessor.cc
@@ -83,12 +83,8 @@ SourcePath SourcePath::resolveSymlinks() const
                     throw Error("infinite symlink recursion in path '%s'", path);
                 if (st->type != InputAccessor::tSymlink) break;
                 auto target = res.readLink();
-                if (hasPrefix(target, "/"))
-                    res = CanonPath(target);
-                else {
-                    res.path.pop();
-                    res.path.extend(CanonPath(target));
-                }
+                res.path.pop();
+                res.path.apply(target);
             } else
                 break;
         }

diff --git a/src/libutil/canon-path.cc b/src/libutil/canon-path.cc
@@ -56,6 +56,30 @@ void CanonPath::extend(const CanonPath & x)
         path += x.abs();
 }
 
+void CanonPath::apply(std::string_view s)
+{
+    if (hasPrefix(s, "/")) {
+        *this = CanonPath(s);
+        return;
+    }
+
+    while (!s.empty()) {
+        auto slash = s.find('/');
+        if (slash == s.npos) {
+            push(s);
+            return;
+        }
+        auto c = s.substr(0, slash);
+        if (c == ".")
+            ;
+        else if (c == "..")
+            pop();
+        else
+            push(c);
+        s = s.substr(slash + 1);
+    }
+}
+
 CanonPath CanonPath::operator + (const CanonPath & x) const
 {
     auto res = *this;

diff --git a/src/libutil/canon-path.hh b/src/libutil/canon-path.hh
@@ -174,6 +174,14 @@ public:
      */
     void extend(const CanonPath & x);
 
+    /**
+     * "Apply" a string representation of a path to this one. If `s`
+     * is an absolute path, it replaces `this`. Otherwise, it is
+     * appended to this, where `..` components cause the previous
+     * component to be removed.
+     */
+    void apply(std::string_view s);
+
     /**
      * Concatenate two paths.
      */

diff --git a/src/libutil/tests/canon-path.cc b/src/libutil/tests/canon-path.cc
@@ -159,4 +159,18 @@ namespace nix {
         ASSERT_EQ(d.makeRelative(CanonPath("/foo/xyzzy/bla")), "../xyzzy/bla");
         ASSERT_EQ(d.makeRelative(CanonPath("/xyzzy/bla")), "../../xyzzy/bla");
     }
+
+    TEST(CanonPath, apply) {
+        {
+            CanonPath d("/common/pc/laptop/ssd");
+            d.pop();
+            d.apply("../ssd");
+            ASSERT_EQ(d, CanonPath("/common/pc/ssd"));
+            d.apply("foo/./bar/../xyzzy");
+            ASSERT_EQ(d, CanonPath("/common/pc/ssd/foo/xyzzy"));
+            d.apply("/foo/bar/../xyzzy");
+            ASSERT_EQ(d, CanonPath("/foo/xyzzy"));
+        }
+    }
+
 }