Tighten up the requirements on workspace names

Fixes #462.

RELNOTES: Workspace names are now restricted to being in their base directory
(that is, the names cannot contain up-level references or /./).

--
MOS_MIGRATED_REVID=103379893

1 files changed, 77 insertions, 22 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/cmdline/PackageIdentifier.java b/src/main/java/com/google/devtools/build/lib/cmdline/PackageIdentifier.java
index 9d0ef0edcf..89167dd433 100644
--- a/src/main/java/com/google/devtools/build/lib/cmdline/PackageIdentifier.java
+++ b/src/main/java/com/google/devtools/build/lib/cmdline/PackageIdentifier.java
@@ -85,35 +85,90 @@ public final class PackageIdentifier implements Comparable<PackageIdentifier>, S
       this.name = name;
     }
 
-    /**
-     * Performs validity checking.  Returns null on success, an error message otherwise.
-     */
-    private static String validate(String name) {
-      if (name.isEmpty()) {
-        return null;
-      }
+    private static class Lexer {
+      private static final char EOF = '\0';
 
-      if (!name.startsWith("@")) {
-        return "workspace name must start with '@'";
+      private final String name;
+      private int pos;
+
+      public Lexer(String name) {
+        this.name = name;
+        this.pos = 0;
       }
 
-      // Check for any character outside of [/0-9A-Za-z_.-]. Try to evaluate the
-      // conditional quickly (by looking in decreasing order of character class
-      // likelihood).
-      if (name.startsWith("@/") || name.endsWith("/")) {
-        return "workspace names cannot start nor end with '/'";
-      } else if (name.contains("//")) {
-        return "workspace names cannot contain multiple '/'s in a row";
+      public String lex() {
+        if (name.isEmpty()) {
+          return null;
+        }
+
+        if (name.charAt(pos) != '@') {
+          return "workspace names must start with '@'";
+        }
+
+        // @// is valid.
+        if (name.length() == 1) {
+          return null;
+        }
+
+        pos++;
+        // Disallow strings starting with “/”,  “./”,  or “../”
+        // Disallow strings identical to        ".",   or “..”
+        if (name.charAt(pos) == '/') {
+          return "workspace names are not allowed to start with '@/'";
+        } else if (name.charAt(pos) == '.') {
+          char next = peek(1);
+          char nextNext = peek(2);
+          // Forbid '@.' and '@..' as complete labels and '@./' and '@../' as label starts.
+          if (next == EOF) {
+            return "workspace names are not allowed to be '@.'";
+          } else if (next == '/') {
+            return "workspace names are not allowed to start with '@./'";
+          } else if (next == '.' && (nextNext == '/' || nextNext == EOF)) {
+            return "workspace names are not allowed to start with '@..'";
+          }
+        }
+
+        // This lexes the first letter a second time, to make sure it fulfills the general
+        // workspace name criteria (as well as the more strict criteria for the beginning of a
+        // workspace name).
+        // Disallow strings containing    “//”, “/./”, or “/../”
+        // Disallow strings ending in     “/”,  "/.",   or “/..”
+        // name = @( <alphanum> | [/._-] )*
+        for (; pos < name.length(); pos++) {
+          char c = name.charAt(pos);
+          if (c == '/') {
+            char next = peek(1);
+            if (next == '/') {
+              return "workspace names are not allowed to contain '//'";
+            } else if (next == EOF) {
+              return "workspace names are not allowed to end with '/'";
+            } else if (next == '.' && (peek(2) == '/' || peek(2) == EOF)) {
+              return "workspace names are not allowed to contain '/./'";
+            } else if (next == '.' && peek(2) == '.' && (peek(3) == '/' || peek(3) == EOF)) {
+              return "workspace names are not allowed to contain '/../'";
+            }
+          } else if ((c < 'a' || c > 'z') && c != '_' && c != '-' && c != '/' && c != '.'
+              && (c < '0' || c > '9') && (c < 'A' || c > 'Z')) {
+            return "workspace names may contain only A-Z, a-z, 0-9, '-', '_', '.', and '/'";
+          }
+        }
+
+        return null;
       }
 
-      for (int i = name.length() - 1; i >= 1; --i) {
-        char c = name.charAt(i);
-        if ((c < 'a' || c > 'z') && c != '_' && c != '-' && c != '/' && c != '.'
-            && (c < '0' || c > '9') && (c < 'A' || c > 'Z')) {
-          return "workspace names may contain only A-Z, a-z, 0-9, '-', '_', '.', and '/'";
+      private char peek(int num) {
+        if (pos + num >= name.length()) {
+          return EOF;
         }
+        return name.charAt(pos + num);
       }
-      return null;
+    }
+
+    /**
+     * Performs validity checking.  Returns null on success, an error message otherwise.
+     */
+    private static String validate(String name) {
+      return new Lexer(name).lex();
     }
 
     /**