Overrule BLOCK with ALLOW on the same project

It was impossible to block a permission for a group and allow the same
permission for a sub-group of that group as the block always won over an
allow. For example, it was impossible to block the "Forge Committer"
permission for all users and then allow it only for a couple of
privileged users.

This change gives an ALLOW permission priority over a BLOCK permission
when they are defined in the same access section of a project. To
achieve the above mentioned policy we define:

  [access "refs/heads/*"]
    forgeCommitter = block group Anonymous Users
    forgeCommitter = group Privileged Users

Across projects the BLOCK permission still wins over an ALLOW
permission. This way one cannot override an inherited BLOCK in a
subproject.

Overruling of BLOCK with ALLOW also works for labels i.e. permission
ranges. If a dedicated Verifiers group need to be the only group who can
vote in the Verified label and we must ensure that even project
owners cannot change this policy then we define the following in a
common parent project:

  [access "refs/heads/*"]
    label-Verified = block -1..+1 group Anonymous Users
    label-Verified = -1..+1 group Verifiers

Change-Id: I8e27b6b060d60bb8a846ce62d0338f613a7d7a3e
Signed-off-by: Sasa Zivkov <sasa.zivkov@sap.com>
Signed-off-by: Edwin Kempin <edwin.kempin@sap.com>

Documentation/access-control.txt

@@ -1109,8 +1109,9 @@ non-blocked rules as they wish. This gives best of both worlds:
 ~~~~~~~~~~~~~~~~~~~
 
 The 'BLOCK' rule blocks a permission globally. An inherited 'BLOCK' rule cannot
-be overridden in the inheriting project. Any 'ALLOW' rule which conflicts with
+be overridden in the inheriting project. Any 'ALLOW' rule, from a different
-an inherited 'BLOCK' rule will not be honored.  Searching for 'BLOCK' rules, in
+access section or from an inheriting project, which conflicts with an
+inherited 'BLOCK' rule will not be honored.  Searching for 'BLOCK' rules, in
 the chain of parent projects, ignores the Exclusive flag that is normally
 applied to access sections.
 
@@ -1131,6 +1132,26 @@ The interpretation of the 'min..max' range in case of a blocking rule is: block
 every vote from '-INFINITE..min' and 'max..INFINITE'. For the example above it
 means that the range '-1..+1' is not affected by this block.
 
+'BLOCK' and 'ALLOW' rules in the same access section
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+When an access section of a project contains a 'BLOCK' and an 'ALLOW' rule for
+the same permission then this 'ALLOW' rule overrides the 'BLOCK' rule:
+
+====
+  [access "refs/heads/*"]
+    push = block group X
+    push = group Y
+====
+
+In this case a user which is a member of the group 'Y' will still be allowed to
+push to 'refs/heads/*' even if it is a member of the group 'X'.
+
+NOTE: An 'ALLOW' rule overrides a 'BLOCK' rule only when both of them are
+inside the same access section of the same project. An 'ALLOW' rule in a
+different access section of the same project or in any access section in an
+inheriting project cannot override a 'BLOCK' rule.
+
 Examples
 ~~~~~~~~
 
@@ -1160,6 +1181,23 @@ owners>> are allowed to create tags, we would extend the example above:
     pushTag = group Project Owners
 ====
 
+Let only a dedicated group vote in a special category
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Assume there is a more restrictive process for submitting changes in stable
+release branches which is manifested as a new voting category
+'Release-Process'. Assume we want to make sure that only a 'Release Engineers'
+group can vote in this category and that even project owners cannot approve
+this category. We have to block everyone except the 'Release Engineers' to vote
+in this category and, of course, allow 'Release Engineers' to vote in that
+category. In the "`All-Projects`" we define the following rules:
+
+====
+  [access "refs/heads/stable*"]
+    label-Release-Proces = block -1..+1 group Anonymous Users
+    label-Release-Proces = -1..+1 group Release Engineers
+====
+
 [[conversion_table]]
 Conversion table from 2.1.x series to 2.2.x series
 --------------------------------------------------

gerrit-server/src/main/java/com/google/gerrit/server/project/RefControl.java

@@ -14,6 +14,8 @@
 
 package com.google.gerrit.server.project;
 
+import com.google.common.collect.Maps;
+import com.google.common.collect.Sets;
 import com.google.gerrit.common.data.AccessSection;
 import com.google.gerrit.common.data.Permission;
 import com.google.gerrit.common.data.PermissionRange;
@@ -42,6 +44,7 @@ import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 
 
 /** Manages access control for Git references (aka branches, tags). */
@@ -117,18 +120,18 @@ public class RefControl {
    */
   public boolean isVisibleByRegisteredUsers() {
     List<PermissionRule> access = relevant.getPermission(Permission.READ);
+    Set<ProjectRef> allows = Sets.newHashSet();
+    Set<ProjectRef> blocks = Sets.newHashSet();
     for (PermissionRule rule : access) {
       if (rule.isBlock()) {
-        return false;
+        blocks.add(relevant.getRuleProps(rule));
-      }
+      } else if (rule.getGroup().getUUID().equals(AccountGroup.ANONYMOUS_USERS)
-    }
-    for (PermissionRule rule : access) {
-      if (rule.getGroup().getUUID().equals(AccountGroup.ANONYMOUS_USERS)
           || rule.getGroup().getUUID().equals(AccountGroup.REGISTERED_USERS)) {
-        return true;
+        allows.add(relevant.getRuleProps(rule));
       }
     }
-    return false;
+    blocks.removeAll(allows);
+    return blocks.isEmpty() && !allows.isEmpty();
   }
 
   /**
@@ -218,16 +221,7 @@ public class RefControl {
       // granting of powers beyond pushing to the configuration.
       return false;
     }
-    boolean result = false;
+    return canForcePerform(Permission.PUSH);
-    for (PermissionRule rule : access(Permission.PUSH)) {
-      if (rule.isBlock()) {
-        return false;
-      }
-      if (rule.getForce()) {
-        result = true;
-      }
-    }
-    return result;
   }
 
   /**
@@ -375,16 +369,7 @@ public class RefControl {
 
   /** @return true if this user can force edit topic names. */
   public boolean canForceEditTopicName() {
-    boolean result = false;
+    return canForcePerform(Permission.EDIT_TOPIC_NAME);
-    for (PermissionRule rule : access(Permission.EDIT_TOPIC_NAME)) {
-      if (rule.isBlock()) {
-        return false;
-      }
-      if (rule.getForce()) {
-        result = true;
-      }
-    }
-    return result;
   }
 
   /** All value ranges of any allowed label permission. */
@@ -416,39 +401,97 @@ public class RefControl {
     return null;
   }
 
-  private static PermissionRange toRange(String permissionName,
+  private static class AllowedRange {
-      List<PermissionRule> ruleList) {
+    private int allowMin = 0;
-    int min = 0;
+    private int allowMax = 0;
-    int max = 0;
+    private int blockMin = Integer.MIN_VALUE;
-    int blockMin = Integer.MIN_VALUE;
+    private int blockMax = Integer.MAX_VALUE;
-    int blockMax = Integer.MAX_VALUE;
+
-    for (PermissionRule rule : ruleList) {
+    void update(PermissionRule rule) {
       if (rule.isBlock()) {
         blockMin = Math.max(blockMin, rule.getMin());
         blockMax = Math.min(blockMax, rule.getMax());
       } else {
-        min = Math.min(min, rule.getMin());
+        allowMin = Math.min(allowMin, rule.getMin());
-        max = Math.max(max, rule.getMax());
+        allowMax = Math.max(allowMax, rule.getMax());
       }
     }
-    if (blockMin > Integer.MIN_VALUE) {
+
-      min = Math.max(min, blockMin + 1);
+    int getAllowMin() {
+      return allowMin;
     }
-    if (blockMax < Integer.MAX_VALUE) {
+    int getAllowMax() {
-      max = Math.min(max, blockMax - 1);
+      return allowMax;
     }
+    int getBlockMin() {
+      // ALLOW wins over BLOCK on the same project
+      return Math.min(blockMin, allowMin - 1);
+    }
+    int getBlockMax() {
+      // ALLOW wins over BLOCK on the same project
+      return Math.max(blockMax, allowMax + 1);
+    }
+  }
+
+  private PermissionRange toRange(String permissionName,
+      List<PermissionRule> ruleList) {
+    Map<ProjectRef, AllowedRange> ranges = Maps.newHashMap();
+    for (PermissionRule rule : ruleList) {
+      ProjectRef p = relevant.getRuleProps(rule);
+      AllowedRange r = ranges.get(p);
+      if (r == null) {
+        r = new AllowedRange();
+        ranges.put(p, r);
+      }
+      r.update(rule);
+    }
+    int allowMin = 0;
+    int allowMax = 0;
+    int blockMin = Integer.MIN_VALUE;
+    int blockMax = Integer.MAX_VALUE;
+    for (AllowedRange r : ranges.values()) {
+      allowMin = Math.min(allowMin, r.getAllowMin());
+      allowMax = Math.max(allowMax, r.getAllowMax());
+      blockMin = Math.max(blockMin, r.getBlockMin());
+      blockMax = Math.min(blockMax, r.getBlockMax());
+    }
+
+    // BLOCK wins over ALLOW across projects
+    int min = Math.max(allowMin, blockMin + 1);
+    int max = Math.min(allowMax, blockMax - 1);
     return new PermissionRange(permissionName, min, max);
   }
 
   /** True if the user has this permission. Works only for non labels. */
   boolean canPerform(String permissionName) {
     List<PermissionRule> access = access(permissionName);
+    Set<ProjectRef> allows = Sets.newHashSet();
+    Set<ProjectRef> blocks = Sets.newHashSet();
     for (PermissionRule rule : access) {
       if (rule.isBlock() && !rule.getForce()) {
-        return false;
+        blocks.add(relevant.getRuleProps(rule));
+      } else {
+        allows.add(relevant.getRuleProps(rule));
       }
     }
-    return !access.isEmpty();
+    blocks.removeAll(allows);
+    return blocks.isEmpty() && !allows.isEmpty();
+  }
+
+  /** True if the user has force this permission. Works only for non labels. */
+  private boolean canForcePerform(String permissionName) {
+    List<PermissionRule> access = access(permissionName);
+    Set<ProjectRef> allows = Sets.newHashSet();
+    Set<ProjectRef> blocks = Sets.newHashSet();
+    for (PermissionRule rule : access) {
+      if (rule.isBlock()) {
+        blocks.add(relevant.getRuleProps(rule));
+      } else if (rule.getForce()) {
+        allows.add(relevant.getRuleProps(rule));
+      }
+    }
+    blocks.removeAll(allows);
+    return blocks.isEmpty() && !allows.isEmpty();
   }
 
   /** Rules for the given permission, or the empty list. */

gerrit-server/src/test/java/com/google/gerrit/server/project/RefControlTest.java

@@ -14,6 +14,7 @@
 
 package com.google.gerrit.server.project;
 
+import static com.google.gerrit.common.data.Permission.EDIT_TOPIC_NAME;
 import static com.google.gerrit.common.data.Permission.LABEL;
 import static com.google.gerrit.common.data.Permission.OWNER;
 import static com.google.gerrit.common.data.Permission.PUSH;
@@ -253,6 +254,139 @@ public class RefControlTest extends TestCase {
     assertFalse("u can't vote -2", range.contains(-2));
     assertFalse("u can't vote 2", range.contains(2));
   }
+
+  public void testUnblockNoForce() {
+    grant(local, PUSH, anonymous, "refs/heads/*").setBlock();
+    grant(local, PUSH, devs, "refs/heads/*");
+
+    ProjectControl u = user(devs);
+    assertTrue("u can push", u.controlForRef("refs/heads/master").canUpdate());
+  }
+
+  public void testUnblockForce() {
+    PermissionRule r = grant(local, PUSH, anonymous, "refs/heads/*");
+    r.setBlock();
+    r.setForce(true);
+    grant(local, PUSH, devs, "refs/heads/*").setForce(true);
+
+    ProjectControl u = user(devs);
+    assertTrue("u can force push", u.controlForRef("refs/heads/master").canForceUpdate());
+  }
+
+  public void testUnblockForceWithAllowNoForce_NotPossible() {
+    PermissionRule r = grant(local, PUSH, anonymous, "refs/heads/*");
+    r.setBlock();
+    r.setForce(true);
+    grant(local, PUSH, devs, "refs/heads/*");
+
+    ProjectControl u = user(devs);
+    assertFalse("u can't force push", u.controlForRef("refs/heads/master").canForceUpdate());
+  }
+
+  public void testUnblockMoreSpecificRef_Fails() {
+    grant(local, PUSH, anonymous, "refs/heads/*").setBlock();
+    grant(local, PUSH, devs, "refs/heads/master");
+
+    ProjectControl u = user(devs);
+    assertFalse("u can't push", u.controlForRef("refs/heads/master").canUpdate());
+  }
+
+  public void testUnblockLargerScope_Fails() {
+    grant(local, PUSH, anonymous, "refs/heads/master").setBlock();
+    grant(local, PUSH, devs, "refs/heads/*");
+
+    ProjectControl u = user(devs);
+    assertFalse("u can't push", u.controlForRef("refs/heads/master").canUpdate());
+  }
+
+  public void testUnblockInLocal_Fails() {
+    grant(parent, PUSH, anonymous, "refs/heads/*").setBlock();
+    grant(local, PUSH, fixers, "refs/heads/*");
+
+    ProjectControl f = user(fixers);
+    assertFalse("u can't push", f.controlForRef("refs/heads/master").canUpdate());
+  }
+
+  public void testUnblockInParentBlockInLocal() {
+    grant(parent, PUSH, anonymous, "refs/heads/*").setBlock();
+    grant(parent, PUSH, devs, "refs/heads/*");
+    grant(local, PUSH, devs, "refs/heads/*").setBlock();
+
+    ProjectControl d = user(devs);
+    assertFalse("u can't push", d.controlForRef("refs/heads/master").canUpdate());
+  }
+
+  public void testUnblockVisibilityByRegisteredUsers() {
+    grant(local, READ, anonymous, "refs/heads/*").setBlock();
+    grant(local, READ, registered, "refs/heads/*");
+
+    ProjectControl u = user(registered);
+    assertTrue("u can read", u.controlForRef("refs/heads/master").isVisibleByRegisteredUsers());
+  }
+
+  public void testUnblockInLocalVisibilityByRegisteredUsers_Fails() {
+    grant(parent, READ, anonymous, "refs/heads/*").setBlock();
+    grant(local, READ, registered, "refs/heads/*");
+
+    ProjectControl u = user(registered);
+    assertFalse("u can't read", u.controlForRef("refs/heads/master").isVisibleByRegisteredUsers());
+  }
+
+  public void testUnblockForceEditTopicName() {
+    grant(local, EDIT_TOPIC_NAME, anonymous, "refs/heads/*").setBlock();
+    grant(local, EDIT_TOPIC_NAME, devs, "refs/heads/*").setForce(true);
+
+    ProjectControl u = user(devs);
+    assertTrue("u can edit topic name", u.controlForRef("refs/heads/master").canForceEditTopicName());
+  }
+
+  public void testUnblockInLocalForceEditTopicName_Fails() {
+    grant(parent, EDIT_TOPIC_NAME, anonymous, "refs/heads/*").setBlock();
+    grant(local, EDIT_TOPIC_NAME, devs, "refs/heads/*").setForce(true);
+
+    ProjectControl u = user(registered);
+    assertFalse("u can't edit topic name", u.controlForRef("refs/heads/master").canForceEditTopicName());
+  }
+
+  public void testUnblockRange() {
+    grant(local, LABEL + "Code-Review", -1, +1, anonymous, "refs/heads/*").setBlock();
+    grant(local, LABEL + "Code-Review", -2, +2, devs, "refs/heads/*");
+
+    ProjectControl u = user(devs);
+    PermissionRange range = u.controlForRef("refs/heads/master").getRange(LABEL + "Code-Review");
+    assertTrue("u can vote -2", range.contains(-2));
+    assertTrue("u can vote +2", range.contains(2));
+  }
+
+  public void testUnblockRangeOnMoreSpecificRef_Fails() {
+    grant(local, LABEL + "Code-Review", -1, +1, anonymous, "refs/heads/*").setBlock();
+    grant(local, LABEL + "Code-Review", -2, +2, devs, "refs/heads/master");
+
+    ProjectControl u = user(devs);
+    PermissionRange range = u.controlForRef("refs/heads/master").getRange(LABEL + "Code-Review");
+    assertFalse("u can't vote -2", range.contains(-2));
+    assertFalse("u can't vote +2", range.contains(-2));
+  }
+
+  public void testUnblockRangeOnLargerScope_Fails() {
+    grant(local, LABEL + "Code-Review", -1, +1, anonymous, "refs/heads/master").setBlock();
+    grant(local, LABEL + "Code-Review", -2, +2, devs, "refs/heads/*");
+
+    ProjectControl u = user(devs);
+    PermissionRange range = u.controlForRef("refs/heads/master").getRange(LABEL + "Code-Review");
+    assertFalse("u can't vote -2", range.contains(-2));
+    assertFalse("u can't vote +2", range.contains(-2));
+  }
+
+  public void testUnblockInLocalRange_Fails() {
+    grant(parent, LABEL + "Code-Review", -1, 1, anonymous, "refs/heads/*").setBlock();
+    grant(local, LABEL + "Code-Review", -2, +2, devs, "refs/heads/*");
+
+    ProjectControl u = user(devs);
+    PermissionRange range = u.controlForRef("refs/heads/master").getRange(LABEL + "Code-Review");
+    assertFalse("u can't vote -2", range.contains(-2));
+    assertFalse("u can't vote 2", range.contains(2));
+  }
   // -----------------------------------------------------------------------
 
   private final Map<Project.NameKey, ProjectState> all;