object: Support numeric comparisons in access rules

Previously, protocol did not support numeric comparisons in access rules
except `==` and `!=`. This may be needed for system attributes such as
payload size or creation epoch, and for user ones if required by the
client application.

New values of `MatchType` enumeration are added: `>`, `>=`, `<`, `<=`.
Being set in the `EACLRecord.Filter`, these operators will allow user to
apply access rules with any decimal attributes. While only base-10
numbers are allowed, additional bases may be supported in the future
without new enumerations.

Closes #255.
Refs #265.

Signed-off-by: Leonard Lyubich <leonard@morphbits.io>

acl/types.proto

@@ -36,6 +36,18 @@ enum MatchType {
 
   // Absence of attribute
   NOT_PRESENT = 3;
+
+  // Numeric 'greater than'
+  NUM_GT = 4;
+
+  // Numeric 'greater or equal than'
+  NUM_GE = 5;
+
+  // Numeric 'less than'
+  NUM_LT = 6;
+
+  // Numeric 'less or equal than'
+  NUM_LE = 7;
 }
 
 // Request's operation type to match if the rule is applicable to a particular
@@ -106,7 +118,8 @@ message EACLRecord {
   // Filter to check particular properties of the request or the object.
   //
   // The `value` field must be empty if `match_type` is an unary operator
-  // (e.g. `NOT_PRESENT`).
+  // (e.g. `NOT_PRESENT`). If `match_type` field is numeric (e.g. `NUM_GT`),
+  // the `value` field must be a base-10 integer.
   //
   // By default `key` field refers to the corresponding object's `Attribute`.
   // Some Object's header fields can also be accessed by adding `$Object:`
@@ -132,6 +145,9 @@ message EACLRecord {
   // * $Object:homomorphicHash \
   //   homomorphic_hash
   //
+  // Numeric `match_type` field can only be used with `$Object:creationEpoch`
+  // and `$Object:payloadLength` system attributes.
+  //
   // Please note, that if request or response does not have object's headers of
   // full object (Range, RangeHash, Search, Delete), it will not be possible to
   // filter by object header fields or user attributes. From the well-known list

proto-docs/acl.md

@@ -96,7 +96,8 @@ Describes a single eACL rule.
 Filter to check particular properties of the request or the object.
 
 The `value` field must be empty if `match_type` is an unary operator
-(e.g. `NOT_PRESENT`).
+(e.g. `NOT_PRESENT`). If `match_type` field is numeric (e.g. `NUM_GT`),
+the `value` field must be a base-10 integer.
 
 By default `key` field refers to the corresponding object's `Attribute`.
 Some Object's header fields can also be accessed by adding `$Object:`
@@ -122,6 +123,9 @@ prefix to the name. For such attributes, field 'match_type' must not be
 * $Object:homomorphicHash \
   homomorphic_hash
 
+Numeric `match_type` field can only be used with `$Object:creationEpoch`
+and `$Object:payloadLength` system attributes.
+
 Please note, that if request or response does not have object's headers of
 full object (Range, RangeHash, Search, Delete), it will not be possible to
 filter by object header fields or user attributes. From the well-known list
@@ -207,6 +211,10 @@ MatchType is an enumeration of match types.
 | STRING_EQUAL | 1 | Return true if strings are equal |
 | STRING_NOT_EQUAL | 2 | Return true if strings are different |
 | NOT_PRESENT | 3 | Absence of attribute |
+| NUM_GT | 4 | Numeric 'greater than' |
+| NUM_GE | 5 | Numeric 'greater or equal than' |
+| NUM_LT | 6 | Numeric 'less than' |
+| NUM_LE | 7 | Numeric 'less or equal than' |