Functions

Functions in matchers

Enhance matcher capabilities by incorporating functions. Use built-in functions or define custom ones. Built-in key-matching functions follow this signature:

bool function_name(string url, string pattern)

These functions return booleans indicating whether url matches pattern.

Available built-in functions:

Function	url	pattern	Example
keyMatch	a URL path like /alice_data/resource1	a URL path or a * pattern like /alice_data/*	keymatch_model.conf/keymatch_policy.csv
keyMatch2	a URL path like /alice_data/resource1	a URL path or a : pattern like /alice_data/:resource	keymatch2_model.conf/keymatch2_policy.csv
keyMatch3	a URL path like /alice_data/resource1	a URL path or a {} pattern like /alice_data/{resource}	https://github.com/casbin/casbin/blob/277c1a2b85698272f764d71a94d2595a8d425915/util/builtin_operators_test.go#L171-L196
keyMatch4	a URL path like /alice_data/123/book/123	a URL path or a {} pattern like /alice_data/{id}/book/{id}	https://github.com/casbin/casbin/blob/277c1a2b85698272f764d71a94d2595a8d425915/util/builtin_operators_test.go#L208-L222
keyMatch5	a URL path like /alice_data/123/?status=1	a URL path, a {} or * pattern like /alice_data/{id}/*	https://github.com/casbin/casbin/blob/1cde2646d10ad1190c0d784c3a1c0e1ace1b5bc9/util/builtin_operators_test.go#L485-L526
regexMatch	any string	a regular expression pattern	keymatch_model.conf/keymatch_policy.csv
ipMatch	an IP address like 192.168.2.123	an IP address or a CIDR like 192.168.2.0/24	ipmatch_model.conf/ipmatch_policy.csv
globMatch	a path-like path like /alice_data/resource1	a glob pattern like /alice_data/*	https://github.com/casbin/casbin/blob/277c1a2b85698272f764d71a94d2595a8d425915/util/builtin_operators_test.go#L426-L466

Key-getting functions generally accept three parameters (except keyGet):

bool function_name(string url, string pattern, string key_name)

These return the key_name value when matching the pattern, otherwise returning "".

Examples: KeyGet2("/resource1/action", "/:res/action", "res") returns "resource1", while KeyGet3("/resource1_admin/action", "/{res}_admin/*", "res") returns "resource1". For KeyGet with two parameters: KeyGet("/resource1/action", "/*") returns "resource1/action".

Function	url	pattern	key_name	example
keyGet	a URL path like /proj/resource1	a URL path or a * pattern like /proj/*	\	keyget_model.conf/keymatch_policy.csv
keyGet2	a URL path like /proj/resource1	a URL path or : pattern like /prooj/:resource	key name specified in the pattern	keyget2_model.conf/keymatch2_policy.csv
keyGet3	a URL path like /proj/res3_admin/	a URL path or {} pattern like /proj/{resource}_admin/*	key name specified in the pattern	https://github.com/casbin/casbin/blob/7bd496f94f5a2739a392d333a9aaaa10ae397673/util/builtin_operators_test.go#L209-L247

Complete function details: https://github.com/casbin/casbin/blob/master/util/builtin_operators_test.go

How to add a customized function

Start by creating your function, accepting multiple parameters and returning a bool:

func KeyMatch(key1 string, key2 string) bool {
    i := strings.Index(key2, "*")
    if i == -1 {
        return key1 == key2
    }

    if len(key1) > i {
        return key1[:i] == key2[:i]
    }
    return key1 == key2[:i]
}

Next, create an interface{} wrapper:

func KeyMatchFunc(args ...interface{}) (interface{}, error) {
    name1 := args[0].(string)
    name2 := args[1].(string)

    return (bool)(KeyMatch(name1, name2)), nil
}

Register the function with the Casbin enforcer:

e.AddFunction("my_func", KeyMatchFunc)

Use the function in your model CONF:

[matchers]
m = r.sub == p.sub && my_func(r.obj, p.obj) && r.act == p.act