micro/auth/rules.go

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package auth
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import (
"fmt"
"sort"
"strings"
)
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// VerifyAccess an account has access to a resource using the rules provided. If the account does not have
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// access an error will be returned. If there are no rules provided which match the resource, an error
// will be returned
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func VerifyAccess(rules []*Rule, acc *Account, res *Resource) error {
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// the rule is only to be applied if the type matches the resource or is catch-all (*)
validTypes := []string{"*", res.Type}
// the rule is only to be applied if the name matches the resource or is catch-all (*)
validNames := []string{"*", res.Name}
// rules can have wildcard excludes on endpoints since this can also be a path for web services,
// e.g. /foo/* would include /foo/bar. We also want to check for wildcards and the exact endpoint
validEndpoints := []string{"*", res.Endpoint}
if comps := strings.Split(res.Endpoint, "/"); len(comps) > 1 {
for i := 1; i < len(comps)+1; i++ {
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wildcard := fmt.Sprintf("%v/*", strings.Join(comps[0:i], "/"))
validEndpoints = append(validEndpoints, wildcard)
}
}
// filter the rules to the ones which match the criteria above
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filteredRules := make([]*Rule, 0)
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for _, rule := range rules {
if !include(validTypes, rule.Resource.Type) {
continue
}
if !include(validNames, rule.Resource.Name) {
continue
}
if !include(validEndpoints, rule.Resource.Endpoint) {
continue
}
filteredRules = append(filteredRules, rule)
}
// sort the filtered rules by priority, highest to lowest
sort.SliceStable(filteredRules, func(i, j int) bool {
return filteredRules[i].Priority > filteredRules[j].Priority
})
// loop through the rules and check for a rule which applies to this account
for _, rule := range filteredRules {
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// a blank scope indicates the rule applies to everyone, even nil accounts
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if rule.Scope == ScopePublic && rule.Access == AccessDenied {
return ErrForbidden
} else if rule.Scope == ScopePublic && rule.Access == AccessGranted {
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return nil
}
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// all further checks require an account
if acc == nil {
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continue
}
// this rule applies to any account
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if rule.Scope == ScopeAccount && rule.Access == AccessDenied {
return ErrForbidden
} else if rule.Scope == ScopeAccount && rule.Access == AccessGranted {
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return nil
}
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// if the account has the necessary scope
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if include(acc.Scopes, rule.Scope) && rule.Access == AccessDenied {
return ErrForbidden
} else if include(acc.Scopes, rule.Scope) && rule.Access == AccessGranted {
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return nil
}
}
// if no rules matched then return forbidden
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return ErrForbidden
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}
// include is a helper function which checks to see if the slice contains the value. includes is
// not case sensitive.
func include(slice []string, val string) bool {
for _, s := range slice {
if strings.ToLower(s) == strings.ToLower(val) {
return true
}
}
return false
}