IAM Tools

StringNotLikeIfExists

StringNotLikeIfExists compares a string in a request to a list of strings in your policy. The policy values can include asterisks (*) to match multiple characters and question marks (?) to match a single character. The comparision is case sensitive.

To match a request, the context key can be absent, but if present it must NOT match any of the strings in your policy.

You can use policy variables in the value of this operator.

So you know:

StringNotLikeIfExists behaves exactly the same as StringNotLike. "Negative" operators such as StringNotLike already match requests if the key is not present so the IfExists suffix has no effect.

There is no harm in adding IfExists to StringNotLike; it probably makes the intent more clear. We know you already knew this, but put this message in for everyone else. 😉

StringNotLikeIfExists in an Allow Statement

Click into any of these polices and change them test how they change the result.

Given the Policy Condition:

"StringNotLikeIfExists": {
  "aws:RequestTag/Department": [
    "Finance:*",
    "Sales:??"
  ]
}

When the Request Context has:

aws:RequestTag/Department: null

Then the result is:

Allowed Assuming no explicit Deny elsewhere

Given the Policy Condition:

"StringNotLikeIfExists": {
  "aws:RequestTag/Department": [
    "Finance:*",
    "Sales:??"
  ]
}

When the Request Context has:

aws:RequestTag/Department: finance:AP

Then the result is:

Allowed Assuming no explicit Deny elsewhere

Given the Policy Condition:

"StringNotLikeIfExists": {
  "aws:RequestTag/Department": [
    "Finance:*",
    "Sales:??"
  ]
}

When the Request Context has:

aws:RequestTag/Department: 
    Finance:AccountsPayable

Then the result is:

Not Allowed Statement does not apply

StringNotLikeIfExists in a Deny Statement

Click into any of these polices and change them test how they change the result.

Given the Policy Condition:

"StringNotLikeIfExists": {
  "aws:RequestTag/Department": [
    "Finance:*",
    "Sales:??"
  ]
}

When the Request Context has:

aws:RequestTag/Department: null

Then the result is:

Denied

Given the Policy Condition:

"StringNotLikeIfExists": {
  "aws:RequestTag/Department": [
    "Finance:*",
    "Sales:??"
  ]
}

When the Request Context has:

aws:RequestTag/Department: finance:AP

Then the result is:

Denied

Given the Policy Condition:

"StringNotLikeIfExists": {
  "aws:RequestTag/Department": [
    "Finance:*",
    "Sales:??"
  ]
}

When the Request Context has:

aws:RequestTag/Department: 
    Finance:AccountsPayable

Then the result is:

Not Denied May be allowed by another statement