macOS Keychain - HackTricks

# macOS Keychain

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## Main Keychains

- The User Keychain (`~/Library/Keychains/login.keychain-db`), which is used to store user-specific credentials like application passwords, internet passwords, user-generated certificates, network passwords, and user-generated public/private keys.
- The System Keychain (`/Library/Keychains/System.keychain`), which stores system-wide credentials such as WiFi passwords, system root certificates, system private keys, and system application passwords.
  - It's possible to find other components like certificates in `/System/Library/Keychains/*`
- In iOS there is only one Keychain located in `/private/var/Keychains/`. This folder also contains databases for the `TrustStore`, certificates authorities (`caissuercache`) and OSCP entries (`ocspache`).
  - Apps will be restricted in the keychain only to their private area based on their application identifier.

### Password Keychain Access

These files, while they do not have inherent protection and can be downloaded, are encrypted and require the user's plaintext password to be decrypted. A tool like Chainbreaker could be used for decryption.

## Keychain Entries Protections

### ACLs

Each entry in the keychain is governed by Access Control Lists (ACLs) which dictate who can perform various actions on the keychain entry, including:

- ACLAuhtorizationExportClear: Allows the holder to get the clear text of the secret.
- ACLAuhtorizationExportWrapped: Allows the holder to get the clear text encrypted with another provided password.
- ACLAuhtorizationAny: Allows the holder to perform any action.

The ACLs are further accompanied by a list of trusted applications that can perform these actions without prompting. This could be:

- N`il` (no authorization required, everyone is trusted)
- An empty list (nobody is trusted)
- List of specific applications.

Also the entry might contain the key `ACLAuthorizationPartitionID`, which is use to identify the teamid, apple, and cdhash.

- If the teamid is specified, then in order to access the entry value withuot a prompt the used application must have the same teamid.
- If the apple is specified, then the app needs to be signed by Apple.
- If the cdhash is indicated, then app must have the specific cdhash.

### Creating a Keychain Entry

When a new entry is created using `Keychain Access.app`, the following rules apply:

- All apps can encrypt.
- No apps can export/decrypt (without prompting the user).
- All apps can see the integrity check.
- No apps can change ACLs.
- The partitionID is set to `apple`.

When an application creates an entry in the keychain, the rules are slightly different:

- All apps can encrypt.
- Only the creating application (or any other apps explicitly added) can export/decrypt (without prompting the user).
- All apps can see the integrity check.
- No apps can change the ACLs.
- The partitionID is set to `teamid:[teamID here]`.

## Accessing the Keychain

### `security`

    # List keychains
    security list-keychains

    # Dump all metadata and decrypted secrets (a lot of pop-ups)
    security dump-keychain -a -d

    # Find generic password for the "Slack" account and print the secrets
    security find-generic-password -a "Slack" -g

    # Change the specified entrys PartitionID entry
    security set-generic-password-parition-list -s "test service" -a "test acount" -S

    # Dump specifically the user keychain
    security dump-keychain ~/Library/Keychains/login.keychain-db

### APIs

> [!TIP] The keychain enumeration and dumping of secrets that won't generate a prompt can be done with the tool LockSmith

> Other API endpoints can be found in SecKeyChain.h source code.

List and get info about each keychain entry using the Security Framework or you could also check the Apple's open source cli tool security. Some API examples:

- The API `SecItemCopyMatching` gives info about each entry and there are some attributes you can set when using it:
  - `kSecReturnData`: If true, it will try to decrypt the data (set to false to avoid potential pop-ups)
  - `kSecReturnRef`: Get also reference to keychain item (set to true in case later you see you can decrypt without pop-up)
  - `kSecReturnAttributes`: Get metadata about entries
  - `kSecMatchLimit`: How many results to return
  - `kSecClass`: What kind of keychain entry

Get ACLs of each entry:

- With the API `SecAccessCopyACLList` you can get the ACL for the keychain item, and it will return a list of ACLs (like `ACLAuhtorizationExportClear` and the others previously mentioned) where each list has:
  - Description
  - Trusted Application List. This could be:
    - An app: /Applications/Slack.app
    - A binary: /usr/libexec/airportd
    - A group: group://AirPort

Export the data:

- The API `SecKeychainItemCopyContent` gets the plaintext
- The API `SecItemExport` exports the keys and certificates but might have to set passwords to export the content encrypted

And these are the requirements to be able to export a secret without a prompt:

- If 1+ trusted apps listed:
  - Need the appropriate authorizations (`Nil`, or be part of the allowed list of apps in the authorization to access the secret info)
  - Need code signature to match PartitionID
  - Need code signature to match that of one trusted app (or be a member of the right KeychainAccessGroup)
- If all applications trusted:
  - Need the appropriate authorizations
  - Need code signature to match PartitionID
    - If no PartitionID, then this isn't needed

> [!CAUTION] Therefore, if there is 1 application listed, you need to inject code in that application.

> If apple is indicated in the partitionID, you could access it with `osascript` so anything that is trusting all applications with apple in the partitionID. `Python` could also be used for this.

### Two additional attributes

- Invisible: It's a boolean flag to hide the entry from the UI Keychain app
- General: It's to store metadata (so it's NOT ENCRYPTED)
  - Microsoft was storing in plain text all the refresh tokens to access sensitive endpoint.

## References

- #OBTS v5.0: "Lock Picking the macOS Keychain" - Cody Thomas

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> Support HackTricks
> - Check the subscription plans!
> - Join the 💬 Discord group or the telegram group or follow us on Twitter 🐦 @hacktricks_live.
> - Share hacking tricks by submitting PRs to the HackTricks and HackTricks Cloud github repos.