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-Security Design of corosync
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-
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-The corosync project intends to mitigate the following threats:
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-
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-1. forged group messaging messages which are intended to fault the corosync
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- executive
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-2. forged group messaging messages which are intended to fault applications
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- using corosync apis
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-3. monitoring of network data to capture sensitive information
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-
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-The corosync project does not intend to mitigate the following threats:
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-
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-1. physical access to the hardware which could expose the private key
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-2. privledged access to the operating system which could expose the private key
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- or be used to inject errors into the corosync executive.
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-3. library user creates requests which are intended to fault the corosync
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- executive
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-
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-The corosync project mitigates the threats using two mechanisms:
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-
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-1. Authentication
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-2. Secrecy
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-
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-Library Interface
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------------------
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-The corosync executive authenticates every library user. The library is only
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-allowed to access services if it's GID is corosync or 0. Unauthorized library
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-users are rejected.
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-
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-The corosync group is a trusted group. If the administrator doesn't trust the
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-application, it should not be added to the group! Any member of the corosync group
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-could potentially send a malformed request to the executive and cause it to
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-fault.
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-
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-Group Messaging Interface
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--------------------------
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-Group messaging uses UDP/IP to communicate with other corosync executives using
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-messages. It is possible without authentication of every packet that an
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-attacker could forge messages. These forged messages could fault the corosync
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-executive distributed state machines. It would also be possible to corrupt
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-end applications by forging changes.
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-
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-Since messages are sent using UDP/IP it would be possible to snoop those
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-messages and rebuild sensitive data.
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-
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-To solve these problems, the group messaging interface uses two new interfaces
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-interal to it's implementation:
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-1. encrypt_and_sign - encrypts and signs a message securely
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-2. authenticate_and_decrypt - authenticates and decrypts a message securely
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-
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-When the executive wants to send a message over the network, it uses
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-encrypt_and_sign to prepare the message to be sent. When the executive
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-wants to receive a message from the network, it uses
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-authenticate_and_decrypt to verify the message is valid and decrypt it.
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-
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-Corosync uses AES256/SHA-1 which from the Mozilla Network Security
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-Services (libnss) library.
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-
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-The internal functions utilize the following algorithms:
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-sha1 - hash algorithm secure for using with hmac
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-hmac - produces a 16 byte digest from any length input
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-
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-Every message starts with a
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-struct security {
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- unsigned char digest[20]; A one way hash digest
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- unsigned char salt[16]; A securely generated random number
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-}
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-
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-USING LIBNSS
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-------------
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-When corosync is started up libnss is initialised,
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-the private key is read into memory and stored for later use by the code.
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-
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-When a message is sent (encrypt_and_sign):
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-------------------------------------------
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-- The message is encrypted using AES.
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-- A digest of that message is then created using SHA256 and based on the
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- private key.
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-- the message is then transmitted.
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-
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-When a message is received (decrypt_and_authenticate):
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-- A Digest of the encrypted message is created using the private key
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-- That digest is compared to the one in the message security_header
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-- If they do not match the packet is rejected
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-- If they do match then the message is decrypted using the private key.
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-- The message is processed.
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-
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-Comments welcome mailto:users@clusterlabs.org
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