public Class AlertDescription

A valid certificate was received, but when access control was applied, the sender decided not to proceed with negotiation. This message is always fatal.

A certificate was corrupt, contained signatures that did not verify correctly, etc.

This alert is sent by servers when a certificate hash does not match a client provided certificate_hash. This message is always fatal.

This alert is sent by clients that receive an invalid certificate status response (see Section 3.6). This message is always fatal.

This alert is returned if a record is received with an incorrect MAC. This alert also MUST be returned if an alert is sent because a TLSCiphertext decrypted in an invalid way: either it wasn't an even multiple of the block length, or its padding values, when checked, weren't correct. This message is always fatal and should never be observed in communication between proper implementations (except when messages were corrupted in the network).

A certificate has expired or is not currently valid.

Sent by servers when a client certificate is desired but none was provided by the client.

A certificate was revoked by its signer.

Some other (unspecified) issue arose in processing the certificate, rendering it unacceptable.

This alert is sent by servers who are unable to retrieve a certificate chain from the URL supplied by the client (see Section 3.3). This message MAY be fatal - for example if client authentication is required by the server for the handshake to continue and the server is unable to retrieve the certificate chain, it may send a fatal alert.

This message notifies the recipient that the sender will not send any more messages on this connection. Note that as of TLS 1.1, failure to properly close a connection no longer requires that a session not be resumed. This is a change from TLS 1.0 ("The session becomes unresumable if any connection is terminated without proper close_notify messages with level equal to warning.") to conform with widespread implementation practice.

A message could not be decoded because some field was out of the specified range or the length of the message was incorrect. This message is always fatal and should never be observed in communication between proper implementations (except when messages were corrupted in the network).

The decompression function received improper input (e.g., data that would expand to excessive length). This message is always fatal and should never be observed in communication between proper implementations.

A handshake cryptographic operation failed, including being unable to correctly verify a signature or validate a Finished message. This message is always fatal.

This alert was used in some earlier versions of TLS, and may have permitted certain attacks against the CBC mode [CBCATT]. It MUST NOT be sent by compliant implementations.

This alert was used in some earlier versions of TLS. It MUST NOT be sent by compliant implementations.

Reception of a handshake_failure alert message indicates that the sender was unable to negotiate an acceptable set of security parameters given the options available. This is a fatal error.

A field in the handshake was out of range or inconsistent with other fields. This message is always fatal.

If TLS_FALLBACK_SCSV appears in ClientHello.cipher_suites and the highest protocol version supported by the server is higher than the version indicated in ClientHello.client_version, the server MUST respond with a fatal inappropriate_fallback alert [..].

Returned instead of handshake_failure when a negotiation has failed specifically because the server requires ciphers more secure than those supported by the client. This message is always fatal.

An internal error unrelated to the peer or the correctness of the protocol (such as a memory allocation failure) makes it impossible to continue. This message is always fatal.

Sent by endpoints that receive a handshake message not containing an extension that is mandatory to send for the offered TLS version or other negotiated parameters.

In the event that the server supports no protocols that the client advertises, then the server SHALL respond with a fatal "no_application_protocol" alert.

This alert was used in SSLv3 but not any version of TLS. It MUST NOT be sent by compliant implementations.

Sent by the client in response to a hello request or by the server in response to a client hello after initial handshaking. Either of these would normally lead to renegotiation; when that is not appropriate, the recipient should respond with this alert. At that point, the original requester can decide whether to proceed with the connection. One case where this would be appropriate is where a server has spawned a process to satisfy a request; the process might receive security parameters (key length, authentication, etc.) at startup, and it might be difficult to communicate changes to these parameters after that point. This message is always a warning.

The protocol version the client has attempted to negotiate is recognized but not supported. (For example, old protocol versions might be avoided for security reasons.) This message is always fatal.

A TLSCiphertext record was received that had a length more than 2^14+2048 bytes, or a record decrypted to a TLSCompressed record with more than 2^14+1024 bytes. This message is always fatal and should never be observed in communication between proper implementations (except when messages were corrupted in the network).

An inappropriate message was received. This alert is always fatal and should never be observed in communication between proper implementations.

A valid certificate chain or partial chain was received, but the certificate was not accepted because the CA certificate could not be located or couldn't be matched with a known, trusted CA. This message is always fatal.

If the server does not recognize the PSK identity, it MAY respond with an "unknown_psk_identity" alert message.

This alert is sent by servers that receive a server_name extension request, but do not recognize the server name. This message MAY be fatal.

A certificate was of an unsupported type.

Sent by clients that receive an extended server hello containing an extension that they did not put in the corresponding client hello. This message is always fatal.

This handshake is being canceled for some reason unrelated to a protocol failure. If the user cancels an operation after the handshake is complete, just closing the connection by sending a close_notify is more appropriate. This alert should be followed by a close_notify. This message is generally a warning.