SSL_alert_type_string(3) | OpenSSL | SSL_alert_type_string(3) |
SSL_alert_type_string_long() returns a string indicating the type of the alert specified by value.
SSL_alert_desc_string() returns a two letter string as a short form describing the reason of the alert specified by value.
SSL_alert_desc_string_long() returns a string describing the reason of the alert specified by value.
A warning alert is sent, when a non-fatal error condition occurs. The "close notify" alert is sent as a warning alert. Other examples for non-fatal errors are certificate errors ("certificate expired", "unsupported certificate"), for which a warning alert may be sent. (The sending party may however decide to send a fatal error.) The receiving side may cancel the connection on reception of a warning alert on it discretion.
Several alert messages must be sent as fatal alert messages as specified by the TLS RFC. A fatal alert always leads to a connection abort.
"W"/"warning" |
"F"/"fatal" |
"U"/"unknown" | This indicates that no support is available for this alert type. Probably value does not contain a correct alert message. |
The following strings can occur for SSL_alert_desc_string() or SSL_alert_desc_string_long():
"CN"/"close notify" | The connection shall be closed. This is a warning alert. |
"UM"/"unexpected message" | An inappropriate message was received. This alert is always fatal and should never be observed in communication between proper implementations. |
"BM"/"bad record mac" | This alert is returned if a record is received with an incorrect MAC. This message is always fatal. |
"DF"/"decompression failure" | The decompression function received improper input (e.g. data that would expand to excessive length). This message is always fatal. |
"HF"/"handshake failure" | 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. |
"NC"/"no certificate" | A client, that was asked to send a certificate, does not send a certificate (SSLv3 only). |
"BC"/"bad certificate" | A certificate was corrupt, contained signatures that did not verify correctly, etc |
"UC"/"unsupported certificate" | A certificate was of an unsupported type. |
"CR"/"certificate revoked" | A certificate was revoked by its signer. |
"CE"/"certificate expired" | A certificate has expired or is not currently valid. |
"CU"/"certificate unknown" | Some other (unspecified) issue arose in processing the certificate, rendering it unacceptable. |
"IP"/"illegal parameter" | A field in the handshake was out of range or inconsistent with other fields. This is always fatal. |
"DC"/"decryption failed" | 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. |
"RO"/"record overflow" | A TLSCiphertext record was received which 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. |
"CA"/"unknown CA" | 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. |
"AD"/"access denied" | A valid certificate was received, but when access control was applied, the sender decided not to proceed with negotiation. This message is always fatal. |
"DE"/"decode error" | 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. |
"CY"/"decrypt error" | A handshake cryptographic operation failed, including being unable to correctly verify a signature, decrypt a key exchange, or validate a finished message. |
"ER"/"export restriction" | A negotiation not in compliance with export restrictions was detected; for example, attempting to transfer a 1024 bit ephemeral RSA key for the RSA_EXPORT handshake method. This message is always fatal. |
"PV"/"protocol version" | 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. |
"IS"/"insufficient security" | 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. |
"IE"/"internal error" | An internal error unrelated to the peer or the correctness of the protocol makes it impossible to continue (such as a memory allocation failure). This message is always fatal. |
"US"/"user canceled" | 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. |
"NR"/"no renegotiation" | 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 would be 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. |
"UK"/"unknown" | This indicates that no description is available for this alert type. Probably value does not contain a correct alert message. |
July 20, 2009 | 1.0.1-dev |