ssl_alert_type_string(3)
NAME
SSL_alert_type_string, SSL_alert_type_string_long,
SSL_alert_desc_string, SSL_alert_desc_string_long - get textual
description of alert information
SYNOPSIS
#include <openssl/ssl.h> const char *SSL_alert_type_string(int value); const char *SSL_alert_type_string_long(int value); const char *SSL_alert_desc_string(int value); const char *SSL_alert_desc_string_long(int value);
DESCRIPTION
SSL_alert_type_string() returns a one letter string indicating the type
of the alert specified by value.
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.
NOTES
When one side of an SSL/TLS communication wants to inform the peer
about a special situation, it sends an alert. The alert is sent as a
special message and does not influence the normal data stream (unless
its contents results in the communication being canceled).
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.
RETURN VALUES
The following strings can occur for SSL_alert_type_string() or SSL_alert_type_string_long():
- "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.