SSL_alert_type_string(3)SSL_alert_type_string(3)NAME
SSL_alert_type_string, SSL_alert_type_string_long - Get textual
description of alert information
SYNOPSIS
#include <openssl/ssl.h>
char *SSL_alert_type_string(
int value ); char *SSL_alert_type_string_long(
int value ); char *SSL_alert_desc_string(
int value ); char *SSL_alert_desc_string_long(
int value );
DESCRIPTION
The SSL_alert_type_string() function returns a one letter string indi‐
cating the type of the alert specified by value.
The SSL_alert_type_string_long() function returns a string indicating
the type of the alert specified by value.
The SSL_alert_desc_string() function returns a two letter string as a
short form describing the reason of the alert specified by value.
The SSL_alert_desc_string_long() function 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 result 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 of
non-fatal errors are certificate errors, such as “certificate expired''
and “unsupported certificate,” for which a warning alert might be sent.
(The sending party might decide to send a fatal error.) The receiving
side, at its discretion, can cancel the connection after receiving a
warning alert.
Several alert messages must be sent as fatal alert messages as speci‐
fied by the TLS RFC. A fatal alert always leads to a connection abort.
RETURN VALUES
The SSL_alert_type_string() or SSL_alert_type_string_long()functions
return a one letter string indicating the type of the alert specified
by value: Warning Fatal 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 the SSL_alert_desc_string() or
SSL_alert_desc_string_long() functions: close notify
The connection will be closed. This is a warning alert. unex‐
pected message
An inappropriate message was received. This alert is always
fatal and should never be observed in communication between
proper implementations. bad record mac
This alert is returned if a record is received with an incorrect
MAC. This message is always fatal. decompression failure
The decompression function received improper input (e.g. data
that would expand to excessive length). This message is always
fatal. 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.
no certificate
A client, that was asked to send a certificate, does not send a
certificate (SSLv3 only). bad certificate
A certificate was corrupt, contained signatures that did not
verify correctly, etc. unsupported certificate
A certificate was of an unsupported type. certificate revoked
A certificate was revoked by its signer. certificate expired
A certificate has expired or is not currently valid. certifi‐
cate unknown
Some other (unspecified) issue arose in processing the certifi‐
cate, rendering it unacceptable. illegal parameter
A field in the handshake was out of range or inconsistent with
other fields. This is always fatal. 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. 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.
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. 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. 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. decrypt error
A handshake cryptographic operation failed, including being
unable to correctly verify a signature, decrypt a key exchange,
or validate a finished message. 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 mes‐
sage is always fatal. protocol version
The protocol version the client has attempted to negotiate is
recognized, but not supported. (For example, old protocol ver‐
sions might be avoided for security reasons). This message is
always fatal. insufficient security
Returned instead of handshake_failure when a negotiation fails,
specifically because the server requires ciphers more secure
than those supported by the client. This message is always
fatal. 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. user can‐
celled
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 connec‐
tion by sending a close_notify is more appropriate. This alert
should be followed by a close_notify. This message is generally
a warning. 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. unknown
This indicates that no description is available for this alert
type. The value probably does not contain a correct alert mes‐
sage.
SEE ALSO
Functions: ssl(3), SSL_CTX_set_info_callback(3),
SSL_alert_desc_string(3)SSL_alert_type_string(3)
