SSL_alert_type_string
SSL_alert_type_string(3) OpenSSL 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 speci-
fied 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 ver-
ify 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 certifi-
cate, 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 rec-
ognized, 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 alloca-
tion 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 hand-
shake 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, authentica-
tion, 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.
SEE ALSO
ssl(3), SSL_CTX_set_info_callback(3)
0.9.7a 2001-09-07 SSL_alert_type_string(3)
