SSL_alert_type_string, SSL_alert_type_string_long,
SSL_alert_desc_string, SSL_alert_desc_string_long - get textual description
of alert information
#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);
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.
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.
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.
- "UP"/"unknown PSK identity"
- Sent by the server to indicate that it does not recognize a PSK identity
or an SRP identity.
- "UK"/"unknown"
- This indicates that no description is available for this alert type.
Probably value does not contain a correct alert message.
Copyright 2001-2016 The OpenSSL Project Authors. All Rights
Reserved.
Licensed under the Apache License 2.0 (the "License").
You may not use this file except in compliance with the License. You can
obtain a copy in the file LICENSE in the source distribution or at
<https://www.openssl.org/source/license.html>.