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0.9.7e/doc/ssl
SSL_alert_type_string(3)/Sep/2001 (0.9.7e)SL_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():
"'/'arning"
"'/'atal"
"'/'nknown"
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/'lose notify"
The connection shall be closed. This is a warning alert.
"UM/'nexpected message"
An inappropriate message was received. This alert is
always fatal and should never be observed in
communication between proper implementations.
"BM/'ad record mac"
This alert is returned if a record is received with an
incorrect MAC. This message is always fatal.
"DF/'ecompression failure"
The decompression function received improper input (e.g.
data that would expand to excessive length). This
message is always fatal.
"HF/'andshake 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/'o certificate"
A client, that was asked to send a certificate, does not
send a certificate (SSLv3 only).
"BC/'ad certificate"
A certificate was corrupt, contained signatures that did
not verify correctly, etc
"UC/'nsupported certificate"
A certificate was of an unsupported type.
"CR/'ertificate revoked"
A certificate was revoked by its signer.
"CE/'ertificate expired"
A certificate has expired or is not currently valid.
"CU/'ertificate unknown"
Some other (unspecified) issue arose in processing the
certificate, rendering it unacceptable.
"IP/'llegal parameter"
A field in the handshake was out of range or
inconsistent with other fields. This is always fatal.
"DC/'ecryption 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/'ecord 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/'nknown 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/'ccess 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/'ecode 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/'ecrypt error"
A handshake cryptographic operation failed, including
being unable to correctly verify a signature, decrypt a
key exchange, or validate a finished message.
"ER/'xport 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/'rotocol 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/'nsufficient 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/'nternal 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/'ser 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/'o 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/'nknown"
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)
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