Ubuntu Manpage: SSL_alert_type_string, SSL_alert_type_string_long, SSL_alert_desc

Provided by: libssl-doc_3.0.13-0ubuntu3.4_all

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.

"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.

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