.\" $OpenBSD: SSL_alert_type_string.3,v 1.7 2024/10/13 08:25:09 jsg Exp $ .\" OpenSSL b97fdb57 Nov 11 09:33:09 2016 +0100 .\" .\" This file was written by Lutz Jaenicke . .\" Copyright (c) 2001, 2011 The OpenSSL Project. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in .\" the documentation and/or other materials provided with the .\" distribution. .\" .\" 3. All advertising materials mentioning features or use of this .\" software must display the following acknowledgment: .\" "This product includes software developed by the OpenSSL Project .\" for use in the OpenSSL Toolkit. 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IN NO EVENT SHALL THE OpenSSL PROJECT OR .\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, .\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; .\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, .\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED .\" OF THE POSSIBILITY OF SUCH DAMAGE. .\" .Dd $Mdocdate: October 13 2024 $ .Dt SSL_ALERT_TYPE_STRING 3 .Os .Sh NAME .Nm SSL_alert_type_string , .Nm SSL_alert_type_string_long , .Nm SSL_alert_desc_string , .Nm SSL_alert_desc_string_long .Nd get textual description of alert information .Sh SYNOPSIS .In openssl/ssl.h .Ft const char * .Fn SSL_alert_type_string "int value" .Ft const char * .Fn SSL_alert_type_string_long "int value" .Ft const char * .Fn SSL_alert_desc_string "int value" .Ft const char * .Fn SSL_alert_desc_string_long "int value" .Sh DESCRIPTION .Fn SSL_alert_type_string returns a one letter string indicating the type of the alert specified by .Fa value . .Pp .Fn SSL_alert_type_string_long returns a string indicating the type of the alert specified by .Fa value . .Pp .Fn SSL_alert_desc_string returns a two letter string as a short form describing the reason of the alert specified by .Fa value . .Pp .Fn SSL_alert_desc_string_long returns a string describing the reason of the alert specified by .Fa value . .Pp 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). .Pp A warning alert is sent, when a non-fatal error condition occurs. The .Dq close notify alert is sent as a warning alert. Other examples for non-fatal errors are certificate errors .Po .Dq certificate expired , .Dq unsupported certificate .Pc , 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 at its discretion. .Pp 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. .Sh RETURN VALUES The following strings can occur for .Fn SSL_alert_type_string or .Fn SSL_alert_type_string_long : .Bl -tag -width Ds .It \(dqW\(dq/\(dqwarning\(dq .It \(dqF\(dq/\(dqfatal\(dq .It \(dqU\(dq/\(dqunknown\(dq This indicates that no support is available for this alert type. Probably .Fa value does not contain a correct alert message. .El .Pp The following strings can occur for .Fn SSL_alert_desc_string or .Fn SSL_alert_desc_string_long : .Bl -tag -width Ds .It \(dqCN\(dq/\(dqclose notify\(dq The connection shall be closed. This is a warning alert. .It \(dqUM\(dq/\(dqunexpected message\(dq An inappropriate message was received. This alert is always fatal and should never be observed in communication between proper implementations. .It \(dqBM\(dq/\(dqbad record mac\(dq This alert is returned if a record is received with an incorrect MAC. This message is always fatal. .It \(dqDF\(dq/\(dqdecompression failure\(dq The decompression function received improper input (e.g., data that would expand to excessive length). This message is always fatal. .It \(dqHF\(dq/\(dqhandshake failure\(dq 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. .It \(dqNC\(dq/\(dqno certificate\(dq A client, that was asked to send a certificate, does not send a certificate (SSLv3 only). .It \(dqBC\(dq/\(dqbad certificate\(dq A certificate was corrupt, contained signatures that did not verify correctly, etc. .It \(dqUC\(dq/\(dqunsupported certificate\(dq A certificate was of an unsupported type. .It \(dqCR\(dq/\(dqcertificate revoked\(dq A certificate was revoked by its signer. .It \(dqCE\(dq/\(dqcertificate expired\(dq A certificate has expired or is not currently valid. .It \(dqCU\(dq/\(dqcertificate unknown\(dq Some other (unspecified) issue arose in processing the certificate, rendering it unacceptable. .It \(dqIP\(dq/\(dqillegal parameter\(dq A field in the handshake was out of range or inconsistent with other fields. This is always fatal. .It \(dqDC\(dq/\(dqdecryption failed\(dq 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. .It \(dqRO\(dq/\(dqrecord overflow\(dq 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. .It \(dqCA\(dq/\(dqunknown CA\(dq 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. .It \(dqAD\(dq/\(dqaccess denied\(dq A valid certificate was received, but when access control was applied, the sender decided not to proceed with negotiation. This message is always fatal. .It \(dqDE\(dq/\(dqdecode error\(dq 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. .It \(dqCY\(dq/\(dqdecrypt error\(dq A handshake cryptographic operation failed, including being unable to correctly verify a signature, decrypt a key exchange, or validate a finished message. .It \(dqER\(dq/\(dqexport restriction\(dq 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. .It \(dqPV\(dq/\(dqprotocol version\(dq 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. .It \(dqIS\(dq/\(dqinsufficient security\(dq 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. .It \(dqIE\(dq/\(dqinternal error\(dq 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. .It \(dqIF\(dq/\(dqinappropriate fallback\(dq Sent by a server in response to an invalid connection retry attempt from a client (see RFC 7507). .It \(dqUS\(dq/\(dquser canceled\(dq 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. .It \(dqNR\(dq/\(dqno renegotiation\(dq 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. .It \(dqUP\(dq/\(dqunknown PSK identity\(dq Sent by the server to indicate that it does not recognize a PSK identity or an SRP identity. .It \(dqCQ\(dq/\(dqcertificate required\(dq Sent by servers when a client certificate is desired but none was provided by the client. .It \(dqAP\(dq/\(dqno application protocol\(dq Sent by servers when a client ALPN extension advertises only protocols that the server does not support (see RFC 7301). .It \(dqUK\(dq/\(dqunknown\(dq This indicates that no description is available for this alert type. Probably .Fa value does not contain a correct alert message. .El .Sh SEE ALSO .Xr ssl 3 , .Xr SSL_CTX_set_info_callback 3 .Sh HISTORY These functions first appeared in SSLeay 0.8.0 and have been available since .Ox 2.4 .