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Diffstat (limited to 'src/lib/libssl/doc/SSL_shutdown.3')
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diff --git a/src/lib/libssl/doc/SSL_shutdown.3 b/src/lib/libssl/doc/SSL_shutdown.3 deleted file mode 100644 index 187e656fe3..0000000000 --- a/src/lib/libssl/doc/SSL_shutdown.3 +++ /dev/null | |||
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1 | .\" | ||
2 | .\" $OpenBSD: SSL_shutdown.3,v 1.2 2014/12/02 14:11:01 jmc Exp $ | ||
3 | .\" | ||
4 | .Dd $Mdocdate: December 2 2014 $ | ||
5 | .Dt SSL_SHUTDOWN 3 | ||
6 | .Os | ||
7 | .Sh NAME | ||
8 | .Nm SSL_shutdown | ||
9 | .Nd shut down a TLS/SSL connection | ||
10 | .Sh SYNOPSIS | ||
11 | .In openssl/ssl.h | ||
12 | .Ft int | ||
13 | .Fn SSL_shutdown "SSL *ssl" | ||
14 | .Sh DESCRIPTION | ||
15 | .Fn SSL_shutdown | ||
16 | shuts down an active TLS/SSL connection. | ||
17 | It sends the | ||
18 | .Dq close notify | ||
19 | shutdown alert to the peer. | ||
20 | .Sh NOTES | ||
21 | .Fn SSL_shutdown | ||
22 | tries to send the | ||
23 | .Dq close notify | ||
24 | shutdown alert to the peer. | ||
25 | Whether the operation succeeds or not, the | ||
26 | .Dv SSL_SENT_SHUTDOWN | ||
27 | flag is set and a currently open session is considered closed and good and will | ||
28 | be kept in the session cache for further reuse. | ||
29 | .Pp | ||
30 | The shutdown procedure consists of 2 steps: the sending of the | ||
31 | .Dq close notify | ||
32 | shutdown alert and the reception of the peer's | ||
33 | .Dq close notify | ||
34 | shutdown alert. | ||
35 | According to the TLS standard, it is acceptable for an application to only send | ||
36 | its shutdown alert and then close the underlying connection without waiting for | ||
37 | the peer's response (this way resources can be saved, as the process can | ||
38 | already terminate or serve another connection). | ||
39 | When the underlying connection shall be used for more communications, | ||
40 | the complete shutdown procedure (bidirectional | ||
41 | .Dq close notify | ||
42 | alerts) must be performed, so that the peers stay synchronized. | ||
43 | .Pp | ||
44 | .Fn SSL_shutdown | ||
45 | supports both uni- and bidirectional shutdown by its 2 step behavior. | ||
46 | .Pp | ||
47 | When the application is the first party to send the | ||
48 | .Dq close notify | ||
49 | alert, | ||
50 | .Fn SSL_shutdown | ||
51 | will only send the alert and then set the | ||
52 | .Dv SSL_SENT_SHUTDOWN | ||
53 | flag (so that the session is considered good and will be kept in cache). | ||
54 | .Fn SSL_shutdown | ||
55 | will then return 0. | ||
56 | If a unidirectional shutdown is enough | ||
57 | (the underlying connection shall be closed anyway), this first call to | ||
58 | .Fn SSL_shutdown | ||
59 | is sufficient. | ||
60 | In order to complete the bidirectional shutdown handshake, | ||
61 | .Fn SSL_shutdown | ||
62 | must be called again. | ||
63 | The second call will make | ||
64 | .Fn SSL_shutdown | ||
65 | wait for the peer's | ||
66 | .Dq close notify | ||
67 | shutdown alert. | ||
68 | On success, the second call to | ||
69 | .Fn SSL_shutdown | ||
70 | will return 1. | ||
71 | .Pp | ||
72 | If the peer already sent the | ||
73 | .Dq close notify | ||
74 | alert and it was already processed implicitly inside another function | ||
75 | .Pq Xr SSL_read 3 , | ||
76 | the | ||
77 | .Dv SSL_RECEIVED_SHUTDOWN | ||
78 | flag is set. | ||
79 | .Fn SSL_shutdown | ||
80 | will send the | ||
81 | .Dq close notify | ||
82 | alert, set the | ||
83 | .Dv SSL_SENT_SHUTDOWN | ||
84 | flag and will immediately return with 1. | ||
85 | Whether | ||
86 | .Dv SSL_RECEIVED_SHUTDOWN | ||
87 | is already set can be checked using the | ||
88 | .Fn SSL_get_shutdown | ||
89 | (see also the | ||
90 | .Xr SSL_set_shutdown 3 | ||
91 | call). | ||
92 | .Pp | ||
93 | It is therefore recommended to check the return value of | ||
94 | .Fn SSL_shutdown | ||
95 | and call | ||
96 | .Fn SSL_shutdown | ||
97 | again, if the bidirectional shutdown is not yet complete (return value of the | ||
98 | first call is 0). | ||
99 | As the shutdown is not specially handled in the SSLv2 protocol, | ||
100 | .Fn SSL_shutdown | ||
101 | will succeed on the first call. | ||
102 | .Pp | ||
103 | The behaviour of | ||
104 | .Fn SSL_shutdown | ||
105 | additionally depends on the underlying | ||
106 | .Vt BIO . | ||
107 | .Pp | ||
108 | If the underlying | ||
109 | .Vt BIO | ||
110 | is | ||
111 | .Em blocking , | ||
112 | .Fn SSL_shutdown | ||
113 | will only return once the | ||
114 | handshake step has been finished or an error occurred. | ||
115 | .Pp | ||
116 | If the underlying | ||
117 | .Vt BIO | ||
118 | is | ||
119 | .Em non-blocking , | ||
120 | .Fn SSL_shutdown | ||
121 | will also return when the underlying | ||
122 | .Vt BIO | ||
123 | could not satisfy the needs of | ||
124 | .Fn SSL_shutdown | ||
125 | to continue the handshake. | ||
126 | In this case a call to | ||
127 | .Xr SSL_get_error 3 | ||
128 | with the | ||
129 | return value of | ||
130 | .Fn SSL_shutdown | ||
131 | will yield | ||
132 | .Dv SSL_ERROR_WANT_READ | ||
133 | or | ||
134 | .Dv SSL_ERROR_WANT_WRITE . | ||
135 | The calling process then must repeat the call after taking appropriate action | ||
136 | to satisfy the needs of | ||
137 | .Fn SSL_shutdown . | ||
138 | The action depends on the underlying | ||
139 | .Vt BIO . | ||
140 | When using a non-blocking socket, nothing is to be done, but | ||
141 | .Xr select 2 | ||
142 | can be used to check for the required condition. | ||
143 | When using a buffering | ||
144 | .Vt BIO , | ||
145 | like a | ||
146 | .Vt BIO | ||
147 | pair, data must be written into or retrieved out of the | ||
148 | .Vt BIO | ||
149 | before being able to continue. | ||
150 | .Pp | ||
151 | .Fn SSL_shutdown | ||
152 | can be modified to only set the connection to | ||
153 | .Dq shutdown | ||
154 | state but not actually send the | ||
155 | .Dq close notify | ||
156 | alert messages; see | ||
157 | .Xr SSL_CTX_set_quiet_shutdown 3 . | ||
158 | When | ||
159 | .Dq quiet shutdown | ||
160 | is enabled, | ||
161 | .Fn SSL_shutdown | ||
162 | will always succeed and return 1. | ||
163 | .Sh RETURN VALUES | ||
164 | The following return values can occur: | ||
165 | .Bl -tag -width Ds | ||
166 | .It 0 | ||
167 | The shutdown is not yet finished. | ||
168 | Call | ||
169 | .Fn SSL_shutdown | ||
170 | for a second time, if a bidirectional shutdown shall be performed. | ||
171 | The output of | ||
172 | .Xr SSL_get_error 3 | ||
173 | may be misleading, as an erroneous | ||
174 | .Dv SSL_ERROR_SYSCALL | ||
175 | may be flagged even though no error occurred. | ||
176 | .It 1 | ||
177 | The shutdown was successfully completed. | ||
178 | The | ||
179 | .Dq close notify | ||
180 | alert was sent and the peer's | ||
181 | .Dq close notify | ||
182 | alert was received. | ||
183 | .It \(mi1 | ||
184 | The shutdown was not successful because a fatal error occurred either | ||
185 | at the protocol level or a connection failure occurred. | ||
186 | It can also occur if action is need to continue the operation for non-blocking | ||
187 | .Vt BIO Ns | ||
188 | s. | ||
189 | Call | ||
190 | .Xr SSL_get_error 3 | ||
191 | with the return value | ||
192 | .Fa ret | ||
193 | to find out the reason. | ||
194 | .El | ||
195 | .Sh SEE ALSO | ||
196 | .Xr bio 3 , | ||
197 | .Xr ssl 3 , | ||
198 | .Xr SSL_accept 3 , | ||
199 | .Xr SSL_clear 3 , | ||
200 | .Xr SSL_connect 3 , | ||
201 | .Xr SSL_CTX_set_quiet_shutdown 3 , | ||
202 | .Xr SSL_free 3 , | ||
203 | .Xr SSL_get_error 3 , | ||
204 | .Xr SSL_set_shutdown 3 | ||