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author | bentley <> | 2014-10-12 09:33:04 +0000 |
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committer | bentley <> | 2014-10-12 09:33:04 +0000 |
commit | 82b7f378b6907ab315a6e50322d2a0a8794a0aa9 (patch) | |
tree | a5087bf8d016a6041c2b6822fbecfd8f6c5e70b1 /src/lib/libssl/doc/SSL_read.3 | |
parent | 0a63f0cf49369e1926567ab62e04e3355cedf0cd (diff) | |
download | openbsd-82b7f378b6907ab315a6e50322d2a0a8794a0aa9.tar.gz openbsd-82b7f378b6907ab315a6e50322d2a0a8794a0aa9.tar.bz2 openbsd-82b7f378b6907ab315a6e50322d2a0a8794a0aa9.zip |
Convert libssl manpages from pod to mdoc(7).
libcrypto has not been started yet.
ok schwarze@ miod@
Diffstat (limited to 'src/lib/libssl/doc/SSL_read.3')
-rw-r--r-- | src/lib/libssl/doc/SSL_read.3 | 190 |
1 files changed, 190 insertions, 0 deletions
diff --git a/src/lib/libssl/doc/SSL_read.3 b/src/lib/libssl/doc/SSL_read.3 new file mode 100644 index 0000000000..aed39c300f --- /dev/null +++ b/src/lib/libssl/doc/SSL_read.3 | |||
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1 | .Dd $Mdocdate: October 12 2014 $ | ||
2 | .Dt SSL_READ 3 | ||
3 | .Os | ||
4 | .Sh NAME | ||
5 | .Nm SSL_read | ||
6 | .Nd read bytes from a TLS/SSL connection. | ||
7 | .Sh SYNOPSIS | ||
8 | .In openssl/ssl.h | ||
9 | .Ft int | ||
10 | .Fn SSL_read "SSL *ssl" "void *buf" "int num" | ||
11 | .Sh DESCRIPTION | ||
12 | .Fn SSL_read | ||
13 | tries to read | ||
14 | .Fa num | ||
15 | bytes from the specified | ||
16 | .Fa ssl | ||
17 | into the buffer | ||
18 | .Fa buf . | ||
19 | .Sh NOTES | ||
20 | If necessary, | ||
21 | .Fn SSL_read | ||
22 | will negotiate a TLS/SSL session, if not already explicitly performed by | ||
23 | .Xr SSL_connect 3 | ||
24 | or | ||
25 | .Xr SSL_accept 3 . | ||
26 | If the peer requests a re-negotiation, | ||
27 | it will be performed transparently during the | ||
28 | .Fn SSL_read | ||
29 | operation. | ||
30 | The behaviour of | ||
31 | .Fn SSL_read | ||
32 | depends on the underlying | ||
33 | .Vt BIO . | ||
34 | .Pp | ||
35 | For the transparent negotiation to succeed, the | ||
36 | .Fa ssl | ||
37 | must have been initialized to client or server mode. | ||
38 | This is being done by calling | ||
39 | .Xr SSL_set_connect_state 3 | ||
40 | or | ||
41 | .Xr SSL_set_accept_state 3 | ||
42 | before the first call to | ||
43 | .Fn SSL_read | ||
44 | or | ||
45 | .Xr SSL_write 3 . | ||
46 | .Pp | ||
47 | .Fn SSL_read | ||
48 | works based on the SSL/TLS records. | ||
49 | The data are received in records (with a maximum record size of 16kB for | ||
50 | SSLv3/TLSv1). | ||
51 | Only after a record has been completely received can it be processed | ||
52 | (decrypted and checked for integrity). | ||
53 | Therefore data not retrieved at the last call of | ||
54 | .Fn SSL_read | ||
55 | can still be buffered inside the SSL layer and will be retrieved on the next | ||
56 | call to | ||
57 | .Fn SSL_read . | ||
58 | If | ||
59 | .Fa num | ||
60 | is higher than the number of bytes buffered, | ||
61 | .Fn SSL_read | ||
62 | will return with the bytes buffered. | ||
63 | If no more bytes are in the buffer, | ||
64 | .Fn SSL_read | ||
65 | will trigger the processing of the next record. | ||
66 | Only when the record has been received and processed completely will | ||
67 | .Fn SSL_read | ||
68 | return reporting success. | ||
69 | At most the contents of the record will be returned. | ||
70 | As the size of an SSL/TLS record may exceed the maximum packet size of the | ||
71 | underlying transport (e.g., TCP), it may be necessary to read several packets | ||
72 | from the transport layer before the record is complete and | ||
73 | .Fn SSL_read | ||
74 | can succeed. | ||
75 | .Pp | ||
76 | If the underlying | ||
77 | .Vt BIO | ||
78 | is | ||
79 | .Em blocking , | ||
80 | .Fn SSL_read | ||
81 | will only return once the read operation has been finished or an error | ||
82 | has occurred, except when a renegotiation take place, in which case a | ||
83 | .Dv SSL_ERROR_WANT_READ | ||
84 | may occur. | ||
85 | This behavior can be controlled with the | ||
86 | .Dv SSL_MODE_AUTO_RETRY | ||
87 | flag of the | ||
88 | .Xr SSL_CTX_set_mode 3 | ||
89 | call. | ||
90 | .Pp | ||
91 | If the underlying | ||
92 | .Vt BIO | ||
93 | is | ||
94 | .Em non-blocking , | ||
95 | .Fn SSL_read | ||
96 | will also return when the underlying | ||
97 | .Vt BIO | ||
98 | could not satisfy the needs of | ||
99 | .Fn SSL_read | ||
100 | to continue the operation. | ||
101 | In this case a call to | ||
102 | .Xr SSL_get_error 3 | ||
103 | with the return value of | ||
104 | .Fn SSL_read | ||
105 | will yield | ||
106 | .Dv SSL_ERROR_WANT_READ | ||
107 | or | ||
108 | .Dv SSL_ERROR_WANT_WRITE . | ||
109 | As at any time a re-negotiation is possible, a call to | ||
110 | .Fn SSL_read | ||
111 | can also cause write operations! | ||
112 | The calling process then must repeat the call after taking appropriate action | ||
113 | to satisfy the needs of | ||
114 | .Fn SSL_read . | ||
115 | The action depends on the underlying | ||
116 | .Vt BIO . | ||
117 | When using a non-blocking socket, nothing is to be done, but | ||
118 | .Xr select 2 | ||
119 | can be used to check for the required condition. | ||
120 | When using a buffering | ||
121 | .Vt BIO , | ||
122 | like a | ||
123 | .Vt BIO | ||
124 | pair, data must be written into or retrieved out of the | ||
125 | .Vt BIO | ||
126 | before being able to continue. | ||
127 | .Pp | ||
128 | .Xr SSL_pending 3 | ||
129 | can be used to find out whether there are buffered bytes available for | ||
130 | immediate retrieval. | ||
131 | In this case | ||
132 | .Fn SSL_read | ||
133 | can be called without blocking or actually receiving new data from the | ||
134 | underlying socket. | ||
135 | .Sh WARNING | ||
136 | When an | ||
137 | .Fn SSL_read | ||
138 | operation has to be repeated because of | ||
139 | .Dv SSL_ERROR_WANT_READ | ||
140 | or | ||
141 | .Dv SSL_ERROR_WANT_WRITE , | ||
142 | it must be repeated with the same arguments. | ||
143 | .Sh RETURN VALUES | ||
144 | The following return values can occur: | ||
145 | .Bl -tag -width Ds | ||
146 | .It >0 | ||
147 | The read operation was successful; the return value is the number of bytes | ||
148 | actually read from the TLS/SSL connection. | ||
149 | .It 0 | ||
150 | The read operation was not successful. | ||
151 | The reason may either be a clean shutdown due to a | ||
152 | .Dq close notify | ||
153 | alert sent by the peer (in which case the | ||
154 | .Dv SSL_RECEIVED_SHUTDOWN | ||
155 | flag in the ssl shutdown state is set (see | ||
156 | .Xr SSL_shutdown 3 | ||
157 | and | ||
158 | .Xr SSL_set_shutdown 3 ) . | ||
159 | It is also possible that the peer simply shut down the underlying transport and | ||
160 | the shutdown is incomplete. | ||
161 | Call | ||
162 | .Fn SSL_get_error | ||
163 | with the return value to find out whether an error occurred or the connection | ||
164 | was shut down cleanly | ||
165 | .Pq Dv SSL_ERROR_ZERO_RETURN . | ||
166 | .Pp | ||
167 | SSLv2 (deprecated) does not support a shutdown alert protocol, so it can only | ||
168 | be detected whether the underlying connection was closed. | ||
169 | It cannot be checked whether the closure was initiated by the peer or by | ||
170 | something else. | ||
171 | .It <0 | ||
172 | The read operation was not successful, because either an error occurred or | ||
173 | action must be taken by the calling process. | ||
174 | Call | ||
175 | .Fn SSL_get_error | ||
176 | with the return value to find out the reason. | ||
177 | .El | ||
178 | .Sh SEE ALSO | ||
179 | .Xr bio 3 , | ||
180 | .Xr ssl 3 , | ||
181 | .Xr SSL_accept 3 , | ||
182 | .Xr SSL_connect 3 , | ||
183 | .Xr SSL_CTX_new 3 , | ||
184 | .Xr SSL_CTX_set_mode 3 , | ||
185 | .Xr SSL_get_error 3 , | ||
186 | .Xr SSL_pending 3 , | ||
187 | .Xr SSL_set_connect_state 3 , | ||
188 | .Xr SSL_set_shutdown 3 , | ||
189 | .Xr SSL_shutdown 3 , | ||
190 | .Xr SSL_write 3 | ||