1.\"	$OpenBSD: SMIME_read_PKCS7.3,v 1.7 2019/06/10 14:58:48 schwarze Exp $
2.\"	OpenSSL 99d63d46 Oct 26 13:56:48 2016 -0400
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51.Dd $Mdocdate: June 10 2019 $
52.Dt SMIME_READ_PKCS7 3
53.Os
54.Sh NAME
55.Nm SMIME_read_PKCS7
56.Nd parse S/MIME message
57.Sh SYNOPSIS
58.In openssl/pkcs7.h
59.Ft PKCS7 *
60.Fo SMIME_read_PKCS7
61.Fa "BIO *in"
62.Fa "BIO **bcont"
63.Fc
64.Sh DESCRIPTION
65.Fn SMIME_read_PKCS7
66parses a message in S/MIME format.
67.Pp
68.Fa in
69is a
70.Vt BIO
71to read the message from.
72.Pp
73If cleartext signing is used, then the content is saved in a memory
74.Vt BIO
75which is written to
76.Pf * Fa bcont ,
77otherwise
78.Pf * Fa bcont
79is set to
80.Dv NULL .
81.Pp
82The parsed PKCS#7 structure is returned, or
83.Dv NULL
84if an error occurred.
85.Pp
86If
87.Pf * Fa bcont
88is not
89.Dv NULL ,
90then the message is clear text signed.
91.Pf * Fa bcont
92can then be passed to
93.Xr PKCS7_verify 3
94with the
95.Dv PKCS7_DETACHED
96flag set.
97.Pp
98Otherwise the type of the returned structure can be determined using the
99.Fn PKCS7_type_is_*
100macros defined in
101.In openssl/pkcs7.h .
102.Pp
103To support future functionality, if
104.Fa bcont
105is not
106.Dv NULL ,
107.Pf * Fa bcont
108should be initialized to
109.Dv NULL .
110For example:
111.Bd -literal -offset indent
112BIO *cont = NULL;
113PKCS7 *p7;
114
115p7 = SMIME_read_PKCS7(in, &cont);
116.Ed
117.Sh RETURN VALUES
118.Fn SMIME_read_PKCS7
119returns a valid
120.Vt PKCS7
121structure or
122.Dv NULL
123if an error occurred.
124The error can be obtained from
125.Xr ERR_get_error 3 .
126.Sh SEE ALSO
127.Xr PKCS7_new 3 ,
128.Xr SMIME_write_PKCS7 3
129.Sh HISTORY
130.Fn SMIME_read_PKCS7
131first appeared in OpenSSL 0.9.5 and has been available since
132.Ox 2.7 .
133.Sh BUGS
134The MIME parser used by
135.Fn SMIME_read_PKCS7
136is somewhat primitive.
137While it will handle most S/MIME messages, more complex compound
138formats may not work.
139.Pp
140The parser assumes that the
141.Vt PKCS7
142structure is always base64 encoded, and it will not handle the case
143where it is in binary format or uses quoted printable format.
144.Pp
145The use of a memory
146.Vt BIO
147to hold the signed content limits the size of the message which can
148be processed due to memory restraints: a streaming single pass
149option should be available.
150