1.\" Automatically generated by Pod::Man 4.07 (Pod::Simple 3.35)
| 1.\" Automatically generated by Pod::Man 4.09 (Pod::Simple 3.35)
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129.\" ========================================================================
130.\"
131.IX Title "CMS_decrypt 3"
| 2.\"
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20.\" double quote, and \*(R" will give a right double quote. \*(C+ will
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22.\" therefore won't be available. \*(C` and \*(C' expand to `' in nroff,
23.\" nothing in troff, for use with C<>.
24.tr \(*W-
25.ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p'
26.ie n \{\
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50.\" titles (.TH), headers (.SH), subsections (.SS), items (.Ip), and index
51.\" entries marked with X<> in POD. Of course, you'll have to process the
52.\" output yourself in some meaningful fashion.
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129.\" ========================================================================
130.\"
131.IX Title "CMS_decrypt 3"
|
132.TH CMS_decrypt 3 "2018-03-27" "1.0.2o" "OpenSSL"
| 132.TH CMS_decrypt 3 "2018-08-14" "1.0.2p" "OpenSSL"
|
133.\" For nroff, turn off justification. Always turn off hyphenation; it makes
134.\" way too many mistakes in technical documents.
135.if n .ad l
136.nh
137.SH "NAME"
138.Vb 1
139\& CMS_decrypt \- decrypt content from a CMS envelopedData structure
140.Ve
141.SH "SYNOPSIS"
142.IX Header "SYNOPSIS"
143.Vb 1
144\& #include <openssl/cms.h>
145\&
146\& int CMS_decrypt(CMS_ContentInfo *cms, EVP_PKEY *pkey, X509 *cert, BIO *dcont, BIO *out, unsigned int flags);
147.Ve
148.SH "DESCRIPTION"
149.IX Header "DESCRIPTION"
150\&\fICMS_decrypt()\fR extracts and decrypts the content from a \s-1CMS\s0 EnvelopedData
151structure. \fBpkey\fR is the private key of the recipient, \fBcert\fR is the
152recipient's certificate, \fBout\fR is a \s-1BIO\s0 to write the content to and
153\&\fBflags\fR is an optional set of flags.
154.PP
155The \fBdcont\fR parameter is used in the rare case where the encrypted content
156is detached. It will normally be set to \s-1NULL.\s0
157.SH "NOTES"
158.IX Header "NOTES"
159\&\fIOpenSSL_add_all_algorithms()\fR (or equivalent) should be called before using this
160function or errors about unknown algorithms will occur.
161.PP
162Although the recipients certificate is not needed to decrypt the data it is
163needed to locate the appropriate (of possible several) recipients in the \s-1CMS\s0
164structure.
165.PP
166If \fBcert\fR is set to \s-1NULL\s0 all possible recipients are tried. This case however
167is problematic. To thwart the \s-1MMA\s0 attack (Bleichenbacher's attack on
168\&\s-1PKCS\s0 #1 v1.5 \s-1RSA\s0 padding) all recipients are tried whether they succeed or
169not. If no recipient succeeds then a random symmetric key is used to decrypt
170the content: this will typically output garbage and may (but is not guaranteed
171to) ultimately return a padding error only. If \fICMS_decrypt()\fR just returned an
172error when all recipient encrypted keys failed to decrypt an attacker could
173use this in a timing attack. If the special flag \fB\s-1CMS_DEBUG_DECRYPT\s0\fR is set
174then the above behaviour is modified and an error \fBis\fR returned if no
175recipient encrypted key can be decrypted \fBwithout\fR generating a random
176content encryption key. Applications should use this flag with
177\&\fBextreme caution\fR especially in automated gateways as it can leave them
178open to attack.
179.PP
180It is possible to determine the correct recipient key by other means (for
181example looking them up in a database) and setting them in the \s-1CMS\s0 structure
182in advance using the \s-1CMS\s0 utility functions such as \fICMS_set1_pkey()\fR. In this
183case both \fBcert\fR and \fBpkey\fR should be set to \s-1NULL.\s0
184.PP
185To process KEKRecipientInfo types \fICMS_set1_key()\fR or \fICMS_RecipientInfo_set0_key()\fR
186and \fICMS_ReceipientInfo_decrypt()\fR should be called before \fICMS_decrypt()\fR and
187\&\fBcert\fR and \fBpkey\fR set to \s-1NULL.\s0
188.PP
189The following flags can be passed in the \fBflags\fR parameter.
190.PP
191If the \fB\s-1CMS_TEXT\s0\fR flag is set \s-1MIME\s0 headers for type \fBtext/plain\fR are deleted
192from the content. If the content is not of type \fBtext/plain\fR then an error is
193returned.
194.SH "RETURN VALUES"
195.IX Header "RETURN VALUES"
196\&\fICMS_decrypt()\fR returns either 1 for success or 0 for failure.
197The error can be obtained from \fIERR_get_error\fR\|(3)
198.SH "BUGS"
199.IX Header "BUGS"
200The lack of single pass processing and the need to hold all data in memory as
201mentioned in \fICMS_verify()\fR also applies to \fICMS_decrypt()\fR.
202.SH "SEE ALSO"
203.IX Header "SEE ALSO"
204\&\fIERR_get_error\fR\|(3), \fICMS_encrypt\fR\|(3)
205.SH "HISTORY"
206.IX Header "HISTORY"
207\&\fICMS_decrypt()\fR was added to OpenSSL 0.9.8
| 133.\" For nroff, turn off justification. Always turn off hyphenation; it makes
134.\" way too many mistakes in technical documents.
135.if n .ad l
136.nh
137.SH "NAME"
138.Vb 1
139\& CMS_decrypt \- decrypt content from a CMS envelopedData structure
140.Ve
141.SH "SYNOPSIS"
142.IX Header "SYNOPSIS"
143.Vb 1
144\& #include <openssl/cms.h>
145\&
146\& int CMS_decrypt(CMS_ContentInfo *cms, EVP_PKEY *pkey, X509 *cert, BIO *dcont, BIO *out, unsigned int flags);
147.Ve
148.SH "DESCRIPTION"
149.IX Header "DESCRIPTION"
150\&\fICMS_decrypt()\fR extracts and decrypts the content from a \s-1CMS\s0 EnvelopedData
151structure. \fBpkey\fR is the private key of the recipient, \fBcert\fR is the
152recipient's certificate, \fBout\fR is a \s-1BIO\s0 to write the content to and
153\&\fBflags\fR is an optional set of flags.
154.PP
155The \fBdcont\fR parameter is used in the rare case where the encrypted content
156is detached. It will normally be set to \s-1NULL.\s0
157.SH "NOTES"
158.IX Header "NOTES"
159\&\fIOpenSSL_add_all_algorithms()\fR (or equivalent) should be called before using this
160function or errors about unknown algorithms will occur.
161.PP
162Although the recipients certificate is not needed to decrypt the data it is
163needed to locate the appropriate (of possible several) recipients in the \s-1CMS\s0
164structure.
165.PP
166If \fBcert\fR is set to \s-1NULL\s0 all possible recipients are tried. This case however
167is problematic. To thwart the \s-1MMA\s0 attack (Bleichenbacher's attack on
168\&\s-1PKCS\s0 #1 v1.5 \s-1RSA\s0 padding) all recipients are tried whether they succeed or
169not. If no recipient succeeds then a random symmetric key is used to decrypt
170the content: this will typically output garbage and may (but is not guaranteed
171to) ultimately return a padding error only. If \fICMS_decrypt()\fR just returned an
172error when all recipient encrypted keys failed to decrypt an attacker could
173use this in a timing attack. If the special flag \fB\s-1CMS_DEBUG_DECRYPT\s0\fR is set
174then the above behaviour is modified and an error \fBis\fR returned if no
175recipient encrypted key can be decrypted \fBwithout\fR generating a random
176content encryption key. Applications should use this flag with
177\&\fBextreme caution\fR especially in automated gateways as it can leave them
178open to attack.
179.PP
180It is possible to determine the correct recipient key by other means (for
181example looking them up in a database) and setting them in the \s-1CMS\s0 structure
182in advance using the \s-1CMS\s0 utility functions such as \fICMS_set1_pkey()\fR. In this
183case both \fBcert\fR and \fBpkey\fR should be set to \s-1NULL.\s0
184.PP
185To process KEKRecipientInfo types \fICMS_set1_key()\fR or \fICMS_RecipientInfo_set0_key()\fR
186and \fICMS_ReceipientInfo_decrypt()\fR should be called before \fICMS_decrypt()\fR and
187\&\fBcert\fR and \fBpkey\fR set to \s-1NULL.\s0
188.PP
189The following flags can be passed in the \fBflags\fR parameter.
190.PP
191If the \fB\s-1CMS_TEXT\s0\fR flag is set \s-1MIME\s0 headers for type \fBtext/plain\fR are deleted
192from the content. If the content is not of type \fBtext/plain\fR then an error is
193returned.
194.SH "RETURN VALUES"
195.IX Header "RETURN VALUES"
196\&\fICMS_decrypt()\fR returns either 1 for success or 0 for failure.
197The error can be obtained from \fIERR_get_error\fR\|(3)
198.SH "BUGS"
199.IX Header "BUGS"
200The lack of single pass processing and the need to hold all data in memory as
201mentioned in \fICMS_verify()\fR also applies to \fICMS_decrypt()\fR.
202.SH "SEE ALSO"
203.IX Header "SEE ALSO"
204\&\fIERR_get_error\fR\|(3), \fICMS_encrypt\fR\|(3)
205.SH "HISTORY"
206.IX Header "HISTORY"
207\&\fICMS_decrypt()\fR was added to OpenSSL 0.9.8
|