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1 | =pod |
2 | ||
3 | =head1 NAME | |
4 | ||
5 | PKCS7_sign - create a PKCS#7 signedData structure | |
6 | ||
7 | =head1 SYNOPSIS | |
8 | ||
c264592d UM |
9 | #include <openssl/pkcs7.h> |
10 | ||
11 | PKCS7 *PKCS7_sign(X509 *signcert, EVP_PKEY *pkey, STACK_OF(X509) *certs, BIO *data, int flags); | |
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12 | |
13 | =head1 DESCRIPTION | |
14 | ||
4cfb986f | 15 | PKCS7_sign() creates and returns a PKCS#7 signedData structure. B<signcert> is |
186bb907 | 16 | the certificate to sign with, B<pkey> is the corresponding private key. |
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17 | B<certs> is an optional additional set of certificates to include in the PKCS#7 |
18 | structure (for example any intermediate CAs in the chain). | |
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19 | |
20 | The data to be signed is read from BIO B<data>. | |
21 | ||
22 | B<flags> is an optional set of flags. | |
23 | ||
24 | =head1 NOTES | |
25 | ||
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26 | Any of the following flags (ored together) can be passed in the B<flags> |
27 | parameter. | |
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28 | |
29 | Many S/MIME clients expect the signed content to include valid MIME headers. If | |
30 | the B<PKCS7_TEXT> flag is set MIME headers for type B<text/plain> are prepended | |
31 | to the data. | |
32 | ||
33 | If B<PKCS7_NOCERTS> is set the signer's certificate will not be included in the | |
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34 | PKCS7 structure, the signer's certificate must still be supplied in the |
35 | B<signcert> parameter though. This can reduce the size of the signature if the | |
36 | signers certificate can be obtained by other means: for example a previously | |
37 | signed message. | |
38 | ||
39 | The data being signed is included in the PKCS7 structure, unless | |
40 | B<PKCS7_DETACHED> is set in which case it is omitted. This is used for PKCS7 | |
41 | detached signatures which are used in S/MIME plaintext signed messages for | |
42 | example. | |
43 | ||
44 | Normally the supplied content is translated into MIME canonical format (as | |
45 | required by the S/MIME specifications) if B<PKCS7_BINARY> is set no translation | |
46 | occurs. This option should be used if the supplied data is in binary format | |
47 | otherwise the translation will corrupt it. | |
48 | ||
49 | The signedData structure includes several PKCS#7 autenticatedAttributes | |
50 | including the signing time, the PKCS#7 content type and the supported list of | |
51 | ciphers in an SMIMECapabilities attribute. If B<PKCS7_NOATTR> is set then no | |
52 | authenticatedAttributes will be used. If B<PKCS7_NOSMIMECAP> is set then just | |
53 | the SMIMECapabilities are omitted. | |
d30e4c5b | 54 | |
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55 | If present the SMIMECapabilities attribute indicates support for the following |
56 | algorithms: triple DES, 128 bit RC2, 64 bit RC2, DES and 40 bit RC2. If any of | |
57 | these algorithms is disabled then it will not be included. | |
d30e4c5b | 58 | |
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59 | If the flags B<PKCS7_STREAM> is set then the returned B<PKCS7> structure is |
60 | just initialized ready to perform the signing operation. The signing is however | |
61 | B<not> performed and the data to be signed is not read from the B<data> | |
62 | parameter. Signing is deferred until after the data has been written. In this | |
63 | way data can be signed in a single pass. | |
d30e4c5b | 64 | |
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65 | If the B<PKCS7_PARTIAL> flag is set a partial B<PKCS7> structure is output to |
66 | which additional signers and capabilities can be added before finalization. | |
4e1b50e2 | 67 | |
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68 | |
69 | =head1 NOTES | |
70 | ||
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71 | If the flag B<PKCS7_STREAM> is set the returned B<PKCS7> structure is B<not> |
72 | complete and outputting its contents via a function that does not properly | |
73 | finalize the B<PKCS7> structure will give unpredictable results. | |
4cadedef | 74 | |
9034c56c | 75 | Several functions including SMIME_write_PKCS7(), i2d_PKCS7_bio_stream(), |
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76 | PEM_write_bio_PKCS7_stream() finalize the structure. Alternatively finalization |
77 | can be performed by obtaining the streaming ASN1 B<BIO> directly using | |
78 | BIO_new_PKCS7(). | |
4cadedef | 79 | |
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80 | If a signer is specified it will use the default digest for the signing |
81 | algorithm. This is B<SHA1> for both RSA and DSA keys. | |
4e1b50e2 | 82 | |
fb552ac6 | 83 | In OpenSSL 1.0.0 the B<certs>, B<signcert> and B<pkey> parameters can all be |
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84 | B<NULL> if the B<PKCS7_PARTIAL> flag is set. One or more signers can be added |
85 | using the function B<PKCS7_sign_add_signer()>. B<PKCS7_final()> must also be | |
86 | called to finalize the structure if streaming is not enabled. Alternative | |
87 | signing digests can also be specified using this method. | |
4e1b50e2 | 88 | |
fb552ac6 | 89 | In OpenSSL 1.0.0 if B<signcert> and B<pkey> are NULL then a certificates only |
4cfb986f | 90 | PKCS#7 structure is output. |
4e1b50e2 | 91 | |
fb552ac6 | 92 | In versions of OpenSSL before 1.0.0 the B<signcert> and B<pkey> parameters must |
4cfb986f | 93 | B<NOT> be NULL. |
4e1b50e2 | 94 | |
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95 | =head1 BUGS |
96 | ||
97 | Some advanced attributes such as counter signatures are not supported. | |
4e1b50e2 | 98 | |
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99 | =head1 RETURN VALUES |
100 | ||
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101 | PKCS7_sign() returns either a valid PKCS7 structure or NULL if an error |
102 | occurred. The error can be obtained from ERR_get_error(3). | |
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103 | |
104 | =head1 SEE ALSO | |
105 | ||
9b86974e | 106 | L<ERR_get_error(3)>, L<PKCS7_verify(3)> |
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107 | |
108 | =head1 HISTORY | |
109 | ||
4e1b50e2 | 110 | PKCS7_sign() was added to OpenSSL 0.9.5 |
d30e4c5b | 111 | |
fb552ac6 | 112 | The B<PKCS7_PARTIAL> flag was added in OpenSSL 1.0.0 |
4cfb986f | 113 | |
fb552ac6 | 114 | The B<PKCS7_STREAM> flag was added in OpenSSL 1.0.0 |
4cadedef | 115 | |
d30e4c5b | 116 | =cut |