1PKCS7_sign_add_signer(3)            OpenSSL           PKCS7_sign_add_signer(3)
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NAME

6       PKCS7_sign_add_signer - add a signer PKCS7 signed data structure.
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SYNOPSIS

9        #include <openssl/pkcs7.h>
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11        PKCS7_SIGNER_INFO *PKCS7_sign_add_signer(PKCS7 *p7, X509 *signcert, EVP_PKEY *pkey, const EVP_MD *md, int flags);
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DESCRIPTION

14       PKCS7_sign_add_signer() adds a signer with certificate signcert and
15       private key pkey using message digest md to a PKCS7 signed data
16       structure p7.
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18       The PKCS7 structure should be obtained from an initial call to
19       PKCS7_sign() with the flag PKCS7_PARTIAL set or in the case or re-
20       signing a valid PKCS7 signed data structure.
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22       If the md parameter is NULL then the default digest for the public key
23       algorithm will be used.
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25       Unless the PKCS7_REUSE_DIGEST flag is set the returned PKCS7 structure
26       is not complete and must be finalized either by streaming (if
27       applicable) or a call to PKCS7_final().
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NOTES

30       The main purpose of this function is to provide finer control over a
31       PKCS#7 signed data structure where the simpler PKCS7_sign() function
32       defaults are not appropriate. For example if multiple signers or non
33       default digest algorithms are needed.
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35       Any of the following flags (ored together) can be passed in the flags
36       parameter.
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38       If PKCS7_REUSE_DIGEST is set then an attempt is made to copy the
39       content digest value from the PKCS7 struture: to add a signer to an
40       existing structure.  An error occurs if a matching digest value cannot
41       be found to copy. The returned PKCS7 structure will be valid and
42       finalized when this flag is set.
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44       If PKCS7_PARTIAL is set in addition to PKCS7_REUSE_DIGEST then the
45       PKCS7_SIGNER_INO structure will not be finalized so additional
46       attributes can be added. In this case an explicit call to
47       PKCS7_SIGNER_INFO_sign() is needed to finalize it.
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49       If PKCS7_NOCERTS is set the signer's certificate will not be included
50       in the PKCS7 structure, the signer's certificate must still be supplied
51       in the signcert parameter though. This can reduce the size of the
52       signature if the signers certificate can be obtained by other means:
53       for example a previously signed message.
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55       The signedData structure includes several PKCS#7 autenticatedAttributes
56       including the signing time, the PKCS#7 content type and the supported
57       list of ciphers in an SMIMECapabilities attribute. If PKCS7_NOATTR is
58       set then no authenticatedAttributes will be used. If PKCS7_NOSMIMECAP
59       is set then just the SMIMECapabilities are omitted.
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61       If present the SMIMECapabilities attribute indicates support for the
62       following algorithms: triple DES, 128 bit RC2, 64 bit RC2, DES and 40
63       bit RC2. If any of these algorithms is disabled then it will not be
64       included.
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66       PKCS7_sign_add_signers() returns an internal pointer to the
67       PKCS7_SIGNER_INFO structure just added, this can be used to set
68       additional attributes before it is finalized.
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RETURN VALUES

71       PKCS7_sign_add_signers() returns an internal pointer to the
72       PKCS7_SIGNER_INFO structure just added or NULL if an error occurs.
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SEE ALSO

75       ERR_get_error(3), PKCS7_sign(3), PKCS7_final(3),
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HISTORY

78       PPKCS7_sign_add_signer() was added to OpenSSL 1.0.0
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821.0.2o                            2019-09-10          PKCS7_sign_add_signer(3)