PKCS7_sign(3)                OpenSSL                PKCS7_sign(3)


     PKCS7_sign - create a PKCS#7 signedData structure


      #include <openssl/pkcs7.h>

      PKCS7 *PKCS7_sign(X509 *signcert, EVP_PKEY *pkey, STACK_OF(X509) *certs, BIO *data, int flags);


     PKCS7_sign() creates and returns a PKCS#7 signedData
     structure. signcert is the certificate to sign with, pkey is
     the corresponsding private key.  certs is an optional
     additional set of certificates to include in the PKCS#7
     structure (for example any intermediate CAs in the chain).

     The data to be signed is read from BIO data.

     flags is an optional set of flags.


     Any of the following flags (ored together) can be passed in
     the flags parameter.

     Many S/MIME clients expect the signed content to include
     valid MIME headers. If the PKCS7_TEXT flag is set MIME
     headers for type text/plain are prepended to the data.

     If PKCS7_NOCERTS is set the signer's certificate will not be
     included in the PKCS7 structure, the signer's certificate
     must still be supplied in the signcert parameter though.
     This can reduce the size of the signature if the signers
     certificate can be obtained by other means: for example a
     previously signed message.

     The data being signed is included in the PKCS7 structure,
     unless PKCS7_DETACHED is set in which case it is omitted.
     This is used for PKCS7 detached signatures which are used in
     S/MIME plaintext signed messages for example.

     Normally the supplied content is translated into MIME
     canonical format (as required by the S/MIME specifications)
     if PKCS7_BINARY is set no translation occurs. This option
     should be used if the supplied data is in binary format
     otherwise the translation will corrupt it.

     The signedData structure includes several PKCS#7
     autenticatedAttributes including the signing time, the
     PKCS#7 content type and the supported list of ciphers in an
     SMIMECapabilities attribute. If PKCS7_NOATTR is set then no
     authenticatedAttributes will be used. If PKCS7_NOSMIMECAP is
     set then just the SMIMECapabilities are omitted.

1.0.2t               Last change: 2019-09-10                    1

PKCS7_sign(3)                OpenSSL                PKCS7_sign(3)

     If present the SMIMECapabilities attribute indicates support
     for the following algorithms: triple DES, 128 bit RC2, 64
     bit RC2, DES and 40 bit RC2. If any of these algorithms is
     disabled then it will not be included.

     If the flags PKCS7_STREAM is set then the returned PKCS7
     structure is just initialized ready to perform the signing
     operation. The signing is however not performed and the data
     to be signed is not read from the data parameter. Signing is
     deferred until after the data has been written. In this way
     data can be signed in a single pass.

     If the PKCS7_PARTIAL flag is set a partial PKCS7 structure
     is output to which additional signers and capabilities can
     be added before finalization.


     If the flag PKCS7_STREAM is set the returned PKCS7 structure
     is not complete and outputting its contents via a function
     that does not properly finalize the PKCS7 structure will
     give unpredictable results.

     Several functions including SMIME_write_PKCS7(),
     i2d_PKCS7_bio_stream(), PEM_write_bio_PKCS7_stream()
     finalize the structure. Alternatively finalization can be
     performed by obtaining the streaming ASN1 BIO directly using

     If a signer is specified it will use the default digest for
     the signing algorithm. This is SHA1 for both RSA and DSA

     In OpenSSL 1.0.0 the certs, signcert and pkey parameters can
     all be NULL if the PKCS7_PARTIAL flag is set. One or more
     signers can be added using the function
     PPKKCCSS77_ssiiggnn_aadddd_ssiiggnneerr(()). PPKKCCSS77_ffiinnaall(()) must also be called
     to finalize the structure if streaming is not enabled.
     Alternative signing digests can also be specified using this

     In OpenSSL 1.0.0 if signcert and pkey are NULL then a
     certificates only PKCS#7 structure is output.

     In versions of OpenSSL before 1.0.0 the signcert and pkey
     parameters must NOT be NULL.


     Some advanced attributes such as counter signatures are not


     PKCS7_sign() returns either a valid PKCS7 structure or NULL

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PKCS7_sign(3)                OpenSSL                PKCS7_sign(3)

     if an error occurred.  The error can be obtained from


     ERR_get_error(3), PKCS7_verify(3)


     PKCS7_sign() was added to OpenSSL 0.9.5

     The PKCS7_PARTIAL flag was added in OpenSSL 1.0.0

     The PKCS7_STREAM flag was added in OpenSSL 1.0.0

1.0.2t               Last change: 2019-09-10                    3

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