EVP_MD_CTX_CTRL(3)         Library Functions Manual         EVP_MD_CTX_CTRL(3)

NAME
     EVP_MD_CTX_ctrl, EVP_MD_CTX_set_flags, EVP_MD_CTX_clear_flags,
     EVP_MD_CTX_test_flags, EVP_MD_CTX_pkey_ctx, EVP_MD_CTX_set_pkey_ctx,
     EVP_MD_CTX_md_data - configure EVP message digest contexts

SYNOPSIS
     #include <openssl/evp.h>

     int
     EVP_MD_CTX_ctrl(EVP_MD_CTX *ctx, int command, int p1, void* p2);

     void
     EVP_MD_CTX_set_flags(EVP_MD_CTX *ctx, int flags);

     void
     EVP_MD_CTX_clear_flags(EVP_MD_CTX *ctx, int flags);

     int
     EVP_MD_CTX_test_flags(const EVP_MD_CTX *ctx, int flags);

     EVP_PKEY_CTX *
     EVP_MD_CTX_pkey_ctx(const EVP_MD_CTX *ctx);

     void
     EVP_MD_CTX_set_pkey_ctx(EVP_MD_CTX *ctx, EVP_PKEY_CTX *pctx);

     void *
     EVP_MD_CTX_md_data(const EVP_MD_CTX *ctx);

DESCRIPTION
     EVP_MD_CTX_ctrl() performs the digest-specific control command with the
     command-specific arguments p1 and p2 on ctx, which needs to already be
     set up with EVP_DigestInit_ex(3) before calling this function.  Other
     restrictions may apply depending on the control command and digest
     implementation.

     If the command is EVP_MD_CTRL_MICALG, p1 is ignored and p2 is an output
     argument of the type char **p2.  A string specifying the digest Message
     Integrity Check algorithm is allocated and a pointer to this string is
     returned in *p2.  It is the responsibility of the caller to free(3) *p2
     when it is no longer needed.  This command is used by SMIME_write_ASN1(3)
     when creating S/MIME multipart/signed messages as specified in RFC 3851.

     EVP_MD_CTX_set_flags() sets and EVP_MD_CTX_clear_flags() clears all the
     flag bits in ctx that are set in the flags argument.
     EVP_MD_CTX_test_flags() tests which of the flag bits that are set in the
     flags argument are also set in ctx.  Possible flag bits are:

       EVP_MD_CTX_FLAG_NO_INIT
               Instruct EVP_DigestInit_ex(3) and functions calling it not to
               initialise the internal data that is specific to the digest
               method and its implementation.

       EVP_MD_CTX_FLAG_ONESHOT
               Instruct the digest to optimize for one update only, if
               possible.  For digest algorithms built into the library, this
               flag usually has no effect.

     EVP_MD_CTX_pkey_ctx() returns the EVP_PKEY_CTX assigned to ctx.  The
     returned pointer should not be freed by the caller.

     EVP_MD_CTX_set_pkey_ctx() assigns pctx to ctx.  This is normally used to
     provide a customized EVP_PKEY_CTX to EVP_DigestSignInit(3) or
     EVP_DigestVerifyInit(3).  The caller retains ownership of the pctx passed
     to this function and is responsible for freeing it when it is no longer
     needed.

     If the ctx already contains a EVP_PKEY_CTX when this function is called,
     that old EVP_PKEY_CTX is freed if it was created internally, but if it
     was also installed with EVP_MD_CTX_set_pkey_ctx(), the pointer to the old
     EVP_PKEY_CTX is merely replaced by the new pointer and ownership of the
     old EVP_PKEY_CTX remains with the previous caller.

     Passing a NULL pointer for the pctx argument is also allowed.  In that
     case, any EVP_PKEY_CTX already assigned to ctx is dissociated from it as
     described above, but no new EVP_PKEY_CTX is assigned.

     EVP_MD_CTX_md_data() returns the digest method private data of ctx.  The
     space is allocated with a size determined at compile time.  The size is
     not exposed by an API.

RETURN VALUES
     EVP_MD_CTX_ctrl() returns 1 for success or 0 for failure.

     EVP_MD_CTX_test_flags() returns the bitwise OR of the flags argument and
     the flags set in ctx.

     EVP_MD_CTX_pkey_ctx() and EVP_MD_CTX_md_data() return pointers to storage
     owned by ctx.

SEE ALSO
     evp(3), EVP_DigestInit(3), EVP_MD_nid(3)

HISTORY
     EVP_MD_CTX_set_flags(), EVP_MD_CTX_clear_flags(), and
     EVP_MD_CTX_test_flags(), first appeared in OpenSSL 0.9.7 and have been
     available since OpenBSD 3.2.

     EVP_MD_CTX_ctrl() first appeared in OpenSSL 1.1.0 and has been available
     since OpenBSD 5.7.

     EVP_MD_CTX_pkey_ctx() and EVP_MD_CTX_md_data() first appeared in OpenSSL
     1.1.0 and EVP_MD_CTX_set_pkey_ctx() in OpenSSL 1.1.1.  These functions
     have been available since OpenBSD 7.1.

Linux 6.8.2-arch2-1              March 5, 2024             Linux 6.8.2-arch2-1