path: root/lib/libcrypto/man/ASN1_TYPE_get.3

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.Dd $Mdocdate: August 26 2019 $
.Dt ASN1_TYPE_GET 3
.Os
.Sh NAME
.Nm ASN1_TYPE_new ,
.Nm ASN1_TYPE_free ,
.Nm ASN1_TYPE_get ,
.Nm ASN1_TYPE_set ,
.Nm ASN1_TYPE_set1 ,
.Nm ASN1_TYPE_cmp
.Nd ASN.1 objects of arbitrary type
.Sh SYNOPSIS
.In openssl/asn1.h
.Ft ASN1_TYPE *
.Fn ASN1_TYPE_new void
.Ft void
.Fn ASN1_TYPE_free "ASN1_TYPE *a"
.Ft int
.Fo ASN1_TYPE_get
.Fa "const ASN1_TYPE *a"
.Fc
.Ft void
.Fo ASN1_TYPE_set
.Fa "ASN1_TYPE *a"
.Fa "int type"
.Fa "void *value"
.Fc
.Ft int
.Fo ASN1_TYPE_set1
.Fa "ASN1_TYPE *a"
.Fa "int type"
.Fa "const void *value"
.Fc
.Ft int
.Fo ASN1_TYPE_cmp
.Fa "const ASN1_TYPE *a"
.Fa "const ASN1_TYPE *b"
.Fc
.Sh DESCRIPTION
.Vt ASN1_TYPE
represents the ASN.1 ANY type.
An
.Vt ASN1_TYPE
object can store an ASN.1 value of arbitrary type,
including constructed types such as a SEQUENCE.
It also remembers internally which type it currently holds.
.Pp
.Fn ASN1_TYPE_new
allocates and initializes an empty
.Vt ASN1_TYPE
object of undefined type.
.Pp
.Fn ASN1_TYPE_free
frees
.Fa a
including the value stored in it, if any.
If
.Fa a
is a
.Dv NULL
pointer, no action occurs.
.Pp
.Fn ASN1_TYPE_get
returns the type of
.Fa a ,
represented by one of the
.Dv V_ASN1_*
constants defined in
.In openssl/asn1.h .
.Pp
.Fn ASN1_TYPE_set
frees the value contained in
.Fa a ,
if any, and sets
.Fa a
to
.Fa type
and
.Fa value .
This function uses the pointer
.Fa value
internally so it must
.Sy not
be freed up after the call.
.Pp
.Fn ASN1_TYPE_set1
sets the type of
.Fa a
to
.Fa type
and its value to a copy of
.Fa value .
If copying succeeds, the previous value that was contained in
.Fa a
is freed.
If copying fails,
.Fa a
remains unchanged.
.Pp
The type and meaning of the
.Fa value
argument of
.Fn ASN1_TYPE_set
and
.Fn ASN1_TYPE_set1
is determined by the
.Fa type
argument.
If
.Fa type
is
.Dv V_ASN1_NULL ,
.Fa value
is ignored.
If
.Fa type
is
.Dv V_ASN1_BOOLEAN ,
then the boolean is set to TRUE if
.Fa value
is not
.Dv NULL .
If
.Fa type
is
.Dv V_ASN1_OBJECT ,
then
.Fa value
is an
.Vt ASN1_OBJECT
structure.
Otherwise
.Fa type
is an
.Vt ASN1_STRING
structure.
If
.Fa type
corresponds to a primitive type or a string type, then the contents
of the
.Vt ASN1_STRING
contains the content octets of the type.
If
.Fa type
corresponds to a constructed type or a tagged type
.Pq Dv V_ASN1_SEQUENCE , V_ASN1_SET , No or Dv V_ASN1_OTHER ,
then the
.Vt ASN1_STRING
contains the entire ASN.1 encoding verbatim, including tag and
length octets.
.Pp
.Fn ASN1_TYPE_cmp
checks that
.Fa a
and
.Fa b
have the same type, the same value, and are encoded in the same way.
.Pp
If the types agree and the values have the same meaning but are
encoded differently, they are considered different.
For example, a boolean value is represented
using a single content octet.
Under BER, any non-zero octet represents the TRUE value, but
.Fn ASN1_TYPE_cmp
will only report a match if the content octet is the same.
.Pp
If either or both of the arguments passed to
.Fn ASN1_TYPE_cmp
is
.Dv NULL ,
the result is a mismatch.
Technically, if both arguments are
.Dv NULL ,
the two types could be absent OPTIONAL fields and so should match,
however passing
.Dv NULL
values could also indicate a programming error (for example an
unparseable type which returns
.Dv NULL )
for types which do
.Sy not
match.
So applications should handle the case of two absent values separately.
.Sh RETURN VALUES
.Fn ASN1_TYPE_new
returns the new
.Vt ASN1_TYPE
object or
.Dv NULL
if an error occurs.
.Pp
.Fn ASN1_TYPE_get
returns the type of
.Fa a
or 0 if an error occurs.
The latter can happen if
.Fa a
does not contain a value even though its type is not
.Dv V_ASN1_NULL .
For example, it will always happen for empty objects
newly constructed with
.Fn ASN1_TYPE_new .
.Pp
.Fn ASN1_TYPE_set1
returns 1 if the copying succeeds or 0 if it fails.
.Pp
.Fn ASN1_TYPE_cmp
returns 0 for a match or non-zero for a mismatch.
.Sh SEE ALSO
.Xr ASN1_generate_nconf 3 ,
.Xr ASN1_item_free 3 ,
.Xr ASN1_OBJECT_new 3 ,
.Xr ASN1_put_object 3 ,
.Xr ASN1_STRING_dup 3 ,
.Xr ASN1_STRING_new 3 ,
.Xr crypto 3 ,
.Xr d2i_ASN1_NULL 3 ,
.Xr d2i_ASN1_SEQUENCE_ANY 3 ,
.Xr d2i_ASN1_TYPE 3 ,
.Xr OBJ_dup 3
.Sh HISTORY
.Fn ASN1_TYPE_new
and
.Fn ASN1_TYPE_free
first appeared in SSLeay 0.5.1.
.Fn ASN1_TYPE_get
and
.Fn ASN1_TYPE_set
first appeared in SSLeay 0.8.0.
These functions have been available since
.Ox 2.4 .
.Pp
.Fn ASN1_TYPE_set1
first appeared in OpenSSL 0.9.8h and has been available since
.Ox 4.5 .
.Pp
.Fn ASN1_TYPE_cmp
first appeared in OpenSSL 0.9.8zd, 1.0.0p, and 1.0.1k
and has been available since
.Ox 4.9 .