.\" $OpenBSD: ASN1_STRING_print_ex.3,v 1.18 2021/12/14 19:36:18 schwarze Exp $
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.Dd $Mdocdate: December 14 2021 $
.Dt ASN1_STRING_PRINT_EX 3
.Os
.Sh NAME
.Nm ASN1_STRING_print_ex ,
.Nm ASN1_STRING_print_ex_fp ,
.Nm ASN1_STRING_print ,
.Nm ASN1_tag2str
.\" M_ASN1_OCTET_STRING_print is a deprecated alias, intentionally undocumented
.Nd ASN1_STRING output routines
.Sh SYNOPSIS
.In openssl/asn1.h
.Ft int
.Fo ASN1_STRING_print_ex
.Fa "BIO *out"
.Fa "const ASN1_STRING *str"
.Fa "unsigned long flags"
.Fc
.Ft int
.Fo ASN1_STRING_print_ex_fp
.Fa "FILE *fp"
.Fa "const ASN1_STRING *str"
.Fa "unsigned long flags"
.Fc
.Ft int
.Fo ASN1_STRING_print
.Fa "BIO *out"
.Fa "const ASN1_STRING *str"
.Fc
.Ft const char *
.Fo ASN1_tag2str
.Fa "int tag"
.Fc
.Sh DESCRIPTION
These functions output an
.Vt ASN1_STRING
structure.
.Vt ASN1_STRING
is used to
represent all the ASN.1 string types.
.Pp
.Fn ASN1_STRING_print_ex
outputs
.Fa str
to
.Fa out ,
the format being determined by the options
.Fa flags .
.Fn ASN1_STRING_print_ex_fp
is identical except it outputs to
.Fa fp
instead.
.Pp
.Fn ASN1_STRING_print
prints
.Fa str
to
.Fa out
but using a different format to
.Fn ASN1_STRING_print_ex .
It replaces unprintable characters (other than CR, LF) with
.Sq \&. .
.Pp
.Fn ASN1_tag2str
returns a human-readable name of the specified ASN.1
.Fa tag .
.Pp
.Fn ASN1_STRING_print
is a deprecated function which should be avoided; use
.Fn ASN1_STRING_print_ex
instead.
.Pp
Although there are a large number of options,
.Dv ASN1_STRFLGS_RFC2253
is often suitable, or on UTF-8 terminals
.Dv ASN1_STRFLGS_RFC2253
and
.Pf ~ Dv ASN1_STRFLGS_ESC_MSB .
.Pp
The complete set of supported options for
.Fa flags
is listed below.
.Pp
Various characters can be escaped.
If
.Dv ASN1_STRFLGS_ESC_2253
is set, the characters determined by RFC 2253 are escaped.
If
.Dv ASN1_STRFLGS_ESC_CTRL
is set, control characters are escaped.
If
.Dv ASN1_STRFLGS_ESC_MSB
is set, characters with the MSB set are escaped: this option should
.Em not
be used if the terminal correctly interprets UTF-8 sequences.
.Pp
Escaping takes several forms.
If the character being escaped is a 16-bit character then the form "\eUXXXX"
is used using exactly four characters for the hex representation.
If it is 32 bits then "\eWXXXXXXXX" is used using eight characters
of its hex representation.
These forms will only be used if UTF-8 conversion is not set (see below).
.Pp
Printable characters are normally escaped using the backslash
.Pq Sq \e
character.
If
.Dv ASN1_STRFLGS_ESC_QUOTE
is set, then the whole string is instead surrounded by double quote
characters: this is arguably more readable than the backslash notation.
Other characters use the "\eXX" using exactly two characters of the hex
representation.
.Pp
If
.Dv ASN1_STRFLGS_UTF8_CONVERT
is set, then characters are converted to UTF-8 format first.
If the terminal supports the display of UTF-8 sequences then this
option will correctly display multi-byte characters.
.Pp
If
.Dv ASN1_STRFLGS_IGNORE_TYPE
is set, then the string type is not interpreted at all:
everything is assumed to be one byte per character.
This is primarily for debugging purposes and can result
in confusing output in multi-character strings.
.Pp
If
.Dv ASN1_STRFLGS_SHOW_TYPE
is set, then the string type itself is printed before its value
(for example "BMPSTRING"), using
.Fn ASN1_tag2str .
.Pp
Instead of being interpreted the contents of a string can be "dumped":
this just outputs the value of the string using the form #XXXX
using hex format for each octet.
.Pp
If
.Dv ASN1_STRFLGS_DUMP_ALL
is set, then any type is dumped.
.Pp
Normally non-character string types (such as OCTET STRING)
are assumed to be one byte per character; if
.Dv ASN1_STRFLGS_DUMP_UNKNOWN
is set, then they will be dumped instead.
.Pp
When a type is dumped normally just the content octets are printed; if
.Dv ASN1_STRFLGS_DUMP_DER
is set, then the complete encoding is dumped
instead (including tag and length octets).
.Pp
.Dv ASN1_STRFLGS_RFC2253
includes all the flags required by RFC 2253.
It is equivalent to
.Dv ASN1_STRFLGS_ESC_2253 |
.Dv ASN1_STRFLGS_ESC_CTRL |
.Dv ASN1_STRFLGS_ESC_MSB |
.Dv ASN1_STRFLGS_UTF8_CONVERT |
.Dv ASN1_STRFLGS_DUMP_UNKNOWN |
.Dv ASN1_STRFLGS_DUMP_DER .
.Sh RETURN VALUES
.Fn ASN1_STRING_print_ex
and
.Fn ASN1_STRING_print_ex_fp
return the number of characters written or \-1 if an error occurred.
.Pp
.Fn ASN1_STRING_print
returns 1 on success or 0 on error.
.Pp
.Fn ASN1_tag2str
returns a static string.
.Sh SEE ALSO
.Xr ASN1_parse_dump 3 ,
.Xr ASN1_STRING_new 3 ,
.Xr X509_NAME_print_ex 3 ,
.Xr X509_signature_dump 3
.Sh HISTORY
.Fn ASN1_STRING_print
first appeared in SSLeay 0.6.5 and has been available since
.Ox 2.4 .
.Pp
.Fn ASN1_tag2str
first appeared in OpenSSL 0.9.5 and has been available since
.Ox 2.7 .
.Pp
.Fn ASN1_STRING_print_ex
and
.Fn ASN1_STRING_print_ex_fp
first appeared in OpenSSL 0.9.6 and have been available since
.Ox 2.9 .