ASN1_MBSTRING_COPY(3) | Library Functions Manual | ASN1_MBSTRING_COPY(3)

# NAME

`ASN1_mbstring_copy`, `ASN1_mbstring_ncopy`, `ASN1_STRING_set_by_NID`, `ASN1_STRING_set_default_mask`, `ASN1_STRING_set_default_mask_asc`, `ASN1_STRING_get_default_mask`, `ASN1_tag2bit` — copy a multibyte string into an ASN.1 string object

# SYNOPSIS

library “libcrypto”
`#include <openssl/asn1.h>`

int
`ASN1_mbstring_copy`(ASN1_STRING **out, const unsigned char *in, int inbytes, int inform, unsigned long mask);

int
`ASN1_mbstring_ncopy`(ASN1_STRING **out, const unsigned char *in, int inbytes, int inform, unsigned long mask, long minchars, long maxchars);

ASN1_STRING *
`ASN1_STRING_set_by_NID`(ASN1_STRING **out, const unsigned char *in, int inbytes, int inform, int nid);

void
`ASN1_STRING_set_default_mask`(unsigned long mask);

int
`ASN1_STRING_set_default_mask_asc`(const char *maskname);

unsigned long
`ASN1_STRING_get_default_mask`(void);

unsigned long
`ASN1_tag2bit`(int tag);

# DESCRIPTION

`ASN1_mbstring_copy`() interprets inbytes bytes starting at in as a multibyte string and copies it to *out, optionally changing the encoding. If the inbytes argument is negative, the strlen(3) of in is used instead.

The inform argument specifies the character encoding of in:

inform | encoding
`MBSTRING_ASC` | ISO-Latin-1
`MBSTRING_BMP` | UTF-16
`MBSTRING_UNIV` | UTF-32
`MBSTRING_UTF8` | UTF-8

The bit mask specifies a set of ASN.1 string types that the user is willing to accept:

bit in mask | acceptable output type | default
`B_ASN1_PRINTABLESTRING` | ASN1_PRINTABLESTRING | yes
`B_ASN1_IA5STRING` | ASN1_IA5STRING | no
`B_ASN1_T61STRING` | ASN1_T61STRING | yes
`B_ASN1_BMPSTRING` | ASN1_BMPSTRING | yes
`B_ASN1_UNIVERSALSTRING` | ASN1_UNIVERSALSTRING | no
any other bit | ASN1_UTF8STRING | yes

The first type from the above table that is included in the mask argument and that can represent in is used as the output type. The “default” column indicates whether the type is considered acceptable if the mask argument has the special value 0.

The following bit mask constants each include several of the bits listed above:

mask constant | PRI | IA5 | T61 | BMP | UNI | UTF8
`B_ASN1_DIRECTORYSTRING` | yes | no | yes | yes | yes | yes
`DIRSTRING_TYPE` | yes | no | yes | yes | no | yes
`PKCS9STRING_TYPE` | yes | yes | yes | yes | no | yes

If out is `NULL`, inform, inbytes, and in are validated and the output type is determined and returned, but nothing is copied.

Otherwise, if *out is `NULL`, a new output object of the output type is allocated and a pointer to it is stored in *out.

Otherwise, **out is used as the output object. Any data already stored in it is freed and its type is changed to the output type.

Finally, in is copied to the output object, changing the character encoding if inform does not match the encoding used by the output type.

`ASN1_mbstring_ncopy`() is similar except that the number of characters in in is restricted to the range from minchars to maxchars, inclusive. If maxchars is 0, no upper limit is enforced on the number of characters.

`ASN1_STRING_set_by_NID`() is similar with the following differences:

- If out is `NULL`, a new output object is allocated and returned instead of skipping the copying.
- If nid has a global string table entry that can be retrieved with ASN1_STRING_TABLE_get(3), mask, minchars, and maxchars are taken from that string table entry. For some values of nid, an additional global mask is AND'ed into the mask before using it. The default value of the global mask is `B_ASN1_UTF8STRING`.
- If nid has no global string table entry, `B_ASN1_PRINTABLESTRING` | `B_ASN1_T61STRING` | `B_ASN1_BMPSTRING` | `B_ASN1_UTF8STRING` is used instead of the mask taken from the table, and the global mask is also AND'ed into it.
- Even though success and failure happen in the same situations, the return value is different. ASN1_STRING_type(3) can be used to determine the type of the return value.

`ASN1_STRING_set_default_mask`() sets the global mask used by `ASN1_STRING_set_by_NID`() to the mask argument.

`ASN1_STRING_set_default_mask_asc`() sets the global mask as follows:

maskname | mask
"default" | anything
"nombstr" | anything except `B_ASN1_BMPSTRING` | `B_ASN1_UTF8STRING`
"pkix" | anything except `B_ASN1_T61STRING`
"utf8only" | `B_ASN1_UTF8STRING`

If the maskname argument starts with the substring "MASK:", the rest of it is interpreted as an unsigned long value using strtoul(3).

`ASN1_tag2bit`() translates ASN.1 data types to type bits as follows:

tag | return value
`V_ASN1_BIT_STRING` | `B_ASN1_BIT_STRING`
`V_ASN1_BMPSTRING` | `B_ASN1_BMPSTRING`
`V_ASN1_BOOLEAN` | 0
`V_ASN1_ENUMERATED` | `B_ASN1_UNKNOWN`
`V_ASN1_EOC` | 0
`V_ASN1_EXTERNAL` | `B_ASN1_UNKNOWN`
`V_ASN1_GENERALIZEDTIME` | `B_ASN1_GENERALIZEDTIME`
`V_ASN1_GENERALSTRING` | `B_ASN1_GENERALSTRING`
`V_ASN1_GRAPHICSTRING` | `B_ASN1_GRAPHICSTRING`
`V_ASN1_IA5STRING` | `B_ASN1_IA5STRING`
`V_ASN1_INTEGER` | 0
`V_ASN1_ISO64STRING` | `B_ASN1_ISO64STRING`
`V_ASN1_NULL` | 0
`V_ASN1_NUMERICSTRING` | `B_ASN1_NUMERICSTRING`
`V_ASN1_OBJECT` | 0
`V_ASN1_OBJECT_DESCRIPTOR` | `B_ASN1_UNKNOWN`
`V_ASN1_OCTET_STRING` | `B_ASN1_OCTET_STRING`
`V_ASN1_PRINTABLESTRING` | `B_ASN1_PRINTABLESTRING`
`V_ASN1_REAL` | `B_ASN1_UNKNOWN`
`V_ASN1_SEQUENCE` | `B_ASN1_SEQUENCE`
`V_ASN1_SET` | 0
`V_ASN1_T61STRING` | `B_ASN1_T61STRING`
`V_ASN1_TELETEXSTRING` | `B_ASN1_TELETEXSTRING`
`V_ASN1_UNDEF` | 0
`V_ASN1_UNIVERSALSTRING` | `B_ASN1_UNIVERSALSTRING`
`V_ASN1_UTCTIME` | `B_ASN1_UTCTIME`
`V_ASN1_UTF8STRING` | `B_ASN1_UTF8STRING`
`V_ASN1_VIDEOTEXSTRING` | `B_ASN1_VIDEOTEXSTRING`
`V_ASN1_VISIBLESTRING` | `B_ASN1_VISIBLESTRING`
11, 13, 14, 15, 29 | `B_ASN1_UNKNOWN`
`other` (< 0, > 30) | `0`

In typical usage, the calling code calculates the bitwise AND of the return value and a mask describing data types that the calling code is willing to use. If the result of the AND operation is non-zero, the data type is adequate; otherwise, the calling code may need to raise an error.

# RETURN VALUES

`ASN1_mbstring_copy`() and `ASN1_mbstring_ncopy`() return the `V_ASN1_*` constant representing the output type or -1 if inform is invalid, if inbytes or in is invalid for the inform encoding, if in contains an UTF-16 surrogate, which is unsupported even for input using the UTF-16 encoding, or if memory allocation fails.

`ASN1_mbstring_ncopy`() also returns -1 if in contains fewer than minchars or more than maxchars characters.

`ASN1_STRING_set_by_NID`() returns the new or changed ASN.1 string object or `NULL` on failure.

`ASN1_STRING_set_default_mask_asc`() returns 1 if successful or 0 if "MASK:" is not followed by a number, if the number is followed by a non-numeric character, or if the maskname is invalid.

`ASN1_STRING_get_default_mask`() returns the global mask.

`ASN1_tag2bit`() returns a `B_ASN1_*` constant or 0.

# SEE ALSO

ASN1_PRINTABLE_type(3), ASN1_STRING_new(3), ASN1_STRING_set(3), ASN1_STRING_TABLE_get(3), ASN1_UNIVERSALSTRING_to_string(3)

# HISTORY

`ASN1_mbstring_copy`(), `ASN1_mbstring_ncopy`(), `ASN1_STRING_set_by_NID`(), `ASN1_STRING_set_default_mask`(), `ASN1_STRING_set_default_mask_asc`(), and `ASN1_STRING_get_default_mask`() first appeared in OpenSSL 0.9.5 and have been available since OpenBSD 2.7.

`ASN1_tag2bit`() first appeared in OpenSSL 0.9.7 and has been available since OpenBSD 3.2.

# BUGS

If integer overflow occurs in `ASN1_STRING_set_default_mask_asc`() while parsing a number following "MASK:", the function succeeds, essentially behaving in the same way as for "default".

Passing "default" to `ASN1_STRING_set_default_mask_asc`() does not restore the default mask. Instead, passing "utf8only" does that.

June 8, 2025 | Debian