ASN1_TYPE_GET(3)

okay so bestie, this is ASN1_TYPE_GET(3) from the Library Functions Manual, and we're about to make ASN.1's "anything goes" type make sense. No cap, it's giving chaotic but iconic 💅✨

🎀 NAME 🎀

ASN1_TYPE_new, ASN1_TYPE_free, ASN1_TYPE_get, ASN1_TYPE_set, ASN1_TYPE_set1, ASN1_TYPE_set_octetstring, ASN1_TYPE_get_octetstring, ASN1_TYPE_set_int_octetstring, ASN1_TYPE_get_int_octetstring, ASN1_TYPE_cmp — ASN.1 objects of arbitrary type

✨ SYNOPSIS ✨

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

ASN1_TYPE *
ASN1_TYPE_new(void);

void
ASN1_TYPE_free(ASN1_TYPE *a);

int
ASN1_TYPE_get(const ASN1_TYPE *a);

void
ASN1_TYPE_set(ASN1_TYPE *a, int type, void *value);

int
ASN1_TYPE_set1(ASN1_TYPE *a, int type, const void *value);

int
ASN1_TYPE_set_octetstring(ASN1_TYPE *a, const unsigned char *data,
    int len);

int
ASN1_TYPE_get_octetstring(const ASN1_TYPE *a, unsigned char *buffer,
    int buflen);

int
ASN1_TYPE_set_int_octetstring(ASN1_TYPE *a, long num,
    const unsigned char *data, int len);

int
ASN1_TYPE_get_int_octetstring(const ASN1_TYPE *a, ,,
    long *num,unsigned char *buffer, ,, int buflen);

int
ASN1_TYPE_cmp(const ASN1_TYPE *a, const ASN1_TYPE *b);

💖 DESCRIPTION 💖

The ASN1_TYPE data type and the V_ASN1_ANY type identifier constant represent the ASN.1 ANY type. An 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. iykyk 🦋

• ASN1_TYPE_new() — allocates and initializes an empty ASN1_TYPE object of type V_ASN1_UNDEF.
• ASN1_TYPE_free() — frees a, including the value stored in it, if any. If a is a NULL pointer, no action occurs.
• ASN1_TYPE_get() — returns the type currently held by a, represented by one of the V_ASN1_* constants defined in <openssl/asn1.h>.
• ASN1_TYPE_set() — frees the value contained in a, if any, and sets the value and type now held in a. This function uses the pointer value internally, so it must not be freed up after the call.
• ASN1_TYPE_set1() — sets the type held by a to type and its value to a copy of value. If copying succeeds, the previous value that was contained in a is freed. If copying fails, a remains unchanged.

The type and meaning of the value argument of ASN1_TYPE_set() and ASN1_TYPE_set1() are determined by the type argument. If type is V_ASN1_NULL, value is ignored. If type is V_ASN1_BOOLEAN, then the boolean is set to TRUE if value is not NULL. If type is V_ASN1_OBJECT, then value is an ASN1_OBJECT structure. Otherwise type is an ASN1_STRING structure. If type corresponds to a primitive type or a string type, then the contents of the ASN1_STRING contains the content octets of the type. If type corresponds to a constructed type or a tagged type (V_ASN1_SEQUENCE, V_ASN1_SET, or V_ASN1_OTHER), then the ASN1_STRING contains the entire ASN.1 encoding verbatim, including tag and length octets.

• ASN1_TYPE_set_octetstring() — allocates a new ASN1_OCTET_STRING object, copies len bytes of data into it using ASN1_STRING_set(3), and replaces the value of a with it by calling ASN1_TYPE_set() with a type of V_ASN1_OCTET_STRING.
• ASN1_TYPE_get_octetstring() — copies the contents of the ASN1_OCTET_STRING object contained in a, but not more than buflen bytes, into the buffer provided by the caller.
• ASN1_TYPE_set_int_octetstring() — frees the value contained in a, if any, sets its type to V_ASN1_SEQUENCE, and sets its value to a two-element ASN.1 sequence consisting of an ASN.1 INTEGER object with the value num and an ASN.1 OCTET STRING object containing a copy of the len bytes pointed to by data.
• ASN1_TYPE_get_int_octetstring() — copies the integer value from the first element of the ASN.1 sequence a to *num unless num is a NULL pointer and copies the octet string value from the second element, but not more than buflen bytes, into the buffer provided by the caller unless buffer is a NULL pointer.
• ASN1_TYPE_cmp() — checks that a and b hold the same type, the same value, and are encoded in the same way.

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 ASN1_TYPE_cmp() will only report a match if the content octet is the same.

If either or both of the arguments passed to ASN1_TYPE_cmp() is NULL, the result is a mismatch. Technically, if both arguments are NULL, the two types could be absent OPTIONAL fields and so should match, however passing NULL values could also indicate a programming error (for example an unparsable type which returns NULL) for types which do not match. So applications should handle the case of two absent values separately. 🙈

🔥 RETURN VALUES 🔥

• ASN1_TYPE_new() — returns the new ASN1_TYPE object or NULL if an error occurs.
• ASN1_TYPE_get() — returns the type currently held by a or 0 if an error occurs. The latter can happen if a does not contain a value even though its type is not V_ASN1_NULL. For example, it will always happen for empty objects newly constructed with ASN1_TYPE_new().
• ASN1_TYPE_set1(), ASN1_TYPE_set_octetstring(), and ASN1_TYPE_set_int_octetstring() — return 1 on success or 0 on failure.
• ASN1_TYPE_get_octetstring() — returns the number of data bytes contained in the ASN1_OCTET_STRING object contained in a or -1 if a is not of the type V_ASN1_OCTET_STRING or does not contain any object. If the return value is greater than the buflen argument, the content was truncated when copied to the buffer.
• ASN1_TYPE_get_int_octetstring() — returns the number of data bytes contained in the ASN1_OCTET_STRING object that is the second element of the ASN.1 sequence a or -1 if a is not of the type V_ASN1_SEQUENCE or if decoding fails. If the return value is greater than the buflen argument, the content was truncated when copied to the buffer.
• ASN1_TYPE_cmp() — returns 0 for a match or non-zero for a mismatch.

🌈 SEE ALSO 🌈

ASN1_generate_nconf(3), ASN1_get_object(3), ASN1_item_free(3), ASN1_OBJECT_new(3), ASN1_parse_dump(3), ASN1_put_object(3), ASN1_STRING_dup(3), ASN1_STRING_new(3), crypto(3), d2i_ASN1_NULL(3), d2i_ASN1_SEQUENCE_ANY(3), d2i_ASN1_TYPE(3), OBJ_dup(3)

👑 HISTORY 👑

• ASN1_TYPE_new() and ASN1_TYPE_free() first appeared in SSLeay 0.5.1, ASN1_TYPE_get() and ASN1_TYPE_set() in SSLeay 0.8.0, and ASN1_TYPE_set_octetstring(), ASN1_TYPE_get_octetstring(), ASN1_TYPE_set_int_octetstring(), and ASN1_TYPE_get_int_octetstring() in SSLeay 0.9.0. These functions have been available since OpenBSD 2.4.
• ASN1_TYPE_set1() first appeared in OpenSSL 0.9.8h and has been available since OpenBSD 4.5.
• ASN1_TYPE_cmp() first appeared in OpenSSL 0.9.8zd, 1.0.0p, and 1.0.1k and has been available since OpenBSD 4.9.

okay that's the whole iconic lore 💖 this page is from Debian, dated June 8, 2025, and it's ASN1_TYPE_GET(3) — periodt. 🎀✨