OSSL_PARAM_INT(3ossl)

📦 version 3.5.0, in opensuse-leap 16.0

Hey bestie, welcome to OSSL_PARAM_INT(3ossl) — the OpenSSL manual page for the whole OSSL_PARAM helper crew 🌸. It’s giving “tiny toolkit, massive main character energy,” and every single name below is part of the page. No cap 💅

🎀 NAME 🎀

Okay so these are all the icons in this manpage, grouped so your brain doesn’t have to do cardio 🫶

Typed helper macros: OSSL_PARAM_double, OSSL_PARAM_int, OSSL_PARAM_int32, OSSL_PARAM_int64, OSSL_PARAM_long, OSSL_PARAM_size_t, OSSL_PARAM_time_t, OSSL_PARAM_uint, OSSL_PARAM_uint32, OSSL_PARAM_uint64, OSSL_PARAM_ulong, OSSL_PARAM_BN, OSSL_PARAM_utf8_string, OSSL_PARAM_octet_string, OSSL_PARAM_utf8_ptr, OSSL_PARAM_octet_ptr, OSSL_PARAM_END, OSSL_PARAM_DEFN
Constructors: OSSL_PARAM_construct_double, OSSL_PARAM_construct_int, OSSL_PARAM_construct_int32, OSSL_PARAM_construct_int64, OSSL_PARAM_construct_long, OSSL_PARAM_construct_size_t, OSSL_PARAM_construct_time_t, OSSL_PARAM_construct_uint, OSSL_PARAM_construct_uint32, OSSL_PARAM_construct_uint64, OSSL_PARAM_construct_ulong, OSSL_PARAM_construct_BN, OSSL_PARAM_construct_utf8_string, OSSL_PARAM_construct_utf8_ptr, OSSL_PARAM_construct_octet_string, OSSL_PARAM_construct_octet_ptr, OSSL_PARAM_construct_end
Locating: OSSL_PARAM_locate, OSSL_PARAM_locate_const
Getters: OSSL_PARAM_get_double, OSSL_PARAM_get_int, OSSL_PARAM_get_int32, OSSL_PARAM_get_int64, OSSL_PARAM_get_long, OSSL_PARAM_get_size_t, OSSL_PARAM_get_time_t, OSSL_PARAM_get_uint, OSSL_PARAM_get_uint32, OSSL_PARAM_get_uint64, OSSL_PARAM_get_ulong, OSSL_PARAM_get_BN, OSSL_PARAM_get_utf8_string, OSSL_PARAM_get_octet_string, OSSL_PARAM_get_utf8_ptr, OSSL_PARAM_get_octet_ptr, OSSL_PARAM_get_utf8_string_ptr, OSSL_PARAM_get_octet_string_ptr
Setters: OSSL_PARAM_set_double, OSSL_PARAM_set_int, OSSL_PARAM_set_int32, OSSL_PARAM_set_int64, OSSL_PARAM_set_long, OSSL_PARAM_set_size_t, OSSL_PARAM_set_time_t, OSSL_PARAM_set_uint, OSSL_PARAM_set_uint32, OSSL_PARAM_set_uint64, OSSL_PARAM_set_ulong, OSSL_PARAM_set_BN, OSSL_PARAM_set_utf8_string, OSSL_PARAM_set_octet_string, OSSL_PARAM_set_utf8_ptr, OSSL_PARAM_set_octet_ptr
Status + reset helpers: OSSL_PARAM_UNMODIFIED, OSSL_PARAM_modified, OSSL_PARAM_set_all_unmodified

And collectively? They’re the OSSL_PARAM helpers 💖✨

✨ SYNOPSIS ✨

Here’s the exact synopsis vibe, bestie — copy it character-for-character and let it slay 🦋

        #include <openssl/params.h>

        /*
         * TYPE in function names is one of:
         * double, int, int32, int64, long, size_t, time_t, uint, uint32, uint64, ulong
         * Corresponding TYPE in function arguments is one of:
         * double, int, int32_t, int64_t, long, size_t, time_t, unsigned int, uint32_t,
         * uint64_t, unsigned long
         */

        #define OSSL_PARAM_TYPE(key, address)
        #define OSSL_PARAM_BN(key, address, size)
        #define OSSL_PARAM_utf8_string(key, address, size)
        #define OSSL_PARAM_octet_string(key, address, size)
        #define OSSL_PARAM_utf8_ptr(key, address, size)
        #define OSSL_PARAM_octet_ptr(key, address, size)
        #define OSSL_PARAM_END

        #define OSSL_PARAM_UNMODIFIED

        #define OSSL_PARAM_DEFN(key, type, addr, sz)    \
           { (key), (type), (addr), (sz), OSSL_PARAM_UNMODIFIED }

        OSSL_PARAM OSSL_PARAM_construct_TYPE(const char *key, TYPE *buf);
        OSSL_PARAM OSSL_PARAM_construct_BN(const char *key, unsigned char *buf,
                                           size_t bsize);
        OSSL_PARAM OSSL_PARAM_construct_utf8_string(const char *key, char *buf,
                                                    size_t bsize);
        OSSL_PARAM OSSL_PARAM_construct_octet_string(const char *key, void *buf,
                                                     size_t bsize);
        OSSL_PARAM OSSL_PARAM_construct_utf8_ptr(const char *key, char **buf,
                                                 size_t bsize);
        OSSL_PARAM OSSL_PARAM_construct_octet_ptr(const char *key, void **buf,
                                                  size_t bsize);
        OSSL_PARAM OSSL_PARAM_construct_end(void);

        OSSL_PARAM *OSSL_PARAM_locate(OSSL_PARAM *array, const char *key);
        const OSSL_PARAM *OSSL_PARAM_locate_const(const OSSL_PARAM *array,
                                                  const char *key);

        int OSSL_PARAM_get_TYPE(const OSSL_PARAM *p, TYPE *val);
        int OSSL_PARAM_set_TYPE(OSSL_PARAM *p, TYPE val);

        int OSSL_PARAM_get_BN(const OSSL_PARAM *p, BIGNUM **val);
        int OSSL_PARAM_set_BN(OSSL_PARAM *p, const BIGNUM *val);

        int OSSL_PARAM_get_utf8_string(const OSSL_PARAM *p, char **val,
                                       size_t max_len);
        int OSSL_PARAM_set_utf8_string(OSSL_PARAM *p, const char *val);

        int OSSL_PARAM_get_octet_string(const OSSL_PARAM *p, void **val,
                                        size_t max_len, size_t *used_len);
        int OSSL_PARAM_set_octet_string(OSSL_PARAM *p, const void *val, size_t len);

        int OSSL_PARAM_get_utf8_ptr(const OSSL_PARAM *p, const char **val);
        int OSSL_PARAM_set_utf8_ptr(OSSL_PARAM *p, const char *val);

        int OSSL_PARAM_get_octet_ptr(const OSSL_PARAM *p, const void **val,
                                     size_t *used_len);
        int OSSL_PARAM_set_octet_ptr(OSSL_PARAM *p, const void *val,
                                     size_t used_len);

        int OSSL_PARAM_get_utf8_string_ptr(const OSSL_PARAM *p, const char **val);
        int OSSL_PARAM_get_octet_string_ptr(const OSSL_PARAM *p, const void **val,
                                            size_t *used_len);

        int OSSL_PARAM_modified(const OSSL_PARAM *param);
        void OSSL_PARAM_set_all_unmodified(OSSL_PARAM *params);

💖 DESCRIPTION 💖

Okay bestie, gather round, because this is the little utility squad that makes OSSL_PARAM(3) arrays actually bareable — it simplifies them and adds type safety, which is the whole vibe. Here's the cast of TYPE names that are supported:

double
int
int32 (int32_t)
int64 (int64_t)
long int (long)
time_t
size_t
uint32 (uint32_t)
uint64 (uint64_t)
unsigned int (uint)
unsigned long int (ulong)

✨ The macros ✨

OSSL_PARAM_TYPE() — a whole series of macros designed to assist initialising an array of OSSL_PARAM(3) structures. Each one defines a parameter of the specified TYPE with the provided key and parameter variable address. Iconic, no notes.
OSSL_PARAM_utf8_string(), OSSL_PARAM_octet_string(), OSSL_PARAM_utf8_ptr(), OSSL_PARAM_octet_ptr(), OSSL_PARAM_BN() — macros that provide support for defining UTF8 strings, OCTET strings and big numbers. A parameter with name key is defined. The storage for this parameter is at address and is of size bytes.
OSSL_PARAM_END — provides an end of parameter list marker. This should terminate all OSSL_PARAM(3) arrays. Like, all of them, fr fr. No list is complete without it 💅
OSSL_PARAM_DEFN() — gives you the ability to construct a single OSSL_PARAM(3) (typically used in the construction of OSSL_PARAM arrays). The key, type, addr and sz arguments correspond to the key, data_type, data and data_size fields of the OSSL_PARAM(3) structure as described on the OSSL_PARAM(3) page.

🦋 The constructors 🦋

OSSL_PARAM_construct_TYPE() — a series of functions that create OSSL_PARAM(3) records dynamically. A parameter with name key is created. The parameter will use storage pointed to by buf and return size of ret.
OSSL_PARAM_construct_BN() — constructs a large integer OSSL_PARAM(3) structure. A parameter with name key, storage buf, size bsize and return size rsize is created.
OSSL_PARAM_construct_utf8_string() — constructs a UTF8 string OSSL_PARAM(3) structure. A parameter with name key, storage buf and size bsize is created. If bsize is zero, the string length is determined using strlen(3). Generally pass zero for bsize instead of calling strlen(3) yourself — let the function do her thing 💅
OSSL_PARAM_construct_octet_string() — constructs an OCTET string OSSL_PARAM(3) structure. A parameter with name key, storage buf and size bsize is created.
OSSL_PARAM_construct_utf8_ptr() — constructs a UTF8 string pointer OSSL_PARAM(3) structure. A parameter with name key, storage pointer *buf and size bsize is created.
OSSL_PARAM_construct_octet_ptr() — constructs an OCTET string pointer OSSL_PARAM(3) structure. A parameter with name key, storage pointer *buf and size bsize is created.
OSSL_PARAM_construct_end() — constructs the terminating OSSL_PARAM(3) structure. The closer. The last one to leave the party 🎀

🔍 Locating stuff 🔍

OSSL_PARAM_locate() — searches an array of parameters for the one matching the key name.
OSSL_PARAM_locate_const() — behaves exactly like OSSL_PARAM_locate() except for the presence of const for the array argument and its return value. Same energy, just const-flavoured.

🌸 Getters & setters for the native types 🌸

OSSL_PARAM_get_TYPE() — retrieves a value of type TYPE from the parameter p. The value is copied to the address val. Type coercion takes place as discussed in the NOTES section.
OSSL_PARAM_set_TYPE() — stores a value val of type TYPE into the parameter p. If the parameter's data field is NULL, then only its return_size field will be assigned the size the parameter's data buffer should have. Type coercion takes place as discussed in the NOTES section.

🧚 Big numbers 🧚

OSSL_PARAM_get_BN() — retrieves a BIGNUM from the parameter pointed to by p. The BIGNUM referenced by val is updated and is allocated if *val is NULL.
OSSL_PARAM_set_BN() — stores the BIGNUM val into the parameter p. If the parameter's data field is NULL, then only its return_size field will be assigned the size the parameter's data buffer should have.

🍓 Strings, but make it copy 🍓

OSSL_PARAM_get_utf8_string() — retrieves a UTF8 string from the parameter pointed to by p. The string is stored into *val with a size limit of max_len, which must be large enough to accommodate a terminating NUL byte, otherwise this function will fail. If *val is NULL, memory is allocated for the string (including the terminating NUL byte) and max_len is ignored. If memory is allocated by this function, it must be freed by the caller. Yes, that means you, bestie — don't leave her hanging 😭
OSSL_PARAM_set_utf8_string() — sets a UTF8 string from the parameter pointed to by p to the value referenced by val. If the parameter's data field isn't NULL, its data_size must indicate that the buffer is large enough to accommodate the string that val points at, not including the terminating NUL byte, or this function will fail. A terminating NUL byte is added only if the parameter's data_size indicates the buffer is longer than the string length, otherwise the string will not be NUL terminated. If the parameter's data field is NULL, then only its return_size field will be assigned the minimum size the parameter's data buffer should have to accommodate the string, not including a terminating NUL byte. That NUL-conditional is doing a LOT of work here, so read it twice 👀
OSSL_PARAM_get_octet_string() — retrieves an OCTET string from the parameter pointed to by p. The OCTETs are either stored into *val with a length limit of max_len or, in the case when *val is NULL, memory is allocated and max_len is ignored. *used_len is populated with the number of OCTETs stored. If val is NULL then the OCTETs are not stored, but *used_len is still populated. If memory is allocated by this function, it must be freed by the caller. Same deal as above, periodt.
OSSL_PARAM_set_octet_string() — sets an OCTET string from the parameter pointed to by p to the value referenced by val. If the parameter's data field is NULL, then only its return_size field will be assigned the size the parameter's data buffer should have.

💜 Pointer flavours 💜

OSSL_PARAM_get_utf8_ptr() — retrieves the UTF8 string pointer from the parameter referenced by p and stores it in *val.
OSSL_PARAM_set_utf8_ptr() — sets the UTF8 string pointer in the parameter referenced by p to the values val.
OSSL_PARAM_get_octet_ptr() — retrieves the OCTET string pointer from the parameter referenced by p and stores it in *val. The length of the OCTET string is stored in *used_len.
OSSL_PARAM_set_octet_ptr() — sets the OCTET string pointer in the parameter referenced by p to the values val. The length of the OCTET string is provided by used_len.

🌈 Pointer-to-string, no copying allowed 🌈

OSSL_PARAM_get_utf8_string_ptr() — retrieves the pointer to a UTF8 string from the parameter pointed to by p, and stores that pointer in *val. This is different from OSSL_PARAM_get_utf8_string(), which copies the string.
OSSL_PARAM_get_octet_string_ptr() — retrieves the pointer to a octet string from the parameter pointed to by p, and stores that pointer in *val, along with the string's length in *used_len. This is different from OSSL_PARAM_get_octet_string(), which copies the string.

👑 The "was it even set tho?" squad 👑

OSSL_PARAM_UNMODIFIED — macro used to detect if a parameter was set. On creation, via either the macros or construct calls, the return_size field is set to this. If the parameter is set using the calls defined herein, the return_size field is changed.
OSSL_PARAM_modified() — queries if the parameter param has been set or not using the calls defined herein.
OSSL_PARAM_set_all_unmodified() — resets the unused indicator for all parameters in the array params.

⭐ RETURN VALUES ⭐

OSSL_PARAM_construct_TYPE(), OSSL_PARAM_construct_BN(), OSSL_PARAM_construct_utf8_string(), OSSL_PARAM_construct_octet_string(), OSSL_PARAM_construct_utf8_ptr() and OSSL_PARAM_construct_octet_ptr() — return a populated OSSL_PARAM(3) structure. She's ready, she's filled in, she's serving 🫶
OSSL_PARAM_locate() and OSSL_PARAM_locate_const() — return a pointer to the matching OSSL_PARAM(3) object. They return NULL on error or when no object matching key exists in the array.
OSSL_PARAM_modified() — returns 1 if the parameter was set and 0 otherwise.
All other functions — return 1 on success and 0 on failure.

💀 NOTES 💀

Native types will be converted as required only if the value is exactly representable by the target type or parameter. Apart from that, the functions must be used appropriately for the expected type of the parameter. So no funny business with lossy conversions, bestie — if it doesn't fit exactly, it's not happening.

OSSL_PARAM_get_BN() and OSSL_PARAM_set_BN() only support nonnegative BIGNUMs when the desired data type is OSSL_PARAM_UNSIGNED_INTEGER. OSSL_PARAM_construct_BN() currently constructs an OSSL_PARAM(3) structure with the data type OSSL_PARAM_UNSIGNED_INTEGER.

For OSSL_PARAM_construct_utf8_ptr() and OSSL_PARAM_consstruct_octet_ptr() — yes, that's literally how it's spelled in the source, three s's and all, she's quirky like that 💅 — bsize is not relevant if the purpose is to send the OSSL_PARAM(3) array to a responder, i.e. to get parameter data back. In that case, bsize can safely be given zero. See "DESCRIPTION" in OSSL_PARAM(3) for further information on the possible purposes.

Quick vibe check: those two pointer constructors only let you skip bsize in the "asking a responder for data" scenario. Any other purpose, and zero is not automatically your friend. Don't @ me, that's just what the page says 🙈

🎀 EXAMPLES 🎀

Reusing the examples from OSSL_PARAM(3) to just show how OSSL_PARAM(3) arrays can be handled using the macros and functions defined herein. We're literally recycling, it's sustainable, mother earth is obsessed 🌸

Example 1

This example is for setting parameters on some object:

#include <openssl/core.h>

const char *foo = "some string";
size_t foo_l = strlen(foo);
const char bar[] = "some other string";
const OSSL_PARAM set[] = {
    OSSL_PARAM_utf8_ptr("foo", &foo, foo_l),
    OSSL_PARAM_utf8_string("bar", bar, sizeof(bar) - 1),
    OSSL_PARAM_END
};

Example 2

This example is for requesting parameters on some object, and also demonstrates that the requester isn't obligated to request all available parameters — you can be picky, it's allowed:

const char *foo = NULL;
char bar[1024];
OSSL_PARAM request[] = {
    OSSL_PARAM_utf8_ptr("foo", &foo, 0),
    OSSL_PARAM_utf8_string("bar", bar, sizeof(bar)),
    OSSL_PARAM_END
};

A responder that receives this array (as params in this example) could fill in the parameters like this:

/* OSSL_PARAM *params */

OSSL_PARAM *p;

if ((p = OSSL_PARAM_locate(params, "foo")) != NULL)
    OSSL_PARAM_set_utf8_ptr(p, "foo value");
if ((p = OSSL_PARAM_locate(params, "bar")) != NULL)
    OSSL_PARAM_set_utf8_string(p, "bar value");
if ((p = OSSL_PARAM_locate(params, "cookie")) != NULL)
    OSSL_PARAM_set_utf8_ptr(p, "cookie value");

🦋 SEE ALSO 🦋

openssl-core.h(7), OSSL_PARAM(3)

✨ HISTORY ✨

These APIs were introduced in OpenSSL 3.0. So they're not new new, but they're still that girl.

💖 COPYRIGHT 💖

Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at <https://www.openssl.org/source/license.html>.

And that's the whole page, bestie — go forth and construct your params with type safety and main character energy 👑 Shoutout to the 3.5.0 docs drop, dated 2026-09-25, living under the page name OSSL_PARAM_INT(3ossl). Slay 💅💖

📦 where this page comes from

opensuse-leap 16.0: openssl-3-doc 3.5.0-160000.11.1 · Apache-2.0
💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash-1017 on 2026-11-04: a language model's rewrite of the original, under its terms