From 476de2e5e598b46289c6087df04d1bc1886d6ef2 Mon Sep 17 00:00:00 2001 From: Richard Levitte Date: Mon, 2 Mar 2020 14:39:30 +0100 Subject: [PATCH] DOC: Add more description of EVP_PKEY_fromdata(), and examples Fixes #11131 Reviewed-by: Paul Dale (Merged from https://github.com/openssl/openssl/pull/11220) --- doc/man3/EVP_PKEY_fromdata.pod | 172 +++++++++++++++++++++++++++++++-- 1 file changed, 165 insertions(+), 7 deletions(-) diff --git a/doc/man3/EVP_PKEY_fromdata.pod b/doc/man3/EVP_PKEY_fromdata.pod index e3ddf68058..0d85e80b95 100644 --- a/doc/man3/EVP_PKEY_fromdata.pod +++ b/doc/man3/EVP_PKEY_fromdata.pod @@ -18,18 +18,29 @@ EVP_PKEY_param_fromdata_settable, EVP_PKEY_key_fromdata_settable =head1 DESCRIPTION +The functions described here are used to create new keys from user +provided key data, such as I, I and I for a minimal RSA +keypair. + +These functions use an B context, which should primarly +be created with L or +L. + +The exact key data that the user can pass depends on the key type. +These are passed as an L array. + EVP_PKEY_param_fromdata_init() initializes a public key algorithm context for creating key parameters from user data. EVP_PKEY_key_fromdata_init() initializes a public key algorithm context for creating a key from user data. -EVP_PKEY_fromdata() creates key parameters or a key, given data from -I and a context that's been initialized with -EVP_PKEY_param_fromdata_init() or EVP_PKEY_key_fromdata_init(). The result is -written to I<*ppkey>. The parameters that can be used for various types of key -are as described in the "Built-in RSA Import/Export Types" section on the -L page. +EVP_PKEY_fromdata() creates the structure to store key parameters or a +key, given data from I and a context that's been initialized with +EVP_PKEY_param_fromdata_init() or EVP_PKEY_key_fromdata_init(). The result +is written to I<*ppkey>. The parameters that can be used are specific to +the L implementations, please see +L for further information. EVP_PKEY_param_fromdata_settable() and EVP_PKEY_key_fromdata_settable() get a constant B array that describes the settable parameters @@ -50,9 +61,156 @@ EVP_PKEY_fromdata() return 1 for success and 0 or a negative value for failure. In particular a return value of -2 indicates the operation is not supported by the public key algorithm. +=head1 EXAMPLES + +These examples are very terse for the sake of staying on topic, which +is the EVP_PKEY_fromdata() set of functions. In real applications, +BIGNUMs would be handled and converted to byte arrays with +BN_bn2nativepad(), but that's off topic here. + +=begin comment + +TODO Write a set of cookbook documents and link to them. + +=end comment + +=head2 Creating an RSA keypair using raw key data + + #include + + /* + * These are extremely small to make this example simple. A real + * and secure application will not use such small numbers. A real + * and secure application is expected to use BIGNUMs, and to build + * this array dynamically. + */ + const unsigned long rsa_n = 0xbc747fc5; + const unsigned long rsa_e = 0x10001; + const unsigned long rsa_d = 0x7b133399; + const OSSL_PARAM[] = { + OSSL_PARAM_ulong("n", &rsa_n), + OSSL_PARAM_ulong("e", &rsa_e), + OSSL_PARAM_ulong("d", &rsa_d), + OSSL_PARAM_END + }; + + int main() + { + EVP_PKEY_CTX *ctx = EVP_PKEY_CTX_new_from_name(NULL, "RSA", NULL); + EVP_PKEY *pkey = NULL; + + if (ctx == NULL + || !EVP_PKEY_key_fromdata_init(ctx) + || !EVP_PKEY_fromdata(ctx, &pkey, params)) + exit(1); + + /* Do what you want with |pkey| */ + } + +=head2 Creating an ECC keypair using raw key data + + #include + + /* + * These arrays represent large numbers, big endian organization. + * In a real application, these would probably be bignums that get + * converted to the native integer organization with BN_bn2nativepad(). + * We're not doing that here, since this is not an example of BIGNUM + * functionality, but an example of EVP_PKEY_fromdata(). + */ + #ifndef B_ENDIAN + # error "We haven't prepared little endian arrays" + #endif + const unsigned char priv[] = { + 0xb9, 0x2f, 0x3c, 0xe6, 0x2f, 0xfb, 0x45, 0x68, + 0x39, 0x96, 0xf0, 0x2a, 0xaf, 0x6c, 0xda, 0xf2, + 0x89, 0x8a, 0x27, 0xbf, 0x39, 0x9b, 0x7e, 0x54, + 0x21, 0xc2, 0xa1, 0xe5, 0x36, 0x12, 0x48, 0x5d + }; + const unsigned char pub[] = { + 0x04, 0xcf, 0x20, 0xfb, 0x9a, 0x1d, 0x11, 0x6c, + 0x5e, 0x9f, 0xec, 0x38, 0x87, 0x6c, 0x1d, 0x2f, + 0x58, 0x47, 0xab, 0xa3, 0x9b, 0x79, 0x23, 0xe6, + 0xeb, 0x94, 0x6f, 0x97, 0xdb, 0xa3, 0x7d, 0xbd, + 0xe5, 0x26, 0xca, 0x07, 0x17, 0x8d, 0x26, 0x75, + 0xff, 0xcb, 0x8e, 0xb6, 0x84, 0xd0, 0x24, 0x02, + 0x25, 0x8f, 0xb9, 0x33, 0x6e, 0xcf, 0x12, 0x16, + 0x2f, 0x5c, 0xcd, 0x86, 0x71, 0xa8, 0xbf, 0x1a, + 0x47 + }; + const OSSL_PARAM params[] = { + OSSL_PARAM_utf8_string("curve-name", "prime256v1"), + OSSL_PARAM_BN("priv", priv, sizeof(priv)), + OSSL_PARAM_BN("pub", pub, sizeof(pub)), + OSSL_PARAM_END + }; + + int main() + { + EVP_PKEY_CTX *ctx = EVP_PKEY_CTX_new_from_name(NULL, "EC", NULL); + EVP_PKEY *pkey = NULL; + + if (ctx == NULL + || !EVP_PKEY_key_fromdata_init(ctx) + || !EVP_PKEY_fromdata(ctx, &pkey, params)) + exit(1); + + /* Do what you want with |pkey| */ + } + +=head2 Finding out params for an unknown key type + + #include + + /* Program expects a key type as first argument */ + int main(int argc, char *argv[]) + { + EVP_PKEY_CTX *ctx = EVP_PKEY_CTX_new_from_name(NULL, argv[1], NULL); + const *OSSL_PARAM *settable_params = NULL; + + if (ctx == NULL + || (settable_params = EVP_PKEY_key_fromdata_settable(ctx)) == NULL) + exit(1); + + for (; settable_params->key != NULL; settable_params++) { + const char *datatype = NULL; + + switch (settable_params->data_type) { + case OSSL_PARAM_INTEGER: + datatype = "integer"; + break; + case OSSL_PARAM_UNSIGNED_INTEGER: + datatype = "unsigned integer"; + break; + case OSSL_PARAM_UTF8_STRING: + datatype = "printable string (utf-8 encoding expected)"; + break; + case OSSL_PARAM_UTF8_PTR: + datatype = "printable string pointer (utf-8 encoding expected)"; + break; + case OSSL_PARAM_OCTET_STRING: + datatype = "octet string"; + break; + case OSSL_PARAM_OCTET_PTR: + datatype = "octet string pointer"; + break; + } + printf("%s : %s ", settable_params->key, datatype); + if (settable_params->data_size == 0) + printf("(unlimited size)"); + else + printf("(maximum size %zu)", settable_params->data_size); + } + } + +The descriptor L returned by +EVP_PKEY_key_fromdata_settable() may also be used programmatically, for +example with L. + =head1 SEE ALSO -L, L, L +L, L, L, +L =head1 HISTORY -- 2.34.1