123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119 |
- =pod
- =head1 NAME
- EVP_SignInit, EVP_SignInit_ex, EVP_SignUpdate,
- EVP_SignFinal_ex, EVP_SignFinal
- - EVP signing functions
- =head1 SYNOPSIS
- #include <openssl/evp.h>
- int EVP_SignInit_ex(EVP_MD_CTX *ctx, const EVP_MD *type, ENGINE *impl);
- int EVP_SignUpdate(EVP_MD_CTX *ctx, const void *d, unsigned int cnt);
- int EVP_SignFinal_ex(EVP_MD_CTX *ctx, unsigned char *md, unsigned int *s,
- EVP_PKEY *pkey, OSSL_LIB_CTX *libctx, const char *propq);
- int EVP_SignFinal(EVP_MD_CTX *ctx, unsigned char *sig, unsigned int *s,
- EVP_PKEY *pkey);
- void EVP_SignInit(EVP_MD_CTX *ctx, const EVP_MD *type);
- =head1 DESCRIPTION
- The EVP signature routines are a high-level interface to digital
- signatures.
- EVP_SignInit_ex() sets up signing context I<ctx> to use digest
- I<type> from B<ENGINE> I<impl>. I<ctx> must be created with
- EVP_MD_CTX_new() before calling this function.
- EVP_SignUpdate() hashes I<cnt> bytes of data at I<d> into the
- signature context I<ctx>. This function can be called several times on the
- same I<ctx> to include additional data.
- EVP_SignFinal_ex() signs the data in I<ctx> using the private key
- I<pkey> and places the signature in I<sig>. The library context I<libctx> and
- property query I<propq> are used when creating a context to use with the key
- I<pkey>. I<sig> must be at least C<EVP_PKEY_get_size(pkey)> bytes in size.
- I<s> is an OUT parameter, and not used as an IN parameter.
- The number of bytes of data written (i.e. the length of the signature)
- will be written to the integer at I<s>, at most C<EVP_PKEY_get_size(pkey)>
- bytes will be written.
- EVP_SignFinal() is similar to EVP_SignFinal_ex() but uses default
- values of NULL for the library context I<libctx> and the property query I<propq>.
- EVP_SignInit() initializes a signing context I<ctx> to use the default
- implementation of digest I<type>.
- =head1 RETURN VALUES
- EVP_SignInit_ex(), EVP_SignUpdate(), EVP_SignFinal_ex() and
- EVP_SignFinal() return 1 for success and 0 for failure.
- The error codes can be obtained by L<ERR_get_error(3)>.
- =head1 NOTES
- The B<EVP> interface to digital signatures should almost always be used in
- preference to the low-level interfaces. This is because the code then becomes
- transparent to the algorithm used and much more flexible.
- When signing with some private key types the random number generator must
- be seeded. If the automatic seeding or reseeding of the OpenSSL CSPRNG fails
- due to external circumstances (see L<RAND(7)>), the operation will fail.
- The call to EVP_SignFinal() internally finalizes a copy of the digest context.
- This means that calls to EVP_SignUpdate() and EVP_SignFinal() can be called
- later to digest and sign additional data.cApplications may disable this
- behavior by setting the EVP_MD_CTX_FLAG_FINALISE context flag via
- L<EVP_MD_CTX_set_flags(3)>.
- Since only a copy of the digest context is ever finalized the context must
- be cleaned up after use by calling EVP_MD_CTX_free() or a memory leak
- will occur.
- Note that not all providers support continuation, in case the selected
- provider does not allow to duplicate contexts EVP_SignFinal() will
- finalize the digest context and attempting to process additional data via
- EVP_SignUpdate() will result in an error.
- =head1 BUGS
- Older versions of this documentation wrongly stated that calls to
- EVP_SignUpdate() could not be made after calling EVP_SignFinal().
- Since the private key is passed in the call to EVP_SignFinal() any error
- relating to the private key (for example an unsuitable key and digest
- combination) will not be indicated until after potentially large amounts of
- data have been passed through EVP_SignUpdate().
- It is not possible to change the signing parameters using these function.
- The previous two bugs are fixed in the newer EVP_DigestSign*() functions.
- =head1 SEE ALSO
- L<EVP_PKEY_get_size(3)>, L<EVP_PKEY_get_bits(3)>,
- L<EVP_PKEY_get_security_bits(3)>,
- L<EVP_VerifyInit(3)>,
- L<EVP_DigestInit(3)>,
- L<evp(7)>, L<HMAC(3)>, L<MD2(3)>,
- L<MD5(3)>, L<MDC2(3)>, L<RIPEMD160(3)>,
- L<SHA1(3)>, L<openssl-dgst(1)>
- =head1 HISTORY
- The function EVP_SignFinal_ex() was added in OpenSSL 3.0.
- =head1 COPYRIGHT
- Copyright 2000-2023 The OpenSSL Project Authors. All Rights Reserved.
- 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
- L<https://www.openssl.org/source/license.html>.
- =cut
|