Update EVP_DigestSignInit() docs

Explicitly state which digests can be used with which algorithms.

Fixes #5854

Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/5992)
This commit is contained in:
Matt Caswell 2018-04-17 15:33:17 +01:00
parent d4da95a773
commit be93b0e863

View File

@ -26,7 +26,54 @@ EVP_DigestSignInit() sets up signing context B<ctx> to use digest B<type> from
ENGINE B<e> and private key B<pkey>. B<ctx> must be created with
EVP_MD_CTX_new() before calling this function. If B<pctx> is not NULL the
EVP_PKEY_CTX of the signing operation will be written to B<*pctx>: this can
be used to set alternative signing options.
be used to set alternative signing options. The digest B<type> may be NULL if
the signing algorithm supports it.
Only EVP_PKEY types that support signing can be used with these functions. This
includes MAC algorithms where the MAC generation is considered as a form of
"signing." Built-in EVP_PKEY types supported by these functions are CMAC,
Poly1305, DSA, HMAC, RSA, SipHash, Ed25519 and Ed448.
Not all digests can be used for all key types. The following combinations apply.
=over 4
=item DSA
Supports SHA1, SHA224, SHA256, SHA384 and SHA512
=item ECDSA
Supports SHA1, SHA224, SHA256, SHA384, SHA512 and SM3
=item RSA with no padding
Supports no digests (the digest B<type> must be NULL)
=item RSA with X931 padding
Supports SHA1, SHA256, SHA384 and SHA512
=item All other RSA padding types
Support SHA1, SHA224, SHA256, SHA384, SHA512, MD5, MD5_SHA1, MD2, MD4, MDC2,
SHA3-224, SHA3-256, SHA3-384, SHA3-512
=item Ed25519 and Ed448
Support no digests (the digest B<type> must be NULL)
=item HMAC
Supports any digest
=item CMAC, Poly1305 and SipHash
Will ignore any digest provided.
=back
If RSA-PSS is used and restrictions apply then the digest must match.
EVP_DigestSignUpdate() hashes B<cnt> bytes of data at B<d> into the
signature context B<ctx>. This function can be called several times on the