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Allow management client to announce pss padding support

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The --management-external-key option can currently indicate support
for 'nopadding' or 'pkcs1' signatures in the client. Add 'pss' as an
option to announce that PSS signing requests are accepted.

To match, extend the algorithm string in PK_SIGN request to
include the following format:

- RSA_PKCS1_PSS_PADDING,hashalg=name,saltlen=[max|digest]

Here 'name' is the short common name of the hash algorithm.
E.g., SHA1, SHA256 etc.

Existing formats 'ECDSA' and 'RSA_PKCS1_PADDING' are unchanged.

v2 changes: Fix typos and other sloppiness in documentation and
commit message.

Signed-off-by: Selva Nair <selva.nair@gmail.com>
Acked-by: Arne Schwabe <arne@rfc2549.org>
Message-Id: <20211214165928.30676-10-selva.nair@gmail.com>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg23430.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>
This commit is contained in:
Selva Nair 2021-12-14 11:59:19 -05:00 committed by Gert Doering
parent cf704eef47
commit a04e3ac047
4 changed files with 34 additions and 8 deletions
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10
doc/man-sections/management-options.rst
View file

@ -85,9 +85,15 @@ server and client mode operations.
management-external-key
management-external-key nopadding
management-external-key pkcs1
management-external-key nopadding pkcs1
management-external-key pss
The optional parameters :code:`nopadding` and :code:`pkcs1` signal
or any combination like:
::
management-external-key nopadding pkcs1
management-external-key pkcs1 pss
The optional parameters :code:`nopadding` :code:`pkcs1` and :code:`pss` signal
support for different padding algorithms. See
:code:`doc/mangement-notes.txt` for a complete description of this
feature.

20
doc/management-notes.txt
View file

@ -907,10 +907,24 @@ can be indicated in the signing request only if the client version is > 2"
The currently defined padding algorithms are:
- RSA_PKCS1_PADDING - PKCS1 padding and RSA signature
- RSA_NO_PADDING - No padding may be added for the signature
- ECDSA - EC signature.
- RSA_PKCS1_PADDING - PKCS1 padding and RSA signature
- RSA_NO_PADDING - No padding may be added for the signature
- ECDSA - EC signature.
- RSA_PKCS1_PSS_PADDING,params - RSA signature with PSS padding
The params for PSS are specified as 'hashalg=name,saltlen=[max|digest]'.
The hashalg names are short common names such as SHA256, SHA224, etc.
PSS saltlen="digest" means use the same size as the hash to sign, while
"max" indicates maximum possible saltlen which is
'(nbits-1)/8 - hlen - 2'. Here 'nbits' is the number of bits in the
key modulus and 'hlen' the size in octets of the hash.
(See: RFC 8017 sec 8.1.1 and 9.1.1)
In the case of PKCS1_PADDING, when the hash algorithm is not legacy
MD5-SHA1, the hash is encoded with DigestInfo header before presenting
to the management interface. This is identical to CKM_RSA_PKCS in Cryptoki
as well as what RSA_private_encrypt() in OpenSSL expects.
COMMAND -- certificate (OpenVPN 2.4 or higher)
----------------------------------------------

1
src/openvpn/manage.h
View file

@ -339,6 +339,7 @@ struct management *management_init(void);
#define MF_QUERY_REMOTE (1<<13)
#define MF_QUERY_PROXY (1<<14)
#define MF_EXTERNAL_CERT (1<<15)
#define MF_EXTERNAL_KEY_PSSPAD (1<<16)
bool management_open(struct management *man,
const char *addr,

11
src/openvpn/options.c
View file

@ -60,6 +60,7 @@
#include "forward.h"
#include "ssl_verify.h"
#include "platform.h"
#include "xkey_common.h"
#include <ctype.h>
#include "memdbg.h"
@ -2207,14 +2208,14 @@ options_postprocess_verify_ce(const struct options *options,
#endif /* ifdef ENABLE_MANAGEMENT */
#if defined(ENABLE_MANAGEMENT)
#if defined(ENABLE_MANAGEMENT) && !defined(HAVE_XKEY_PROVIDER)
if ((tls_version_max() >= TLS_VER_1_3)
&& (options->management_flags & MF_EXTERNAL_KEY)
&& !(options->management_flags & (MF_EXTERNAL_KEY_NOPADDING))
)
{
msg(M_ERR, "management-external-key with OpenSSL 1.1.1 requires "
"the nopadding argument/support");
msg(M_FATAL, "management-external-key with TLS 1.3 or later requires "
"nopadding argument/support");
}
#endif
/*
@ -5520,6 +5521,10 @@ add_option(struct options *options,
{
options->management_flags |= MF_EXTERNAL_KEY_PKCS1PAD;
}
else if (streq(p[j], "pss"))
{
options->management_flags |= MF_EXTERNAL_KEY_PSSPAD;
}
else
{
msg(msglevel, "Unknown management-external-key flag: %s", p[j]);