From 0f6781fa3639d05ce1afb83a45c3bb12c6f97f1b Mon Sep 17 00:00:00 2001 From: Selva Nair Date: Tue, 14 Dec 2021 11:59:21 -0500 Subject: [PATCH] Support sending DigestSign request to management client To receive undigested message for signing, indicate support for handling message digesting in the client using an argument "digest" to --management-external-key. For example, to announce pkcs1 padding and digesting support use: --management-external-key pkcs1 pss digest In PK_SIGN, the algorithm string will get data=message in addition to other relevant options. Note that it is not guaranteed that the client will be prompted with undigested message. This is possible only when OpenSSL calls our provider for DigestSign() as opposed to Sign(). In practice, signature operation always appears to result in a DigestSign() call through the provider interface. Signed-off-by: Selva Nair Acked-by: Arne Schwabe Message-Id: <20211214165928.30676-12-selva.nair@gmail.com> URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg23435.html Signed-off-by: Gert Doering --- src/openvpn/manage.h | 1 + src/openvpn/options.c | 4 +++ src/openvpn/xkey_helper.c | 52 ++++++++++++++++++++++++++++++--------- 3 files changed, 45 insertions(+), 12 deletions(-) diff --git a/src/openvpn/manage.h b/src/openvpn/manage.h index 5ed27c0c5..9621f479d 100644 --- a/src/openvpn/manage.h +++ b/src/openvpn/manage.h @@ -340,6 +340,7 @@ struct management *management_init(void); #define MF_QUERY_PROXY (1<<14) #define MF_EXTERNAL_CERT (1<<15) #define MF_EXTERNAL_KEY_PSSPAD (1<<16) +#define MF_EXTERNAL_KEY_DIGEST (1<<17) bool management_open(struct management *man, const char *addr, diff --git a/src/openvpn/options.c b/src/openvpn/options.c index 42ea3baea..eeb745473 100644 --- a/src/openvpn/options.c +++ b/src/openvpn/options.c @@ -5525,6 +5525,10 @@ add_option(struct options *options, { options->management_flags |= MF_EXTERNAL_KEY_PSSPAD; } + else if (streq(p[j], "digest")) + { + options->management_flags |= MF_EXTERNAL_KEY_DIGEST; + } else { msg(msglevel, "Unknown management-external-key flag: %s", p[j]); diff --git a/src/openvpn/xkey_helper.c b/src/openvpn/xkey_helper.c index 8a42c2495..56e6c4708 100644 --- a/src/openvpn/xkey_helper.c +++ b/src/openvpn/xkey_helper.c @@ -138,17 +138,22 @@ int xkey_management_sign(void *unused, unsigned char *sig, size_t *siglen, const unsigned char *tbs, size_t tbslen, XKEY_SIGALG alg) { + dmsg(D_LOW, "In xkey_management_sign with keytype = %s, op = %s", + alg.keytype, alg.op); + (void) unused; char alg_str[128]; unsigned char buf[EVP_MAX_MD_SIZE]; /* for computing digest if required */ size_t buflen = sizeof(buf); - unsigned char enc[EVP_MAX_MD_SIZE + 32]; /* 32 bytes enough for digest inf structure */ + unsigned char enc[EVP_MAX_MD_SIZE + 32]; /* 32 bytes enough for digest info structure */ size_t enc_len = sizeof(enc); unsigned int flags = management->settings.flags; + bool is_message = !strcmp(alg.op, "DigestSign"); /* tbs is message, not digest */ - if (!strcmp(alg.op, "DigestSign")) + /* if management client cannot do digest -- we do it here */ + if (!strcmp(alg.op, "DigestSign") && !(flags & MF_EXTERNAL_KEY_DIGEST)) { dmsg(D_LOW, "xkey_management_sign: computing digest"); if (xkey_digest(tbs, tbslen, buf, &buflen, alg.mdname)) @@ -156,6 +161,7 @@ xkey_management_sign(void *unused, unsigned char *sig, size_t *siglen, tbs = buf; tbslen = buflen; alg.op = "Sign"; + is_message = false; } else { @@ -165,22 +171,38 @@ xkey_management_sign(void *unused, unsigned char *sig, size_t *siglen, if (!strcmp(alg.keytype, "EC")) { - strncpynt(alg_str, "ECDSA", sizeof(alg_str)); + if (!strcmp(alg.op, "Sign")) + { + strncpynt(alg_str, "ECDSA", sizeof(alg_str)); + } + else + { + openvpn_snprintf(alg_str, sizeof(alg_str), "ECDSA,hashalg=%s", alg.mdname); + } } /* else assume RSA key */ else if (!strcmp(alg.padmode, "pkcs1") && (flags & MF_EXTERNAL_KEY_PKCS1PAD)) { - /* management interface expects a pkcs1 encoded digest -- add it */ - if (!encode_pkcs1(enc, &enc_len, alg.mdname, tbs, tbslen)) + /* For Sign, management interface expects a pkcs1 encoded digest -- add it */ + if (!strcmp(alg.op, "Sign")) { - return 0; + if (!encode_pkcs1(enc, &enc_len, alg.mdname, tbs, tbslen)) + { + return 0; + } + tbs = enc; + tbslen = enc_len; + strncpynt(alg_str, "RSA_PKCS1_PADDING", sizeof(alg_str)); + } + /* For undigested message, add hashalg=digest parameter */ + else + { + openvpn_snprintf(alg_str, sizeof(alg_str), "%s,hashalg=%s", + "RSA_PKCS1_PADDING", alg.mdname); } - tbs = enc; - tbslen = enc_len; - - strncpynt(alg_str, "RSA_PKCS1_PADDING", sizeof(alg_str)); } - else if (!strcmp(alg.padmode, "none") && (flags & MF_EXTERNAL_KEY_NOPADDING)) + else if (!strcmp(alg.padmode, "none") && (flags & MF_EXTERNAL_KEY_NOPADDING) + &&!strcmp(alg.op, "Sign")) /* NO_PADDING requires digested data */ { strncpynt(alg_str, "RSA_NO_PADDING", sizeof(alg_str)); } @@ -190,10 +212,16 @@ xkey_management_sign(void *unused, unsigned char *sig, size_t *siglen, "RSA_PKCS1_PSS_PADDING", alg.mdname,alg.saltlen); } else { - msg(M_NONFATAL, "RSA padding mode unknown or not supported by management-client <%s>", + msg(M_NONFATAL, "RSA padding mode not supported by management-client <%s>", alg.padmode); return 0; } + + if (is_message) + { + strncat(alg_str, ",data=message", sizeof(alg_str) - strlen(alg_str) - 1); + } + dmsg(D_LOW, "xkey management_sign: requesting sig with algorithm <%s>", alg_str); char *in_b64 = NULL; -- 2.47.2