From b4f8964ad1903e24cd2ee07f42ce97c3047f4af4 Mon Sep 17 00:00:00 2001
From: Clemens Lang <cllang@redhat.com>
Date: Mon, 21 Feb 2022 17:24:44 +0100
Subject: [PATCH] Allow disabling of SHA1 signatures
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
NOTE: This patch is ported from CentOS 9 / RHEL 9, where it defaults to
denying SHA1 signatures. On Fedora, the default is – for now – to allow
SHA1 signatures.
In order to phase out SHA1 signatures, introduce a new configuration
option in the alg_section named 'rh-allow-sha1-signatures'. This option
defaults to true. If set to false, any signature creation or
verification operations that involve SHA1 as digest will fail.
This also affects TLS, where the signature_algorithms extension of any
ClientHello message sent by OpenSSL will no longer include signatures
with the SHA1 digest if rh-allow-sha1-signatures is false. For servers
that request a client certificate, the same also applies for
CertificateRequest messages sent by them.
For signatures created using the EVP_PKEY API, this is a best-effort
check that will deny signatures in cases where the digest algorithm is
known. This means, for example, that that following steps will still
work:
$> openssl dgst -sha1 -binary -out sha1 infile
$> openssl pkeyutl -inkey key.pem -sign -in sha1 -out sha1sig
$> openssl pkeyutl -inkey key.pem -verify -sigfile sha1sig -in sha1
whereas these will not:
$> openssl dgst -sha1 -binary -out sha1 infile
$> openssl pkeyutl -inkey kem.pem -sign -in sha1 -out sha1sig -pkeyopt digest:sha1
$> openssl pkeyutl -inkey kem.pem -verify -sigfile sha1sig -in sha1 -pkeyopt digest:sha1
This happens because in the first case, OpenSSL's signature
implementation does not know that it is signing a SHA1 hash (it could be
signing arbitrary data).
---
crypto/evp/evp_cnf.c | 13 +++
crypto/evp/m_sigver.c | 85 +++++++++++++++++++
crypto/evp/pmeth_lib.c | 15 ++++
doc/man5/config.pod | 13 +++
include/internal/cryptlib.h | 3 +-
include/internal/sslconf.h | 4 +
providers/common/securitycheck.c | 20 +++++
providers/common/securitycheck_default.c | 9 +-
providers/implementations/signature/dsa_sig.c | 11 ++-
.../implementations/signature/ecdsa_sig.c | 4 +
providers/implementations/signature/rsa_sig.c | 20 ++++-
ssl/t1_lib.c | 8 ++
util/libcrypto.num | 2 +
13 files changed, 198 insertions(+), 9 deletions(-)
diff --git a/crypto/evp/evp_cnf.c b/crypto/evp/evp_cnf.c
index 0e7fe64cf9..b9d3b6d226 100644
--- a/crypto/evp/evp_cnf.c
+++ b/crypto/evp/evp_cnf.c
@@ -10,6 +10,7 @@
#include <stdio.h>
#include <openssl/crypto.h>
#include "internal/cryptlib.h"
+#include "internal/sslconf.h"
#include <openssl/conf.h>
#include <openssl/x509.h>
#include <openssl/x509v3.h>
@@ -57,6 +58,18 @@ static int alg_module_init(CONF_IMODULE *md, const CONF *cnf)
ERR_raise(ERR_LIB_EVP, EVP_R_SET_DEFAULT_PROPERTY_FAILURE);
return 0;
}
+ } else if (strcmp(oval->name, "rh-allow-sha1-signatures") == 0) {
+ int m;
+
+ /* Detailed error already reported. */
+ if (!X509V3_get_value_bool(oval, &m))
+ return 0;
+
+ if (!ossl_ctx_legacy_digest_signatures_allowed_set(
+ NCONF_get0_libctx((CONF *)cnf), m > 0, 0)) {
+ ERR_raise(ERR_LIB_EVP, EVP_R_SET_DEFAULT_PROPERTY_FAILURE);
+ return 0;
+ }
} else {
ERR_raise_data(ERR_LIB_EVP, EVP_R_UNKNOWN_OPTION,
"name=%s, value=%s", oval->name, oval->value);
diff --git a/crypto/evp/m_sigver.c b/crypto/evp/m_sigver.c
index 76a6814b42..8da2183ce0 100644
--- a/crypto/evp/m_sigver.c
+++ b/crypto/evp/m_sigver.c
@@ -16,6 +16,79 @@
#include "internal/numbers.h" /* includes SIZE_MAX */
#include "evp_local.h"
+typedef struct ossl_legacy_digest_signatures_st {
+ int allowed;
+} OSSL_LEGACY_DIGEST_SIGNATURES;
+
+static void ossl_ctx_legacy_digest_signatures_free(void *vldsigs)
+{
+ OSSL_LEGACY_DIGEST_SIGNATURES *ldsigs = vldsigs;
+
+ if (ldsigs != NULL) {
+ OPENSSL_free(ldsigs);
+ }
+}
+
+static void *ossl_ctx_legacy_digest_signatures_new(OSSL_LIB_CTX *ctx)
+{
+ OSSL_LEGACY_DIGEST_SIGNATURES* ldsigs = OPENSSL_zalloc(sizeof(OSSL_LEGACY_DIGEST_SIGNATURES));
+ /* Warning: This patch differs from the same patch in CentOS and RHEL here,
+ * because the default on Fedora is to allow SHA-1 and support disabling
+ * it, while CentOS/RHEL disable it by default and allow enabling it. */
+ ldsigs->allowed = 1;
+ return ldsigs;
+}
+
+static const OSSL_LIB_CTX_METHOD ossl_ctx_legacy_digest_signatures_method = {
+ OSSL_LIB_CTX_METHOD_DEFAULT_PRIORITY,
+ ossl_ctx_legacy_digest_signatures_new,
+ ossl_ctx_legacy_digest_signatures_free,
+};
+
+static OSSL_LEGACY_DIGEST_SIGNATURES *ossl_ctx_legacy_digest_signatures(
+ OSSL_LIB_CTX *libctx, int loadconfig)
+{
+#ifndef FIPS_MODULE
+ if (loadconfig && !OPENSSL_init_crypto(OPENSSL_INIT_LOAD_CONFIG, NULL))
+ return NULL;
+#endif
+
+ return ossl_lib_ctx_get_data(libctx, OSSL_LIB_CTX_LEGACY_DIGEST_SIGNATURES,
+ &ossl_ctx_legacy_digest_signatures_method);
+}
+
+int ossl_ctx_legacy_digest_signatures_allowed(OSSL_LIB_CTX *libctx, int loadconfig)
+{
+ OSSL_LEGACY_DIGEST_SIGNATURES *ldsigs
+ = ossl_ctx_legacy_digest_signatures(libctx, loadconfig);
+
+#ifndef FIPS_MODULE
+ if (ossl_safe_getenv("OPENSSL_ENABLE_SHA1_SIGNATURES") != NULL)
+ /* used in tests */
+ return 1;
+#endif
+
+ /* Warning: This patch differs from the same patch in CentOS and RHEL here,
+ * because the default on Fedora is to allow SHA-1 and support disabling
+ * it, while CentOS/RHEL disable it by default and allow enabling it. */
+ return ldsigs != NULL ? ldsigs->allowed : 1;
+}
+
+int ossl_ctx_legacy_digest_signatures_allowed_set(OSSL_LIB_CTX *libctx, int allow,
+ int loadconfig)
+{
+ OSSL_LEGACY_DIGEST_SIGNATURES *ldsigs
+ = ossl_ctx_legacy_digest_signatures(libctx, loadconfig);
+
+ if (ldsigs == NULL) {
+ ERR_raise(ERR_LIB_EVP, ERR_R_INTERNAL_ERROR);
+ return 0;
+ }
+
+ ldsigs->allowed = allow;
+ return 1;
+}
+
#ifndef FIPS_MODULE
static int update(EVP_MD_CTX *ctx, const void *data, size_t datalen)
@@ -258,6 +331,18 @@ static int do_sigver_init(EVP_MD_CTX *ctx, EVP_PKEY_CTX **pctx,
}
}
+ if (ctx->reqdigest != NULL
+ && !EVP_PKEY_is_a(locpctx->pkey, SN_hmac)
+ && !EVP_PKEY_is_a(locpctx->pkey, SN_tls1_prf)
+ && !EVP_PKEY_is_a(locpctx->pkey, SN_hkdf)) {
+ int mdnid = EVP_MD_nid(ctx->reqdigest);
+ if (!ossl_ctx_legacy_digest_signatures_allowed(locpctx->libctx, 0)
+ && (mdnid == NID_sha1 || mdnid == NID_md5_sha1)) {
+ ERR_raise(ERR_LIB_EVP, EVP_R_INVALID_DIGEST);
+ goto err;
+ }
+ }
+
if (ver) {
if (signature->digest_verify_init == NULL) {
ERR_raise(ERR_LIB_EVP, EVP_R_INITIALIZATION_ERROR);
diff --git a/crypto/evp/pmeth_lib.c b/crypto/evp/pmeth_lib.c
index 2b9c6c2351..3c5a1e6f5d 100644
--- a/crypto/evp/pmeth_lib.c
+++ b/crypto/evp/pmeth_lib.c
@@ -33,6 +33,7 @@
#include "internal/ffc.h"
#include "internal/numbers.h"
#include "internal/provider.h"
+#include "internal/sslconf.h"
#include "evp_local.h"
#ifndef FIPS_MODULE
@@ -946,6 +947,20 @@ static int evp_pkey_ctx_set_md(EVP_PKEY_CTX *ctx, const EVP_MD *md,
return -2;
}
+ if (EVP_PKEY_CTX_IS_SIGNATURE_OP(ctx)
+ && md != NULL
+ && ctx->pkey != NULL
+ && !EVP_PKEY_is_a(ctx->pkey, SN_hmac)
+ && !EVP_PKEY_is_a(ctx->pkey, SN_tls1_prf)
+ && !EVP_PKEY_is_a(ctx->pkey, SN_hkdf)) {
+ int mdnid = EVP_MD_nid(md);
+ if ((mdnid == NID_sha1 || mdnid == NID_md5_sha1)
+ && !ossl_ctx_legacy_digest_signatures_allowed(ctx->libctx, 0)) {
+ ERR_raise(ERR_LIB_EVP, EVP_R_INVALID_DIGEST);
+ return -1;
+ }
+ }
+
if (fallback)
return EVP_PKEY_CTX_ctrl(ctx, -1, op, ctrl, 0, (void *)(md));
diff --git a/doc/man5/config.pod b/doc/man5/config.pod
index 77a8055e81..0c9110d28a 100644
--- a/doc/man5/config.pod
+++ b/doc/man5/config.pod
@@ -296,6 +296,19 @@ Within the algorithm properties section, the following names have meaning:
The value may be anything that is acceptable as a property query
string for EVP_set_default_properties().
+=item B<rh-allow-sha1-signatures>
+
+The value is a boolean that can be B<yes> or B<no>. If the value is not set,
+it behaves as if it was set to B<yes>.
+
+When set to B<no>, any attempt to create or verify a signature with a SHA1
+digest will fail. To test whether your software will work with future versions
+of OpenSSL, set this option to B<no>. This setting also affects TLS, where
+signature algorithms that use SHA1 as digest will no longer be supported if
+this option is set to B<no>. Because TLS 1.1 or lower use MD5-SHA1 as
+pseudorandom function (PRF) to derive key material, disabling
+B<rh-allow-sha1-signatures> requires the use of TLS 1.2 or newer.
+
=item B<fips_mode> (deprecated)
The value is a boolean that can be B<yes> or B<no>. If the value is
diff --git a/include/internal/cryptlib.h b/include/internal/cryptlib.h
index 1291299b6e..e234341e6a 100644
--- a/include/internal/cryptlib.h
+++ b/include/internal/cryptlib.h
@@ -168,7 +168,8 @@ typedef struct ossl_ex_data_global_st {
# define OSSL_LIB_CTX_PROVIDER_CONF_INDEX 16
# define OSSL_LIB_CTX_BIO_CORE_INDEX 17
# define OSSL_LIB_CTX_CHILD_PROVIDER_INDEX 18
-# define OSSL_LIB_CTX_MAX_INDEXES 19
+# define OSSL_LIB_CTX_LEGACY_DIGEST_SIGNATURES 19
+# define OSSL_LIB_CTX_MAX_INDEXES 20
# define OSSL_LIB_CTX_METHOD_LOW_PRIORITY -1
# define OSSL_LIB_CTX_METHOD_DEFAULT_PRIORITY 0
diff --git a/include/internal/sslconf.h b/include/internal/sslconf.h
index fd7f7e3331..05464b0655 100644
--- a/include/internal/sslconf.h
+++ b/include/internal/sslconf.h
@@ -18,4 +18,8 @@ int conf_ssl_name_find(const char *name, size_t *idx);
void conf_ssl_get_cmd(const SSL_CONF_CMD *cmd, size_t idx, char **cmdstr,
char **arg);
+/* Methods to support disabling all signatures with legacy digests */
+int ossl_ctx_legacy_digest_signatures_allowed(OSSL_LIB_CTX *libctx, int loadconfig);
+int ossl_ctx_legacy_digest_signatures_allowed_set(OSSL_LIB_CTX *libctx, int allow,
+ int loadconfig);
#endif
diff --git a/providers/common/securitycheck.c b/providers/common/securitycheck.c
index 699ada7c52..e534ad0a5f 100644
--- a/providers/common/securitycheck.c
+++ b/providers/common/securitycheck.c
@@ -19,6 +19,7 @@
#include <openssl/core_names.h>
#include <openssl/obj_mac.h>
#include "prov/securitycheck.h"
+#include "internal/sslconf.h"
/*
* FIPS requires a minimum security strength of 112 bits (for encryption or
@@ -235,6 +236,15 @@ int ossl_digest_get_approved_nid_with_sha1(OSSL_LIB_CTX *ctx, const EVP_MD *md,
mdnid = -1; /* disallowed by security checks */
}
# endif /* OPENSSL_NO_FIPS_SECURITYCHECKS */
+
+#ifndef FIPS_MODULE
+ if (!ossl_ctx_legacy_digest_signatures_allowed(ctx, 0))
+ /* SHA1 is globally disabled, check whether we want to locally allow
+ * it. */
+ if (mdnid == NID_sha1 && !sha1_allowed)
+ mdnid = -1;
+#endif
+
return mdnid;
}
@@ -244,5 +254,15 @@ int ossl_digest_is_allowed(OSSL_LIB_CTX *ctx, const EVP_MD *md)
if (ossl_securitycheck_enabled(ctx))
return ossl_digest_get_approved_nid(md) != NID_undef;
# endif /* OPENSSL_NO_FIPS_SECURITYCHECKS */
+
+#ifndef FIPS_MODULE
+ {
+ int mdnid = EVP_MD_nid(md);
+ if ((mdnid == NID_sha1 || mdnid == NID_md5_sha1)
+ && !ossl_ctx_legacy_digest_signatures_allowed(ctx, 0))
+ return 0;
+ }
+#endif
+
return 1;
}
diff --git a/providers/common/securitycheck_default.c b/providers/common/securitycheck_default.c
index de7f0d3a0a..ce54a94fbc 100644
--- a/providers/common/securitycheck_default.c
+++ b/providers/common/securitycheck_default.c
@@ -15,6 +15,7 @@
#include <openssl/obj_mac.h>
#include "prov/securitycheck.h"
#include "internal/nelem.h"
+#include "internal/sslconf.h"
/* Disable the security checks in the default provider */
int ossl_securitycheck_enabled(OSSL_LIB_CTX *libctx)
@@ -23,9 +24,10 @@ int ossl_securitycheck_enabled(OSSL_LIB_CTX *libctx)
}
int ossl_digest_rsa_sign_get_md_nid(OSSL_LIB_CTX *ctx, const EVP_MD *md,
- ossl_unused int sha1_allowed)
+ int sha1_allowed)
{
int mdnid;
+ int ldsigs_allowed;
static const OSSL_ITEM name_to_nid[] = {
{ NID_md5, OSSL_DIGEST_NAME_MD5 },
@@ -36,8 +38,11 @@ int ossl_digest_rsa_sign_get_md_nid(OSSL_LIB_CTX *ctx, const EVP_MD *md,
{ NID_ripemd160, OSSL_DIGEST_NAME_RIPEMD160 },
};
- mdnid = ossl_digest_get_approved_nid_with_sha1(ctx, md, 1);
+ ldsigs_allowed = ossl_ctx_legacy_digest_signatures_allowed(ctx, 0);
+ mdnid = ossl_digest_get_approved_nid_with_sha1(ctx, md, sha1_allowed || ldsigs_allowed);
if (mdnid == NID_undef)
mdnid = ossl_digest_md_to_nid(md, name_to_nid, OSSL_NELEM(name_to_nid));
+ if (mdnid == NID_md5_sha1 && !ldsigs_allowed)
+ mdnid = -1;
return mdnid;
}
diff --git a/providers/implementations/signature/dsa_sig.c b/providers/implementations/signature/dsa_sig.c
index 28fd7c498e..fa3822f39f 100644
--- a/providers/implementations/signature/dsa_sig.c
+++ b/providers/implementations/signature/dsa_sig.c
@@ -124,12 +124,17 @@ static int dsa_setup_md(PROV_DSA_CTX *ctx,
mdprops = ctx->propq;
if (mdname != NULL) {
- int sha1_allowed = (ctx->operation != EVP_PKEY_OP_SIGN);
WPACKET pkt;
EVP_MD *md = EVP_MD_fetch(ctx->libctx, mdname, mdprops);
- int md_nid = ossl_digest_get_approved_nid_with_sha1(ctx->libctx, md,
- sha1_allowed);
+ int md_nid;
size_t mdname_len = strlen(mdname);
+#ifdef FIPS_MODULE
+ int sha1_allowed = (ctx->operation != EVP_PKEY_OP_SIGN);
+#else
+ int sha1_allowed = 0;
+#endif
+ md_nid = ossl_digest_get_approved_nid_with_sha1(ctx->libctx, md,
+ sha1_allowed);
if (md == NULL || md_nid < 0) {
if (md == NULL)
diff --git a/providers/implementations/signature/ecdsa_sig.c b/providers/implementations/signature/ecdsa_sig.c
index 865d49d100..99b228e82c 100644
--- a/providers/implementations/signature/ecdsa_sig.c
+++ b/providers/implementations/signature/ecdsa_sig.c
@@ -237,7 +237,11 @@ static int ecdsa_setup_md(PROV_ECDSA_CTX *ctx, const char *mdname,
"%s could not be fetched", mdname);
return 0;
}
+#ifdef FIPS_MODULE
sha1_allowed = (ctx->operation != EVP_PKEY_OP_SIGN);
+#else
+ sha1_allowed = 0;
+#endif
md_nid = ossl_digest_get_approved_nid_with_sha1(ctx->libctx, md,
sha1_allowed);
if (md_nid < 0) {
diff --git a/providers/implementations/signature/rsa_sig.c b/providers/implementations/signature/rsa_sig.c
index 325e855333..bea397f0c1 100644
--- a/providers/implementations/signature/rsa_sig.c
+++ b/providers/implementations/signature/rsa_sig.c
@@ -26,6 +26,7 @@
#include "internal/cryptlib.h"
#include "internal/nelem.h"
#include "internal/sizes.h"
+#include "internal/sslconf.h"
#include "crypto/rsa.h"
#include "prov/providercommon.h"
#include "prov/implementations.h"
@@ -34,6 +35,7 @@
#include "prov/securitycheck.h"
#define RSA_DEFAULT_DIGEST_NAME OSSL_DIGEST_NAME_SHA1
+#define RSA_DEFAULT_DIGEST_NAME_NONLEGACY OSSL_DIGEST_NAME_SHA2_256
static OSSL_FUNC_signature_newctx_fn rsa_newctx;
static OSSL_FUNC_signature_sign_init_fn rsa_sign_init;
@@ -289,10 +291,15 @@ static int rsa_setup_md(PROV_RSA_CTX *ctx, const char *mdname,
if (mdname != NULL) {
EVP_MD *md = EVP_MD_fetch(ctx->libctx, mdname, mdprops);
+ int md_nid;
+ size_t mdname_len = strlen(mdname);
+#ifdef FIPS_MODULE
int sha1_allowed = (ctx->operation != EVP_PKEY_OP_SIGN);
- int md_nid = ossl_digest_rsa_sign_get_md_nid(ctx->libctx, md,
+#else
+ int sha1_allowed = 0;
+#endif
+ md_nid = ossl_digest_rsa_sign_get_md_nid(ctx->libctx, md,
sha1_allowed);
- size_t mdname_len = strlen(mdname);
if (md == NULL
|| md_nid <= 0
@@ -1348,8 +1355,15 @@ static int rsa_set_ctx_params(void *vprsactx, const OSSL_PARAM params[])
prsactx->pad_mode = pad_mode;
if (prsactx->md == NULL && pmdname == NULL
- && pad_mode == RSA_PKCS1_PSS_PADDING)
+ && pad_mode == RSA_PKCS1_PSS_PADDING) {
pmdname = RSA_DEFAULT_DIGEST_NAME;
+#ifndef FIPS_MODULE
+ if (!ossl_ctx_legacy_digest_signatures_allowed(prsactx->libctx, 0)) {
+ pmdname = RSA_DEFAULT_DIGEST_NAME_NONLEGACY;
+ }
+#endif
+ }
+
if (pmgf1mdname != NULL
&& !rsa_setup_mgf1_md(prsactx, pmgf1mdname, pmgf1mdprops))
diff --git a/ssl/t1_lib.c b/ssl/t1_lib.c
index 41fddf22a7..dcd487ec2e 100644
--- a/ssl/t1_lib.c
+++ b/ssl/t1_lib.c
@@ -20,6 +20,7 @@
#include <openssl/bn.h>
#include <openssl/provider.h>
#include <openssl/param_build.h>
+#include "internal/sslconf.h"
#include "internal/nelem.h"
#include "internal/sizes.h"
#include "internal/tlsgroups.h"
@@ -1145,11 +1146,13 @@ int ssl_setup_sig_algs(SSL_CTX *ctx)
= OPENSSL_malloc(sizeof(*lu) * OSSL_NELEM(sigalg_lookup_tbl));
EVP_PKEY *tmpkey = EVP_PKEY_new();
int ret = 0;
+ int ldsigs_allowed;
if (cache == NULL || tmpkey == NULL)
goto err;
ERR_set_mark();
+ ldsigs_allowed = ossl_ctx_legacy_digest_signatures_allowed(ctx->libctx, 0);
for (i = 0, lu = sigalg_lookup_tbl;
i < OSSL_NELEM(sigalg_lookup_tbl); lu++, i++) {
EVP_PKEY_CTX *pctx;
@@ -1169,6 +1172,11 @@ int ssl_setup_sig_algs(SSL_CTX *ctx)
cache[i].enabled = 0;
continue;
}
+ if ((lu->hash == NID_sha1 || lu->hash == NID_md5_sha1)
+ && !ldsigs_allowed) {
+ cache[i].enabled = 0;
+ continue;
+ }
if (!EVP_PKEY_set_type(tmpkey, lu->sig)) {
cache[i].enabled = 0;
diff --git a/util/libcrypto.num b/util/libcrypto.num
index 10b4e57d79..2d3c363bb0 100644
--- a/util/libcrypto.num
+++ b/util/libcrypto.num
@@ -5426,3 +5426,5 @@ ASN1_item_d2i_ex 5552 3_0_0 EXIST::FUNCTION:
EVP_PKEY_get0_provider 5554 3_0_0 EXIST::FUNCTION:
EVP_PKEY_CTX_get0_provider 5555 3_0_0 EXIST::FUNCTION:
ossl_safe_getenv ? 3_0_0 EXIST::FUNCTION:
+ossl_ctx_legacy_digest_signatures_allowed ? 3_0_1 EXIST::FUNCTION:
+ossl_ctx_legacy_digest_signatures_allowed_set ? 3_0_1 EXIST::FUNCTION:
--
2.35.1