Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752544AbaFFVuJ (ORCPT ); Fri, 6 Jun 2014 17:50:09 -0400 Received: from mail-wg0-f46.google.com ([74.125.82.46]:48088 "EHLO mail-wg0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752108AbaFFVuH (ORCPT ); Fri, 6 Jun 2014 17:50:07 -0400 MIME-Version: 1.0 In-Reply-To: <1401818318-15780-3-git-send-email-zohar@linux.vnet.ibm.com> References: <1401818318-15780-1-git-send-email-zohar@linux.vnet.ibm.com> <1401818318-15780-3-git-send-email-zohar@linux.vnet.ibm.com> Date: Sat, 7 Jun 2014 00:50:05 +0300 Message-ID: Subject: Re: [RFC PATCH v5 2/4] KEYS: verify a certificate is signed by a 'trusted' key From: Dmitry Kasatkin To: Mimi Zohar Cc: linux-security-module , Dmitry Kasatkin , David Howells , Josh Boyer , keyrings , linux-kernel Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3 June 2014 20:58, Mimi Zohar wrote: > Only public keys, with certificates signed by an existing > 'trusted' key on the system trusted keyring, should be added > to a trusted keyring. This patch adds support for verifying > a certificate's signature. > > This is derived from David Howells pkcs7_request_asymmetric_key() patch. > > Changelog: > - define get_system_trusted_keyring() to fix kbuild issues > > Signed-off-by: Mimi Zohar > Signed-off-by: David Howells Acked-by: me > --- > crypto/asymmetric_keys/x509_public_key.c | 84 +++++++++++++++++++++++++++++++- > include/keys/system_keyring.h | 10 +++- > 2 files changed, 92 insertions(+), 2 deletions(-) > > diff --git a/crypto/asymmetric_keys/x509_public_key.c b/crypto/asymmetric_keys/x509_public_key.c > index 382ef0d..1af8a30 100644 > --- a/crypto/asymmetric_keys/x509_public_key.c > +++ b/crypto/asymmetric_keys/x509_public_key.c > @@ -18,12 +18,60 @@ > #include > #include > #include > +#include > #include > #include "asymmetric_keys.h" > #include "public_key.h" > #include "x509_parser.h" > > /* > + * Find a key in the given keyring by issuer and authority. > + */ > +static struct key *x509_request_asymmetric_key( > + struct key *keyring, > + const char *signer, size_t signer_len, > + const char *authority, size_t auth_len) > +{ > + key_ref_t key; > + char *id; > + > + /* Construct an identifier. */ > + id = kmalloc(signer_len + 2 + auth_len + 1, GFP_KERNEL); > + if (!id) > + return ERR_PTR(-ENOMEM); > + > + memcpy(id, signer, signer_len); > + id[signer_len + 0] = ':'; > + id[signer_len + 1] = ' '; > + memcpy(id + signer_len + 2, authority, auth_len); > + id[signer_len + 2 + auth_len] = 0; > + > + pr_debug("Look up: \"%s\"\n", id); > + > + key = keyring_search(make_key_ref(keyring, 1), > + &key_type_asymmetric, id); > + if (IS_ERR(key)) > + pr_debug("Request for module key '%s' err %ld\n", > + id, PTR_ERR(key)); > + kfree(id); > + > + if (IS_ERR(key)) { > + switch (PTR_ERR(key)) { > + /* Hide some search errors */ > + case -EACCES: > + case -ENOTDIR: > + case -EAGAIN: > + return ERR_PTR(-ENOKEY); > + default: > + return ERR_CAST(key); > + } > + } > + > + pr_devel("<==%s() = 0 [%x]\n", __func__, key_serial(key_ref_to_ptr(key))); > + return key_ref_to_ptr(key); > +} > + > +/* > * Set up the signature parameters in an X.509 certificate. This involves > * digesting the signed data and extracting the signature. > */ > @@ -103,6 +151,36 @@ int x509_check_signature(const struct public_key *pub, > EXPORT_SYMBOL_GPL(x509_check_signature); > > /* > + * Check the new certificate against the ones in the trust keyring. If one of > + * those is the signing key and validates the new certificate, then mark the > + * new certificate as being trusted. > + * > + * Return 0 if the new certificate was successfully validated, 1 if we couldn't > + * find a matching parent certificate in the trusted list and an error if there > + * is a matching certificate but the signature check fails. > + */ > +static int x509_validate_trust(struct x509_certificate *cert, > + struct key *trust_keyring) > +{ > + const struct public_key *pk; > + struct key *key; > + int ret = 1; > + > + if (!trust_keyring) > + return -EOPNOTSUPP; > + > + key = x509_request_asymmetric_key(trust_keyring, > + cert->issuer, strlen(cert->issuer), > + cert->authority, > + strlen(cert->authority)); > + if (!IS_ERR(key)) { > + pk = key->payload.data; > + ret = x509_check_signature(pk, cert); > + } > + return ret; > +} > + > +/* > * Attempt to parse a data blob for a key as an X509 certificate. > */ > static int x509_key_preparse(struct key_preparsed_payload *prep) > @@ -155,9 +233,13 @@ static int x509_key_preparse(struct key_preparsed_payload *prep) > /* Check the signature on the key if it appears to be self-signed */ > if (!cert->authority || > strcmp(cert->fingerprint, cert->authority) == 0) { > - ret = x509_check_signature(cert->pub, cert); > + ret = x509_check_signature(cert->pub, cert); /* self-signed */ > if (ret < 0) > goto error_free_cert; > + } else { > + ret = x509_validate_trust(cert, get_system_trusted_keyring()); > + if (!ret) > + prep->trusted = 1; > } > > /* Propose a description */ > diff --git a/include/keys/system_keyring.h b/include/keys/system_keyring.h > index 8dabc39..72665eb 100644 > --- a/include/keys/system_keyring.h > +++ b/include/keys/system_keyring.h > @@ -17,7 +17,15 @@ > #include > > extern struct key *system_trusted_keyring; > - > +static inline struct key *get_system_trusted_keyring(void) > +{ > + return system_trusted_keyring; > +} > +#else > +static inline struct key *get_system_trusted_keyring(void) > +{ > + return NULL; > +} > #endif > > #endif /* _KEYS_SYSTEM_KEYRING_H */ > -- > 1.8.1.4 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-security-module" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- Thanks, Dmitry -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/