From 09fbc47373826d67531380662b516de2da120545 Mon Sep 17 00:00:00 2001 From: Mimi Zohar Date: Tue, 20 Aug 2013 14:36:27 -0400 Subject: [PATCH] KEYS: verify a certificate is signed by a 'trusted' key 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. Signed-off-by: Mimi Zohar Signed-off-by: David Howells --- crypto/asymmetric_keys/x509_public_key.c | 81 +++++++++++++++++++++++- 1 file changed, 80 insertions(+), 1 deletion(-) diff --git a/crypto/asymmetric_keys/x509_public_key.c b/crypto/asymmetric_keys/x509_public_key.c index c1540e8f454a..87612642f1b1 100644 --- a/crypto/asymmetric_keys/x509_public_key.c +++ b/crypto/asymmetric_keys/x509_public_key.c @@ -18,11 +18,59 @@ #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. @@ -102,6 +150,33 @@ 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; + + 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. */ @@ -155,9 +230,13 @@ 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, system_trusted_keyring); + if (!ret) + prep->trusted = 1; } /* Propose a description */ -- 2.20.1