From: Thiago Jung Bauermann Subject: [PATCH v5 16/18] ima: Add functions to read and verify a modsig signature Date: Tue, 17 Oct 2017 22:53:29 -0200 Message-ID: <20171018005331.2688-17-bauerman@linux.vnet.ibm.com> References: <20171018005331.2688-1-bauerman@linux.vnet.ibm.com> Cc: linux-security-module@vger.kernel.org, keyrings@vger.kernel.org, linux-crypto@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, Mimi Zohar , Dmitry Kasatkin , James Morris , "Serge E. Hallyn" , David Howells , David Woodhouse , Jessica Yu , Rusty Russell , Herbert Xu , "David S. Miller" , "AKASHI, Takahiro" , Thiago Jung Bauermann To: linux-integrity@vger.kernel.org Return-path: In-Reply-To: <20171018005331.2688-1-bauerman@linux.vnet.ibm.com> Sender: owner-linux-security-module@vger.kernel.org List-Id: linux-crypto.vger.kernel.org This is the code needed by IMA-appraise to work with modsig signatures. It will be used by the next patch. Signed-off-by: Thiago Jung Bauermann --- security/integrity/ima/Kconfig | 3 + security/integrity/ima/ima.h | 34 +++++++++++ security/integrity/ima/ima_modsig.c | 119 ++++++++++++++++++++++++++++++++++++ security/integrity/integrity.h | 1 + 4 files changed, 157 insertions(+) diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig index 40c6618d00e6..55f734a6124b 100644 --- a/security/integrity/ima/Kconfig +++ b/security/integrity/ima/Kconfig @@ -166,6 +166,9 @@ config IMA_APPRAISE_BOOTPARAM config IMA_APPRAISE_MODSIG bool "Support module-style signatures for appraisal" depends on IMA_APPRAISE + depends on INTEGRITY_ASYMMETRIC_KEYS + select PKCS7_MESSAGE_PARSER + select MODULE_SIG_FORMAT default n help Adds support for signatures appended to files. The format of the diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h index 156ba218e0b6..eb58af06566f 100644 --- a/security/integrity/ima/ima.h +++ b/security/integrity/ima/ima.h @@ -257,6 +257,14 @@ int ima_read_xattr(struct dentry *dentry, #ifdef CONFIG_IMA_APPRAISE_MODSIG bool ima_hook_supports_modsig(enum ima_hooks func); +int ima_read_modsig(enum ima_hooks func, const void *buf, loff_t buf_len, + struct evm_ima_xattr_data **xattr_value, + int *xattr_len); +int ima_get_modsig_hash(struct evm_ima_xattr_data *hdr, enum hash_algo *algo, + void const **hash, u8 *len); +int ima_modsig_verify(const unsigned int keyring_id, + struct evm_ima_xattr_data *hdr); +void ima_free_xattr_data(struct evm_ima_xattr_data *hdr); #endif #else @@ -307,6 +315,32 @@ static inline bool ima_hook_supports_modsig(enum ima_hooks func) { return false; } + +static inline int ima_read_modsig(enum ima_hooks func, const void *buf, + loff_t buf_len, + struct evm_ima_xattr_data **xattr_value, + int *xattr_len) +{ + return -ENOTSUPP; +} + +static inline int ima_get_modsig_hash(struct evm_ima_xattr_data *hdr, + enum hash_algo *algo, void const **hash, + u8 *len) +{ + return -ENOTSUPP; +} + +static inline int ima_modsig_verify(const unsigned int keyring_id, + struct evm_ima_xattr_data *hdr) +{ + return -ENOTSUPP; +} + +static inline void ima_free_xattr_data(struct evm_ima_xattr_data *hdr) +{ + kfree(hdr); +} #endif /* LSM based policy rules require audit */ diff --git a/security/integrity/ima/ima_modsig.c b/security/integrity/ima/ima_modsig.c index 452ce6048a7e..2786aa97060e 100644 --- a/security/integrity/ima/ima_modsig.c +++ b/security/integrity/ima/ima_modsig.c @@ -16,8 +16,19 @@ * GNU General Public License for more details. */ +#include +#include +#include + #include "ima.h" +struct modsig_hdr { + uint8_t type; /* Should be IMA_MODSIG. */ + const void *data; /* Pointer to data covered by pkcs7_msg. */ + size_t data_len; + struct pkcs7_message *pkcs7_msg; +}; + /** * ima_hook_supports_modsig - can the policy allow modsig for this hook? * @@ -37,3 +48,111 @@ bool ima_hook_supports_modsig(enum ima_hooks func) return false; } } + +int ima_read_modsig(enum ima_hooks func, const void *buf, loff_t buf_len, + struct evm_ima_xattr_data **xattr_value, + int *xattr_len) +{ + const size_t marker_len = sizeof(MODULE_SIG_STRING) - 1; + const struct module_signature *sig; + struct modsig_hdr *hdr; + size_t sig_len; + const void *p; + int rc; + + /* + * Not supposed to happen. Hooks that support modsig are + * whitelisted when parsing the policy using + * ima_hooks_supports_modsig. + */ + if (!buf || !buf_len) { + WARN_ONCE(true, "%s doesn't support modsig\n", + func_tokens[func]); + return -ENOENT; + } else if (buf_len <= marker_len + sizeof(*sig)) + return -ENOENT; + + p = buf + buf_len - marker_len; + if (memcmp(p, MODULE_SIG_STRING, marker_len)) + return -ENOENT; + + buf_len -= marker_len; + sig = (const struct module_signature *) (p - sizeof(*sig)); + + rc = validate_module_sig(sig, buf_len); + if (rc) + return rc; + + sig_len = be32_to_cpu(sig->sig_len); + buf_len -= sig_len + sizeof(*sig); + + hdr = kmalloc(sizeof(*hdr), GFP_KERNEL); + if (!hdr) + return -ENOMEM; + + hdr->pkcs7_msg = pkcs7_parse_message(buf + buf_len, sig_len); + if (IS_ERR(hdr->pkcs7_msg)) { + rc = PTR_ERR(hdr->pkcs7_msg); + kfree(hdr); + return rc; + } + + hdr->type = IMA_MODSIG; + hdr->data = buf; + hdr->data_len = buf_len; + + *xattr_value = (typeof(*xattr_value)) hdr; + *xattr_len = sizeof(*hdr); + + return 0; +} + +int ima_get_modsig_hash(struct evm_ima_xattr_data *hdr, enum hash_algo *algo, + void const **hash, u8 *len) +{ + const struct public_key_signature *pks; + struct modsig_hdr *modsig = (typeof(modsig)) hdr; + int i; + + pks = pkcs7_get_message_sig(modsig->pkcs7_msg); + if (!pks) + return -EBADMSG; + + for (i = 0; i < HASH_ALGO__LAST; i++) + if (!strcmp(hash_algo_name[i], pks->hash_algo)) + break; + + *algo = i; + *hash = pks->digest; + *len = pks->digest_size; + + return 0; +} + +int ima_modsig_verify(const unsigned int keyring_id, + struct evm_ima_xattr_data *hdr) +{ + struct modsig_hdr *modsig = (struct modsig_hdr *) hdr; + struct key *trusted_keys = integrity_keyring_from_id(keyring_id); + + if (IS_ERR(trusted_keys)) + return -EINVAL; + + return verify_pkcs7_message_sig(modsig->data, modsig->data_len, + modsig->pkcs7_msg, trusted_keys, + VERIFYING_MODULE_SIGNATURE, NULL, NULL); +} + +void ima_free_xattr_data(struct evm_ima_xattr_data *hdr) +{ + if (!hdr) + return; + + if (hdr->type == IMA_MODSIG) { + struct modsig_hdr *modsig = (struct modsig_hdr *) hdr; + + pkcs7_free_message(modsig->pkcs7_msg); + } + + kfree(hdr); +} diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h index da709558ec8b..ce2bd9d5afa5 100644 --- a/security/integrity/integrity.h +++ b/security/integrity/integrity.h @@ -59,6 +59,7 @@ enum evm_ima_xattr_type { EVM_XATTR_HMAC, EVM_IMA_XATTR_DIGSIG, IMA_XATTR_DIGEST_NG, + IMA_MODSIG, IMA_XATTR_LAST };