From: Thiago Jung Bauermann Subject: [PATCH v5 18/18] ima: Write modsig to the measurement list Date: Tue, 17 Oct 2017 22:53:31 -0200 Message-ID: <20171018005331.2688-19-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 Add modsig support for templates which require the contents of the file signature to be included in the measurement list. Suggested-by: Mimi Zohar Signed-off-by: Thiago Jung Bauermann --- security/integrity/ima/ima.h | 8 ++++++++ security/integrity/ima/ima_api.c | 8 +++++++- security/integrity/ima/ima_main.c | 30 +++++++++++++++++++++++++++++- security/integrity/ima/ima_modsig.c | 20 +++++++++++++++++++- security/integrity/ima/ima_template.c | 12 ++++++++++++ security/integrity/ima/ima_template_lib.c | 17 +++++++++++++++-- 6 files changed, 90 insertions(+), 5 deletions(-) diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h index b082138461b3..68f471666151 100644 --- a/security/integrity/ima/ima.h +++ b/security/integrity/ima/ima.h @@ -148,6 +148,7 @@ int ima_init_crypto(void); void ima_putc(struct seq_file *m, void *data, int datalen); void ima_print_digest(struct seq_file *m, u8 *digest, u32 size); struct ima_template_desc *ima_template_desc_current(void); +bool ima_current_template_has_sig(void); int ima_restore_measurement_entry(struct ima_template_entry *entry); int ima_restore_measurement_list(loff_t bufsize, void *buf); int ima_measurements_show(struct seq_file *m, void *v); @@ -264,6 +265,7 @@ int ima_read_modsig(enum ima_hooks func, const void *buf, loff_t buf_len, 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_serialize_data(struct evm_ima_xattr_data **data, int *data_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); @@ -334,6 +336,12 @@ static inline int ima_get_modsig_hash(struct evm_ima_xattr_data *hdr, return -ENOTSUPP; } +static inline int ima_modsig_serialize_data(struct evm_ima_xattr_data **data, + int *data_len) +{ + return -ENOTSUPP; +} + static inline int ima_modsig_verify(const unsigned int keyring_id, struct evm_ima_xattr_data *hdr) { diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c index c6d346e9f708..59a5b044b48b 100644 --- a/security/integrity/ima/ima_api.c +++ b/security/integrity/ima/ima_api.c @@ -284,7 +284,13 @@ void ima_store_measurement(struct integrity_iint_cache *iint, xattr_len, NULL}; int violation = 0; - if (iint->measured_pcrs & (0x1 << pcr)) + /* + * We still need to store the measurement in the case of MODSIG because + * we only have its contents to put in the list at the time of + * appraisal. See comment in process_measurement for more details. + */ + if ((iint->measured_pcrs & (0x1 << pcr)) && + (!xattr_value || xattr_value->type != IMA_MODSIG)) return; result = ima_alloc_init_template(&event_data, &entry); diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c index 6a2d960fbd92..0d3390de7432 100644 --- a/security/integrity/ima/ima_main.c +++ b/security/integrity/ima/ima_main.c @@ -246,7 +246,35 @@ static int process_measurement(struct file *file, char *buf, loff_t size, rc = ima_appraise_measurement(func, iint, file, buf, size, pathname, &xattr_value, &xattr_len, opened); - if (action & IMA_MEASURE) + + /* + * MODSIG has one corner case we need to deal with here: + * + * Suppose the policy has one measure rule for one hook and an appraise + * rule for a different hook. Suppose also that the template requires + * the signature to be stored in the measurement list. + * + * If a file containing a MODSIG is measured by the first hook before + * being appraised by the second one, the corresponding entry in the + * measurement list will not contain the MODSIG because we only fetch it + * for IMA_APPRAISAL. We don't fetch it earlier because if the file has + * both a DIGSIG and a MODSIG it's not possible to know which one will + * be valid without actually doing the appraisal. + * + * Therefore, after appraisal of a MODSIG signature we need to store the + * measurement again if the current template requires storing the + * signature. + * + * With the opposite ordering (the appraise rule triggering before the + * measurement rule) there is the same problem but it's not possible to + * do anything about it because at the time we are appraising the + * signature it's impossible to know whether a measurement will ever + * need to be stored for this file. + */ + if ((action & IMA_MEASURE) || ((iint->flags & IMA_MEASURE) && + xattr_value && + xattr_value->type == IMA_MODSIG && + ima_current_template_has_sig())) ima_store_measurement(iint, file, pathname, xattr_value, xattr_len, pcr); if (action & IMA_AUDIT) diff --git a/security/integrity/ima/ima_modsig.c b/security/integrity/ima/ima_modsig.c index 2786aa97060e..82c3e2693982 100644 --- a/security/integrity/ima/ima_modsig.c +++ b/security/integrity/ima/ima_modsig.c @@ -27,6 +27,10 @@ struct modsig_hdr { const void *data; /* Pointer to data covered by pkcs7_msg. */ size_t data_len; struct pkcs7_message *pkcs7_msg; + int raw_pkcs7_len; + + /* This will be in the measurement list if required by the template. */ + struct evm_ima_xattr_data raw_pkcs7; }; /** @@ -86,7 +90,7 @@ int ima_read_modsig(enum ima_hooks func, const void *buf, loff_t buf_len, sig_len = be32_to_cpu(sig->sig_len); buf_len -= sig_len + sizeof(*sig); - hdr = kmalloc(sizeof(*hdr), GFP_KERNEL); + hdr = kmalloc(sizeof(*hdr) + sig_len, GFP_KERNEL); if (!hdr) return -ENOMEM; @@ -97,6 +101,10 @@ int ima_read_modsig(enum ima_hooks func, const void *buf, loff_t buf_len, return rc; } + memcpy(hdr->raw_pkcs7.data, buf + buf_len, sig_len); + hdr->raw_pkcs7_len = sig_len + 1; + hdr->raw_pkcs7.type = IMA_MODSIG; + hdr->type = IMA_MODSIG; hdr->data = buf; hdr->data_len = buf_len; @@ -129,6 +137,16 @@ int ima_get_modsig_hash(struct evm_ima_xattr_data *hdr, enum hash_algo *algo, return 0; } +int ima_modsig_serialize_data(struct evm_ima_xattr_data **data, int *data_len) +{ + struct modsig_hdr *modsig = (struct modsig_hdr *) *data; + + *data = &modsig->raw_pkcs7; + *data_len = modsig->raw_pkcs7_len; + + return 0; +} + int ima_modsig_verify(const unsigned int keyring_id, struct evm_ima_xattr_data *hdr) { diff --git a/security/integrity/ima/ima_template.c b/security/integrity/ima/ima_template.c index 3cc1d2763fd2..a5bad6996334 100644 --- a/security/integrity/ima/ima_template.c +++ b/security/integrity/ima/ima_template.c @@ -228,6 +228,18 @@ struct ima_template_desc *ima_template_desc_current(void) return ima_template; } +bool ima_current_template_has_sig(void) +{ + struct ima_template_desc *template = ima_template_desc_current(); + int i; + + for (i = 0; i < template->num_fields; i++) + if (!strcmp(template->fields[i]->field_id, "sig")) + return true; + + return false; +} + int __init ima_init_template(void) { struct ima_template_desc *template = ima_template_desc_current(); diff --git a/security/integrity/ima/ima_template_lib.c b/security/integrity/ima/ima_template_lib.c index e8ec783b6a8d..d0e85def0ae9 100644 --- a/security/integrity/ima/ima_template_lib.c +++ b/security/integrity/ima/ima_template_lib.c @@ -379,10 +379,23 @@ int ima_eventsig_init(struct ima_event_data *event_data, struct ima_field_data *field_data) { struct evm_ima_xattr_data *xattr_value = event_data->xattr_value; + int xattr_len = event_data->xattr_len; - if (!xattr_value || xattr_value->type != EVM_IMA_XATTR_DIGSIG) + if (!is_ima_sig(xattr_value)) return 0; - return ima_write_template_field_data(xattr_value, event_data->xattr_len, + /* + * The xattr_value for IMA_MODSIG is a runtime structure containing + * pointers. Get its raw data instead. + */ + if (xattr_value->type == IMA_MODSIG) { + int rc; + + rc = ima_modsig_serialize_data(&xattr_value, &xattr_len); + if (rc) + return rc; + } + + return ima_write_template_field_data(xattr_value, xattr_len, DATA_FMT_HEX, field_data); }