x86/sev: Extend the config-fs attestation support for an SVSM

When an SVSM is present, the guest can also request attestation reports
from it. These SVSM attestation reports can be used to attest the SVSM
and any services running within the SVSM.

Extend the config-fs attestation support to provide such. This involves
creating four new config-fs attributes:

  - 'service-provider' (input)
    This attribute is used to determine whether the attestation request
    should be sent to the specified service provider or to the SEV
    firmware. The SVSM service provider is represented by the value
    'svsm'.

  - 'service_guid' (input)
    Used for requesting the attestation of a single service within the
    service provider. A null GUID implies that the SVSM_ATTEST_SERVICES
    call should be used to request the attestation report. A non-null
    GUID implies that the SVSM_ATTEST_SINGLE_SERVICE call should be used.

  - 'service_manifest_version' (input)
    Used with the SVSM_ATTEST_SINGLE_SERVICE call, the service version
    represents a specific service manifest version be used for the
    attestation report.

  - 'manifestblob' (output)
    Used to return the service manifest associated with the attestation
    report.

Only display these new attributes when running under an SVSM.

  [ bp: Massage.
   - s/svsm_attestation_call/svsm_attest_call/g ]

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/965015dce3c76bb8724839d50c5dea4e4b5d598f.1717600736.git.thomas.lendacky@amd.com

2 files changed, 270 insertions, 2 deletions

diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
index 0c70a38c8cc0..37522886ae95 100644
--- a/drivers/virt/coco/sev-guest/sev-guest.c
+++ b/drivers/virt/coco/sev-guest/sev-guest.c
@@ -39,6 +39,8 @@
 #define SNP_REQ_MAX_RETRY_DURATION	(60*HZ)
 #define SNP_REQ_RETRY_DELAY		(2*HZ)
 
+#define SVSM_MAX_RETRIES		3
+
 struct snp_guest_crypto {
 	struct crypto_aead *tfm;
 	u8 *iv, *authtag;
@@ -791,6 +793,143 @@ struct snp_msg_cert_entry {
 	u32 length;
 };
 
+static int sev_svsm_report_new(struct tsm_report *report, void *data)
+{
+	unsigned int rep_len, man_len, certs_len;
+	struct tsm_desc *desc = &report->desc;
+	struct svsm_attest_call ac = {};
+	unsigned int retry_count;
+	void *rep, *man, *certs;
+	struct svsm_call call;
+	unsigned int size;
+	bool try_again;
+	void *buffer;
+	u64 call_id;
+	int ret;
+
+	/*
+	 * Allocate pages for the request:
+	 * - Report blob (4K)
+	 * - Manifest blob (4K)
+	 * - Certificate blob (16K)
+	 *
+	 * Above addresses must be 4K aligned
+	 */
+	rep_len = SZ_4K;
+	man_len = SZ_4K;
+	certs_len = SEV_FW_BLOB_MAX_SIZE;
+
+	guard(mutex)(&snp_cmd_mutex);
+
+	if (guid_is_null(&desc->service_guid)) {
+		call_id = SVSM_ATTEST_CALL(SVSM_ATTEST_SERVICES);
+	} else {
+		export_guid(ac.service_guid, &desc->service_guid);
+		ac.service_manifest_ver = desc->service_manifest_version;
+
+		call_id = SVSM_ATTEST_CALL(SVSM_ATTEST_SINGLE_SERVICE);
+	}
+
+	retry_count = 0;
+
+retry:
+	memset(&call, 0, sizeof(call));
+
+	size = rep_len + man_len + certs_len;
+	buffer = alloc_pages_exact(size, __GFP_ZERO);
+	if (!buffer)
+		return -ENOMEM;
+
+	rep = buffer;
+	ac.report_buf.pa = __pa(rep);
+	ac.report_buf.len = rep_len;
+
+	man = rep + rep_len;
+	ac.manifest_buf.pa = __pa(man);
+	ac.manifest_buf.len = man_len;
+
+	certs = man + man_len;
+	ac.certificates_buf.pa = __pa(certs);
+	ac.certificates_buf.len = certs_len;
+
+	ac.nonce.pa = __pa(desc->inblob);
+	ac.nonce.len = desc->inblob_len;
+
+	ret = snp_issue_svsm_attest_req(call_id, &call, &ac);
+	if (ret) {
+		free_pages_exact(buffer, size);
+
+		switch (call.rax_out) {
+		case SVSM_ERR_INVALID_PARAMETER:
+			try_again = false;
+
+			if (ac.report_buf.len > rep_len) {
+				rep_len = PAGE_ALIGN(ac.report_buf.len);
+				try_again = true;
+			}
+
+			if (ac.manifest_buf.len > man_len) {
+				man_len = PAGE_ALIGN(ac.manifest_buf.len);
+				try_again = true;
+			}
+
+			if (ac.certificates_buf.len > certs_len) {
+				certs_len = PAGE_ALIGN(ac.certificates_buf.len);
+				try_again = true;
+			}
+
+			/* If one of the buffers wasn't large enough, retry the request */
+			if (try_again && retry_count < SVSM_MAX_RETRIES) {
+				retry_count++;
+				goto retry;
+			}
+
+			return -EINVAL;
+		default:
+			pr_err_ratelimited("SVSM attestation request failed (%d / 0x%llx)\n",
+					   ret, call.rax_out);
+			return -EINVAL;
+		}
+	}
+
+	/*
+	 * Allocate all the blob memory buffers at once so that the cleanup is
+	 * done for errors that occur after the first allocation (i.e. before
+	 * using no_free_ptr()).
+	 */
+	rep_len = ac.report_buf.len;
+	void *rbuf __free(kvfree) = kvzalloc(rep_len, GFP_KERNEL);
+
+	man_len = ac.manifest_buf.len;
+	void *mbuf __free(kvfree) = kvzalloc(man_len, GFP_KERNEL);
+
+	certs_len = ac.certificates_buf.len;
+	void *cbuf __free(kvfree) = certs_len ? kvzalloc(certs_len, GFP_KERNEL) : NULL;
+
+	if (!rbuf || !mbuf || (certs_len && !cbuf)) {
+		free_pages_exact(buffer, size);
+		return -ENOMEM;
+	}
+
+	memcpy(rbuf, rep, rep_len);
+	report->outblob = no_free_ptr(rbuf);
+	report->outblob_len = rep_len;
+
+	memcpy(mbuf, man, man_len);
+	report->manifestblob = no_free_ptr(mbuf);
+	report->manifestblob_len = man_len;
+
+	if (certs_len) {
+		memcpy(cbuf, certs, certs_len);
+		report->auxblob = no_free_ptr(cbuf);
+		report->auxblob_len = certs_len;
+	}
+
+	free_pages_exact(buffer, size);
+
+	return 0;
+}
+
 static int sev_report_new(struct tsm_report *report, void *data)
 {
 	struct snp_msg_cert_entry *cert_table;
@@ -805,6 +944,13 @@ static int sev_report_new(struct tsm_report *report, void *data)
 	if (desc->inblob_len != SNP_REPORT_USER_DATA_SIZE)
 		return -EINVAL;
 
+	if (desc->service_provider) {
+		if (strcmp(desc->service_provider, "svsm"))
+			return -EINVAL;
+
+		return sev_svsm_report_new(report, data);
+	}
+
 	void *buf __free(kvfree) = kvzalloc(size, GFP_KERNEL);
 	if (!buf)
 		return -ENOMEM;
@@ -893,9 +1039,42 @@ static int sev_report_new(struct tsm_report *report, void *data)
 	return 0;
 }
 
+static bool sev_report_attr_visible(int n)
+{
+	switch (n) {
+	case TSM_REPORT_GENERATION:
+	case TSM_REPORT_PROVIDER:
+	case TSM_REPORT_PRIVLEVEL:
+	case TSM_REPORT_PRIVLEVEL_FLOOR:
+		return true;
+	case TSM_REPORT_SERVICE_PROVIDER:
+	case TSM_REPORT_SERVICE_GUID:
+	case TSM_REPORT_SERVICE_MANIFEST_VER:
+		return snp_vmpl;
+	}
+
+	return false;
+}
+
+static bool sev_report_bin_attr_visible(int n)
+{
+	switch (n) {
+	case TSM_REPORT_INBLOB:
+	case TSM_REPORT_OUTBLOB:
+	case TSM_REPORT_AUXBLOB:
+		return true;
+	case TSM_REPORT_MANIFESTBLOB:
+		return snp_vmpl;
+	}
+
+	return false;
+}
+
 static struct tsm_ops sev_tsm_ops = {
 	.name = KBUILD_MODNAME,
 	.report_new = sev_report_new,
+	.report_attr_visible = sev_report_attr_visible,
+	.report_bin_attr_visible = sev_report_bin_attr_visible,
 };
 
 static void unregister_sev_tsm(void *data)
diff --git a/drivers/virt/coco/tsm.c b/drivers/virt/coco/tsm.c
index 7db534b63c9f..9432d4e303f1 100644
--- a/drivers/virt/coco/tsm.c
+++ b/drivers/virt/coco/tsm.c
@@ -34,7 +34,7 @@ static DECLARE_RWSEM(tsm_rwsem);
  * The attestation report format is TSM provider specific, when / if a standard
  * materializes that can be published instead of the vendor layout. Until then
  * the 'provider' attribute indicates the format of 'outblob', and optionally
- * 'auxblob'.
+ * 'auxblob' and 'manifestblob'.
  */
 
 struct tsm_report_state {
@@ -47,6 +47,7 @@ struct tsm_report_state {
 enum tsm_data_select {
 	TSM_REPORT,
 	TSM_CERTS,
+	TSM_MANIFEST,
 };
 
 static struct tsm_report *to_tsm_report(struct config_item *cfg)
@@ -118,6 +119,74 @@ static ssize_t tsm_report_privlevel_floor_show(struct config_item *cfg,
 }
 CONFIGFS_ATTR_RO(tsm_report_, privlevel_floor);
 
+static ssize_t tsm_report_service_provider_store(struct config_item *cfg,
+						 const char *buf, size_t len)
+{
+	struct tsm_report *report = to_tsm_report(cfg);
+	size_t sp_len;
+	char *sp;
+	int rc;
+
+	guard(rwsem_write)(&tsm_rwsem);
+	rc = try_advance_write_generation(report);
+	if (rc)
+		return rc;
+
+	sp_len = (buf[len - 1] != '\n') ? len : len - 1;
+
+	sp = kstrndup(buf, sp_len, GFP_KERNEL);
+	if (!sp)
+		return -ENOMEM;
+	kfree(report->desc.service_provider);
+
+	report->desc.service_provider = sp;
+
+	return len;
+}
+CONFIGFS_ATTR_WO(tsm_report_, service_provider);
+
+static ssize_t tsm_report_service_guid_store(struct config_item *cfg,
+					     const char *buf, size_t len)
+{
+	struct tsm_report *report = to_tsm_report(cfg);
+	int rc;
+
+	guard(rwsem_write)(&tsm_rwsem);
+	rc = try_advance_write_generation(report);
+	if (rc)
+		return rc;
+
+	report->desc.service_guid = guid_null;
+
+	rc = guid_parse(buf, &report->desc.service_guid);
+	if (rc)
+		return rc;
+
+	return len;
+}
+CONFIGFS_ATTR_WO(tsm_report_, service_guid);
+
+static ssize_t tsm_report_service_manifest_version_store(struct config_item *cfg,
+							 const char *buf, size_t len)
+{
+	struct tsm_report *report = to_tsm_report(cfg);
+	unsigned int val;
+	int rc;
+
+	rc = kstrtouint(buf, 0, &val);
+	if (rc)
+		return rc;
+
+	guard(rwsem_write)(&tsm_rwsem);
+	rc = try_advance_write_generation(report);
+	if (rc)
+		return rc;
+	report->desc.service_manifest_version = val;
+
+	return len;
+}
+CONFIGFS_ATTR_WO(tsm_report_, service_manifest_version);
+
 static ssize_t tsm_report_inblob_write(struct config_item *cfg,
 				       const void *buf, size_t count)
 {
@@ -162,6 +231,9 @@ static ssize_t __read_report(struct tsm_report *report, void *buf, size_t count,
 	if (select == TSM_REPORT) {
 		out = report->outblob;
 		len = report->outblob_len;
+	} else if (select == TSM_MANIFEST) {
+		out = report->manifestblob;
+		len = report->manifestblob_len;
 	} else {
 		out = report->auxblob;
 		len = report->auxblob_len;
@@ -187,7 +259,7 @@ static ssize_t read_cached_report(struct tsm_report *report, void *buf,
 
 	/*
 	 * A given TSM backend always fills in ->outblob regardless of
-	 * whether the report includes an auxblob or not.
+	 * whether the report includes an auxblob/manifestblob or not.
 	 */
 	if (!report->outblob ||
 	    state->read_generation != state->write_generation)
@@ -223,8 +295,10 @@ static ssize_t tsm_report_read(struct tsm_report *report, void *buf,
 
 	kvfree(report->outblob);
 	kvfree(report->auxblob);
+	kvfree(report->manifestblob);
 	report->outblob = NULL;
 	report->auxblob = NULL;
+	report->manifestblob = NULL;
 	rc = ops->report_new(report, provider.data);
 	if (rc < 0)
 		return rc;
@@ -251,11 +325,23 @@ static ssize_t tsm_report_auxblob_read(struct config_item *cfg, void *buf,
 }
 CONFIGFS_BIN_ATTR_RO(tsm_report_, auxblob, NULL, TSM_OUTBLOB_MAX);
 
+static ssize_t tsm_report_manifestblob_read(struct config_item *cfg, void *buf,
+					    size_t count)
+{
+	struct tsm_report *report = to_tsm_report(cfg);
+
+	return tsm_report_read(report, buf, count, TSM_MANIFEST);
+}
+CONFIGFS_BIN_ATTR_RO(tsm_report_, manifestblob, NULL, TSM_OUTBLOB_MAX);
+
 static struct configfs_attribute *tsm_report_attrs[] = {
 	[TSM_REPORT_GENERATION] = &tsm_report_attr_generation,
 	[TSM_REPORT_PROVIDER] = &tsm_report_attr_provider,
 	[TSM_REPORT_PRIVLEVEL] = &tsm_report_attr_privlevel,
 	[TSM_REPORT_PRIVLEVEL_FLOOR] = &tsm_report_attr_privlevel_floor,
+	[TSM_REPORT_SERVICE_PROVIDER] = &tsm_report_attr_service_provider,
+	[TSM_REPORT_SERVICE_GUID] = &tsm_report_attr_service_guid,
+	[TSM_REPORT_SERVICE_MANIFEST_VER] = &tsm_report_attr_service_manifest_version,
 	NULL,
 };
 
@@ -263,6 +349,7 @@ static struct configfs_bin_attribute *tsm_report_bin_attrs[] = {
 	[TSM_REPORT_INBLOB] = &tsm_report_attr_inblob,
 	[TSM_REPORT_OUTBLOB] = &tsm_report_attr_outblob,
 	[TSM_REPORT_AUXBLOB] = &tsm_report_attr_auxblob,
+	[TSM_REPORT_MANIFESTBLOB] = &tsm_report_attr_manifestblob,
 	NULL,
 };
 
@@ -271,8 +358,10 @@ static void tsm_report_item_release(struct config_item *cfg)
 	struct tsm_report *report = to_tsm_report(cfg);
 	struct tsm_report_state *state = to_state(report);
 
+	kvfree(report->manifestblob);
 	kvfree(report->auxblob);
 	kvfree(report->outblob);
+	kfree(report->desc.service_provider);
 	kfree(state);
 }