TPM: integrity interface

This patch adds internal kernel support for:
 - reading/extending a pcr value
 - looking up the tpm_chip for a given chip number

Signed-off-by: Rajiv Andrade <srajiv@linux.vnet.ibm.com>
Signed-off-by: Mimi Zohar <zohar@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 110 insertions, 19 deletions

diff --git a/drivers/char/tpm/tpm.c b/drivers/char/tpm/tpm.c
index 9b9eb761cba9..62a5682578ca 100644
--- a/drivers/char/tpm/tpm.c
+++ b/drivers/char/tpm/tpm.c
@@ -661,28 +661,125 @@ ssize_t tpm_show_temp_deactivated(struct device * dev,
 }
 EXPORT_SYMBOL_GPL(tpm_show_temp_deactivated);
 
-static const u8 pcrread[] = {
-        0, 193,                 /* TPM_TAG_RQU_COMMAND */
-        0, 0, 0, 14,            /* length */
-        0, 0, 0, 21,            /* TPM_ORD_PcrRead */
-        0, 0, 0, 0              /* PCR index */
+/*
+ * tpm_chip_find_get - return tpm_chip for given chip number
+ */
+static struct tpm_chip *tpm_chip_find_get(int chip_num)
+{
+        struct tpm_chip *pos;
+
+        rcu_read_lock();
+        list_for_each_entry_rcu(pos, &tpm_chip_list, list) {
+                if (chip_num != TPM_ANY_NUM && chip_num != pos->dev_num)
+                        continue;
+
+                if (try_module_get(pos->dev->driver->owner))
+                        break;
+        }
+        rcu_read_unlock();
+        return pos;
+}
+
+#define TPM_ORDINAL_PCRREAD cpu_to_be32(21)
+#define READ_PCR_RESULT_SIZE 30
+static struct tpm_input_header pcrread_header = {
+        .tag = TPM_TAG_RQU_COMMAND,
+        .length = cpu_to_be32(14),
+        .ordinal = TPM_ORDINAL_PCRREAD
+};
+
+int __tpm_pcr_read(struct tpm_chip *chip, int pcr_idx, u8 *res_buf)
+{
+        int rc;
+        struct tpm_cmd_t cmd;
+
+        cmd.header.in = pcrread_header;
+        cmd.params.pcrread_in.pcr_idx = cpu_to_be32(pcr_idx);
+        BUILD_BUG_ON(cmd.header.in.length > READ_PCR_RESULT_SIZE);
+        rc = transmit_cmd(chip, &cmd, cmd.header.in.length,
+                          "attempting to read a pcr value");
+
+        if (rc == 0)
+                memcpy(res_buf, cmd.params.pcrread_out.pcr_result,
+                       TPM_DIGEST_SIZE);
+        return rc;
+}
+
+/**
+ * tpm_pcr_read - read a pcr value
+ * @chip_num:   tpm idx # or ANY
+ * @pcr_idx:    pcr idx to retrieve
+ * @res_buf:    TPM_PCR value
+ *              size of res_buf is 20 bytes (or NULL if you don't care)
+ *
+ * The TPM driver should be built-in, but for whatever reason it
+ * isn't, protect against the chip disappearing, by incrementing
+ * the module usage count.
+ */
+int tpm_pcr_read(u32 chip_num, int pcr_idx, u8 *res_buf)
+{
+        struct tpm_chip *chip;
+        int rc;
+
+        chip = tpm_chip_find_get(chip_num);
+        if (chip == NULL)
+                return -ENODEV;
+        rc = __tpm_pcr_read(chip, pcr_idx, res_buf);
+        module_put(chip->dev->driver->owner);
+        return rc;
+}
+EXPORT_SYMBOL_GPL(tpm_pcr_read);
+
+/**
+ * tpm_pcr_extend - extend pcr value with hash
+ * @chip_num:   tpm idx # or AN&
+ * @pcr_idx:    pcr idx to extend
+ * @hash:       hash value used to extend pcr value
+ *
+ * The TPM driver should be built-in, but for whatever reason it
+ * isn't, protect against the chip disappearing, by incrementing
+ * the module usage count.
+ */
+#define TPM_ORD_PCR_EXTEND cpu_to_be32(20)
+#define EXTEND_PCR_SIZE 34
+static struct tpm_input_header pcrextend_header = {
+        .tag = TPM_TAG_RQU_COMMAND,
+        .length = cpu_to_be32(34),
+        .ordinal = TPM_ORD_PCR_EXTEND
 };
 
+int tpm_pcr_extend(u32 chip_num, int pcr_idx, const u8 *hash)
+{
+        struct tpm_cmd_t cmd;
+        int rc;
+        struct tpm_chip *chip;
+
+        chip = tpm_chip_find_get(chip_num);
+        if (chip == NULL)
+                return -ENODEV;
+
+        cmd.header.in = pcrextend_header;
+        BUILD_BUG_ON(be32_to_cpu(cmd.header.in.length) > EXTEND_PCR_SIZE);
+        cmd.params.pcrextend_in.pcr_idx = cpu_to_be32(pcr_idx);
+        memcpy(cmd.params.pcrextend_in.hash, hash, TPM_DIGEST_SIZE);
+        rc = transmit_cmd(chip, &cmd, cmd.header.in.length,
+                          "attempting extend a PCR value");
+
+        module_put(chip->dev->driver->owner);
+        return rc;
+}
+EXPORT_SYMBOL_GPL(tpm_pcr_extend);
+
 ssize_t tpm_show_pcrs(struct device *dev, struct device_attribute *attr,
                       char *buf)
 {
         cap_t cap;
-        u8 *data;
+        u8 digest[TPM_DIGEST_SIZE];
         ssize_t rc;
         int i, j, num_pcrs;
-        __be32 index;
         char *str = buf;
         struct tpm_chip *chip = dev_get_drvdata(dev);
 
-        data = kzalloc(TPM_INTERNAL_RESULT_SIZE, GFP_KERNEL);
-        if (!data)
-                return -ENOMEM;
-
         rc = tpm_getcap(dev, TPM_CAP_PROP_PCR, &cap,
                         "attempting to determine the number of PCRS");
         if (rc)
@@ -690,20 +787,14 @@ ssize_t tpm_show_pcrs(struct device *dev, struct device_attribute *attr,
 
         num_pcrs = be32_to_cpu(cap.num_pcrs);
         for (i = 0; i < num_pcrs; i++) {
-                memcpy(data, pcrread, sizeof(pcrread));
-                index = cpu_to_be32(i);
-                memcpy(data + 10, &index, 4);
-                rc = transmit_cmd(chip, (struct tpm_cmd_t *)data,
-                                  TPM_INTERNAL_RESULT_SIZE,
-                                  "attempting to read a PCR");
+                rc = __tpm_pcr_read(chip, i, digest);
                 if (rc)
                         break;
                 str += sprintf(str, "PCR-%02d: ", i);
                 for (j = 0; j < TPM_DIGEST_SIZE; j++)
-                        str += sprintf(str, "%02X ", *(data + 10 + j));
+                        str += sprintf(str, "%02X ", digest[j]);
                 str += sprintf(str, "\n");
         }
-        kfree(data);
         return str - buf;
 }
 EXPORT_SYMBOL_GPL(tpm_show_pcrs);