tpm: Move tpm_get_random api into the TPM device driver

Move the tpm_get_random api from the trusted keys code into the TPM
device driver itself so that other callers can make use of it. Also,
change the api slightly so that the number of bytes read is returned in
the call, since the TPM command can potentially return fewer bytes than
requested.

Acked-by: David Safford <safford@linux.vnet.ibm.com>
Reviewed-by: H. Peter Anvin <hpa@linux.intel.com>
Signed-off-by: Kent Yoder <key@linux.vnet.ibm.com>

diff --git a/drivers/char/tpm/tpm.c b/drivers/char/tpm/tpm.c
index 677c6e26593ffc94ae23f166e7fc049c1d69218e..36e43e50dcef7cdc7702908edba37861ad82f3ab 100644 (file)
--- a/drivers/char/tpm/tpm.c
+++ b/drivers/char/tpm/tpm.c
@@ -32,12 +32,6 @@
 #include "tpm.h"
 #include "tpm_eventlog.h"
 
-enum tpm_const {
-       TPM_MINOR = 224,        /* officially assigned */
-       TPM_BUFSIZE = 4096,
-       TPM_NUM_DEVICES = 256,
-};
-
 enum tpm_duration {
        TPM_SHORT = 0,
        TPM_MEDIUM = 1,
@@ -483,6 +477,7 @@ static ssize_t transmit_cmd(struct tpm_chip *chip, struct tpm_cmd_t *cmd,
 #define TPM_INTERNAL_RESULT_SIZE 200
 #define TPM_TAG_RQU_COMMAND cpu_to_be16(193)
 #define TPM_ORD_GET_CAP cpu_to_be32(101)
+#define TPM_ORD_GET_RANDOM cpu_to_be32(70)
 
 static const struct tpm_input_header tpm_getcap_header = {
        .tag = TPM_TAG_RQU_COMMAND,
@@ -1327,6 +1322,58 @@ int tpm_pm_resume(struct device *dev)
 }
 EXPORT_SYMBOL_GPL(tpm_pm_resume);
 
+#define TPM_GETRANDOM_RESULT_SIZE      18
+static struct tpm_input_header tpm_getrandom_header = {
+       .tag = TPM_TAG_RQU_COMMAND,
+       .length = cpu_to_be32(14),
+       .ordinal = TPM_ORD_GET_RANDOM
+};
+
+/**
+ * tpm_get_random() - Get random bytes from the tpm's RNG
+ * @chip_num: A specific chip number for the request or TPM_ANY_NUM
+ * @out: destination buffer for the random bytes
+ * @max: the max number of bytes to write to @out
+ *
+ * Returns < 0 on error and the number of bytes read on success
+ */
+int tpm_get_random(u32 chip_num, u8 *out, size_t max)
+{
+       struct tpm_chip *chip;
+       struct tpm_cmd_t tpm_cmd;
+       u32 recd, num_bytes = min_t(u32, max, TPM_MAX_RNG_DATA);
+       int err, total = 0, retries = 5;
+       u8 *dest = out;
+
+       chip = tpm_chip_find_get(chip_num);
+       if (chip == NULL)
+               return -ENODEV;
+
+       if (!out || !num_bytes || max > TPM_MAX_RNG_DATA)
+               return -EINVAL;
+
+       do {
+               tpm_cmd.header.in = tpm_getrandom_header;
+               tpm_cmd.params.getrandom_in.num_bytes = cpu_to_be32(num_bytes);
+
+               err = transmit_cmd(chip, &tpm_cmd,
+                                  TPM_GETRANDOM_RESULT_SIZE + num_bytes,
+                                  "attempting get random");
+               if (err)
+                       break;
+
+               recd = be32_to_cpu(tpm_cmd.params.getrandom_out.rng_data_len);
+               memcpy(dest, tpm_cmd.params.getrandom_out.rng_data, recd);
+
+               dest += recd;
+               total += recd;
+               num_bytes -= recd;
+       } while (retries-- && total < max);
+
+       return total ? total : -EIO;
+}
+EXPORT_SYMBOL_GPL(tpm_get_random);
+
 /* In case vendor provided release function, call it too.*/
 
 void tpm_dev_vendor_release(struct tpm_chip *chip)

diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index 917f727e674059b7e7daa2fc36a9920a306deef6..645136eea890e70da2541af1f3fa07378782cdf1 100644 (file)
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -28,6 +28,12 @@
 #include <linux/io.h>
 #include <linux/tpm.h>
 
+enum tpm_const {
+       TPM_MINOR = 224,        /* officially assigned */
+       TPM_BUFSIZE = 4096,
+       TPM_NUM_DEVICES = 256,
+};
+
 enum tpm_timeout {
        TPM_TIMEOUT = 5,        /* msecs */
 };
@@ -269,6 +275,21 @@ struct tpm_pcrextend_in {
        u8      hash[TPM_DIGEST_SIZE];
 }__attribute__((packed));
 
+/* 128 bytes is an arbitrary cap. This could be as large as TPM_BUFSIZE - 18
+ * bytes, but 128 is still a relatively large number of random bytes and
+ * anything much bigger causes users of struct tpm_cmd_t to start getting
+ * compiler warnings about stack frame size. */
+#define TPM_MAX_RNG_DATA       128
+
+struct tpm_getrandom_out {
+       __be32 rng_data_len;
+       u8     rng_data[TPM_MAX_RNG_DATA];
+}__attribute__((packed));
+
+struct tpm_getrandom_in {
+       __be32 num_bytes;
+}__attribute__((packed));
+
 typedef union {
        struct  tpm_getcap_params_out getcap_out;
        struct  tpm_readpubek_params_out readpubek_out;
@@ -277,6 +298,8 @@ typedef union {
        struct  tpm_pcrread_in  pcrread_in;
        struct  tpm_pcrread_out pcrread_out;
        struct  tpm_pcrextend_in pcrextend_in;
+       struct  tpm_getrandom_in getrandom_in;
+       struct  tpm_getrandom_out getrandom_out;
 } tpm_cmd_params;
 
 struct tpm_cmd_t {

diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index fdc718abf83becac29f7dd3a01cabd8b6ad7f068..fcb627ff8d3eb71ad49ced6763a0ff061b83f62e 100644 (file)
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -32,6 +32,7 @@
 extern int tpm_pcr_read(u32 chip_num, int pcr_idx, u8 *res_buf);
 extern int tpm_pcr_extend(u32 chip_num, int pcr_idx, const u8 *hash);
 extern int tpm_send(u32 chip_num, void *cmd, size_t buflen);
+extern int tpm_get_random(u32 chip_num, u8 *data, size_t max);
 #else
 static inline int tpm_pcr_read(u32 chip_num, int pcr_idx, u8 *res_buf) {
        return -ENODEV;
@@ -42,5 +43,8 @@ static inline int tpm_pcr_extend(u32 chip_num, int pcr_idx, const u8 *hash) {
 static inline int tpm_send(u32 chip_num, void *cmd, size_t buflen) {
        return -ENODEV;
 }
+static inline int tpm_get_random(u32 chip_num, u8 *data, size_t max) {
+       return -ENODEV;
+}
 #endif
 #endif

diff --git a/security/keys/trusted.c b/security/keys/trusted.c
index 2d5d041f2049f323e5072c701f068d695f3f2c6c..3f163d0489ad2e8705a8f57c4751038b9d7d6f36 100644 (file)
--- a/security/keys/trusted.c
+++ b/security/keys/trusted.c
@@ -368,38 +368,6 @@ static int trusted_tpm_send(const u32 chip_num, unsigned char *cmd,
        return rc;
 }
 
-/*
- * get a random value from TPM
- */
-static int tpm_get_random(struct tpm_buf *tb, unsigned char *buf, uint32_t len)
-{
-       int ret;
-
-       INIT_BUF(tb);
-       store16(tb, TPM_TAG_RQU_COMMAND);
-       store32(tb, TPM_GETRANDOM_SIZE);
-       store32(tb, TPM_ORD_GETRANDOM);
-       store32(tb, len);
-       ret = trusted_tpm_send(TPM_ANY_NUM, tb->data, sizeof tb->data);
-       if (!ret)
-               memcpy(buf, tb->data + TPM_GETRANDOM_SIZE, len);
-       return ret;
-}
-
-static int my_get_random(unsigned char *buf, int len)
-{
-       struct tpm_buf *tb;
-       int ret;
-
-       tb = kmalloc(sizeof *tb, GFP_KERNEL);
-       if (!tb)
-               return -ENOMEM;
-       ret = tpm_get_random(tb, buf, len);
-
-       kfree(tb);
-       return ret;
-}
-
 /*
  * Lock a trusted key, by extending a selected PCR.
  *
@@ -413,8 +381,8 @@ static int pcrlock(const int pcrnum)
 
        if (!capable(CAP_SYS_ADMIN))
                return -EPERM;
-       ret = my_get_random(hash, SHA1_DIGEST_SIZE);
-       if (ret < 0)
+       ret = tpm_get_random(TPM_ANY_NUM, hash, SHA1_DIGEST_SIZE);
+       if (ret != SHA1_DIGEST_SIZE)
                return ret;
        return tpm_pcr_extend(TPM_ANY_NUM, pcrnum, hash) ? -EINVAL : 0;
 }
@@ -429,8 +397,8 @@ static int osap(struct tpm_buf *tb, struct osapsess *s,
        unsigned char ononce[TPM_NONCE_SIZE];
        int ret;
 
-       ret = tpm_get_random(tb, ononce, TPM_NONCE_SIZE);
-       if (ret < 0)
+       ret = tpm_get_random(TPM_ANY_NUM, ononce, TPM_NONCE_SIZE);
+       if (ret != TPM_NONCE_SIZE)
                return ret;
 
        INIT_BUF(tb);
@@ -524,8 +492,8 @@ static int tpm_seal(struct tpm_buf *tb, uint16_t keytype,
        if (ret < 0)
                goto out;
 
-       ret = tpm_get_random(tb, td->nonceodd, TPM_NONCE_SIZE);
-       if (ret < 0)
+       ret = tpm_get_random(TPM_ANY_NUM, td->nonceodd, TPM_NONCE_SIZE);
+       if (ret != TPM_NONCE_SIZE)
                goto out;
        ordinal = htonl(TPM_ORD_SEAL);
        datsize = htonl(datalen);
@@ -634,8 +602,8 @@ static int tpm_unseal(struct tpm_buf *tb,
 
        ordinal = htonl(TPM_ORD_UNSEAL);
        keyhndl = htonl(SRKHANDLE);
-       ret = tpm_get_random(tb, nonceodd, TPM_NONCE_SIZE);
-       if (ret < 0) {
+       ret = tpm_get_random(TPM_ANY_NUM, nonceodd, TPM_NONCE_SIZE);
+       if (ret != TPM_NONCE_SIZE) {
                pr_info("trusted_key: tpm_get_random failed (%d)\n", ret);
                return ret;
        }
@@ -935,6 +903,7 @@ static int trusted_instantiate(struct key *key, const void *data,
        char *datablob;
        int ret = 0;
        int key_cmd;
+       size_t key_len;
 
        if (datalen <= 0 || datalen > 32767 || !data)
                return -EINVAL;
@@ -974,8 +943,9 @@ static int trusted_instantiate(struct key *key, const void *data,
                        pr_info("trusted_key: key_unseal failed (%d)\n", ret);
                break;
        case Opt_new:
-               ret = my_get_random(payload->key, payload->key_len);
-               if (ret < 0) {
+               key_len = payload->key_len;
+               ret = tpm_get_random(TPM_ANY_NUM, payload->key, key_len);
+               if (ret != key_len) {
                        pr_info("trusted_key: key_create failed (%d)\n", ret);
                        goto out;
                }