keys: add new trusted key-type

Define a new kernel key-type called 'trusted'.  Trusted keys are random
number symmetric keys, generated and RSA-sealed by the TPM.  The TPM
only unseals the keys, if the boot PCRs and other criteria match.
Userspace can only ever see encrypted blobs.

Based on suggestions by Jason Gunthorpe, several new options have been
added to support additional usages.

The new options are:
migratable=  designates that the key may/may not ever be updated
             (resealed under a new key, new pcrinfo or new auth.)

pcrlock=n    extends the designated PCR 'n' with a random value,
             so that a key sealed to that PCR may not be unsealed
             again until after a reboot.

keyhandle=   specifies the sealing/unsealing key handle.

keyauth=     specifies the sealing/unsealing key auth.

blobauth=    specifies the sealed data auth.

Implementation of a kernel reserved locality for trusted keys will be
investigated for a possible future extension.

Changelog:
- Updated and added examples to Documentation/keys-trusted-encrypted.txt
- Moved generic TPM constants to include/linux/tpm_command.h
  (David Howell's suggestion.)
- trusted_defined.c: replaced kzalloc with kmalloc, added pcrlock failure
  error handling, added const qualifiers where appropriate.
- moved to late_initcall
- updated from hash to shash (suggestion by David Howells)
- reduced worst stack usage (tpm_seal) from 530 to 312 bytes
- moved documentation to Documentation directory (suggestion by David Howells)
- all the other code cleanups suggested by David Howells
- Add pcrlock CAP_SYS_ADMIN dependency (based on comment by Jason Gunthorpe)
- New options: migratable, pcrlock, keyhandle, keyauth, blobauth (based on
  discussions with Jason Gunthorpe)
- Free payload on failure to create key(reported/fixed by Roberto Sassu)
- Updated Kconfig and other descriptions (based on Serge Hallyn's suggestion)
- Replaced kzalloc() with kmalloc() (reported by Serge Hallyn)

Signed-off-by: David Safford <safford@watson.ibm.com>
Signed-off-by: Mimi Zohar <zohar@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 134 insertions, 0 deletions

diff --git a/security/keys/trusted_defined.h b/security/keys/trusted_defined.h
new file mode 100644
index 000000000000..3249fbd2b653
--- /dev/null
+++ b/security/keys/trusted_defined.h
@@ -0,0 +1,134 @@
+#ifndef __TRUSTED_KEY_H
+#define __TRUSTED_KEY_H
+
+/* implementation specific TPM constants */
+#define MAX_PCRINFO_SIZE		64
+#define MAX_BUF_SIZE			512
+#define TPM_GETRANDOM_SIZE		14
+#define TPM_OSAP_SIZE			36
+#define TPM_OIAP_SIZE			10
+#define TPM_SEAL_SIZE			87
+#define TPM_UNSEAL_SIZE			104
+#define TPM_SIZE_OFFSET			2
+#define TPM_RETURN_OFFSET		6
+#define TPM_DATA_OFFSET			10
+
+#define LOAD32(buffer, offset)	(ntohl(*(uint32_t *)&buffer[offset]))
+#define LOAD32N(buffer, offset)	(*(uint32_t *)&buffer[offset])
+#define LOAD16(buffer, offset)	(ntohs(*(uint16_t *)&buffer[offset]))
+
+struct tpm_buf {
+	int len;
+	unsigned char data[MAX_BUF_SIZE];
+};
+
+#define INIT_BUF(tb) (tb->len = 0)
+
+struct osapsess {
+	uint32_t handle;
+	unsigned char secret[SHA1_DIGEST_SIZE];
+	unsigned char enonce[TPM_NONCE_SIZE];
+};
+
+/* discrete values, but have to store in uint16_t for TPM use */
+enum {
+	SEAL_keytype = 1,
+	SRK_keytype = 4
+};
+
+struct trusted_key_options {
+	uint16_t keytype;
+	uint32_t keyhandle;
+	unsigned char keyauth[SHA1_DIGEST_SIZE];
+	unsigned char blobauth[SHA1_DIGEST_SIZE];
+	uint32_t pcrinfo_len;
+	unsigned char pcrinfo[MAX_PCRINFO_SIZE];
+	int pcrlock;
+};
+
+#define TPM_DEBUG 0
+
+#if TPM_DEBUG
+static inline void dump_options(struct trusted_key_options *o)
+{
+	pr_info("trusted_key: sealing key type %d\n", o->keytype);
+	pr_info("trusted_key: sealing key handle %0X\n", o->keyhandle);
+	pr_info("trusted_key: pcrlock %d\n", o->pcrlock);
+	pr_info("trusted_key: pcrinfo %d\n", o->pcrinfo_len);
+	print_hex_dump(KERN_INFO, "pcrinfo ", DUMP_PREFIX_NONE,
+		       16, 1, o->pcrinfo, o->pcrinfo_len, 0);
+}
+
+static inline void dump_payload(struct trusted_key_payload *p)
+{
+	pr_info("trusted_key: key_len %d\n", p->key_len);
+	print_hex_dump(KERN_INFO, "key ", DUMP_PREFIX_NONE,
+		       16, 1, p->key, p->key_len, 0);
+	pr_info("trusted_key: bloblen %d\n", p->blob_len);
+	print_hex_dump(KERN_INFO, "blob ", DUMP_PREFIX_NONE,
+		       16, 1, p->blob, p->blob_len, 0);
+	pr_info("trusted_key: migratable %d\n", p->migratable);
+}
+
+static inline void dump_sess(struct osapsess *s)
+{
+	print_hex_dump(KERN_INFO, "trusted-key: handle ", DUMP_PREFIX_NONE,
+		       16, 1, &s->handle, 4, 0);
+	pr_info("trusted-key: secret:\n");
+	print_hex_dump(KERN_INFO, "", DUMP_PREFIX_NONE,
+		       16, 1, &s->secret, SHA1_DIGEST_SIZE, 0);
+	pr_info("trusted-key: enonce:\n");
+	print_hex_dump(KERN_INFO, "", DUMP_PREFIX_NONE,
+		       16, 1, &s->enonce, SHA1_DIGEST_SIZE, 0);
+}
+
+static inline void dump_tpm_buf(unsigned char *buf)
+{
+	int len;
+
+	pr_info("\ntrusted-key: tpm buffer\n");
+	len = LOAD32(buf, TPM_SIZE_OFFSET);
+	print_hex_dump(KERN_INFO, "", DUMP_PREFIX_NONE, 16, 1, buf, len, 0);
+}
+#else
+static inline void dump_options(struct trusted_key_options *o)
+{
+}
+
+static inline void dump_payload(struct trusted_key_payload *p)
+{
+}
+
+static inline void dump_sess(struct osapsess *s)
+{
+}
+
+static inline void dump_tpm_buf(unsigned char *buf)
+{
+}
+#endif
+
+static inline void store8(struct tpm_buf *buf, const unsigned char value)
+{
+	buf->data[buf->len++] = value;
+}
+
+static inline void store16(struct tpm_buf *buf, const uint16_t value)
+{
+	*(uint16_t *) & buf->data[buf->len] = htons(value);
+	buf->len += sizeof value;
+}
+
+static inline void store32(struct tpm_buf *buf, const uint32_t value)
+{
+	*(uint32_t *) & buf->data[buf->len] = htonl(value);
+	buf->len += sizeof value;
+}
+
+static inline void storebytes(struct tpm_buf *buf, const unsigned char *in,
+			      const int len)
+{
+	memcpy(buf->data + buf->len, in, len);
+	buf->len += len;
+}
+#endif