[SeaBIOS] [PATCH 3/3] tpm: Extend tpm20_extend to support extending to multiple PCR banks

[Stefan Berger]

Extend the tpm20_extend function to support extending a hash to
multiple PCR banks. The sha1 hash that's being extended into the
sha256 bank for example, will be filled with zero-bytes to the
size of a sha256 hash.

Signed-off-by: Stefan Berger <stefanb at linux.vnet.ibm.com>
---
 src/std/tcg.h | 14 +++++++--
 src/tcgbios.c | 99 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++---
 2 files changed, 105 insertions(+), 8 deletions(-)

diff --git a/src/std/tcg.h b/src/std/tcg.h
index 1644684..9e4ef57 100644
--- a/src/std/tcg.h
+++ b/src/std/tcg.h
@@ -100,6 +100,10 @@ enum irq_ids {
 #define EV_IPL_PARTITION_DATA   14
 
 #define SHA1_BUFSIZE                20
+#define SHA256_BUFSIZE              32
+#define SHA384_BUFSIZE              48
+#define SHA512_BUFSIZE              64
+#define SM3_256_BUFSIZE             32
 
 /* Input and Output blocks for the TCG BIOS commands */
 
@@ -381,6 +385,10 @@ struct tpm_res_sha1complete {
 #define TPM2_RH_PLATFORM            0x4000000c
 
 #define TPM2_ALG_SHA1               0x0004
+#define TPM2_ALG_SHA256             0x000b
+#define TPM2_ALG_SHA384             0x000c
+#define TPM2_ALG_SHA512             0x000d
+#define TPM2_ALG_SM3_256            0x0012
 
 /* TPM 2 command tags */
 #define TPM2_ST_NO_SESSIONS         0x8001
@@ -442,8 +450,8 @@ struct tpm2_req_hierarchychangeauth {
 } PACKED;
 
 struct tpm2_digest_value {
-    u16 hashalg; /* TPM2_ALG_SHA1 */
-    u8 sha1[SHA1_BUFSIZE];
+    u16 hashAlg; /* TPM2_ALG_SHA1 */
+    u8 hash[0]; /* size depends on hashAlg */
 } PACKED;
 
 struct tpm2_req_extend {
@@ -452,7 +460,7 @@ struct tpm2_req_extend {
     u32 authblocksize;
     struct tpm2_authblock authblock;
     u32 count;
-    struct tpm2_digest_value digest;
+    struct tpm2_digest_value digest[0];
 } PACKED;
 
 struct tpm2_req_clearcontrol {
diff --git a/src/tcgbios.c b/src/tcgbios.c
index 72ae3c6..acd0b71 100644
--- a/src/tcgbios.c
+++ b/src/tcgbios.c
@@ -446,11 +446,94 @@ tpm12_extend(u32 pcrindex, const u8 *digest)
     return 0;
 }
 
+static int
+tpm20_get_hash_buffersize(u16 hashAlg)
+{
+    switch (hashAlg) {
+    case TPM2_ALG_SHA1:
+        return SHA1_BUFSIZE;
+    case TPM2_ALG_SHA256:
+        return SHA256_BUFSIZE;
+    case TPM2_ALG_SHA384:
+        return SHA384_BUFSIZE;
+    case TPM2_ALG_SHA512:
+        return SHA512_BUFSIZE;
+    case TPM2_ALG_SM3_256:
+        return SM3_256_BUFSIZE;
+    default:
+        return -1;
+    }
+}
+
+/*
+ * Write the TPM2 PCR Extend 'body' containing the hashes. Follow
+ * the PCR bank configuration of the TPM.
+ *
+ * dest: destinatiobn buffer to write into; if NULL, nothing is written
+ * pcrindex: the PCR index
+ * hash: the hash value to write
+ * hashAlg: the hash alogorithm determining the size of the hash
+ * count: pointer to a counter for how many entries were writte
+ *
+ * Returns the number of bytes written into the buffer; -1 on fatal error
+ */
+static int
+tpm20_write_extend_body(char *dest, u32 pcrindex, const u8 *hash,
+                        u16 hashAlg, u32 *count)
+{
+    int offset = 0, hsize;
+    struct tpms_pcr_selection *sel = tpm20_pcr_selection->selections;
+    void *nsel, *end = (void *)tpm20_pcr_selection + tpm20_pcr_selection_size;
+    int hash_size = tpm20_get_hash_buffersize(hashAlg);
+
+    for (*count = 0;
+         *count < be32_to_cpu(tpm20_pcr_selection->count);
+         (*count)++) {
+        u8 sizeOfSelect = sel->sizeOfSelect;
+
+        nsel = (void *)sel +
+               offsetof(struct tpms_pcr_selection, pcrSelect) +
+               sizeOfSelect;
+        if (nsel > end)
+            break;
+
+        u8 idx = pcrindex >> 3;
+        u8 mask = (1 << (pcrindex & 7));
+        /* skip if PCR not used in this bank */
+        if (idx > sizeOfSelect || !(sel->pcrSelect[idx] & mask))
+            continue;
+
+        hsize = tpm20_get_hash_buffersize(be16_to_cpu(sel->hashAlg));
+        if (hsize < 0) {
+            dprintf(DEBUG_tcg, "TPM is using an unsupported hash: %d\n",
+                    be16_to_cpu(sel->hashAlg));
+            return -1;
+        }
+
+        if (dest) {
+            struct tpm2_digest_value *v =
+              (struct tpm2_digest_value *)&dest[offset];
+            v->hashAlg = sel->hashAlg;
+            memset(v->hash, 0, hsize);
+            memcpy(v->hash, hash, hash_size);
+        }
+        offset += sizeof(sel->hashAlg) + hsize;
+        sel = nsel;
+    }
+
+    if (sel != end) {
+        dprintf(DEBUG_tcg, "Malformed pcr selection structure fron TPM\n");
+        return -1;
+    }
+
+    return offset;
+}
+
 static int tpm20_extend(u32 pcrindex, const u8 *digest, u16 hashAlg)
 {
     struct tpm2_req_extend tmp_tre = {
         .hdr.tag     = cpu_to_be16(TPM2_ST_SESSIONS),
-        .hdr.totlen  = cpu_to_be32(sizeof(tmp_tre)),
+        .hdr.totlen  = cpu_to_be32(0),
         .hdr.ordinal = cpu_to_be32(TPM2_CC_PCR_Extend),
         .pcrindex    = cpu_to_be32(pcrindex),
         .authblocksize = cpu_to_be32(sizeof(tmp_tre.authblock)),
@@ -461,14 +544,20 @@ static int tpm20_extend(u32 pcrindex, const u8 *digest, u16 hashAlg)
             .pwdsize = cpu_to_be16(0),
         },
     };
-    u32 count = 1;
-    u8 buffer[sizeof(tmp_tre) + sizeof(struct tpm2_digest_value)];
+    u32 count = 0;
+    int bsize = tpm20_write_extend_body(NULL, pcrindex, digest, hashAlg,
+                                        &count);
+    if (bsize < 0)
+        return bsize;
+
+    u8 buffer[sizeof(tmp_tre) + bsize];
     struct tpm2_req_extend *tre = (struct tpm2_req_extend *)buffer;
 
     memcpy(tre, &tmp_tre, sizeof(tmp_tre));
+    tre->hdr.totlen = cpu_to_be32(sizeof(buffer));
+    tpm20_write_extend_body((char *)&tre->digest, pcrindex, digest, hashAlg,
+                            &count);
     tre->count = cpu_to_be32(count);
-    tre->digest.hashalg = cpu_to_be16(hashAlg);
-    memcpy(tre->digest.sha1, digest, sizeof(tmp_tre.digest.sha1));
 
     struct tpm_rsp_header rsp;
     u32 resp_length = sizeof(rsp);
-- 
2.5.5