Replace the call out to the command line tools with C functions.
The algorithm_string_to_algid() function supports only the digest
algorithms in use. The table has place holders for other algorithms as
they are needed and the C strings are defined.
The table can also be used for an algorithm ID to string function if
it's ever needed.
Signed-off-by: Ken Goldman <kgoldman@xxxxxxxxxx>
---
src/pcr_tsspcrread.c | 156 +++++++++++++++++++++++++++++++++----------
1 file changed, 122 insertions(+), 34 deletions(-)
diff --git a/src/pcr_tsspcrread.c b/src/pcr_tsspcrread.c
index 118c7d2..5694e68 100644
--- a/src/pcr_tsspcrread.c
+++ b/src/pcr_tsspcrread.c
@@ -50,6 +50,10 @@
#include "utils.h"
#include "imaevm.h"
+#define TPM_POSIX /* use Posix, not Windows constructs in TSS */
+#undef MAX_DIGEST_SIZE /* imaevm uses a different value than the TSS */
+#include <ibmtss/tss.h>
+
#define CMD "tsspcrread"
static char path[PATH_MAX];
@@ -68,44 +72,128 @@ int tpm2_pcr_supported(void)
return 1;
}
-int tpm2_pcr_read(const char *algo_name, uint32_t pcrHandle, uint8_t *hwpcr,
- int len, char **errmsg)
-{
- FILE *fp;
- char pcr[100]; /* may contain an error */
- char cmd[PATH_MAX + 50];
- int ret;
-
- sprintf(cmd, "%s -halg %s -ha %d -ns 2> /dev/null",
- path, algo_name, pcrHandle);
- fp = popen(cmd, "r");
- if (!fp) {
- ret = asprintf(errmsg, "popen failed: %s", strerror(errno));
- if (ret == -1) /* the contents of errmsg is undefined */
- *errmsg = NULL;
- return -1;
- }
+/* Table mapping C strings to TCG algorithm identifiers */
+
+typedef struct tdAlgorithm_Map {
+ const char *algorithm_string;
+ TPMI_ALG_HASH algid;
+} Algorithm_Map;
- if (fgets(pcr, sizeof(pcr), fp) == NULL) {
- ret = asprintf(errmsg, "tsspcrread failed: %s",
- strerror(errno));
- if (ret == -1) /* the contents of errmsg is undefined */
- *errmsg = NULL;
- ret = pclose(fp);
- return -1;
+Algorithm_Map algorithm_map[] = {
+ { "sha1", TPM_ALG_SHA1},
+ { "sha256", TPM_ALG_SHA256},
+#if 0 /* uncomment as these digest algorithms are supported */
+ { "", TPM_ALG_SHA384},
+ { "", TPM_ALG_SHA512},
+ { "", TPM_ALG_SM3_256},
+ { "", TPM_ALG_SHA3_256},
+ { "", TPM_ALG_SHA3_384},
+ { "", TPM_ALG_SHA3_512},
+#endif
+};
+
+/* algorithm_string_to_algid() converts a digest algorithm from a C string to a TCG algorithm
+ identifier as defined in the TCG Algorithm Registry..
+
+ Returns TPM_ALG_ERROR if the string has an unsupported value.
+*/
+
+static TPMI_ALG_HASH algorithm_string_to_algid(const char *algorithm_string)
+{
+ size_t i;
+ for (i=0 ; i < sizeof(algorithm_map)/sizeof(Algorithm_Map) ; i++) {
+ if (strcmp(algorithm_string, algorithm_map[i].algorithm_string) == 0) {
+ return algorithm_map[i].algid; /* if match */
}
+ }
+ return TPM_ALG_ERROR;
+}
- /* get the popen "cmd" return code */
- ret = pclose(fp);
+/* tpm2_pcr_read() reads the PCR
- /* Treat an unallocated bank as an error */
- if (!ret && (strlen(pcr) < SHA_DIGEST_LENGTH))
- ret = -1;
+ algo_name is the PCR digest algorithm (the PCR bank) as a C string
+ pcrHandle is the PCR number to read
+ hwpcr is a buffer for the PCR output in binary
+ len is the allocated size of hwpcr and should match the digest algorithm
+*/
- if (!ret)
- hex2bin(hwpcr, pcr, len);
- else
- *errmsg = strndup(pcr, strlen(pcr) - 1); /* remove newline */
+int tpm2_pcr_read(const char *algo_name, uint32_t pcrHandle, uint8_t *hwpcr,
+ int len, char **errmsg)
+{
+ int ret = 0; /* function return code */
+ TPM_RC rc = 0; /* TCG return code */
+ PCR_Read_In pcrReadIn; /* command input */
+ PCR_Read_Out pcrReadOut; /* response output */
+ TSS_CONTEXT *tssContext = NULL;
+ TPMI_ALG_HASH alg_id; /* PCR algorithm */
- return ret;
+ if (rc == 0) { /* map algorithm string to TCG value */
+ alg_id = algorithm_string_to_algid(algo_name);
+ if (alg_id == TPM_ALG_ERROR) {
+ ret = asprintf(errmsg, "tpm2_pcr_read: unknown algorithm %s", algo_name);
+ if (ret == -1) { /* the contents of errmsg is undefined */
+ *errmsg = NULL;
+ }
+ rc = 1;
+ }
+ }
+ if (rc == 0) {
+ rc = TSS_Create(&tssContext);
+ }
+ /* call TSS to execute the command */
+ if (rc == 0) {
+ pcrReadIn.pcrSelectionIn.count = 1;
+ pcrReadIn.pcrSelectionIn.pcrSelections[0].hash = alg_id;
+ pcrReadIn.pcrSelectionIn.pcrSelections[0].sizeofSelect = 3;
+ pcrReadIn.pcrSelectionIn.pcrSelections[0].pcrSelect[0] = 0;
+ pcrReadIn.pcrSelectionIn.pcrSelections[0].pcrSelect[1] = 0;
+ pcrReadIn.pcrSelectionIn.pcrSelections[0].pcrSelect[2] = 0;
+ pcrReadIn.pcrSelectionIn.pcrSelections[0].pcrSelect[pcrHandle / 8] =
+ 1 << (pcrHandle % 8);
+ rc = TSS_Execute(tssContext,
+ (RESPONSE_PARAMETERS *)&pcrReadOut,
+ (COMMAND_PARAMETERS *)&pcrReadIn,
+ NULL,
+ TPM_CC_PCR_Read,
+ TPM_RH_NULL, NULL, 0);
+ }
+ if (rc == 0) {
+ /* nothing read, bank missing */
+ if (pcrReadOut.pcrValues.count == 0) {
+ ret = asprintf(errmsg, "tpm2_pcr_read: returned count 0 for %s", algo_name);
+ if (ret == -1) { /* the contents of errmsg is undefined */
+ *errmsg = NULL;
+ }
+ rc = 1;
+ }
+ /* len parameter did not match the digest algorithm */
+ else if (pcrReadOut.pcrValues.digests[0].t.size != len) {
+ ret = asprintf(errmsg,
+ "tpm2_pcr_read: expected length %d actual %u for %s",
+ len, pcrReadOut.pcrValues.digests[0].t.size, algo_name);
+ if (ret == -1) { /* the contents of errmsg is undefined */
+ *errmsg = NULL;
+ }
+ rc = 1;
+ }
+ else {
+ memcpy(hwpcr,
+ pcrReadOut.pcrValues.digests[0].t.buffer,
+ pcrReadOut.pcrValues.digests[0].t.size);
+ }
+ }
+ {
+ TPM_RC rc1 = TSS_Delete(tssContext);
+ if (rc == 0) {
+ rc = rc1;
+ }
+ }
+ /* map TCG return code to function return code */
+ if (rc == 0) {
+ return 0;
+ }
+ else {
+ return -1;
+ }
}
+
--
2.25.1
