[PATCH 0/3] additional "ima-measurement" support

[PATCH 0/3] additional "ima-measurement" support

[Mimi Zohar]

"evmctl ima_measurement" walks the IMA measurement list re-calculating
the TPM PCR banks.

- Support the original method of extending the TPM 2.0 banks with the
  padded SHA1 digest.
- Instead of reading the hardware or software TPM PCRs, support
  providing the TPM 1.2 PCRs as a file


Mimi Zohar (3):
  ima-evm-utils: improve reading TPM 1.2 PCRs
  ima_evm_utils: support extending TPM 2.0 banks w/original SHA1 padded
    digest
  ima-evm-utils: support providing the TPM 1.2 PCRs as a file

 src/evmctl.c | 128 +++++++++++++++++++++++++++++++++++++++++------------------
 1 file changed, 90 insertions(+), 38 deletions(-)

-- 
2.7.5

[PATCH 1/3] ima-evm-utils: improve reading TPM 1.2 PCRs

[Mimi Zohar]

Instead of reading the TPM 1.2 PCRs one at a time, opening and closing
the securityfs file each time, read all of PCRs at once.

Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
---
 src/evmctl.c | 39 ++++++++++++++++++---------------------
 1 file changed, 18 insertions(+), 21 deletions(-)

diff --git a/src/evmctl.c b/src/evmctl.c
index 21809b3229e9..0e489e2c7ba6 100644
--- a/src/evmctl.c
+++ b/src/evmctl.c
@@ -152,6 +152,14 @@ static void print_usage(struct command *cmd);
 static const char *xattr_ima = "security.ima";
 static const char *xattr_evm = "security.evm";
 
+struct tpm_bank_info {
+	int digest_size;
+	int supported;
+	const char *algo_name;
+	uint8_t digest[MAX_DIGEST_SIZE];
+	uint8_t pcr[NUM_PCRS][MAX_DIGEST_SIZE];
+};
+
 static int bin2file(const char *file, const char *ext, const unsigned char *data, int len)
 {
 	FILE *fp;
@@ -1366,13 +1374,13 @@ static int cmd_ima_clear(struct command *cmd)
 static char *pcrs = "/sys/class/tpm/tpm0/device/pcrs";  /* Kernels >= 4.0 */
 static char *misc_pcrs = "/sys/class/misc/tpm0/device/pcrs";
 
-static int tpm_pcr_read(int idx, uint8_t *pcr, int len)
+/* Read all of the TPM 1.2 PCRs */
+static int tpm_pcr_read(struct tpm_bank_info *tpm_banks, int len)
 {
 	FILE *fp;
 	char *p, pcr_str[7], buf[70]; /* length of the TPM string */
 	int result = -1;
-
-	sprintf(pcr_str, "PCR-%2.2d", idx);
+	int i = 0;
 
 	fp = fopen(pcrs, "r");
 	if (!fp)
@@ -1385,11 +1393,10 @@ static int tpm_pcr_read(int idx, uint8_t *pcr, int len)
 		p = fgets(buf, sizeof(buf), fp);
 		if (!p)
 			break;
-		if (!strncmp(p, pcr_str, 6)) {
-			hex2bin(pcr, p + 7, len);
-			result = 0;
-			break;
-		}
+		sprintf(pcr_str, "PCR-%2.2d", i);
+		if (!strncmp(p, pcr_str, 6))
+			hex2bin(tpm_banks[0].pcr[i++], p + 7, len);
+		result = 0;
 	}
 	fclose(fp);
 	return result;
@@ -1571,14 +1578,6 @@ void ima_ng_show(struct template_entry *entry)
 	}
 }
 
-struct tpm_bank_info {
-	int digest_size;
-	int supported;
-	const char *algo_name;
-	uint8_t digest[MAX_DIGEST_SIZE];
-	uint8_t pcr[NUM_PCRS][MAX_DIGEST_SIZE];
-};
-
 static void set_bank_info(struct tpm_bank_info *bank, const char *algo_name)
 {
 	const EVP_MD *md;
@@ -1771,11 +1770,9 @@ static int read_tpm_pcrs(int num_banks, struct tpm_bank_info *tpm_banks)
 {
 	int i;
 
-	for (i = 0; i < NUM_PCRS; i++) {
-		if (tpm_pcr_read(i, tpm_banks[0].pcr[i], SHA_DIGEST_LENGTH)) {
-			log_debug("Failed to read TPM 1.2 PCRs.\n");
-			return -1;
-		}
+	if (tpm_pcr_read(tpm_banks, SHA_DIGEST_LENGTH)) {
+		log_debug("Failed to read TPM 1.2 PCRs.\n");
+		return -1;
 	}
 
 	tpm_banks[0].supported = 1;
-- 
2.7.5

[PATCH 2/3] ima_evm_utils: support extending TPM 2.0 banks w/original SHA1 padded digest

[Mimi Zohar]

Initially the sha1 digest, including violations, was padded with zeroes
before being extended into the other TPM banks.  Support walking the
IMA measurement list, calculating the per TPM bank SHA1 padded
digest(s).

Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
---
 src/evmctl.c | 73 +++++++++++++++++++++++++++++++++++++++++++++++-------------
 1 file changed, 58 insertions(+), 15 deletions(-)

diff --git a/src/evmctl.c b/src/evmctl.c
index 0e489e2c7ba6..814aa6b75571 100644
--- a/src/evmctl.c
+++ b/src/evmctl.c
@@ -1613,6 +1613,10 @@ static struct tpm_bank_info *init_tpm_banks(int *num_banks)
 	return banks;
 }
 
+/*
+ * Compare the calculated TPM PCR banks against the PCR values read.
+ * On failure to match any TPM bank, fail comparison.
+ */
 static int compare_tpm_banks(int num_banks, struct tpm_bank_info *bank,
 			     struct tpm_bank_info *tpm_bank)
 {
@@ -1632,14 +1636,15 @@ static int compare_tpm_banks(int num_banks, struct tpm_bank_info *bank,
 			log_info("%s: TPM PCR-%d: ", tpm_bank[i].algo_name, j);
 			log_dump(tpm_bank[i].pcr[j], tpm_bank[i].digest_size);
 
-			ret = memcmp(bank[i].pcr[j], tpm_bank[i].pcr[j],
-				     bank[i].digest_size);
-			if (!ret)
+			if (memcmp(bank[i].pcr[j], tpm_bank[i].pcr[j],
+				     bank[i].digest_size) == 0) {
 				log_info("%s PCR-%d: succeed\n",
 					 bank[i].algo_name, j);
-			else
+			} else {
+				ret = 1;
 				log_info("%s: PCRAgg %d does not match TPM PCR-%d\n",
 					 bank[i].algo_name, j, j);
+			}
 		}
 	}
 	return ret;
@@ -1695,10 +1700,7 @@ static int extend_tpm_bank(EVP_MD_CTX *pctx, const EVP_MD *md,
 		goto out;
 	}
 
-	if (validate && !memcmp(entry->header.digest, zero, SHA_DIGEST_LENGTH))
-		err = EVP_DigestUpdate(pctx, fox, bank->digest_size);
-	else
-		err = EVP_DigestUpdate(pctx, bank->digest, bank->digest_size);
+	err = EVP_DigestUpdate(pctx, bank->digest, bank->digest_size);
 	if (!err) {
 		printf("EVP_DigestUpdate() failed\n");
 		goto out;
@@ -1716,7 +1718,8 @@ out:
 
 /* Calculate and extend the template hash for multiple hash algorithms */
 static void extend_tpm_banks(struct template_entry *entry, int num_banks,
-			     struct tpm_bank_info *bank)
+			     struct tpm_bank_info *bank,
+			     struct tpm_bank_info *padded_bank)
 {
 	EVP_MD_CTX *pctx;
 	const EVP_MD *md;
@@ -1741,24 +1744,53 @@ static void extend_tpm_banks(struct template_entry *entry, int num_banks,
 		}
 
 		/*
-		 * Measurement violations are 0x00 digests.  No need to
-		 * calculate the per TPM bank template digests.
+		 * Measurement violations are 0x00 digests, which are extended
+		 * into the TPM as 0xff.  Verifying the IMA measurement list
+		 * will fail, unless the 0x00 digests are converted to 0xff's.
+		 *
+		 * Initially the sha1 digest, including violations, was padded
+		 * with zeroes before being extended into the TPM.  With the
+		 * per TPM bank digest, violations are the full per bank digest
+		 * size.
 		 */
-		if (memcmp(entry->header.digest, zero, SHA_DIGEST_LENGTH) == 0)
-			memset(bank[i].digest, 0x00, bank[i].digest_size);
-		else {
+		if (memcmp(entry->header.digest, zero, SHA_DIGEST_LENGTH) == 0) {
+			if (!validate) {
+				memset(bank[i].digest, 0x00, bank[i].digest_size);
+				memset(padded_bank[i].digest, 0x00, padded_bank[i].digest_size);
+			} else {
+				memset(bank[i].digest, 0xff,
+				       bank[i].digest_size);
+
+				memset(padded_bank[i].digest, 0x00,
+				       padded_bank[i].digest_size);
+				memset(padded_bank[i].digest, 0xff,
+				       SHA_DIGEST_LENGTH);
+			}
+		} else {
 			err = calculate_template_digest(pctx, md, entry,
 							&bank[i]);
 			if (!err) {
 				bank[i].supported = 0;
 				continue;
 			}
+
+			/*
+			 * calloc set the memory to zero, so just copy the
+			 * sha1 digest.
+			 */
+			memcpy(padded_bank[i].digest, entry->header.digest,
+			       SHA_DIGEST_LENGTH);
 		}
 
 		/* extend TPM BANK with template digest */
 		err = extend_tpm_bank(pctx, md, entry, &bank[i]);
 		if (!err)
 			bank[i].supported = 0;
+
+		/* extend TPM BANK with zero padded sha1 template digest */
+		err = extend_tpm_bank(pctx, md, entry, &padded_bank[i]);
+		if (!err)
+			padded_bank[i].supported = 0;
 	}
 #if OPENSSL_VERSION_NUMBER >= 0x10100000
 	EVP_MD_CTX_free(pctx);
@@ -1825,6 +1857,7 @@ static int read_tpm_banks(int num_banks, struct tpm_bank_info *bank)
 
 static int ima_measurement(const char *file)
 {
+	struct tpm_bank_info *pseudo_padded_banks;
 	struct tpm_bank_info *pseudo_banks;
 	struct tpm_bank_info *tpm_banks;
 	int is_ima_template, cur_template_fmt;
@@ -1839,6 +1872,7 @@ static int ima_measurement(const char *file)
 	memset(zero, 0, MAX_DIGEST_SIZE);
 	memset(fox, 0xff, MAX_DIGEST_SIZE);
 
+	pseudo_padded_banks = init_tpm_banks(&num_banks);
 	pseudo_banks = init_tpm_banks(&num_banks);
 	tpm_banks = init_tpm_banks(&num_banks);
 
@@ -1939,7 +1973,8 @@ static int ima_measurement(const char *file)
 			       entry.template_buf_len - len);
 		}
 
-		extend_tpm_banks(&entry, num_banks, pseudo_banks);
+		extend_tpm_banks(&entry, num_banks, pseudo_banks,
+				 pseudo_padded_banks);
 
 		if (verify)
 			ima_verify_template_hash(&entry);
@@ -1954,7 +1989,15 @@ static int ima_measurement(const char *file)
 		err = 0;
 		log_info("Failed to read any TPM PCRs\n");
 	} else {
+		log_info("Comparing with per TPM digest\n");
 		err = compare_tpm_banks(num_banks, pseudo_banks, tpm_banks);
+
+		/* On failure, check older SHA1 zero padded hashes */
+		if (err) {
+			log_info("Comparing with SHA1 padded digest\n");
+			err = compare_tpm_banks(num_banks, pseudo_padded_banks,
+						tpm_banks);
+		}
 	}
 
 out:
-- 
2.7.5

[PATCH 3/3] ima-evm-utils: support providing the TPM 1.2 PCRs as a file

[Mimi Zohar]

"evmctl ima_measurement" walks the IMA measurement list calculating the
PCRs and verifies the calculated values against the system's PCRs.
Instead of reading the system's PCRs, provide the PCRs as a file.  For
TPM 1.2 the PCRs are exported via a securityfs file.

Verifying the IMA measurement list against the exported TPM 1.2 PCRs
file may be used remotely for regression testing.  If used in a
production environment, the provided TPM PCRs must be compared with
those included in the TPM 1.2 quote as well.

This patch defines an evmctl ima_measurement "--pcrs <filename>" option.

Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
---
 src/evmctl.c | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/src/evmctl.c b/src/evmctl.c
index 814aa6b75571..21ae1c7ca5a7 100644
--- a/src/evmctl.c
+++ b/src/evmctl.c
@@ -160,6 +160,8 @@ struct tpm_bank_info {
 	uint8_t pcr[NUM_PCRS][MAX_DIGEST_SIZE];
 };
 
+static char *pcrfile;
+
 static int bin2file(const char *file, const char *ext, const unsigned char *data, int len)
 {
 	FILE *fp;
@@ -1377,12 +1379,18 @@ static char *misc_pcrs = "/sys/class/misc/tpm0/device/pcrs";
 /* Read all of the TPM 1.2 PCRs */
 static int tpm_pcr_read(struct tpm_bank_info *tpm_banks, int len)
 {
-	FILE *fp;
+	FILE *fp = NULL;
 	char *p, pcr_str[7], buf[70]; /* length of the TPM string */
 	int result = -1;
 	int i = 0;
 
-	fp = fopen(pcrs, "r");
+	/* Use the provided TPM 1.2 pcrs file */
+	if (pcrfile)
+		fp = fopen(pcrfile, "r");
+
+	if (!fp)
+		fp = fopen(pcrs, "r");
+
 	if (!fp)
 		fp = fopen(misc_pcrs, "r");
 
@@ -2347,7 +2355,7 @@ struct command cmds[] = {
 	{"ima_verify", cmd_verify_ima, 0, "file", "Verify IMA signature (for debugging).\n"},
 	{"ima_setxattr", cmd_setxattr_ima, 0, "[--sigfile file]", "Set IMA signature from sigfile\n"},
 	{"ima_hash", cmd_hash_ima, 0, "file", "Make file content hash.\n"},
-	{"ima_measurement", cmd_ima_measurement, 0, "[--validate] [--verify] file", "Verify measurement list (experimental).\n"},
+	{"ima_measurement", cmd_ima_measurement, 0, "[--validate] [--verify] [--pcrs file] file", "Verify measurement list (experimental).\n"},
 	{"ima_boot_aggregate", cmd_ima_bootaggr, 0, "[file]", "Calculate per TPM bank boot_aggregate digests\n"},
 	{"ima_fix", cmd_ima_fix, 0, "[-t fdsxm] path", "Recursively fix IMA/EVM xattrs in fix mode.\n"},
 	{"ima_clear", cmd_ima_clear, 0, "[-t fdsxm] path", "Recursively remove IMA/EVM xattrs.\n"},
@@ -2388,6 +2396,7 @@ static struct option opts[] = {
 	{"xattr-user", 0, 0, 140},
 	{"validate", 0, 0, 141},
 	{"verify", 0, 0, 142},
+	{"pcrs", 1, 0, 143},
 	{}
 
 };
@@ -2572,6 +2581,9 @@ int main(int argc, char *argv[])
 		case 142: /* --verify */
 			verify = 1;
 			break;
+		case 143:
+			pcrfile = optarg;
+			break;
 		case '?':
 			exit(1);
 			break;
-- 
2.7.5