[PATCH v3 0/3] ima-evm-utils: Add --keyid option

[PATCH v3 0/3] ima-evm-utils: Add --keyid option

[Vitaly Chikunov]

Allow user to set signature's keyid using `--keyid' option. Keyid should
correspond to SKID in certificate. When keyid is calculated using SHA-1
in libimaevm it may mismatch keyid extracted by the kernel from SKID of
certificate (the way public key is presented to the kernel), thus making
signatures not verifiable. This may happen when certificate is using non
SHA-1 SKID (see rfc7093) or just 'unique number' (see rfc5280 4.2.1.2).
As a last resort user may specify arbitrary keyid using the new option.
Certificate @filename could be used instead of the hex number. And,
third option is to read keyid from the cert appended to the key file.

These commits create backward incompatible ABI change for libimaevm,
 thus soname should be incremented on release.

Changes from v2:
- Add ima_read_keyid() function to libemaevm and use it in both evmctl
  (for --keyid) and sign_hash_v2() (for concatenated PEMs). Suggested
  by Stefan Berger.
- Autodetect PEM by openssl reading it instead of magic string.
  Suggested by Stefan Berger.
- Trivial change: s/unsigned long int/unsigned long/ for keyid type.

Changes from v1:
- Extract keyid from cert associated to key file.
- Use sizeof instead of constant.

Changes since rfc version:
- `imaevm_params.keyid' now stored as native integer (instead of network
  order). Suggested by Stefan Berger.
- Added support for `--keyid=@filename'.


Vitaly Chikunov (3):
  ima-evm-utils: Allow manual setting keyid for signing
  ima-evm-utils: Allow manual setting keyid from a cert file
  ima-evm-utils: Read keyid from the cert appended to the key file

 README                 |  5 ++++
 src/evmctl.c           | 27 +++++++++++++++++++
 src/imaevm.h           |  2 ++
 src/libimaevm.c        | 72 +++++++++++++++++++++++++++++++++++++++++++++++---
 tests/sign_verify.test |  2 ++
 5 files changed, 105 insertions(+), 3 deletions(-)

-- 
2.11.0

[PATCH v3 1/3] ima-evm-utils: Allow manual setting keyid for signing

[Vitaly Chikunov]

Allow user to set signature's keyid using `--keyid' option. Keyid should
correspond to SKID in certificate, when keyid is calculated using SHA-1
in libimaevm it may mismatch keyid extracted by the kernel from SKID of
certificate (the way public key is presented to the kernel), thus making
signatures not verifiable. This may happen when certificate is using non
SHA-1 SKID (see rfc7093) or just 'unique number' (see rfc5280 4.2.1.2).
As a last resort user may specify arbitrary keyid using the new option.

This commit creates ABI change for libimaevm, because of adding
additional parameter to imaevm_params - newer libimaevm cannot work
with older clients.

Signed-off-by: Vitaly Chikunov <vt@altlinux.org>
Reported-by: Elvira Khabirova <lineprinter0@gmail.com>
Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
---
 README                 |  1 +
 src/evmctl.c           | 15 +++++++++++++++
 src/imaevm.h           |  1 +
 src/libimaevm.c        |  8 +++++---
 tests/sign_verify.test |  1 +
 5 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/README b/README
index 321045d..8cd66e0 100644
--- a/README
+++ b/README
@@ -48,6 +48,7 @@ OPTIONS
       --xattr-user   store xattrs in user namespace (for testing purposes)
       --rsa          use RSA key type and signing scheme v1
   -k, --key          path to signing key (default: /etc/keys/{privkey,pubkey}_evm.pem)
+      --keyid val    overwrite signature keyid with a value (for signing)
   -o, --portable     generate portable EVM signatures
   -p, --pass         password for encrypted signing key
   -r, --recursive    recurse into directories (sign)
diff --git a/src/evmctl.c b/src/evmctl.c
index 1815f55..8ae5488 100644
--- a/src/evmctl.c
+++ b/src/evmctl.c
@@ -2446,6 +2446,7 @@ static void usage(void)
 		"      --xattr-user   store xattrs in user namespace (for testing purposes)\n"
 		"      --rsa          use RSA key type and signing scheme v1\n"
 		"  -k, --key          path to signing key (default: /etc/keys/{privkey,pubkey}_evm.pem)\n"
+		"      --keyid val    overwrite signature keyid with a value (for signing)\n"
 		"  -o, --portable     generate portable EVM signatures\n"
 		"  -p, --pass         password for encrypted signing key\n"
 		"  -r, --recursive    recurse into directories (sign)\n"
@@ -2525,6 +2526,7 @@ static struct option opts[] = {
 	{"xattr-user", 0, 0, 140},
 	{"ignore-violations", 0, 0, 141},
 	{"pcrs", 1, 0, 142},
+	{"keyid", 1, 0, 143},
 	{}
 
 };
@@ -2569,6 +2571,8 @@ int main(int argc, char *argv[])
 {
 	int err = 0, c, lind;
 	ENGINE *eng = NULL;
+	unsigned long keyid;
+	char *eptr;
 
 #if !(OPENSSL_VERSION_NUMBER < 0x10100000)
 	OPENSSL_init_crypto(
@@ -2713,6 +2717,17 @@ int main(int argc, char *argv[])
 			}
 			pcrfile[npcrfile++] = optarg;
 			break;
+		case 143:
+			errno = 0;
+			keyid = strtoul(optarg, &eptr, 16);
+			if (errno || eptr - optarg != strlen(optarg) ||
+			    keyid == ULONG_MAX || keyid > UINT_MAX ||
+			    keyid == 0) {
+				log_err("Invalid keyid value.\n");
+				exit(1);
+			}
+			imaevm_params.keyid = keyid;
+			break;
 		case '?':
 			exit(1);
 			break;
diff --git a/src/imaevm.h b/src/imaevm.h
index 4503919..9f38059 100644
--- a/src/imaevm.h
+++ b/src/imaevm.h
@@ -196,6 +196,7 @@ struct libimaevm_params {
 	const char *hash_algo;
 	const char *keyfile;
 	const char *keypass;
+	uint32_t keyid;		/* keyid overriding value, unless 0. */
 };
 
 struct RSA_ASN1_template {
diff --git a/src/libimaevm.c b/src/libimaevm.c
index fa6c278..481d29d 100644
--- a/src/libimaevm.c
+++ b/src/libimaevm.c
@@ -45,6 +45,7 @@
 #include <sys/param.h>
 #include <sys/stat.h>
 #include <asm/byteorder.h>
+#include <arpa/inet.h>
 #include <unistd.h>
 #include <dirent.h>
 #include <string.h>
@@ -894,7 +895,6 @@ static int sign_hash_v2(const char *algo, const unsigned char *hash,
 	const EVP_MD *md;
 	size_t sigsize;
 	const char *st;
-	uint32_t keyid;
 
 	if (!hash) {
 		log_err("sign_hash_v2: hash is null\n");
@@ -932,8 +932,10 @@ static int sign_hash_v2(const char *algo, const unsigned char *hash,
 		return -1;
 	}
 
-	calc_keyid_v2(&keyid, name, pkey);
-	hdr->keyid = keyid;
+	if (imaevm_params.keyid)
+		hdr->keyid = htonl(imaevm_params.keyid);
+	else
+		calc_keyid_v2(&hdr->keyid, name, pkey);
 
 	st = "EVP_PKEY_CTX_new";
 	if (!(ctx = EVP_PKEY_CTX_new(pkey, NULL)))
diff --git a/tests/sign_verify.test b/tests/sign_verify.test
index 288e133..2c21812 100755
--- a/tests/sign_verify.test
+++ b/tests/sign_verify.test
@@ -359,6 +359,7 @@ sign_verify  rsa1024  sha256  0x0301 --rsa
 sign_verify  rsa1024  md5     0x030201:K:0080
 sign_verify  rsa1024  sha1    0x030202:K:0080
 sign_verify  rsa1024  sha224  0x030207:K:0080
+expect_pass check_sign TYPE=ima KEY=rsa1024 ALG=sha256 PREFIX=0x030204aabbccdd0080 OPTS=--keyid=aabbccdd
 sign_verify  rsa1024  sha256  0x030204:K:0080
   try_different_keys
   try_different_sigs
-- 
2.11.0

[PATCH v3 2/3] ima-evm-utils: Allow manual setting keyid from a cert file

[Vitaly Chikunov]

Allow user to specify `--keyid @/path/to/cert.pem' to extract keyid from
SKID of the certificate file. PEM or DER format is auto-detected.

`--keyid' option is reused instead of adding a new option (like possible
`--cert') to signify to the user it's only keyid extraction and nothing
more.

This commit creates ABI change for libimaevm, due to adding new function
ima_read_keyid(). Newer clients cannot work with older libimaevm.
Together with previous commit it creates backward-incompatible ABI
change, thus soname should be incremented on release.

Signed-off-by: Vitaly Chikunov <vt@altlinux.org>
---
 README                 |  1 +
 src/evmctl.c           | 22 ++++++++++++++----
 src/imaevm.h           |  1 +
 src/libimaevm.c        | 62 ++++++++++++++++++++++++++++++++++++++++++++++++++
 tests/sign_verify.test |  1 +
 5 files changed, 82 insertions(+), 5 deletions(-)

diff --git a/README b/README
index 8cd66e0..0e1f6ba 100644
--- a/README
+++ b/README
@@ -49,6 +49,7 @@ OPTIONS
       --rsa          use RSA key type and signing scheme v1
   -k, --key          path to signing key (default: /etc/keys/{privkey,pubkey}_evm.pem)
       --keyid val    overwrite signature keyid with a value (for signing)
+                     val is a x509 cert file if prefixed with '@'
   -o, --portable     generate portable EVM signatures
   -p, --pass         password for encrypted signing key
   -r, --recursive    recurse into directories (sign)
diff --git a/src/evmctl.c b/src/evmctl.c
index 8ae5488..6a60599 100644
--- a/src/evmctl.c
+++ b/src/evmctl.c
@@ -42,6 +42,7 @@
 #include <sys/param.h>
 #include <sys/stat.h>
 #include <sys/ioctl.h>
+#include <arpa/inet.h>
 #include <fcntl.h>
 #include <unistd.h>
 #include <stdlib.h>
@@ -57,12 +58,14 @@
 #include <termios.h>
 #include <assert.h>
 
+#include <openssl/asn1.h>
 #include <openssl/sha.h>
 #include <openssl/pem.h>
 #include <openssl/hmac.h>
 #include <openssl/err.h>
 #include <openssl/rsa.h>
 #include <openssl/engine.h>
+#include <openssl/x509v3.h>
 #include "hash_info.h"
 #include "pcr.h"
 #include "utils.h"
@@ -2447,6 +2450,7 @@ static void usage(void)
 		"      --rsa          use RSA key type and signing scheme v1\n"
 		"  -k, --key          path to signing key (default: /etc/keys/{privkey,pubkey}_evm.pem)\n"
 		"      --keyid val    overwrite signature keyid with a value (for signing)\n"
+		"                     val is a x509 cert file if prefixed with '@'\n"
 		"  -o, --portable     generate portable EVM signatures\n"
 		"  -p, --pass         password for encrypted signing key\n"
 		"  -r, --recursive    recurse into directories (sign)\n"
@@ -2572,7 +2576,6 @@ int main(int argc, char *argv[])
 	int err = 0, c, lind;
 	ENGINE *eng = NULL;
 	unsigned long keyid;
-	char *eptr;
 
 #if !(OPENSSL_VERSION_NUMBER < 0x10100000)
 	OPENSSL_init_crypto(
@@ -2718,10 +2721,19 @@ int main(int argc, char *argv[])
 			pcrfile[npcrfile++] = optarg;
 			break;
 		case 143:
-			errno = 0;
-			keyid = strtoul(optarg, &eptr, 16);
-			if (errno || eptr - optarg != strlen(optarg) ||
-			    keyid == ULONG_MAX || keyid > UINT_MAX ||
+			if (optarg[0] == '@') {
+				keyid = ima_read_keyid(optarg + 1, NULL);
+			} else {
+				char *eptr;
+
+				errno = 0;
+				keyid = strtoul(optarg, &eptr, 16);
+				if (eptr - optarg != strlen(optarg) || errno) {
+					log_err("Invalid keyid value.\n");
+					exit(1);
+				}
+			}
+			if (keyid == ULONG_MAX || keyid > UINT_MAX ||
 			    keyid == 0) {
 				log_err("Invalid keyid value.\n");
 				exit(1);
diff --git a/src/imaevm.h b/src/imaevm.h
index 9f38059..eab7f32 100644
--- a/src/imaevm.h
+++ b/src/imaevm.h
@@ -219,6 +219,7 @@ EVP_PKEY *read_pub_pkey(const char *keyfile, int x509);
 void calc_keyid_v1(uint8_t *keyid, char *str, const unsigned char *pkey, int len);
 void calc_keyid_v2(uint32_t *keyid, char *str, EVP_PKEY *pkey);
 int key2bin(RSA *key, unsigned char *pub);
+unsigned long ima_read_keyid(const char *certfile, uint32_t *keyid);
 
 int sign_hash(const char *algo, const unsigned char *hash, int size, const char *keyfile, const char *keypass, unsigned char *sig);
 int verify_hash(const char *file, const unsigned char *hash, int size, unsigned char *sig, int siglen);
diff --git a/src/libimaevm.c b/src/libimaevm.c
index 481d29d..17d1c26 100644
--- a/src/libimaevm.c
+++ b/src/libimaevm.c
@@ -57,6 +57,7 @@
 #include <openssl/pem.h>
 #include <openssl/evp.h>
 #include <openssl/x509.h>
+#include <openssl/x509v3.h>
 #include <openssl/err.h>
 
 #include "imaevm.h"
@@ -748,6 +749,67 @@ void calc_keyid_v2(uint32_t *keyid, char *str, EVP_PKEY *pkey)
 	X509_PUBKEY_free(pk);
 }
 
+/**
+ * ima_read_keyid() - Read 32-bit keyid from the cert file.
+ * @certfile:	File possibly containing certificate in DER/PEM format.
+ * @keyid:	Output keyid in network order.
+ *
+ * Try to read keyid from Subject Key Identifier (SKID) of certificate.
+ * Autodetect if cert is in PEM or DER encoding.
+ *
+ * Return: -1 (ULONG_MAX) on error;
+ *         32-bit keyid as unsigned integer in host order.
+ */
+unsigned long ima_read_keyid(const char *certfile, uint32_t *keyid)
+{
+	uint32_t keyid_raw;
+	const ASN1_OCTET_STRING *skid;
+	int skid_len;
+	X509 *x = NULL;
+	FILE *fp;
+
+	if (!(fp = fopen(certfile, "r"))) {
+		log_err("Cannot open cert file %s: %s\n", certfile,
+			strerror(errno));
+		return -1;
+	}
+	if (!PEM_read_X509(fp, &x, NULL, NULL)) {
+		if (ERR_GET_REASON(ERR_peek_last_error()) == PEM_R_NO_START_LINE) {
+			ERR_clear_error();
+			rewind(fp);
+			d2i_X509_fp(fp, &x);
+		}
+		if (!x) {
+			ERR_print_errors_fp(stderr);
+			log_err("Error reading cert from file %s\n", certfile);
+			fclose(fp);
+			return -1;
+		}
+	}
+	fclose(fp);
+
+	if (!(skid = X509_get0_subject_key_id(x))) {
+		log_err("%s: SKID not found\n", certfile);
+		goto err_free;
+	}
+	skid_len = ASN1_STRING_length(skid);
+	if (skid_len < sizeof(keyid_raw)) {
+		log_err("%s: SKID too short (len %d)\n", certfile, skid_len);
+		goto err_free;
+	}
+	memcpy(&keyid_raw, ASN1_STRING_get0_data(skid) + skid_len
+	       - sizeof(keyid_raw), sizeof(keyid_raw));
+	if (keyid)
+		memcpy(keyid, &keyid_raw, sizeof(*keyid));
+	log_info("keyid %04x (from %s)\n", ntohl(keyid_raw), certfile);
+	return ntohl(keyid_raw);
+
+err_free:
+	X509_free(x);
+	return -1;
+
+}
+
 static EVP_PKEY *read_priv_pkey(const char *keyfile, const char *keypass)
 {
 	FILE *fp;
diff --git a/tests/sign_verify.test b/tests/sign_verify.test
index 2c21812..52ea33a 100755
--- a/tests/sign_verify.test
+++ b/tests/sign_verify.test
@@ -360,6 +360,7 @@ sign_verify  rsa1024  md5     0x030201:K:0080
 sign_verify  rsa1024  sha1    0x030202:K:0080
 sign_verify  rsa1024  sha224  0x030207:K:0080
 expect_pass check_sign TYPE=ima KEY=rsa1024 ALG=sha256 PREFIX=0x030204aabbccdd0080 OPTS=--keyid=aabbccdd
+expect_pass check_sign TYPE=ima KEY=rsa1024 ALG=sha256 PREFIX=0x030204:K:0080 OPTS=--keyid=@test-rsa1024.cer
 sign_verify  rsa1024  sha256  0x030204:K:0080
   try_different_keys
   try_different_sigs
-- 
2.11.0

[PATCH v3 3/3] ima-evm-utils: Read keyid from the cert appended to the key file

[Vitaly Chikunov]

Allow to have certificate appended to the private key of `--key'
specified (PEM) file (for v2 signing) to facilitate reading of keyid
from the associated cert. This will allow users to have private and
public key as a single file. There is no check that public key form the
cert matches associated private key.

Signed-off-by: Vitaly Chikunov <vt@altlinux.org>
---
 README          | 3 +++
 src/libimaevm.c | 8 +++++---
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/README b/README
index 0e1f6ba..ea11bde 100644
--- a/README
+++ b/README
@@ -127,6 +127,9 @@ for signing and importing the key.
 Second key format uses X509 DER encoded public key certificates and uses asymmetric key support
 in the kernel (since kernel 3.9). CONFIG_INTEGRITY_ASYMMETRIC_KEYS must be enabled (default).
 
+For v2 signatures x509 certificate with the public key could be appended to the private
+key (both are in PEM format) to properly determine its Subject Key Identifier (SKID).
+
 
 Integrity keyrings
 ----------------
diff --git a/src/libimaevm.c b/src/libimaevm.c
index 17d1c26..95b30f5 100644
--- a/src/libimaevm.c
+++ b/src/libimaevm.c
@@ -994,10 +994,12 @@ static int sign_hash_v2(const char *algo, const unsigned char *hash,
 		return -1;
 	}
 
-	if (imaevm_params.keyid)
+	if (imaevm_params.keyid) {
 		hdr->keyid = htonl(imaevm_params.keyid);
-	else
-		calc_keyid_v2(&hdr->keyid, name, pkey);
+	} else {
+		if (ima_read_keyid(keyfile, &hdr->keyid) == ULONG_MAX)
+			calc_keyid_v2(&hdr->keyid, name, pkey);
+	}
 
 	st = "EVP_PKEY_CTX_new";
 	if (!(ctx = EVP_PKEY_CTX_new(pkey, NULL)))
-- 
2.11.0