Allow manual setting keyid for signing

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>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>

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 n      overwrite signature keyid with a 32-bit value in hex (for signing)
   -o, --portable     generate portable EVM signatures
   -p, --pass         password for encrypted signing key
   -r, --recursive    recurse into directories (sign)

src/evmctl.c

@@ -2500,6 +2500,7 @@ 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 n      overwrite signature keyid with a 32-bit value in hex (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"
@@ -2580,6 +2581,7 @@ static struct option opts[] = {
 	{"ignore-violations", 0, 0, 141},
 	{"pcrs", 1, 0, 142},
 	{"verify-bank", 2, 0, 143},
+	{"keyid", 1, 0, 144},
 	{}
 
 };
@@ -2624,6 +2626,8 @@ 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(
@@ -2771,6 +2775,22 @@ int main(int argc, char *argv[])
 		case 143:
 			verify_bank = optarg;
 			break;
+		case 144:
+			errno = 0;
+			keyid = strtoul(optarg, &eptr, 16);
+			/*
+			 * ULONG_MAX is error from strtoul(3),
+			 * UINT_MAX is `imaevm_params.keyid' maximum value,
+			 * 0 is reserved for keyid being unset.
+			 */
+			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;

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. (Host order.) */
 };
 
 struct RSA_ASN1_template {

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>
@@ -859,7 +860,10 @@ static int sign_hash_v2(const char *algo, const unsigned char *hash,
 		return -1;
 	}
 
-	calc_keyid_v2(&keyid, name, pkey);
+	if (imaevm_params.keyid)
+		keyid = htonl(imaevm_params.keyid);
+	else
+		calc_keyid_v2(&keyid, name, pkey);
 	hdr->keyid = keyid;
 
 	st = "EVP_PKEY_CTX_new";

tests/sign_verify.test

@@ -365,6 +365,7 @@ 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