fips update: show minimum RSA public exponent in icainfo

In fips mode the minimum allowed RSA public exponent is 65537.
RSA key generation is always performed via openssl. Check at
runtime what openssl supports.

Signed-off-by: Joerg Schmidbauer <jschmidb@de.ibm.com>

Author: jschmidb

src/icainfo.c

@@ -174,6 +174,44 @@ int rsa_keylen_supported_by_openssl(unsigned int modulus_bitlength)
 	return rc == 0 ? 1 : 0;
 }
 
+int rsa_pubexp_supported_by_openssl(unsigned int pubexp)
+{
+	unsigned char modexpo_public_e[256] = { 0 };
+	unsigned char modexpo_public_n[256] = { 0 };
+	unsigned char crt_private_p[128] = { 0 };
+	unsigned char crt_private_q[128] = { 0 };
+	unsigned char crt_private_dp[128] = { 0 };
+	unsigned char crt_private_dq[128] = { 0 };
+	unsigned char crt_private_inv_q[128] = { 0 };
+	ica_adapter_handle_t ah;
+	ica_rsa_key_mod_expo_t public_key;
+	ica_rsa_key_crt_t private_key;
+	int rc;
+
+	rc = ica_open_adapter(&ah);
+	if (rc != 0)
+		return 0;
+
+	public_key.modulus = modexpo_public_n;
+	public_key.exponent = modexpo_public_e;
+	public_key.key_length = 256;
+
+	private_key.p = crt_private_p;
+	private_key.q = crt_private_q;
+	private_key.dp = crt_private_dp;
+	private_key.dq = crt_private_dq;
+	private_key.qInverse = crt_private_inv_q;
+	private_key.key_length = 256;
+
+	*(int*)((unsigned char *)public_key.exponent + 256 - sizeof(int)) = pubexp;
+
+	rc = ica_rsa_key_generate_crt(ah, 2048, &public_key, &private_key);
+
+	ica_close_adapter(ah);
+
+	return rc == 0 ? 1 : 0;
+}
+
 int get_rsa_minlen(void)
 {
 	int keylen_array[] = { 57, 512, 1024, 2048, 4096 };
@@ -188,21 +226,43 @@ int get_rsa_minlen(void)
 	return -1;
 }
 
+int get_rsa_min_pubexp(void)
+{
+	int pubexp_array[] = { 3, 65537 };
+	size_t i;
+
+	for (i = 0; i < sizeof(pubexp_array) / sizeof(int); i++) {
+		if (rsa_pubexp_supported_by_openssl(pubexp_array[i])) {
+			return pubexp_array[i];
+		}
+	}
+
+	return -1;
+}
+
 /**
  * Print out the minimum and maximum RSA key length. The maximum length is
  * restricted to 4096 bits by crypto cards. The minimum accepted length in
  * libica is 57 bits, but the available min length depends on the openssl
  * version and fips mode.
+ * Also print the minimum allowed value of the public exponent. In FIPS mode
+ * the minimum public exponent is 65537.
  */
 void print_rsa(void)
 {
 	int minlen = get_rsa_minlen();
+	int min_pubexp = get_rsa_min_pubexp();
 
 	if (minlen > 0)
 		printf("RSA key lengths: %d ... 4096 bits.\n", minlen);
 	else
 		printf("Error: cannot determine supported RSA key lengths via openssl.\n");
 
+	if (min_pubexp > 0)
+		printf("RSA public exponents greater or equal to %d.\n", min_pubexp);
+	else
+		printf("Error: cannot determine supported RSA public exponents via openssl.\n");
+
 #ifdef ICA_FIPS
 	printf("Built-in FIPS support: FIPS 140-3 mode %s.\n",
 	    ica_fips_status() & ICA_FIPS_MODE ? "active" : "inactive");