Example code for rsakeygen, pubkey, sign and verify

rsa/Makefile

@@ -0,0 +1,13 @@
+all:
+	gcc genrsa.c  -L/opt/openssl/lib -lcrypto -o genrsa
+	gcc rsa.c  -L/opt/openssl/lib -lcrypto -o rsa
+	gcc rsasign.c  -L/opt/openssl/lib -lcrypto -o rsasign
+	gcc rsaverify.c  -L/opt/openssl/lib -lcrypto -o rsaverify
+
+
+clean:
+	rm genrsa -rf
+	rm rsa -rf
+	rm rsasign -rf
+	rm rsaverify -rf
+

rsa/genrsa.c

@@ -0,0 +1,124 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <openssl/rsa.h>
+#include <openssl/evp.h>
+#include <openssl/bn.h>
+#include <openssl/err.h>
+#include <openssl/pem.h>
+
+char *prtkeyfile=NULL;
+BIO  *bio_log=NULL;
+unsigned int rsabits = 2048;
+
+void usage(void){
+	printf("\n rsagen -s <rsa size in bits> -o <private key file>");
+	printf("\n rsagen -h  -- For help");
+	printf("\n");
+}
+
+
+void generate_rsa(void){
+	BIGNUM *bn=NULL;
+ 	RSA *rsa=NULL;
+	EVP_PKEY *pkey=NULL;
+	BIO *prtbio;
+
+	if((bn = BN_new()) == NULL) {
+		BIO_printf(bio_log, "Failed to allocate BN\n");
+		goto end;
+	} 
+	BN_set_word(bn, RSA_F4);
+
+	rsa = RSA_new();	
+	RSA_generate_key_ex(rsa, rsabits, bn, NULL);
+
+	if((pkey = EVP_PKEY_new()) == NULL) {
+		BIO_printf(bio_log, "EVP_PKEY_New failed\n");
+		goto end;
+	}
+	EVP_PKEY_assign_RSA(pkey, rsa);
+
+	if (prtkeyfile) {
+		if ((prtbio = BIO_new_file(prtkeyfile, "w")) == NULL) {
+			BIO_printf(bio_log, "\n BIO_new_file %s failed\n", prtkeyfile);
+			goto end;
+		}
+	}
+	else {
+		if ((prtbio = BIO_new_fp(stdout, BIO_NOCLOSE)) == NULL) {
+			BIO_printf(bio_log, "\n BIO_new_file  failed\n");
+			goto end;
+		}
+	}
+
+	if (!PEM_write_bio_PrivateKey(prtbio, pkey, NULL, NULL, 0, NULL, NULL)) {
+		BIO_printf(bio_log, "PEM_write_bio_PrivateKey failed\n");
+		goto end;
+	}
+
+	end:
+		if (bn) {
+			BN_free(bn);
+		}
+
+		if(pkey) {
+			EVP_PKEY_free(pkey);
+		}
+
+
+	return;
+}
+
+int main(int argc, char **argv) {
+
+	unsigned int opt;
+
+	while( (opt=getopt(argc, argv, "o:s:h")) != -1) {
+		switch(opt) {
+			case 's':
+				rsabits = atoi(optarg);
+				break;
+
+			case 'o':
+				if((prtkeyfile = (char *) OPENSSL_malloc(strlen(optarg)+1)) == NULL) {
+					printf("\n %s: OPENSSL_malloc failed. \n", optarg);
+				}
+
+				memset(prtkeyfile, 0, strlen(optarg)+1);
+				memcpy(prtkeyfile, optarg, strlen(optarg));
+				break;
+
+			case 'h':
+				usage();
+				goto end;
+				break;
+
+			case '?':
+				printf("\n Invalid parameter passed\n");
+				break;
+		}		
+	}
+
+	bio_log = BIO_new_fp(stdout, BIO_NOCLOSE);
+	if(bio_log == NULL) {
+		printf("BIO_new_fp failed\n");
+		goto end;
+	}
+
+	generate_rsa();	
+
+
+end:
+
+	if(prtkeyfile) {
+		OPENSSL_free(prtkeyfile);
+	}
+
+	if(bio_log) {
+		BIO_free_all(bio_log);
+	}
+
+	return 0;
+}

rsa/rsa.c

@@ -0,0 +1,141 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <openssl/rsa.h>
+#include <openssl/evp.h>
+#include <openssl/bn.h>
+#include <openssl/err.h>
+#include <openssl/pem.h>
+
+char *pubkeyfile=NULL;
+char *prtkeyfile=NULL;
+BIO  *bio_log=NULL;
+unsigned int print;
+
+void usage(void){
+	printf("\n rsa -i <private key file> -o <public key file> -p ");
+	printf("\n rsa -h  -- For help");
+	printf("\n");
+}
+
+
+void getrsa(void){
+
+	BIO *prtbio, *pubbio;
+	EVP_PKEY *pkey;
+
+	if (prtkeyfile) {
+		if ((prtbio = BIO_new_file(prtkeyfile, "r")) == NULL) {
+			BIO_printf(bio_log, "\n BIO_new_file %s failed\n", prtkeyfile);
+			goto end;
+		}
+	}
+	else {
+		BIO_printf(bio_log, "\n Private key file not provided\n");
+		goto end;
+	}
+
+	if (pubkeyfile) {
+		if ((pubbio = BIO_new_file(pubkeyfile, "w")) == NULL) {
+			BIO_printf(bio_log, "\n BIO_new_file %s failed\n", pubkeyfile);
+			goto end;
+		}
+	}
+	else {
+		pubbio = bio_log;
+	}
+
+	if ((pkey = PEM_read_bio_PrivateKey(prtbio, NULL, NULL, NULL)) == NULL) {
+		BIO_printf(bio_log, "\n Unable to load\n");
+		goto end;
+	}
+
+	if( !PEM_write_bio_PUBKEY(pubbio, pkey)) {
+		BIO_printf(bio_log, "\n Public key extract failed\n");
+		goto end;
+	}
+
+	if (print) {
+		EVP_PKEY_print_private(pubbio, pkey, 0, NULL);
+	}
+
+	end:
+		if(prtbio) {
+			BIO_free(prtbio);
+		}
+
+		if(pubkeyfile && pubbio) {
+			BIO_free(pubbio);
+		}
+
+		if(pkey) {
+			EVP_PKEY_free(pkey);
+		}
+
+	return;
+}
+
+int main(int argc, char **argv) {
+
+	unsigned int opt;
+
+	while( (opt=getopt(argc, argv, "i:o:hp")) != -1) {
+		switch(opt) {
+			case 'i':
+				if((prtkeyfile = (char *) OPENSSL_malloc(strlen(optarg)+1)) == NULL) {
+					printf("\n %s: OPENSSL_malloc failed. \n", optarg);
+				}
+
+				memset(prtkeyfile, 0, strlen(optarg)+1);
+				memcpy(prtkeyfile, optarg, strlen(optarg));
+				break;
+
+			case 'o':
+				if((pubkeyfile = (char *) OPENSSL_malloc(strlen(optarg)+1)) == NULL) {
+					printf("\n %s: OPENSSL_malloc failed. \n", optarg);
+				}
+
+				memset(pubkeyfile, 0, strlen(optarg)+1);
+				memcpy(pubkeyfile, optarg, strlen(optarg));
+				break;
+
+			case 'p':
+				print = 1;
+				break;
+			case 'h':
+				usage();
+				goto end;
+				break;
+
+			case '?':
+				printf("\n Invalid parameter passed\n");
+				break;
+		}		
+	}
+
+	bio_log = BIO_new_fp(stdout, BIO_NOCLOSE);
+	if(bio_log == NULL) {
+		printf("BIO_new_fp failed\n");
+		goto end;
+	}
+
+	getrsa();	
+
+
+end:
+
+	if(pubkeyfile) {
+		OPENSSL_free(pubkeyfile);
+	}
+
+	if(prtkeyfile) {
+		OPENSSL_free(prtkeyfile);
+	}
+
+	if(bio_log) {
+		BIO_free_all(bio_log);
+	}
+
+	return 0;
+}