Add test cases for AES OFB block mode

Adds test cases from NIST SP800-38A for OFB block mode to AES-128/192/256, for
the configuration of MBEDTLS_CIPHER_MODE_OFB.
diff --git a/tests/Makefile b/tests/Makefile
index 8efecf3..e68c1f3 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -46,7 +46,8 @@
 endif
 
 APPS =	test_suite_aes.ecb$(EXEXT)	test_suite_aes.cbc$(EXEXT)	\
-	test_suite_aes.cfb$(EXEXT)	test_suite_aes.rest$(EXEXT)	\
+	test_suite_aes.cfb$(EXEXT)		test_suite_aes.ofb$(EXEXT)	\
+	test_suite_aes.rest$(EXEXT)	\
 	test_suite_arc4$(EXEXT)		test_suite_asn1write$(EXEXT)	\
 	test_suite_base64$(EXEXT)	test_suite_blowfish$(EXEXT)	\
 	test_suite_camellia$(EXEXT)	test_suite_ccm$(EXEXT)		\
@@ -110,6 +111,10 @@
 	echo "  Gen   $@"
 	perl scripts/generate_code.pl suites test_suite_aes test_suite_aes.cfb
 
+test_suite_aes.ofb.c : suites/test_suite_aes.function suites/test_suite_aes.ofb.data scripts/generate_code.pl suites/helpers.function suites/main_test.function
+	echo "  Gen   $@"
+	perl scripts/generate_code.pl suites test_suite_aes test_suite_aes.ofb
+
 test_suite_aes.rest.c : suites/test_suite_aes.function suites/test_suite_aes.rest.data scripts/generate_code.pl suites/helpers.function suites/main_test.function
 	echo "  Gen   $@"
 	perl scripts/generate_code.pl suites test_suite_aes test_suite_aes.rest
@@ -210,6 +215,10 @@
 	echo "  CC    $<"
 	$(CC) $(LOCAL_CFLAGS) $(CFLAGS) $<	$(LOCAL_LDFLAGS) $(LDFLAGS) -o $@
 
+test_suite_aes.ofb$(EXEXT): test_suite_aes.ofb.c $(DEP)
+	echo "  CC    $<"
+	$(CC) $(LOCAL_CFLAGS) $(CFLAGS) $<	$(LOCAL_LDFLAGS) $(LDFLAGS) -o $@
+
 test_suite_aes.rest$(EXEXT): test_suite_aes.rest.c $(DEP)
 	echo "  CC    $<"
 	$(CC) $(LOCAL_CFLAGS) $(CFLAGS) $<	$(LOCAL_LDFLAGS) $(LDFLAGS) -o $@
diff --git a/tests/suites/test_suite_aes.function b/tests/suites/test_suite_aes.function
index c5f0eaa..e1792dd 100644
--- a/tests/suites/test_suite_aes.function
+++ b/tests/suites/test_suite_aes.function
@@ -289,6 +289,58 @@
 }
 /* END_CASE */
 
+/* BEGIN_CASE depends_on:MBEDTLS_CIPHER_MODE_OFB */
+void aes_encrypt_ofb( int fragment_size, char *hex_key_string,
+                        char *hex_iv_string, char *hex_src_string,
+                        char *hex_dst_string )
+{
+    unsigned char key_str[100];
+    unsigned char iv_str[100];
+    unsigned char src_str[200];
+    unsigned char dst_str[200];
+    unsigned char output[200];
+    mbedtls_aes_context ctx;
+    size_t iv_offset = 0;
+    int in_buffer_len;
+    unsigned char* src_str_next;
+    int key_len, iv_len;
+
+    memset(key_str, 0x00, 100);
+    memset(iv_str, 0x00, 100);
+    memset(src_str, 0x00, 200);
+    memset(dst_str, 0x00, 200);
+    memset(output, 0x00, 200);
+    mbedtls_aes_init( &ctx );
+
+    key_len = unhexify( key_str, hex_key_string );
+    iv_len = unhexify( iv_str, hex_iv_string );
+    in_buffer_len = unhexify( src_str, hex_src_string );
+
+    mbedtls_aes_setkey_enc( &ctx, key_str, key_len * 8 );
+    src_str_next = src_str;
+
+    while( in_buffer_len > 0 )
+    {
+        TEST_ASSERT( mbedtls_aes_crypt_ofb( &ctx, fragment_size, &iv_offset,
+                                            iv_str, src_str_next, output ) == 0 );
+
+        hexify( dst_str, output, fragment_size );
+        TEST_ASSERT( strncmp( (char *) dst_str, hex_dst_string,
+                                ( 2 * fragment_size) ) == 0 );
+
+        in_buffer_len -= fragment_size;
+        hex_dst_string += ( fragment_size * 2 );
+        src_str_next += fragment_size;
+
+        if( in_buffer_len < fragment_size )
+            fragment_size = in_buffer_len;
+    }
+
+exit:
+    mbedtls_aes_free( &ctx );
+}
+/* END_CASE */
+
 /* BEGIN_CASE depends_on:MBEDTLS_SELF_TEST */
 void aes_selftest()
 {
diff --git a/tests/suites/test_suite_aes.ofb.data b/tests/suites/test_suite_aes.ofb.data
new file mode 100644
index 0000000..4b9d80e
--- /dev/null
+++ b/tests/suites/test_suite_aes.ofb.data
@@ -0,0 +1,35 @@
+# NIST Special Publication 800-38A
+# Recommendation for Block Cipher Modes of Operation
+# Test Vectors - Appendix F, Section F.4
+OFB-AES128.Encrypt - Single block
+depends_on:MBEDTLS_CIPHER_MODE_OFB
+aes_encrypt_ofb:16:"2b7e151628aed2a6abf7158809cf4f3c":"000102030405060708090a0b0c0d0e0f":"6bc1bee22e409f96e93d7e117393172a":"3b3fd92eb72dad20333449f8e83cfb4a"
+
+OFB-AES128.Encrypt - Partial blocks - 7 bytes
+depends_on:MBEDTLS_CIPHER_MODE_OFB
+aes_encrypt_ofb:5:"2b7e151628aed2a6abf7158809cf4f3c":"000102030405060708090a0b0c0d0e0f":"6bc1bee22e409f96e93d7e117393172aae2d8a571e03ac9c9eb76fac45af8e5130c81c46a35ce411e5fbc1191a0a52eff69f2445df4f9b17ad2b417be66c3710":"3b3fd92eb72dad20333449f8e83cfb4a7789508d16918f03f53c52dac54ed8259740051e9c5fecf64344f7a82260edcc304c6528f659c77866a510d9c1d6ae5e"
+
+OFB-AES128.Encrypt - Test NIST SP800-38A - F.4.1
+depends_on:MBEDTLS_CIPHER_MODE_OFB
+aes_encrypt_ofb:16:"2b7e151628aed2a6abf7158809cf4f3c":"000102030405060708090a0b0c0d0e0f":"6bc1bee22e409f96e93d7e117393172aae2d8a571e03ac9c9eb76fac45af8e5130c81c46a35ce411e5fbc1191a0a52eff69f2445df4f9b17ad2b417be66c3710":"3b3fd92eb72dad20333449f8e83cfb4a7789508d16918f03f53c52dac54ed8259740051e9c5fecf64344f7a82260edcc304c6528f659c77866a510d9c1d6ae5e"
+
+OFB-AES128.Decrypt - Test NIST SP800-38A - F.4.2
+depends_on:MBEDTLS_CIPHER_MODE_OFB
+aes_encrypt_ofb:16:"2b7e151628aed2a6abf7158809cf4f3c":"000102030405060708090a0b0c0d0e0f":"3b3fd92eb72dad20333449f8e83cfb4a7789508d16918f03f53c52dac54ed8259740051e9c5fecf64344f7a82260edcc304c6528f659c77866a510d9c1d6ae5e":"6bc1bee22e409f96e93d7e117393172aae2d8a571e03ac9c9eb76fac45af8e5130c81c46a35ce411e5fbc1191a0a52eff69f2445df4f9b17ad2b417be66c3710"
+
+OFB-AES192.Encrypt - Test NIST SP800-38A - F.4.3
+depends_on:MBEDTLS_CIPHER_MODE_OFB
+aes_encrypt_ofb:16:"8e73b0f7da0e6452c810f32b809079e562f8ead2522c6b7b":"000102030405060708090a0b0c0d0e0f":"6bc1bee22e409f96e93d7e117393172aae2d8a571e03ac9c9eb76fac45af8e5130c81c46a35ce411e5fbc1191a0a52eff69f2445df4f9b17ad2b417be66c3710":"cdc80d6fddf18cab34c25909c99a4174fcc28b8d4c63837c09e81700c11004018d9a9aeac0f6596f559c6d4daf59a5f26d9f200857ca6c3e9cac524bd9acc92a"
+
+OFB-AES192.Decrypt - Test NIST SP800-38A - F.4.4
+depends_on:MBEDTLS_CIPHER_MODE_OFB
+aes_encrypt_ofb:16:"8e73b0f7da0e6452c810f32b809079e562f8ead2522c6b7b":"000102030405060708090a0b0c0d0e0f":"cdc80d6fddf18cab34c25909c99a4174fcc28b8d4c63837c09e81700c11004018d9a9aeac0f6596f559c6d4daf59a5f26d9f200857ca6c3e9cac524bd9acc92a":"6bc1bee22e409f96e93d7e117393172aae2d8a571e03ac9c9eb76fac45af8e5130c81c46a35ce411e5fbc1191a0a52eff69f2445df4f9b17ad2b417be66c3710"
+
+OFB-AES256.Encrypt - Test NIST SP800-38A - F.4.5
+depends_on:MBEDTLS_CIPHER_MODE_OFB
+aes_encrypt_ofb:16:"603deb1015ca71be2b73aef0857d77811f352c073b6108d72d9810a30914dff4":"000102030405060708090a0b0c0d0e0f":"6bc1bee22e409f96e93d7e117393172aae2d8a571e03ac9c9eb76fac45af8e5130c81c46a35ce411e5fbc1191a0a52eff69f2445df4f9b17ad2b417be66c3710":"dc7e84bfda79164b7ecd8486985d38604febdc6740d20b3ac88f6ad82a4fb08d71ab47a086e86eedf39d1c5bba97c4080126141d67f37be8538f5a8be740e484"
+
+OFB-AES256.Decrypt - Test NIST SP800-38A - F.4.6
+depends_on:MBEDTLS_CIPHER_MODE_OFB
+aes_encrypt_ofb:16:"603deb1015ca71be2b73aef0857d77811f352c073b6108d72d9810a30914dff4":"000102030405060708090a0b0c0d0e0f":"dc7e84bfda79164b7ecd8486985d38604febdc6740d20b3ac88f6ad82a4fb08d71ab47a086e86eedf39d1c5bba97c4080126141d67f37be8538f5a8be740e484":"6bc1bee22e409f96e93d7e117393172aae2d8a571e03ac9c9eb76fac45af8e5130c81c46a35ce411e5fbc1191a0a52eff69f2445df4f9b17ad2b417be66c3710"
+