pgcrypto: Add support for CFB mode in AES encryption

Cipher Feedback Mode, CFB, is a self-synchronizing stream cipher which
is very similar to CBC performed in reverse. Since OpenSSL supports it,
we can easily plug it into the existing cipher selection code without
any need for infrastructure changes.

This patch was simultaneously submitted by Umar Hayat and Vladyslav
Nebozhyn, the latter whom suggested the feauture. The committed patch
is Umar's version.

Author: Umar Hayat <postgresql.wizard@gmail.com>
Reviewed-by: Daniel Gustafsson <daniel@yesql.se>
Reviewed-by: Álvaro Herrera <alvherre@alvh.no-ip.org>
Discussion: https://postgr.es/m/CAPBGcbxo9ASzq14VTpQp3mnUJ5omdgTWUJOvWV0L6nNigWE5jw@mail.gmail.com

contrib/pgcrypto/expected/rijndael.out

@@ -135,3 +135,121 @@ select encode(decrypt(encrypt('Lets try a longer message.', '0123456789', 'aes')
  Lets try a longer message.
 (1 row)
 
+-- cfb
+SELECT encrypt(
+'\x00112233445566778899aabbccddeeff',
+'\x000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f',
+'aes-cfb/pad:none');
+              encrypt               
+------------------------------------
+ \xf28122856e1cf9a7216a30d111f3997f
+(1 row)
+
+-- without padding, input not multiple of block size
+SELECT encrypt(
+'\x00112233445566778899aabbccddeeff00',
+'\x000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f',
+'aes-cfb/pad:none');
+               encrypt                
+--------------------------------------
+ \xf28122856e1cf9a7216a30d111f3997fcb
+(1 row)
+
+-- key padding
+SELECT encrypt(
+'\x0011223344',
+'\x000102030405',
+'aes-cfb');
+   encrypt    
+--------------
+ \x8145d1a0ef
+(1 row)
+
+SELECT encrypt(
+'\x0011223344',
+'\x000102030405060708090a0b0c0d0e0f10111213',
+'aes-cfb');
+   encrypt    
+--------------
+ \x52642c3b9c
+(1 row)
+
+SELECT encrypt(
+'\x0011223344',
+'\x000102030405060708090a0b0c0d0e0f101112131415161718191a1b',
+'aes-cfb');
+   encrypt    
+--------------
+ \xc93b4468a4
+(1 row)
+
+-- empty data
+select encrypt('', 'foo', 'aes-cfb');
+ encrypt 
+---------
+ \x
+(1 row)
+
+-- 10 bytes key
+select encrypt('foo', '0123456789', 'aes-cfb');
+ encrypt  
+----------
+ \x6f8ced
+(1 row)
+
+-- 22 bytes key
+select encrypt('foo', '0123456789012345678901', 'aes-cfb');
+ encrypt  
+----------
+ \xfb47d2
+(1 row)
+
+-- decrypt
+select encode(decrypt(encrypt('foo', '0123456', 'aes-cfb'), '0123456', 'aes-cfb'), 'escape');
+ encode 
+--------
+ foo
+(1 row)
+
+-- data not multiple of block size
+select encode(decrypt(encrypt('foo', '0123456', 'aes-cfb') || '\x00'::bytea, '0123456', 'aes-cfb'), 'escape');
+ encode  
+---------
+ foo\337
+(1 row)
+
+-- bad padding
+-- (The input value is the result of encrypt_iv('abcdefghijklmnopqrstuvwxyz', '0123456', 'abcd', 'aes-cfb')
+-- with the 16th byte changed (s/c5/d5/) to corrupt the padding of the last block.)
+select encode(decrypt_iv('\xf9ad6817cb58d31dd9ba6571fbc4f55d56f65b631f0f437cb828', '0123456', 'abcd', 'aes-cfb'), 'escape');
+                     encode                      
+-------------------------------------------------
+ abcdefghijklmnoq\243:\205o\x7F\x05z\276\x07\332
+(1 row)
+
+-- iv
+select encrypt_iv('foo', '0123456', 'abcd', 'aes-cfb');
+ encrypt_iv 
+------------
+ \xfea064
+(1 row)
+
+select encode(decrypt_iv('\xfea064', '0123456', 'abcd', 'aes-cfb'), 'escape');
+ encode 
+--------
+ foo
+(1 row)
+
+-- long message
+select encrypt('Lets try a longer message.', '0123456789', 'aes-cfb');
+                        encrypt                         
+--------------------------------------------------------
+ \x4586f6c6351055051f723b1b0aad52c877eaf0c421d18fd73a28
+(1 row)
+
+select encode(decrypt(encrypt('Lets try a longer message.', '0123456789', 'aes-cfb'), '0123456789', 'aes-cfb'), 'escape');
+           encode           
+----------------------------
+ Lets try a longer message.
+(1 row)
+

contrib/pgcrypto/openssl.c

@@ -617,6 +617,36 @@ ossl_aes_cbc_init(PX_Cipher *c, const uint8 *key, unsigned klen, const uint8 *iv
 	return err;
 }
 
+static int
+ossl_aes_cfb_init(PX_Cipher *c, const uint8 *key, unsigned klen, const uint8 *iv)
+{
+	OSSLCipher *od = c->ptr;
+	int			err;
+
+	err = ossl_aes_init(c, key, klen, iv);
+	if (err)
+		return err;
+
+	switch (od->klen)
+	{
+		case 128 / 8:
+			od->evp_ciph = EVP_aes_128_cfb();
+			break;
+		case 192 / 8:
+			od->evp_ciph = EVP_aes_192_cfb();
+			break;
+		case 256 / 8:
+			od->evp_ciph = EVP_aes_256_cfb();
+			break;
+		default:
+			/* shouldn't happen */
+			err = PXE_CIPHER_INIT;
+			break;
+	}
+
+	return err;
+}
+
 /*
  * aliases
  */
@@ -636,6 +666,7 @@ static PX_Alias ossl_aliases[] = {
 	{"rijndael", "aes-cbc"},
 	{"rijndael-cbc", "aes-cbc"},
 	{"rijndael-ecb", "aes-ecb"},
+	{"rijndael-cfb", "aes-cfb"},
 	{NULL}
 };
 
@@ -707,6 +738,13 @@ static const struct ossl_cipher ossl_aes_cbc = {
 	128 / 8, 256 / 8
 };
 
+static const struct ossl_cipher ossl_aes_cfb = {
+	ossl_aes_cfb_init,
+	NULL,						/* EVP_aes_XXX_cfb(), determined in init
+								 * function */
+	128 / 8, 256 / 8
+};
+
 /*
  * Special handlers
  */
@@ -728,6 +766,7 @@ static const struct ossl_cipher_lookup ossl_cipher_types[] = {
 	{"cast5-cbc", &ossl_cast_cbc},
 	{"aes-ecb", &ossl_aes_ecb},
 	{"aes-cbc", &ossl_aes_cbc},
+	{"aes-cfb", &ossl_aes_cfb},
 	{NULL}
 };
 

contrib/pgcrypto/sql/rijndael.sql

@@ -70,3 +70,56 @@ select encode(decrypt_iv('\x2c24cb7da91d6d5699801268b0f5adad', '0123456', 'abcd'
 -- long message
 select encrypt('Lets try a longer message.', '0123456789', 'aes');
 select encode(decrypt(encrypt('Lets try a longer message.', '0123456789', 'aes'), '0123456789', 'aes'), 'escape');
+
+-- cfb
+SELECT encrypt(
+'\x00112233445566778899aabbccddeeff',
+'\x000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f',
+'aes-cfb/pad:none');
+
+-- without padding, input not multiple of block size
+SELECT encrypt(
+'\x00112233445566778899aabbccddeeff00',
+'\x000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f',
+'aes-cfb/pad:none');
+
+-- key padding
+
+SELECT encrypt(
+'\x0011223344',
+'\x000102030405',
+'aes-cfb');
+
+SELECT encrypt(
+'\x0011223344',
+'\x000102030405060708090a0b0c0d0e0f10111213',
+'aes-cfb');
+
+SELECT encrypt(
+'\x0011223344',
+'\x000102030405060708090a0b0c0d0e0f101112131415161718191a1b',
+'aes-cfb');
+
+-- empty data
+select encrypt('', 'foo', 'aes-cfb');
+-- 10 bytes key
+select encrypt('foo', '0123456789', 'aes-cfb');
+-- 22 bytes key
+select encrypt('foo', '0123456789012345678901', 'aes-cfb');
+
+-- decrypt
+select encode(decrypt(encrypt('foo', '0123456', 'aes-cfb'), '0123456', 'aes-cfb'), 'escape');
+-- data not multiple of block size
+select encode(decrypt(encrypt('foo', '0123456', 'aes-cfb') || '\x00'::bytea, '0123456', 'aes-cfb'), 'escape');
+-- bad padding
+-- (The input value is the result of encrypt_iv('abcdefghijklmnopqrstuvwxyz', '0123456', 'abcd', 'aes-cfb')
+-- with the 16th byte changed (s/c5/d5/) to corrupt the padding of the last block.)
+select encode(decrypt_iv('\xf9ad6817cb58d31dd9ba6571fbc4f55d56f65b631f0f437cb828', '0123456', 'abcd', 'aes-cfb'), 'escape');
+
+-- iv
+select encrypt_iv('foo', '0123456', 'abcd', 'aes-cfb');
+select encode(decrypt_iv('\xfea064', '0123456', 'abcd', 'aes-cfb'), 'escape');
+
+-- long message
+select encrypt('Lets try a longer message.', '0123456789', 'aes-cfb');
+select encode(decrypt(encrypt('Lets try a longer message.', '0123456789', 'aes-cfb'), '0123456789', 'aes-cfb'), 'escape');

doc/src/sgml/pgcrypto.sgml

@@ -1082,6 +1082,11 @@ decrypt_iv(data bytea, key bytea, iv bytea, type text) returns bytea
     <literal>cbc</literal> &mdash; next block depends on previous (default)
     </para>
    </listitem>
+   <listitem>
+    <para>
+    <literal>cfb</literal> &mdash; next block depends on previous encrypted block
+    </para>
+   </listitem>
    <listitem>
     <para>
     <literal>ecb</literal> &mdash; each block is encrypted separately (for
@@ -1112,7 +1117,8 @@ encrypt(data, 'fooz', 'bf-cbc/pad:pkcs')
   </para>
   <para>
    In <function>encrypt_iv</function> and <function>decrypt_iv</function>, the
-   <parameter>iv</parameter> parameter is the initial value for the CBC mode;
+   <parameter>iv</parameter> parameter is the initial value for the CBC and
+   CFB mode;
    it is ignored for ECB.
    It is clipped or padded with zeroes if not exactly block size.
    It defaults to all zeroes in the functions without this parameter.