pgcrypto: Remove internal padding implementation

Use the padding provided by OpenSSL instead of doing it ourselves.
The internal implementation was once applicable to the non-OpenSSL
code paths, but those have since been removed.  The padding algorithm
is still the same.

The OpenSSL padding implementation is stricter than the previous
internal one: Bad padding during decryption is now an error, and
encryption without padding now requires the input size to be a
multiple of the block size, otherwise it is also an error.
Previously, these cases silently proceeded, in spite of the
documentation saying otherwise.

Add some test cases about this, too.  (The test cases are in
rijndael.sql, but they apply to all encryption algorithms.)

Reviewed-by: Jacob Champion <pchampion@vmware.com>
Reviewed-by: Nathan Bossart <nathandbossart@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/ba94c26b-0c58-c97e-7a44-f44e08b4cca2%40enterprisedb.com

Author: petere

contrib/pgcrypto/expected/rijndael.out

@@ -39,6 +39,12 @@ SELECT encrypt(
  \x8ea2b7ca516745bfeafc49904b496089
 (1 row)
 
+-- without padding, input not multiple of block size
+SELECT encrypt(
+'\x00112233445566778899aabbccddeeff00',
+'\x000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f',
+'aes-cbc/pad:none');
+ERROR:  encrypt error: Encryption failed
 -- key padding
 SELECT encrypt(
 '\x0011223344',
@@ -95,6 +101,14 @@ select encode(decrypt(encrypt('foo', '0123456', 'aes'), '0123456', 'aes'), 'esca
  foo
 (1 row)
 
+-- data not multiple of block size
+select encode(decrypt(encrypt('foo', '0123456', 'aes') || '\x00'::bytea, '0123456', 'aes'), 'escape');
+ERROR:  decrypt error: Decryption failed
+-- bad padding
+-- (The input value is the result of encrypt_iv('abcdefghijklmnopqrstuvwxyz', '0123456', 'abcd', 'aes')
+-- with the 16th byte changed (s/db/eb/) to corrupt the padding of the last block.)
+select encode(decrypt_iv('\xa21a9c15231465964e3396d32095e67eb52bab05f556a581621dee1b85385789', '0123456', 'abcd', 'aes'), 'escape');
+ERROR:  decrypt_iv error: Decryption failed
 -- iv
 select encrypt_iv('foo', '0123456', 'abcd', 'aes');
              encrypt_iv             

contrib/pgcrypto/openssl.c

@@ -369,17 +369,17 @@ gen_ossl_free(PX_Cipher *c)
 }
 
 static int
-gen_ossl_decrypt(PX_Cipher *c, const uint8 *data, unsigned dlen,
-				 uint8 *res)
+gen_ossl_decrypt(PX_Cipher *c, int padding, const uint8 *data, unsigned dlen,
+				 uint8 *res, unsigned *rlen)
 {
 	OSSLCipher *od = c->ptr;
-	int			outlen;
+	int			outlen, outlen2;
 
 	if (!od->init)
 	{
 		if (!EVP_DecryptInit_ex(od->evp_ctx, od->evp_ciph, NULL, NULL, NULL))
 			return PXE_CIPHER_INIT;
-		if (!EVP_CIPHER_CTX_set_padding(od->evp_ctx, 0))
+		if (!EVP_CIPHER_CTX_set_padding(od->evp_ctx, padding))
 			return PXE_CIPHER_INIT;
 		if (!EVP_CIPHER_CTX_set_key_length(od->evp_ctx, od->klen))
 			return PXE_CIPHER_INIT;
@@ -390,22 +390,25 @@ gen_ossl_decrypt(PX_Cipher *c, const uint8 *data, unsigned dlen,
 
 	if (!EVP_DecryptUpdate(od->evp_ctx, res, &outlen, data, dlen))
 		return PXE_DECRYPT_FAILED;
+	if (!EVP_DecryptFinal_ex(od->evp_ctx, res + outlen, &outlen2))
+		return PXE_DECRYPT_FAILED;
+	*rlen = outlen + outlen2;
 
 	return 0;
 }
 
 static int
-gen_ossl_encrypt(PX_Cipher *c, const uint8 *data, unsigned dlen,
-				 uint8 *res)
+gen_ossl_encrypt(PX_Cipher *c, int padding, const uint8 *data, unsigned dlen,
+				 uint8 *res, unsigned *rlen)
 {
 	OSSLCipher *od = c->ptr;
-	int			outlen;
+	int			outlen, outlen2;
 
 	if (!od->init)
 	{
 		if (!EVP_EncryptInit_ex(od->evp_ctx, od->evp_ciph, NULL, NULL, NULL))
 			return PXE_CIPHER_INIT;
-		if (!EVP_CIPHER_CTX_set_padding(od->evp_ctx, 0))
+		if (!EVP_CIPHER_CTX_set_padding(od->evp_ctx, padding))
 			return PXE_CIPHER_INIT;
 		if (!EVP_CIPHER_CTX_set_key_length(od->evp_ctx, od->klen))
 			return PXE_CIPHER_INIT;
@@ -416,6 +419,9 @@ gen_ossl_encrypt(PX_Cipher *c, const uint8 *data, unsigned dlen,
 
 	if (!EVP_EncryptUpdate(od->evp_ctx, res, &outlen, data, dlen))
 		return PXE_ENCRYPT_FAILED;
+	if (!EVP_EncryptFinal_ex(od->evp_ctx, res + outlen, &outlen2))
+		return PXE_ENCRYPT_FAILED;
+	*rlen = outlen + outlen2;
 
 	return 0;
 }

contrib/pgcrypto/pgp-cfb.c

@@ -220,7 +220,9 @@ cfb_process(PGP_CFB *ctx, const uint8 *data, int len, uint8 *dst,
 
 	while (len > 0)
 	{
-		px_cipher_encrypt(ctx->ciph, ctx->fr, ctx->block_size, ctx->fre);
+		unsigned	rlen;
+
+		px_cipher_encrypt(ctx->ciph, 0, ctx->fr, ctx->block_size, ctx->fre, &rlen);
 		if (ctx->block_no < 5)
 			ctx->block_no++;
 

contrib/pgcrypto/px.c

@@ -44,7 +44,6 @@ static const struct error_desc px_err_list[] = {
 	{PXE_ERR_GENERIC, "Some PX error (not specified)"},
 	{PXE_NO_HASH, "No such hash algorithm"},
 	{PXE_NO_CIPHER, "No such cipher algorithm"},
-	{PXE_NOTBLOCKSIZE, "Data not a multiple of block size"},
 	{PXE_BAD_OPTION, "Unknown option"},
 	{PXE_BAD_FORMAT, "Badly formatted type"},
 	{PXE_KEY_TOO_BIG, "Key was too big"},
@@ -221,129 +220,14 @@ static int
 combo_encrypt(PX_Combo *cx, const uint8 *data, unsigned dlen,
 			  uint8 *res, unsigned *rlen)
 {
-	int			err = 0;
-	uint8	   *bbuf;
-	unsigned	bs,
-				bpos,
-				i,
-				pad;
-
-	PX_Cipher  *c = cx->cipher;
-
-	bbuf = NULL;
-	bs = px_cipher_block_size(c);
-
-	/* encrypt */
-	if (bs > 1)
-	{
-		bbuf = palloc(bs * 4);
-		bpos = dlen % bs;
-		*rlen = dlen - bpos;
-		memcpy(bbuf, data + *rlen, bpos);
-
-		/* encrypt full-block data */
-		if (*rlen)
-		{
-			err = px_cipher_encrypt(c, data, *rlen, res);
-			if (err)
-				goto out;
-		}
-
-		/* bbuf has now bpos bytes of stuff */
-		if (cx->padding)
-		{
-			pad = bs - (bpos % bs);
-			for (i = 0; i < pad; i++)
-				bbuf[bpos++] = pad;
-		}
-		else if (bpos % bs)
-		{
-			/* ERROR? */
-			pad = bs - (bpos % bs);
-			for (i = 0; i < pad; i++)
-				bbuf[bpos++] = 0;
-		}
-
-		/* encrypt the rest - pad */
-		if (bpos)
-		{
-			err = px_cipher_encrypt(c, bbuf, bpos, res + *rlen);
-			*rlen += bpos;
-		}
-	}
-	else
-	{
-		/* stream cipher/mode - no pad needed */
-		err = px_cipher_encrypt(c, data, dlen, res);
-		if (err)
-			goto out;
-		*rlen = dlen;
-	}
-out:
-	if (bbuf)
-		pfree(bbuf);
-
-	return err;
+	return px_cipher_encrypt(cx->cipher, cx->padding, data, dlen, res, rlen);
 }
 
 static int
 combo_decrypt(PX_Combo *cx, const uint8 *data, unsigned dlen,
 			  uint8 *res, unsigned *rlen)
 {
-	int			err = 0;
-	unsigned	bs,
-				i,
-				pad;
-	unsigned	pad_ok;
-
-	PX_Cipher  *c = cx->cipher;
-
-	/* decide whether zero-length input is allowed */
-	if (dlen == 0)
-	{
-		/* with padding, empty ciphertext is not allowed */
-		if (cx->padding)
-			return PXE_DECRYPT_FAILED;
-
-		/* without padding, report empty result */
-		*rlen = 0;
-		return 0;
-	}
-
-	bs = px_cipher_block_size(c);
-	if (bs > 1 && (dlen % bs) != 0)
-		goto block_error;
-
-	/* decrypt */
-	*rlen = dlen;
-	err = px_cipher_decrypt(c, data, dlen, res);
-	if (err)
-		return err;
-
-	/* unpad */
-	if (bs > 1 && cx->padding)
-	{
-		pad = res[*rlen - 1];
-		pad_ok = 0;
-		if (pad > 0 && pad <= bs && pad <= *rlen)
-		{
-			pad_ok = 1;
-			for (i = *rlen - pad; i < *rlen; i++)
-				if (res[i] != pad)
-				{
-					pad_ok = 0;
-					break;
-				}
-		}
-
-		if (pad_ok)
-			*rlen -= pad;
-	}
-
-	return 0;
-
-block_error:
-	return PXE_NOTBLOCKSIZE;
+	return px_cipher_decrypt(cx->cipher, cx->padding, data, dlen, res, rlen);
 }
 
 static void

contrib/pgcrypto/px.h

@@ -47,7 +47,7 @@
 #define PXE_ERR_GENERIC				-1
 #define PXE_NO_HASH					-2
 #define PXE_NO_CIPHER				-3
-#define PXE_NOTBLOCKSIZE			-4
+/* -4 is unused */
 #define PXE_BAD_OPTION				-5
 #define PXE_BAD_FORMAT				-6
 #define PXE_KEY_TOO_BIG				-7
@@ -144,8 +144,8 @@ struct px_cipher
 	unsigned	(*iv_size) (PX_Cipher *c);
 
 	int			(*init) (PX_Cipher *c, const uint8 *key, unsigned klen, const uint8 *iv);
-	int			(*encrypt) (PX_Cipher *c, const uint8 *data, unsigned dlen, uint8 *res);
-	int			(*decrypt) (PX_Cipher *c, const uint8 *data, unsigned dlen, uint8 *res);
+	int			(*encrypt) (PX_Cipher *c, int padding, const uint8 *data, unsigned dlen, uint8 *res, unsigned *rlen);
+	int			(*decrypt) (PX_Cipher *c, int padding, const uint8 *data, unsigned dlen, uint8 *res, unsigned *rlen);
 	void		(*free) (PX_Cipher *c);
 	/* private */
 	void	   *ptr;
@@ -208,10 +208,10 @@ void		px_debug(const char *fmt,...) pg_attribute_printf(1, 2);
 #define px_cipher_block_size(c)		(c)->block_size(c)
 #define px_cipher_iv_size(c)		(c)->iv_size(c)
 #define px_cipher_init(c, k, klen, iv)	(c)->init(c, k, klen, iv)
-#define px_cipher_encrypt(c, data, dlen, res) \
-					(c)->encrypt(c, data, dlen, res)
-#define px_cipher_decrypt(c, data, dlen, res) \
-					(c)->decrypt(c, data, dlen, res)
+#define px_cipher_encrypt(c, padding, data, dlen, res, rlen) \
+					(c)->encrypt(c, padding, data, dlen, res, rlen)
+#define px_cipher_decrypt(c, padding, data, dlen, res, rlen) \
+					(c)->decrypt(c, padding, data, dlen, res, rlen)
 #define px_cipher_free(c)		(c)->free(c)
 
 

contrib/pgcrypto/sql/rijndael.sql

@@ -24,6 +24,12 @@ SELECT encrypt(
 '\x000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f',
 'aes-cbc/pad:none');
 
+-- without padding, input not multiple of block size
+SELECT encrypt(
+'\x00112233445566778899aabbccddeeff00',
+'\x000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f',
+'aes-cbc/pad:none');
+
 -- key padding
 
 SELECT encrypt(
@@ -50,6 +56,12 @@ select encrypt('foo', '0123456789012345678901', 'aes');
 
 -- decrypt
 select encode(decrypt(encrypt('foo', '0123456', 'aes'), '0123456', 'aes'), 'escape');
+-- data not multiple of block size
+select encode(decrypt(encrypt('foo', '0123456', 'aes') || '\x00'::bytea, '0123456', 'aes'), 'escape');
+-- bad padding
+-- (The input value is the result of encrypt_iv('abcdefghijklmnopqrstuvwxyz', '0123456', 'abcd', 'aes')
+-- with the 16th byte changed (s/db/eb/) to corrupt the padding of the last block.)
+select encode(decrypt_iv('\xa21a9c15231465964e3396d32095e67eb52bab05f556a581621dee1b85385789', '0123456', 'abcd', 'aes'), 'escape');
 
 -- iv
 select encrypt_iv('foo', '0123456', 'abcd', 'aes');