+/* $OpenBSD: packet.c,v 1.136 2006/07/17 01:31:09 stevesk Exp $ */
/*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
*
*
* SSH2 packet format added by Markus Friedl.
- * Copyright (c) 2000 Markus Friedl. All rights reserved.
+ * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
*/
#include "includes.h"
-RCSID("$OpenBSD: packet.c,v 1.61 2001/04/05 10:42:51 markus Exp $");
+
+#include <sys/types.h>
+#include "openbsd-compat/sys-queue.h"
+#include <sys/socket.h>
+
+#include <netinet/in_systm.h>
+#include <netinet/in.h>
+#include <netinet/ip.h>
+
+#include <errno.h>
+#include <stdarg.h>
+#include <unistd.h>
#include "xmalloc.h"
#include "buffer.h"
#include "packet.h"
#include "bufaux.h"
#include "crc32.h"
-#include "getput.h"
#include "compress.h"
#include "deattack.h"
#include "mac.h"
#include "log.h"
#include "canohost.h"
+#include "misc.h"
+#include "ssh.h"
#ifdef PACKET_DEBUG
#define DBG(x) x
static int connection_in = -1;
static int connection_out = -1;
-/*
- * Cipher type. This value is only used to determine whether to pad the
- * packets with zeroes or random data.
- */
-static int cipher_type = SSH_CIPHER_NONE;
-
/* Protocol flags for the remote side. */
static u_int remote_protocol_flags = 0;
static CipherContext send_context;
/* Buffer for raw input data from the socket. */
-static Buffer input;
+Buffer input;
/* Buffer for raw output data going to the socket. */
-static Buffer output;
+Buffer output;
/* Buffer for the partial outgoing packet being constructed. */
static Buffer outgoing_packet;
static int packet_compression = 0;
/* default maximum packet size */
-int max_packet_size = 32768;
+u_int max_packet_size = 32768;
/* Flag indicating whether this module has been initialized. */
static int initialized = 0;
/* Set to true if the connection is interactive. */
static int interactive_mode = 0;
-/* True if SSH2 packet format is used */
-int use_ssh2_packet_format = 0;
+/* Set to true if we are the server side. */
+static int server_side = 0;
+
+/* Set to true if we are authenticated. */
+static int after_authentication = 0;
/* Session key information for Encryption and MAC */
Newkeys *newkeys[MODE_MAX];
+static struct packet_state {
+ u_int32_t seqnr;
+ u_int32_t packets;
+ u_int64_t blocks;
+} p_read, p_send;
-void
-packet_set_ssh2_format(void)
-{
- DBG(debug("use_ssh2_packet_format"));
- use_ssh2_packet_format = 1;
- newkeys[MODE_IN] = newkeys[MODE_OUT] = NULL;
-}
+static u_int64_t max_blocks_in, max_blocks_out;
+static u_int32_t rekey_limit;
+
+/* Session key for protocol v1 */
+static u_char ssh1_key[SSH_SESSION_KEY_LENGTH];
+static u_int ssh1_keylen;
+
+/* roundup current message to extra_pad bytes */
+static u_char extra_pad = 0;
+
+struct packet {
+ TAILQ_ENTRY(packet) next;
+ u_char type;
+ Buffer payload;
+};
+TAILQ_HEAD(, packet) outgoing;
/*
* Sets the descriptors used for communication. Disables encryption until
packet_set_connection(int fd_in, int fd_out)
{
Cipher *none = cipher_by_name("none");
+
if (none == NULL)
fatal("packet_set_connection: cannot load cipher 'none'");
connection_in = fd_in;
connection_out = fd_out;
- cipher_type = SSH_CIPHER_NONE;
- cipher_init(&send_context, none, (u_char *) "", 0, NULL, 0);
- cipher_init(&receive_context, none, (u_char *) "", 0, NULL, 0);
+ cipher_init(&send_context, none, (const u_char *)"",
+ 0, NULL, 0, CIPHER_ENCRYPT);
+ cipher_init(&receive_context, none, (const u_char *)"",
+ 0, NULL, 0, CIPHER_DECRYPT);
+ newkeys[MODE_IN] = newkeys[MODE_OUT] = NULL;
if (!initialized) {
initialized = 1;
buffer_init(&input);
buffer_init(&output);
buffer_init(&outgoing_packet);
buffer_init(&incoming_packet);
+ TAILQ_INIT(&outgoing);
}
- /* Kludge: arrange the close function to be called from fatal(). */
- fatal_add_cleanup((void (*) (void *)) packet_close, NULL);
}
/* Returns 1 if remote host is connected via socket, 0 if not. */
int
-packet_connection_is_on_socket()
+packet_connection_is_on_socket(void)
{
struct sockaddr_storage from, to;
socklen_t fromlen, tolen;
return 1;
}
+/*
+ * Exports an IV from the CipherContext required to export the key
+ * state back from the unprivileged child to the privileged parent
+ * process.
+ */
+
+void
+packet_get_keyiv(int mode, u_char *iv, u_int len)
+{
+ CipherContext *cc;
+
+ if (mode == MODE_OUT)
+ cc = &send_context;
+ else
+ cc = &receive_context;
+
+ cipher_get_keyiv(cc, iv, len);
+}
+
+int
+packet_get_keycontext(int mode, u_char *dat)
+{
+ CipherContext *cc;
+
+ if (mode == MODE_OUT)
+ cc = &send_context;
+ else
+ cc = &receive_context;
+
+ return (cipher_get_keycontext(cc, dat));
+}
+
+void
+packet_set_keycontext(int mode, u_char *dat)
+{
+ CipherContext *cc;
+
+ if (mode == MODE_OUT)
+ cc = &send_context;
+ else
+ cc = &receive_context;
+
+ cipher_set_keycontext(cc, dat);
+}
+
+int
+packet_get_keyiv_len(int mode)
+{
+ CipherContext *cc;
+
+ if (mode == MODE_OUT)
+ cc = &send_context;
+ else
+ cc = &receive_context;
+
+ return (cipher_get_keyiv_len(cc));
+}
+
+void
+packet_set_iv(int mode, u_char *dat)
+{
+ CipherContext *cc;
+
+ if (mode == MODE_OUT)
+ cc = &send_context;
+ else
+ cc = &receive_context;
+
+ cipher_set_keyiv(cc, dat);
+}
+
+int
+packet_get_ssh1_cipher(void)
+{
+ return (cipher_get_number(receive_context.cipher));
+}
+
+void
+packet_get_state(int mode, u_int32_t *seqnr, u_int64_t *blocks, u_int32_t *packets)
+{
+ struct packet_state *state;
+
+ state = (mode == MODE_IN) ? &p_read : &p_send;
+ *seqnr = state->seqnr;
+ *blocks = state->blocks;
+ *packets = state->packets;
+}
+
+void
+packet_set_state(int mode, u_int32_t seqnr, u_int64_t blocks, u_int32_t packets)
+{
+ struct packet_state *state;
+
+ state = (mode == MODE_IN) ? &p_read : &p_send;
+ state->seqnr = seqnr;
+ state->blocks = blocks;
+ state->packets = packets;
+}
+
/* returns 1 if connection is via ipv4 */
int
-packet_connection_is_ipv4()
+packet_connection_is_ipv4(void)
{
struct sockaddr_storage to;
socklen_t tolen = sizeof(to);
memset(&to, 0, sizeof(to));
if (getsockname(connection_out, (struct sockaddr *)&to, &tolen) < 0)
return 0;
- if (to.ss_family != AF_INET)
- return 0;
- return 1;
+ if (to.ss_family == AF_INET)
+ return 1;
+#ifdef IPV4_IN_IPV6
+ if (to.ss_family == AF_INET6 &&
+ IN6_IS_ADDR_V4MAPPED(&((struct sockaddr_in6 *)&to)->sin6_addr))
+ return 1;
+#endif
+ return 0;
}
/* Sets the connection into non-blocking mode. */
void
-packet_set_nonblocking()
+packet_set_nonblocking(void)
{
/* Set the socket into non-blocking mode. */
- if (fcntl(connection_in, F_SETFL, O_NONBLOCK) < 0)
- error("fcntl O_NONBLOCK: %.100s", strerror(errno));
+ set_nonblock(connection_in);
- if (connection_out != connection_in) {
- if (fcntl(connection_out, F_SETFL, O_NONBLOCK) < 0)
- error("fcntl O_NONBLOCK: %.100s", strerror(errno));
- }
+ if (connection_out != connection_in)
+ set_nonblock(connection_out);
}
/* Returns the socket used for reading. */
int
-packet_get_connection_in()
+packet_get_connection_in(void)
{
return connection_in;
}
/* Returns the descriptor used for writing. */
int
-packet_get_connection_out()
+packet_get_connection_out(void)
{
return connection_out;
}
/* Closes the connection and clears and frees internal data structures. */
void
-packet_close()
+packet_close(void)
{
if (!initialized)
return;
buffer_free(&compression_buffer);
buffer_compress_uninit();
}
+ cipher_cleanup(&send_context);
+ cipher_cleanup(&receive_context);
}
/* Sets remote side protocol flags. */
packet_set_protocol_flags(u_int protocol_flags)
{
remote_protocol_flags = protocol_flags;
- channel_set_options((protocol_flags & SSH_PROTOFLAG_HOST_IN_FWD_OPEN) != 0);
}
/* Returns the remote protocol flags set earlier by the above function. */
u_int
-packet_get_protocol_flags()
+packet_get_protocol_flags(void)
{
return remote_protocol_flags;
}
* Level is compression level 1 (fastest) - 9 (slow, best) as in gzip.
*/
-void
-packet_init_compression()
+static void
+packet_init_compression(void)
{
if (compression_buffer_ready == 1)
return;
void
packet_start_compression(int level)
{
- if (packet_compression && !use_ssh2_packet_format)
+ if (packet_compression && !compat20)
fatal("Compression already enabled.");
packet_compression = 1;
packet_init_compression();
buffer_compress_init_recv();
}
-/*
- * Encrypts the given number of bytes, copying from src to dest. bytes is
- * known to be a multiple of 8.
- */
-
-void
-packet_encrypt(CipherContext * cc, void *dest, void *src,
- u_int bytes)
-{
- cipher_encrypt(cc, dest, src, bytes);
-}
-
-/*
- * Decrypts the given number of bytes, copying from src to dest. bytes is
- * known to be a multiple of 8.
- */
-
-void
-packet_decrypt(CipherContext *context, void *dest, void *src, u_int bytes)
-{
- /*
- * Cryptographic attack detector for ssh - Modifications for packet.c
- * (C)1998 CORE-SDI, Buenos Aires Argentina Ariel Futoransky(futo@core-sdi.com)
- */
- if (!compat20 &&
- context->cipher->number != SSH_CIPHER_NONE &&
- detect_attack(src, bytes, NULL) == DEATTACK_DETECTED)
- packet_disconnect("crc32 compensation attack: network attack detected");
-
- cipher_decrypt(context, dest, src, bytes);
-}
-
/*
* Causes any further packets to be encrypted using the given key. The same
* key is used for both sending and reception. However, both directions are
int number)
{
Cipher *cipher = cipher_by_number(number);
+
if (cipher == NULL)
fatal("packet_set_encryption_key: unknown cipher number %d", number);
if (keylen < 20)
fatal("packet_set_encryption_key: keylen too small: %d", keylen);
- cipher_init(&receive_context, cipher, key, keylen, NULL, 0);
- cipher_init(&send_context, cipher, key, keylen, NULL, 0);
+ if (keylen > SSH_SESSION_KEY_LENGTH)
+ fatal("packet_set_encryption_key: keylen too big: %d", keylen);
+ memcpy(ssh1_key, key, keylen);
+ ssh1_keylen = keylen;
+ cipher_init(&send_context, cipher, key, keylen, NULL, 0, CIPHER_ENCRYPT);
+ cipher_init(&receive_context, cipher, key, keylen, NULL, 0, CIPHER_DECRYPT);
}
-/* Starts constructing a packet to send. */
-
-void
-packet_start1(int type)
+u_int
+packet_get_encryption_key(u_char *key)
{
- char buf[9];
-
- buffer_clear(&outgoing_packet);
- memset(buf, 0, 8);
- buf[8] = type;
- buffer_append(&outgoing_packet, buf, 9);
+ if (key == NULL)
+ return (ssh1_keylen);
+ memcpy(key, ssh1_key, ssh1_keylen);
+ return (ssh1_keylen);
}
+/* Start constructing a packet to send. */
void
-packet_start2(int type)
+packet_start(u_char type)
{
- char buf[4+1+1];
+ u_char buf[9];
+ int len;
+ DBG(debug("packet_start[%d]", type));
+ len = compat20 ? 6 : 9;
+ memset(buf, 0, len - 1);
+ buf[len - 1] = type;
buffer_clear(&outgoing_packet);
- memset(buf, 0, sizeof buf);
- /* buf[0..3] = payload_len; */
- /* buf[4] = pad_len; */
- buf[5] = type & 0xff;
- buffer_append(&outgoing_packet, buf, sizeof buf);
+ buffer_append(&outgoing_packet, buf, len);
}
-void
-packet_start(int type)
-{
- DBG(debug("packet_start[%d]", type));
- if (use_ssh2_packet_format)
- packet_start2(type);
- else
- packet_start1(type);
-}
-
-/* Appends a character to the packet data. */
-
+/* Append payload. */
void
packet_put_char(int value)
{
char ch = value;
+
buffer_append(&outgoing_packet, &ch, 1);
}
-/* Appends an integer to the packet data. */
-
void
packet_put_int(u_int value)
{
buffer_put_int(&outgoing_packet, value);
}
-/* Appends a string to packet data. */
-
void
-packet_put_string(const char *buf, u_int len)
+packet_put_string(const void *buf, u_int len)
{
buffer_put_string(&outgoing_packet, buf, len);
}
+
void
packet_put_cstring(const char *str)
{
- buffer_put_string(&outgoing_packet, str, strlen(str));
+ buffer_put_cstring(&outgoing_packet, str);
}
void
-packet_put_raw(const char *buf, u_int len)
+packet_put_raw(const void *buf, u_int len)
{
buffer_append(&outgoing_packet, buf, len);
}
-
-/* Appends an arbitrary precision integer to packet data. */
-
void
packet_put_bignum(BIGNUM * value)
{
buffer_put_bignum(&outgoing_packet, value);
}
+
void
packet_put_bignum2(BIGNUM * value)
{
* encrypts the packet before sending.
*/
-void
+static void
packet_send1(void)
{
- char buf[8], *cp;
+ u_char buf[8], *cp;
int i, padding, len;
u_int checksum;
- u_int32_t rand = 0;
+ u_int32_t rnd = 0;
/*
* If using packet compression, compress the payload of the outgoing
buffer_compress(&outgoing_packet, &compression_buffer);
buffer_clear(&outgoing_packet);
buffer_append(&outgoing_packet, buffer_ptr(&compression_buffer),
- buffer_len(&compression_buffer));
+ buffer_len(&compression_buffer));
}
/* Compute packet length without padding (add checksum, remove padding). */
len = buffer_len(&outgoing_packet) + 4 - 8;
/* Insert padding. Initialized to zero in packet_start1() */
padding = 8 - len % 8;
- if (cipher_type != SSH_CIPHER_NONE) {
+ if (!send_context.plaintext) {
cp = buffer_ptr(&outgoing_packet);
for (i = 0; i < padding; i++) {
if (i % 4 == 0)
- rand = arc4random();
- cp[7 - i] = rand & 0xff;
- rand >>= 8;
+ rnd = arc4random();
+ cp[7 - i] = rnd & 0xff;
+ rnd >>= 8;
}
}
buffer_consume(&outgoing_packet, 8 - padding);
/* Add check bytes. */
- checksum = ssh_crc32((u_char *) buffer_ptr(&outgoing_packet),
+ checksum = ssh_crc32(buffer_ptr(&outgoing_packet),
buffer_len(&outgoing_packet));
- PUT_32BIT(buf, checksum);
+ put_u32(buf, checksum);
buffer_append(&outgoing_packet, buf, 4);
#ifdef PACKET_DEBUG
#endif
/* Append to output. */
- PUT_32BIT(buf, len);
+ put_u32(buf, len);
buffer_append(&output, buf, 4);
- buffer_append_space(&output, &cp, buffer_len(&outgoing_packet));
- packet_encrypt(&send_context, cp, buffer_ptr(&outgoing_packet),
- buffer_len(&outgoing_packet));
+ cp = buffer_append_space(&output, buffer_len(&outgoing_packet));
+ cipher_crypt(&send_context, cp, buffer_ptr(&outgoing_packet),
+ buffer_len(&outgoing_packet));
#ifdef PACKET_DEBUG
fprintf(stderr, "encrypted: ");
buffer_clear(&outgoing_packet);
/*
- * Note that the packet is now only buffered in output. It won\'t be
+ * Note that the packet is now only buffered in output. It won't be
* actually sent until packet_write_wait or packet_write_poll is
* called.
*/
Mac *mac;
Comp *comp;
CipherContext *cc;
+ u_int64_t *max_blocks;
+ int crypt_type;
- debug("newkeys: mode %d", mode);
+ debug2("set_newkeys: mode %d", mode);
- cc = (mode == MODE_OUT) ? &send_context : &receive_context;
+ if (mode == MODE_OUT) {
+ cc = &send_context;
+ crypt_type = CIPHER_ENCRYPT;
+ p_send.packets = p_send.blocks = 0;
+ max_blocks = &max_blocks_out;
+ } else {
+ cc = &receive_context;
+ crypt_type = CIPHER_DECRYPT;
+ p_read.packets = p_read.blocks = 0;
+ max_blocks = &max_blocks_in;
+ }
if (newkeys[mode] != NULL) {
- debug("newkeys: rekeying");
- /* todo: free old keys, reset compression/cipher-ctxt; */
- memset(cc, 0, sizeof(*cc));
+ debug("set_newkeys: rekeying");
+ cipher_cleanup(cc);
enc = &newkeys[mode]->enc;
mac = &newkeys[mode]->mac;
comp = &newkeys[mode]->comp;
if (mac->md != NULL)
mac->enabled = 1;
DBG(debug("cipher_init_context: %d", mode));
- cipher_init(cc, enc->cipher, enc->key, enc->cipher->key_len,
- enc->iv, enc->cipher->block_size);
- memset(enc->iv, 0, enc->cipher->block_size);
- memset(enc->key, 0, enc->cipher->key_len);
- if (comp->type != 0 && comp->enabled == 0) {
+ cipher_init(cc, enc->cipher, enc->key, enc->key_len,
+ enc->iv, enc->block_size, crypt_type);
+ /* Deleting the keys does not gain extra security */
+ /* memset(enc->iv, 0, enc->block_size);
+ memset(enc->key, 0, enc->key_len); */
+ if ((comp->type == COMP_ZLIB ||
+ (comp->type == COMP_DELAYED && after_authentication)) &&
+ comp->enabled == 0) {
packet_init_compression();
if (mode == MODE_OUT)
buffer_compress_init_send(6);
buffer_compress_init_recv();
comp->enabled = 1;
}
+ /*
+ * The 2^(blocksize*2) limit is too expensive for 3DES,
+ * blowfish, etc, so enforce a 1GB limit for small blocksizes.
+ */
+ if (enc->block_size >= 16)
+ *max_blocks = (u_int64_t)1 << (enc->block_size*2);
+ else
+ *max_blocks = ((u_int64_t)1 << 30) / enc->block_size;
+ if (rekey_limit)
+ *max_blocks = MIN(*max_blocks, rekey_limit / enc->block_size);
+}
+
+/*
+ * Delayed compression for SSH2 is enabled after authentication:
+ * This happans on the server side after a SSH2_MSG_USERAUTH_SUCCESS is sent,
+ * and on the client side after a SSH2_MSG_USERAUTH_SUCCESS is received.
+ */
+static void
+packet_enable_delayed_compress(void)
+{
+ Comp *comp = NULL;
+ int mode;
+
+ /*
+ * Remember that we are past the authentication step, so rekeying
+ * with COMP_DELAYED will turn on compression immediately.
+ */
+ after_authentication = 1;
+ for (mode = 0; mode < MODE_MAX; mode++) {
+ comp = &newkeys[mode]->comp;
+ if (comp && !comp->enabled && comp->type == COMP_DELAYED) {
+ packet_init_compression();
+ if (mode == MODE_OUT)
+ buffer_compress_init_send(6);
+ else
+ buffer_compress_init_recv();
+ comp->enabled = 1;
+ }
+ }
}
/*
* Finalize packet in SSH2 format (compress, mac, encrypt, enqueue)
*/
-void
-packet_send2(void)
+static void
+packet_send2_wrapped(void)
{
- static u_int32_t seqnr = 0;
- u_char *macbuf = NULL;
- char *cp;
+ u_char type, *cp, *macbuf = NULL;
+ u_char padlen, pad;
u_int packet_length = 0;
- u_int i, padlen, len;
- u_int32_t rand = 0;
- int type;
+ u_int i, len;
+ u_int32_t rnd = 0;
Enc *enc = NULL;
Mac *mac = NULL;
Comp *comp = NULL;
mac = &newkeys[MODE_OUT]->mac;
comp = &newkeys[MODE_OUT]->comp;
}
- block_size = enc ? enc->cipher->block_size : 8;
+ block_size = enc ? enc->block_size : 8;
cp = buffer_ptr(&outgoing_packet);
- type = cp[5] & 0xff;
+ type = cp[5];
#ifdef PACKET_DEBUG
fprintf(stderr, "plain: ");
padlen = block_size - (len % block_size);
if (padlen < 4)
padlen += block_size;
- buffer_append_space(&outgoing_packet, &cp, padlen);
- if (enc && enc->cipher->number != SSH_CIPHER_NONE) {
+ if (extra_pad) {
+ /* will wrap if extra_pad+padlen > 255 */
+ extra_pad = roundup(extra_pad, block_size);
+ pad = extra_pad - ((len + padlen) % extra_pad);
+ debug3("packet_send2: adding %d (len %d padlen %d extra_pad %d)",
+ pad, len, padlen, extra_pad);
+ padlen += pad;
+ extra_pad = 0;
+ }
+ cp = buffer_append_space(&outgoing_packet, padlen);
+ if (enc && !send_context.plaintext) {
/* random padding */
for (i = 0; i < padlen; i++) {
if (i % 4 == 0)
- rand = arc4random();
- cp[i] = rand & 0xff;
- rand >>= 8;
+ rnd = arc4random();
+ cp[i] = rnd & 0xff;
+ rnd >>= 8;
}
} else {
/* clear padding */
/* packet_length includes payload, padding and padding length field */
packet_length = buffer_len(&outgoing_packet) - 4;
cp = buffer_ptr(&outgoing_packet);
- PUT_32BIT(cp, packet_length);
- cp[4] = padlen & 0xff;
+ put_u32(cp, packet_length);
+ cp[4] = padlen;
DBG(debug("send: len %d (includes padlen %d)", packet_length+4, padlen));
/* compute MAC over seqnr and packet(length fields, payload, padding) */
if (mac && mac->enabled) {
- macbuf = mac_compute(mac, seqnr,
- (u_char *) buffer_ptr(&outgoing_packet),
+ macbuf = mac_compute(mac, p_send.seqnr,
+ buffer_ptr(&outgoing_packet),
buffer_len(&outgoing_packet));
- DBG(debug("done calc MAC out #%d", seqnr));
+ DBG(debug("done calc MAC out #%d", p_send.seqnr));
}
/* encrypt packet and append to output buffer. */
- buffer_append_space(&output, &cp, buffer_len(&outgoing_packet));
- packet_encrypt(&send_context, cp, buffer_ptr(&outgoing_packet),
+ cp = buffer_append_space(&output, buffer_len(&outgoing_packet));
+ cipher_crypt(&send_context, cp, buffer_ptr(&outgoing_packet),
buffer_len(&outgoing_packet));
/* append unencrypted MAC */
if (mac && mac->enabled)
- buffer_append(&output, (char *)macbuf, mac->mac_len);
+ buffer_append(&output, macbuf, mac->mac_len);
#ifdef PACKET_DEBUG
fprintf(stderr, "encrypted: ");
buffer_dump(&output);
#endif
/* increment sequence number for outgoing packets */
- if (++seqnr == 0)
- log("outgoing seqnr wraps around");
+ if (++p_send.seqnr == 0)
+ logit("outgoing seqnr wraps around");
+ if (++p_send.packets == 0)
+ if (!(datafellows & SSH_BUG_NOREKEY))
+ fatal("XXX too many packets with same key");
+ p_send.blocks += (packet_length + 4) / block_size;
buffer_clear(&outgoing_packet);
if (type == SSH2_MSG_NEWKEYS)
set_newkeys(MODE_OUT);
+ else if (type == SSH2_MSG_USERAUTH_SUCCESS && server_side)
+ packet_enable_delayed_compress();
+}
+
+static void
+packet_send2(void)
+{
+ static int rekeying = 0;
+ struct packet *p;
+ u_char type, *cp;
+
+ cp = buffer_ptr(&outgoing_packet);
+ type = cp[5];
+
+ /* during rekeying we can only send key exchange messages */
+ if (rekeying) {
+ if (!((type >= SSH2_MSG_TRANSPORT_MIN) &&
+ (type <= SSH2_MSG_TRANSPORT_MAX))) {
+ debug("enqueue packet: %u", type);
+ p = xmalloc(sizeof(*p));
+ p->type = type;
+ memcpy(&p->payload, &outgoing_packet, sizeof(Buffer));
+ buffer_init(&outgoing_packet);
+ TAILQ_INSERT_TAIL(&outgoing, p, next);
+ return;
+ }
+ }
+
+ /* rekeying starts with sending KEXINIT */
+ if (type == SSH2_MSG_KEXINIT)
+ rekeying = 1;
+
+ packet_send2_wrapped();
+
+ /* after a NEWKEYS message we can send the complete queue */
+ if (type == SSH2_MSG_NEWKEYS) {
+ rekeying = 0;
+ while ((p = TAILQ_FIRST(&outgoing))) {
+ type = p->type;
+ debug("dequeue packet: %u", type);
+ buffer_free(&outgoing_packet);
+ memcpy(&outgoing_packet, &p->payload,
+ sizeof(Buffer));
+ TAILQ_REMOVE(&outgoing, p, next);
+ xfree(p);
+ packet_send2_wrapped();
+ }
+ }
}
void
-packet_send()
+packet_send(void)
{
- if (use_ssh2_packet_format)
+ if (compat20)
packet_send2();
else
packet_send1();
*/
int
-packet_read(int *payload_len_ptr)
+packet_read_seqnr(u_int32_t *seqnr_p)
{
int type, len;
fd_set *setp;
char buf[8192];
DBG(debug("packet_read()"));
- setp = (fd_set *)xmalloc(howmany(connection_in+1, NFDBITS) *
+ setp = (fd_set *)xcalloc(howmany(connection_in+1, NFDBITS),
sizeof(fd_mask));
/* Since we are blocking, ensure that all written packets have been sent. */
/* Stay in the loop until we have received a complete packet. */
for (;;) {
/* Try to read a packet from the buffer. */
- type = packet_read_poll(payload_len_ptr);
- if (!use_ssh2_packet_format && (
+ type = packet_read_poll_seqnr(seqnr_p);
+ if (!compat20 && (
type == SSH_SMSG_SUCCESS
|| type == SSH_SMSG_FAILURE
|| type == SSH_CMSG_EOF
|| type == SSH_CMSG_EXIT_CONFIRMATION))
- packet_integrity_check(*payload_len_ptr, 0, type);
+ packet_check_eom();
/* If we got a packet, return it. */
if (type != SSH_MSG_NONE) {
xfree(setp);
/* Read data from the socket. */
len = read(connection_in, buf, sizeof(buf));
if (len == 0) {
- log("Connection closed by %.200s", get_remote_ipaddr());
- fatal_cleanup();
+ logit("Connection closed by %.200s", get_remote_ipaddr());
+ cleanup_exit(255);
}
if (len < 0)
fatal("Read from socket failed: %.100s", strerror(errno));
/* NOTREACHED */
}
+int
+packet_read(void)
+{
+ return packet_read_seqnr(NULL);
+}
+
/*
* Waits until a packet has been received, verifies that its type matches
* that given, and gives a fatal error and exits if there is a mismatch.
*/
void
-packet_read_expect(int *payload_len_ptr, int expected_type)
+packet_read_expect(int expected_type)
{
int type;
- type = packet_read(payload_len_ptr);
+ type = packet_read();
if (type != expected_type)
packet_disconnect("Protocol error: expected packet type %d, got %d",
expected_type, type);
* SSH_MSG_DISCONNECT is handled specially here. Also,
* SSH_MSG_IGNORE messages are skipped by this function and are never returned
* to higher levels.
- *
- * The returned payload_len does include space consumed by:
- * Packet length
- * Padding
- * Packet type
- * Check bytes
*/
-int
-packet_read_poll1(int *payload_len_ptr)
+static int
+packet_read_poll1(void)
{
u_int len, padded_len;
- u_char *ucp;
- char buf[8], *cp;
+ u_char *cp, type;
u_int checksum, stored_checksum;
/* Check if input size is less than minimum packet size. */
if (buffer_len(&input) < 4 + 8)
return SSH_MSG_NONE;
/* Get length of incoming packet. */
- ucp = (u_char *) buffer_ptr(&input);
- len = GET_32BIT(ucp);
+ cp = buffer_ptr(&input);
+ len = get_u32(cp);
if (len < 1 + 2 + 2 || len > 256 * 1024)
- packet_disconnect("Bad packet length %d.", len);
+ packet_disconnect("Bad packet length %u.", len);
padded_len = (len + 8) & ~7;
/* Check if the packet has been entirely received. */
/* Consume packet length. */
buffer_consume(&input, 4);
- /* Copy data to incoming_packet. */
+ /*
+ * Cryptographic attack detector for ssh
+ * (C)1998 CORE-SDI, Buenos Aires Argentina
+ * Ariel Futoransky(futo@core-sdi.com)
+ */
+ if (!receive_context.plaintext &&
+ detect_attack(buffer_ptr(&input), padded_len) == DEATTACK_DETECTED)
+ packet_disconnect("crc32 compensation attack: network attack detected");
+
+ /* Decrypt data to incoming_packet. */
buffer_clear(&incoming_packet);
- buffer_append_space(&incoming_packet, &cp, padded_len);
- packet_decrypt(&receive_context, cp, buffer_ptr(&input), padded_len);
+ cp = buffer_append_space(&incoming_packet, padded_len);
+ cipher_crypt(&receive_context, cp, buffer_ptr(&input), padded_len);
+
buffer_consume(&input, padded_len);
#ifdef PACKET_DEBUG
#endif
/* Compute packet checksum. */
- checksum = ssh_crc32((u_char *) buffer_ptr(&incoming_packet),
+ checksum = ssh_crc32(buffer_ptr(&incoming_packet),
buffer_len(&incoming_packet) - 4);
/* Skip padding. */
buffer_consume(&incoming_packet, 8 - len % 8);
/* Test check bytes. */
-
if (len != buffer_len(&incoming_packet))
- packet_disconnect("packet_read_poll: len %d != buffer_len %d.",
+ packet_disconnect("packet_read_poll1: len %d != buffer_len %d.",
len, buffer_len(&incoming_packet));
- ucp = (u_char *) buffer_ptr(&incoming_packet) + len - 4;
- stored_checksum = GET_32BIT(ucp);
+ cp = (u_char *)buffer_ptr(&incoming_packet) + len - 4;
+ stored_checksum = get_u32(cp);
if (checksum != stored_checksum)
packet_disconnect("Corrupted check bytes on input.");
buffer_consume_end(&incoming_packet, 4);
- /* If using packet compression, decompress the packet. */
if (packet_compression) {
buffer_clear(&compression_buffer);
buffer_uncompress(&incoming_packet, &compression_buffer);
buffer_append(&incoming_packet, buffer_ptr(&compression_buffer),
buffer_len(&compression_buffer));
}
- /* Get packet type. */
- buffer_get(&incoming_packet, &buf[0], 1);
-
- /* Return length of payload (without type field). */
- *payload_len_ptr = buffer_len(&incoming_packet);
-
- /* Return type. */
- return (u_char) buf[0];
+ type = buffer_get_char(&incoming_packet);
+ if (type < SSH_MSG_MIN || type > SSH_MSG_MAX)
+ packet_disconnect("Invalid ssh1 packet type: %d", type);
+ return type;
}
-int
-packet_read_poll2(int *payload_len_ptr)
+static int
+packet_read_poll2(u_int32_t *seqnr_p)
{
- static u_int32_t seqnr = 0;
static u_int packet_length = 0;
u_int padlen, need;
- u_char buf[8], *macbuf;
- u_char *ucp;
- char *cp;
- int type;
- int maclen, block_size;
+ u_char *macbuf, *cp, type;
+ u_int maclen, block_size;
Enc *enc = NULL;
Mac *mac = NULL;
Comp *comp = NULL;
comp = &newkeys[MODE_IN]->comp;
}
maclen = mac && mac->enabled ? mac->mac_len : 0;
- block_size = enc ? enc->cipher->block_size : 8;
+ block_size = enc ? enc->block_size : 8;
if (packet_length == 0) {
/*
if (buffer_len(&input) < block_size)
return SSH_MSG_NONE;
buffer_clear(&incoming_packet);
- buffer_append_space(&incoming_packet, &cp, block_size);
- packet_decrypt(&receive_context, cp, buffer_ptr(&input),
+ cp = buffer_append_space(&incoming_packet, block_size);
+ cipher_crypt(&receive_context, cp, buffer_ptr(&input),
block_size);
- ucp = (u_char *) buffer_ptr(&incoming_packet);
- packet_length = GET_32BIT(ucp);
+ cp = buffer_ptr(&incoming_packet);
+ packet_length = get_u32(cp);
if (packet_length < 1 + 4 || packet_length > 256 * 1024) {
+#ifdef PACKET_DEBUG
buffer_dump(&incoming_packet);
- packet_disconnect("Bad packet length %d.", packet_length);
+#endif
+ packet_disconnect("Bad packet length %u.", packet_length);
}
- DBG(debug("input: packet len %d", packet_length+4));
+ DBG(debug("input: packet len %u", packet_length+4));
buffer_consume(&input, block_size);
}
/* we have a partial packet of block_size bytes */
fprintf(stderr, "read_poll enc/full: ");
buffer_dump(&input);
#endif
- buffer_append_space(&incoming_packet, &cp, need);
- packet_decrypt(&receive_context, cp, buffer_ptr(&input), need);
+ cp = buffer_append_space(&incoming_packet, need);
+ cipher_crypt(&receive_context, cp, buffer_ptr(&input), need);
buffer_consume(&input, need);
/*
* compute MAC over seqnr and packet,
* increment sequence number for incoming packet
*/
if (mac && mac->enabled) {
- macbuf = mac_compute(mac, seqnr,
- (u_char *) buffer_ptr(&incoming_packet),
+ macbuf = mac_compute(mac, p_read.seqnr,
+ buffer_ptr(&incoming_packet),
buffer_len(&incoming_packet));
if (memcmp(macbuf, buffer_ptr(&input), mac->mac_len) != 0)
packet_disconnect("Corrupted MAC on input.");
- DBG(debug("MAC #%d ok", seqnr));
+ DBG(debug("MAC #%d ok", p_read.seqnr));
buffer_consume(&input, mac->mac_len);
}
- if (++seqnr == 0)
- log("incoming seqnr wraps around");
+ if (seqnr_p != NULL)
+ *seqnr_p = p_read.seqnr;
+ if (++p_read.seqnr == 0)
+ logit("incoming seqnr wraps around");
+ if (++p_read.packets == 0)
+ if (!(datafellows & SSH_BUG_NOREKEY))
+ fatal("XXX too many packets with same key");
+ p_read.blocks += (packet_length + 4) / block_size;
/* get padlen */
- cp = buffer_ptr(&incoming_packet) + 4;
- padlen = *cp & 0xff;
+ cp = buffer_ptr(&incoming_packet);
+ padlen = cp[4];
DBG(debug("input: padlen %d", padlen));
if (padlen < 4)
packet_disconnect("Corrupted padlen %d on input.", padlen);
buffer_clear(&incoming_packet);
buffer_append(&incoming_packet, buffer_ptr(&compression_buffer),
buffer_len(&compression_buffer));
- DBG(debug("input: len after de-compress %d", buffer_len(&incoming_packet)));
+ DBG(debug("input: len after de-compress %d",
+ buffer_len(&incoming_packet)));
}
/*
* get packet type, implies consume.
* return length of payload (without type field)
*/
- buffer_get(&incoming_packet, (char *)&buf[0], 1);
- *payload_len_ptr = buffer_len(&incoming_packet);
-
- /* reset for next packet */
- packet_length = 0;
-
- /* extract packet type */
- type = (u_char)buf[0];
-
+ type = buffer_get_char(&incoming_packet);
+ if (type < SSH2_MSG_MIN || type >= SSH2_MSG_LOCAL_MIN)
+ packet_disconnect("Invalid ssh2 packet type: %d", type);
if (type == SSH2_MSG_NEWKEYS)
set_newkeys(MODE_IN);
-
+ else if (type == SSH2_MSG_USERAUTH_SUCCESS && !server_side)
+ packet_enable_delayed_compress();
#ifdef PACKET_DEBUG
fprintf(stderr, "read/plain[%d]:\r\n", type);
buffer_dump(&incoming_packet);
#endif
- return (u_char)type;
+ /* reset for next packet */
+ packet_length = 0;
+ return type;
}
int
-packet_read_poll(int *payload_len_ptr)
+packet_read_poll_seqnr(u_int32_t *seqnr_p)
{
+ u_int reason, seqnr;
+ u_char type;
char *msg;
- for (;;) {
- int type = use_ssh2_packet_format ?
- packet_read_poll2(payload_len_ptr):
- packet_read_poll1(payload_len_ptr);
- if(compat20) {
- int reason;
- if (type != 0)
+ for (;;) {
+ if (compat20) {
+ type = packet_read_poll2(seqnr_p);
+ if (type)
DBG(debug("received packet type %d", type));
- switch(type) {
+ switch (type) {
case SSH2_MSG_IGNORE:
break;
case SSH2_MSG_DEBUG:
case SSH2_MSG_DISCONNECT:
reason = packet_get_int();
msg = packet_get_string(NULL);
- log("Received disconnect from %s: %d: %.400s", get_remote_ipaddr(),
- reason, msg);
+ logit("Received disconnect from %s: %u: %.400s",
+ get_remote_ipaddr(), reason, msg);
xfree(msg);
- fatal_cleanup();
+ cleanup_exit(255);
+ break;
+ case SSH2_MSG_UNIMPLEMENTED:
+ seqnr = packet_get_int();
+ debug("Received SSH2_MSG_UNIMPLEMENTED for %u",
+ seqnr);
break;
default:
return type;
- break;
}
} else {
- switch(type) {
+ type = packet_read_poll1();
+ switch (type) {
case SSH_MSG_IGNORE:
break;
case SSH_MSG_DEBUG:
break;
case SSH_MSG_DISCONNECT:
msg = packet_get_string(NULL);
- log("Received disconnect from %s: %.400s", get_remote_ipaddr(),
- msg);
- fatal_cleanup();
+ logit("Received disconnect from %s: %.400s",
+ get_remote_ipaddr(), msg);
+ cleanup_exit(255);
xfree(msg);
break;
default:
- if (type != 0)
+ if (type)
DBG(debug("received packet type %d", type));
return type;
- break;
}
}
}
}
+int
+packet_read_poll(void)
+{
+ return packet_read_poll_seqnr(NULL);
+}
+
/*
* Buffers the given amount of input characters. This is intended to be used
* together with packet_read_poll.
/* Returns a character from the packet. */
u_int
-packet_get_char()
+packet_get_char(void)
{
char ch;
+
buffer_get(&incoming_packet, &ch, 1);
return (u_char) ch;
}
/* Returns an integer from the packet data. */
u_int
-packet_get_int()
+packet_get_int(void)
{
return buffer_get_int(&incoming_packet);
}
*/
void
-packet_get_bignum(BIGNUM * value, int *length_ptr)
+packet_get_bignum(BIGNUM * value)
{
- *length_ptr = buffer_get_bignum(&incoming_packet, value);
+ buffer_get_bignum(&incoming_packet, value);
}
void
-packet_get_bignum2(BIGNUM * value, int *length_ptr)
+packet_get_bignum2(BIGNUM * value)
{
- *length_ptr = buffer_get_bignum2(&incoming_packet, value);
+ buffer_get_bignum2(&incoming_packet, value);
}
-char *
-packet_get_raw(int *length_ptr)
+void *
+packet_get_raw(u_int *length_ptr)
{
- int bytes = buffer_len(&incoming_packet);
+ u_int bytes = buffer_len(&incoming_packet);
+
if (length_ptr != NULL)
*length_ptr = bytes;
return buffer_ptr(&incoming_packet);
* integer into which the length of the string is stored.
*/
-char *
+void *
packet_get_string(u_int *length_ptr)
{
return buffer_get_string(&incoming_packet, length_ptr);
char buf[1024];
va_list args;
static int disconnecting = 0;
+
if (disconnecting) /* Guard against recursive invocations. */
fatal("packet_disconnect called recursively.");
disconnecting = 1;
vsnprintf(buf, sizeof(buf), fmt, args);
va_end(args);
+ /* Display the error locally */
+ logit("Disconnecting: %.100s", buf);
+
/* Send the disconnect message to the other side, and wait for it to get sent. */
if (compat20) {
packet_start(SSH2_MSG_DISCONNECT);
packet_put_cstring("");
} else {
packet_start(SSH_MSG_DISCONNECT);
- packet_put_string(buf, strlen(buf));
+ packet_put_cstring(buf);
}
packet_send();
packet_write_wait();
/* Stop listening for connections. */
- channel_stop_listening();
+ channel_close_all();
/* Close the connection. */
packet_close();
-
- /* Display the error locally and exit. */
- log("Disconnecting: %.100s", buf);
- fatal_cleanup();
+ cleanup_exit(255);
}
/* Checks if there is any buffered output, and tries to write some of the output. */
void
-packet_write_poll()
+packet_write_poll(void)
{
int len = buffer_len(&output);
+
if (len > 0) {
len = write(connection_out, buffer_ptr(&output), len);
if (len <= 0) {
*/
void
-packet_write_wait()
+packet_write_wait(void)
{
fd_set *setp;
- setp = (fd_set *)xmalloc(howmany(connection_out + 1, NFDBITS) *
+ setp = (fd_set *)xcalloc(howmany(connection_out + 1, NFDBITS),
sizeof(fd_mask));
packet_write_poll();
while (packet_have_data_to_write()) {
/* Returns true if there is buffered data to write to the connection. */
int
-packet_have_data_to_write()
+packet_have_data_to_write(void)
{
return buffer_len(&output) != 0;
}
/* Returns true if there is not too much data to write to the connection. */
int
-packet_not_very_much_data_to_write()
+packet_not_very_much_data_to_write(void)
{
if (interactive_mode)
return buffer_len(&output) < 16384;
return buffer_len(&output) < 128 * 1024;
}
+
+static void
+packet_set_tos(int interactive)
+{
+#if defined(IP_TOS) && !defined(IP_TOS_IS_BROKEN)
+ int tos = interactive ? IPTOS_LOWDELAY : IPTOS_THROUGHPUT;
+
+ if (!packet_connection_is_on_socket() ||
+ !packet_connection_is_ipv4())
+ return;
+ if (setsockopt(connection_in, IPPROTO_IP, IP_TOS, &tos,
+ sizeof(tos)) < 0)
+ error("setsockopt IP_TOS %d: %.100s:",
+ tos, strerror(errno));
+#endif
+}
+
/* Informs that the current session is interactive. Sets IP flags for that. */
void
packet_set_interactive(int interactive)
{
static int called = 0;
-#if defined(IP_TOS) && !defined(IP_TOS_IS_BROKEN)
- int lowdelay = IPTOS_LOWDELAY;
- int throughput = IPTOS_THROUGHPUT;
-#endif
- int on = 1;
if (called)
return;
/* Only set socket options if using a socket. */
if (!packet_connection_is_on_socket())
return;
- /*
- * IPTOS_LOWDELAY and IPTOS_THROUGHPUT are IPv4 only
- */
- if (interactive) {
- /*
- * Set IP options for an interactive connection. Use
- * IPTOS_LOWDELAY and TCP_NODELAY.
- */
-#if defined(IP_TOS) && !defined(IP_TOS_IS_BROKEN)
- if (packet_connection_is_ipv4()) {
- if (setsockopt(connection_in, IPPROTO_IP, IP_TOS,
- (void *) &lowdelay, sizeof(lowdelay)) < 0)
- error("setsockopt IPTOS_LOWDELAY: %.100s",
- strerror(errno));
- }
-#endif
- if (setsockopt(connection_in, IPPROTO_TCP, TCP_NODELAY, (void *) &on,
- sizeof(on)) < 0)
- error("setsockopt TCP_NODELAY: %.100s", strerror(errno));
- } else if (packet_connection_is_ipv4()) {
- /*
- * Set IP options for a non-interactive connection. Use
- * IPTOS_THROUGHPUT.
- */
-#if defined(IP_TOS) && !defined(IP_TOS_IS_BROKEN)
- if (setsockopt(connection_in, IPPROTO_IP, IP_TOS, (void *) &throughput,
- sizeof(throughput)) < 0)
- error("setsockopt IPTOS_THROUGHPUT: %.100s", strerror(errno));
-#endif
- }
+ set_nodelay(connection_in);
+ packet_set_tos(interactive);
}
/* Returns true if the current connection is interactive. */
int
-packet_is_interactive()
+packet_is_interactive(void)
{
return interactive_mode;
}
int
-packet_set_maxsize(int s)
+packet_set_maxsize(u_int s)
{
static int called = 0;
+
if (called) {
- log("packet_set_maxsize: called twice: old %d new %d",
+ logit("packet_set_maxsize: called twice: old %d new %d",
max_packet_size, s);
return -1;
}
if (s < 4 * 1024 || s > 1024 * 1024) {
- log("packet_set_maxsize: bad size %d", s);
+ logit("packet_set_maxsize: bad size %d", s);
return -1;
}
- log("packet_set_maxsize: setting to %d", s);
+ called = 1;
+ debug("packet_set_maxsize: setting to %d", s);
max_packet_size = s;
return s;
}
+/* roundup current message to pad bytes */
+void
+packet_add_padding(u_char pad)
+{
+ extra_pad = pad;
+}
+
/*
* 9.2. Ignored Data Message
*
* required to send them. This message can be used as an additional
* protection measure against advanced traffic analysis techniques.
*/
-/* size of current + ignore message should be n*sumlen bytes (w/o mac) */
-void
-packet_inject_ignore(int sumlen)
-{
- int blocksize, padlen, have, need, nb, mini, nbytes;
- Enc *enc = NULL;
-
- if (use_ssh2_packet_format == 0)
- return;
-
- have = buffer_len(&outgoing_packet);
- debug2("packet_inject_ignore: current %d", have);
- if (newkeys[MODE_OUT] != NULL)
- enc = &newkeys[MODE_OUT]->enc;
- blocksize = enc ? enc->cipher->block_size : 8;
- padlen = blocksize - (have % blocksize);
- if (padlen < 4)
- padlen += blocksize;
- have += padlen;
- have /= blocksize; /* # of blocks for current message */
-
- nb = roundup(sumlen, blocksize) / blocksize; /* blocks for both */
- mini = roundup(5+1+4+4, blocksize) / blocksize; /* minsize ignore msg */
- need = nb - (have % nb); /* blocks for ignore */
- if (need <= mini)
- need += nb;
- nbytes = (need - mini) * blocksize; /* size of ignore payload */
- debug2("packet_inject_ignore: block %d have %d nb %d mini %d need %d",
- blocksize, have, nb, mini, need);
-
- /* enqueue current message and append a ignore message */
- packet_send();
- packet_send_ignore(nbytes);
-}
-
void
packet_send_ignore(int nbytes)
{
- u_int32_t rand = 0;
+ u_int32_t rnd = 0;
int i;
packet_start(compat20 ? SSH2_MSG_IGNORE : SSH_MSG_IGNORE);
packet_put_int(nbytes);
- for(i = 0; i < nbytes; i++) {
+ for (i = 0; i < nbytes; i++) {
if (i % 4 == 0)
- rand = arc4random();
- packet_put_char(rand & 0xff);
- rand >>= 8;
+ rnd = arc4random();
+ packet_put_char((u_char)rnd & 0xff);
+ rnd >>= 8;
}
}
+
+#define MAX_PACKETS (1U<<31)
+int
+packet_need_rekeying(void)
+{
+ if (datafellows & SSH_BUG_NOREKEY)
+ return 0;
+ return
+ (p_send.packets > MAX_PACKETS) ||
+ (p_read.packets > MAX_PACKETS) ||
+ (max_blocks_out && (p_send.blocks > max_blocks_out)) ||
+ (max_blocks_in && (p_read.blocks > max_blocks_in));
+}
+
+void
+packet_set_rekey_limit(u_int32_t bytes)
+{
+ rekey_limit = bytes;
+}
+
+void
+packet_set_server(void)
+{
+ server_side = 1;
+}
+
+void
+packet_set_authenticated(void)
+{
+ after_authentication = 1;
+}
andersk / openssh.git / blobdiff