[git commit] tls: was psAesDecrypt'ing one block too many, trashing buffered data
Denys Vlasenko
vda.linux at googlemail.com
Fri Jan 20 17:04:04 UTC 2017
commit: https://git.busybox.net/busybox/commit/?id=e7863f394e6a963d1e2c6af77ea064442d3ef594
branch: https://git.busybox.net/busybox/commit/?id=refs/heads/master
For the first time
printf "GET / HTTP/1.1\r\nHost: kernel.org\r\n\r\n" | ./busybox tls kernel.org
successfully reads entire server response and TLS shutdown.
Signed-off-by: Denys Vlasenko <vda.linux at googlemail.com>
---
networking/tls.c | 136 +++++++++++++++++++++++++++++--------------------------
1 file changed, 73 insertions(+), 63 deletions(-)
diff --git a/networking/tls.c b/networking/tls.c
index 2674997..cdce100 100644
--- a/networking/tls.c
+++ b/networking/tls.c
@@ -26,7 +26,7 @@
//#include "common_bufsiz.h"
#define TLS_DEBUG 1
-#define TLS_DEBUG_HASH 1
+#define TLS_DEBUG_HASH 0
#define TLS_DEBUG_DER 0
#define TLS_DEBUG_FIXED_SECRETS 0
@@ -42,6 +42,18 @@
# define dbg_der(...) ((void)0)
#endif
+#if 0
+# define dump_raw_out(...) dump_hex(__VA_ARGS__)
+#else
+# define dump_raw_out(...) ((void)0)
+#endif
+
+#if 1
+# define dump_raw_in(...) dump_hex(__VA_ARGS__)
+#else
+# define dump_raw_in(...) ((void)0)
+#endif
+
#define RECORD_TYPE_CHANGE_CIPHER_SPEC 20
#define RECORD_TYPE_ALERT 21
#define RECORD_TYPE_HANDSHAKE 22
@@ -482,49 +494,11 @@ static void *tls_get_outbuf(tls_state_t *tls, int len)
return tls->outbuf + OUTBUF_PFX;
}
-// RFC 5246
-// 6.2.3.1. Null or Standard Stream Cipher
-//
-// Stream ciphers (including BulkCipherAlgorithm.null; see Appendix A.6)
-// convert TLSCompressed.fragment structures to and from stream
-// TLSCiphertext.fragment structures.
-//
-// stream-ciphered struct {
-// opaque content[TLSCompressed.length];
-// opaque MAC[SecurityParameters.mac_length];
-// } GenericStreamCipher;
-//
-// The MAC is generated as:
-// MAC(MAC_write_key, seq_num +
-// TLSCompressed.type +
-// TLSCompressed.version +
-// TLSCompressed.length +
-// TLSCompressed.fragment);
-// where "+" denotes concatenation.
-// seq_num
-// The sequence number for this record.
-// MAC
-// The MAC algorithm specified by SecurityParameters.mac_algorithm.
-//
-// Note that the MAC is computed before encryption. The stream cipher
-// encrypts the entire block, including the MAC.
-//...
-// Appendix C. Cipher Suite Definitions
-//...
-// Key IV Block
-// Cipher Type Material Size Size
-// ------------ ------ -------- ---- -----
-// AES_128_CBC Block 16 16 16
-// AES_256_CBC Block 32 16 16
-//
-// MAC Algorithm mac_length mac_key_length
-// -------- ----------- ---------- --------------
-// SHA HMAC-SHA1 20 20
-// SHA256 HMAC-SHA256 32 32
static void xwrite_encrypted(tls_state_t *tls, unsigned size, unsigned type)
{
uint8_t *buf = tls->outbuf + OUTBUF_PFX;
struct record_hdr *xhdr;
+ uint8_t padding_length;
xhdr = (void*)(buf - RECHDR_LEN);
if (CIPHER_ID != TLS_RSA_WITH_NULL_SHA256)
@@ -549,17 +523,49 @@ static void xwrite_encrypted(tls_state_t *tls, unsigned size, unsigned type)
size += SHA256_OUTSIZE;
+ // RFC 5246
+ // 6.2.3.1. Null or Standard Stream Cipher
+ //
+ // Stream ciphers (including BulkCipherAlgorithm.null; see Appendix A.6)
+ // convert TLSCompressed.fragment structures to and from stream
+ // TLSCiphertext.fragment structures.
+ //
+ // stream-ciphered struct {
+ // opaque content[TLSCompressed.length];
+ // opaque MAC[SecurityParameters.mac_length];
+ // } GenericStreamCipher;
+ //
+ // The MAC is generated as:
+ // MAC(MAC_write_key, seq_num +
+ // TLSCompressed.type +
+ // TLSCompressed.version +
+ // TLSCompressed.length +
+ // TLSCompressed.fragment);
+ // where "+" denotes concatenation.
+ // seq_num
+ // The sequence number for this record.
+ // MAC
+ // The MAC algorithm specified by SecurityParameters.mac_algorithm.
+ //
+ // Note that the MAC is computed before encryption. The stream cipher
+ // encrypts the entire block, including the MAC.
+ //...
+ // Appendix C. Cipher Suite Definitions
+ //...
+ // MAC Algorithm mac_length mac_key_length
+ // -------- ----------- ---------- --------------
+ // SHA HMAC-SHA1 20 20
+ // SHA256 HMAC-SHA256 32 32
if (CIPHER_ID == TLS_RSA_WITH_NULL_SHA256) {
/* No encryption, only signing */
xhdr->len16_hi = size >> 8;
xhdr->len16_lo = size & 0xff;
- dump_hex(">> %s\n", xhdr, RECHDR_LEN + size);
+ dump_raw_out(">> %s\n", xhdr, RECHDR_LEN + size);
xwrite(tls->fd, xhdr, RECHDR_LEN + size);
dbg("wrote %u bytes (NULL crypt, SHA256 hash)\n", size);
return;
}
- // RFC 5246
// 6.2.3.2. CBC Block Cipher
// For block ciphers (such as 3DES or AES), the encryption and MAC
// functions convert TLSCompressed.fragment structures to and from block
@@ -595,10 +601,6 @@ static void xwrite_encrypted(tls_state_t *tls, unsigned size, unsigned type)
// ------------ ------ -------- ---- -----
// AES_128_CBC Block 16 16 16
// AES_256_CBC Block 32 16 16
- {
- psCipherContext_t ctx;
- uint8_t *p;
- uint8_t padding_length;
/* Build IV+content+MAC+padding in outbuf */
tls_get_random(buf - AES_BLOCKSIZE, AES_BLOCKSIZE); /* IV */
@@ -618,22 +620,23 @@ static void xwrite_encrypted(tls_state_t *tls, unsigned size, unsigned type)
// If you need no bytes to reach BLOCKSIZE, you have to pad a full
// BLOCKSIZE with bytes of value (BLOCKSIZE-1).
// It's ok to have more than minimum padding, but we do minimum.
- p = buf + size;
padding_length = (~size) & (AES_BLOCKSIZE - 1);
do {
- *p++ = padding_length; /* padding */
- size++;
+ buf[size++] = padding_length; /* padding */
} while ((size & (AES_BLOCKSIZE - 1)) != 0);
/* Encrypt content+MAC+padding in place */
- psAesInit(&ctx, buf - AES_BLOCKSIZE, /* IV */
+ {
+ psCipherContext_t ctx;
+ psAesInit(&ctx, buf - AES_BLOCKSIZE, /* IV */
tls->client_write_key, sizeof(tls->client_write_key)
- );
- psAesEncrypt(&ctx,
+ );
+ psAesEncrypt(&ctx,
buf, /* plaintext */
buf, /* ciphertext */
size
- );
+ );
+ }
/* Write out */
dbg("writing 5 + %u IV + %u encrypted bytes, padding_length:0x%02x\n",
@@ -641,10 +644,9 @@ static void xwrite_encrypted(tls_state_t *tls, unsigned size, unsigned type)
size += AES_BLOCKSIZE; /* + IV */
xhdr->len16_hi = size >> 8;
xhdr->len16_lo = size & 0xff;
- dump_hex(">> %s\n", xhdr, RECHDR_LEN + size);
+ dump_raw_out(">> %s\n", xhdr, RECHDR_LEN + size);
xwrite(tls->fd, xhdr, RECHDR_LEN + size);
dbg("wrote %u bytes\n", (int)RECHDR_LEN + size);
- }
}
static void xwrite_and_update_handshake_hash(tls_state_t *tls, unsigned size)
@@ -658,7 +660,7 @@ static void xwrite_and_update_handshake_hash(tls_state_t *tls, unsigned size)
xhdr->proto_min = TLS_MIN;
xhdr->len16_hi = size >> 8;
xhdr->len16_lo = size & 0xff;
- dump_hex(">> %s\n", xhdr, RECHDR_LEN + size);
+ dump_raw_out(">> %s\n", xhdr, RECHDR_LEN + size);
xwrite(tls->fd, xhdr, RECHDR_LEN + size);
dbg("wrote %u bytes\n", (int)RECHDR_LEN + size);
/* Handshake hash does not include record headers */
@@ -677,10 +679,13 @@ static int xread_tls_block(tls_state_t *tls)
again:
dbg("insize:%u tail:%u\n", tls->insize, tls->tail);
- if (tls->tail != 0)
- memmove(tls->inbuf, tls->inbuf + tls->insize, tls->tail);
- errno = 0;
total = tls->tail;
+ if (total != 0) {
+ memmove(tls->inbuf, tls->inbuf + tls->insize, total);
+ //dbg("<< remaining at %d [%d] ", tls->insize, total);
+ //dump_raw_in("<< %s\n", tls->inbuf, total);
+ }
+ errno = 0;
target = sizeof(tls->inbuf);
for (;;) {
if (total >= RECHDR_LEN && target == sizeof(tls->inbuf)) {
@@ -692,7 +697,11 @@ static int xread_tls_block(tls_state_t *tls)
tls->insize = total;
tls_error_die(tls);
}
- // can also check type/proto_maj/proto_min here
+ /* can also check type/proto_maj/proto_min here */
+ dbg("xhdr type:%d ver:%d.%d len:%d\n",
+ xhdr->type, xhdr->proto_maj, xhdr->proto_min,
+ 0x100 * xhdr->len16_hi + xhdr->len16_lo
+ );
}
/* if total >= target, we have a full packet (and possibly more)... */
if (total - target >= 0)
@@ -707,12 +716,13 @@ static int xread_tls_block(tls_state_t *tls)
}
bb_perror_msg_and_die("short read, have only %d", total);
}
- dbg("read():%d\n", sz);
+ dump_raw_in("<< %s\n", tls->inbuf + total, sz);
total += sz;
}
tls->tail = total - target;
tls->insize = target;
- dbg("new insize:%u tail:%u\n", tls->insize, tls->tail);
+ //dbg("<< stashing at %d [%d] ", tls->insize, tls->tail);
+ //dump_hex("<< %s\n", tls->inbuf + tls->insize, tls->tail);
sz = target - RECHDR_LEN;
@@ -734,7 +744,7 @@ static int xread_tls_block(tls_state_t *tls)
psAesDecrypt(&ctx,
p + AES_BLOCKSIZE, /* ciphertext */
p + AES_BLOCKSIZE, /* plaintext */
- sz
+ sz - AES_BLOCKSIZE
);
padding_len = p[sz - 1];
dbg("encrypted size:%u type:0x%02x padding_length:0x%02x\n", sz, p[AES_BLOCKSIZE], padding_len);
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