tls: work-in-progress TLS1.2 test applet

function                                             old     new   delta
tls_main                                               -     733    +733
dump                                                   -     230    +230
xread_tls_block                                        -     180    +180
get_der_len                                            -      76     +76
enter_der_item                                         -      70     +70
skip_der_item                                          -      56     +56
get24be                                                -      24     +24
tls_error_die                                          -      19     +19
packed_usage                                       31010   31027     +17
applet_names                                        2549    2553      +4
applet_main                                         1472    1476      +4
applet_suid                                           92      93      +1
applet_install_loc                                   184     185      +1
------------------------------------------------------------------------------
(add/remove: 9/0 grow/shrink: 5/0 up/down: 1415/0)           Total: 1415 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 643 insertions, 0 deletions

diff --git a/networking/tls.c b/networking/tls.c
new file mode 100644
index 0000000..983ed50
--- /dev/null
+++ b/networking/tls.c
@@ -0,0 +1,643 @@
+/*
+ * Licensed under GPLv2, see file LICENSE in this source tree.
+ *
+ * Copyright (C) 2017 Denys Vlasenko
+ */
+//config:config TLS
+//config:	bool "tls (debugging)"
+//config:	default n
+
+//applet:IF_TLS(APPLET(tls, BB_DIR_USR_BIN, BB_SUID_DROP))
+
+//kbuild:lib-$(CONFIG_TLS) += tls.o
+////kbuild:lib-$(CONFIG_TLS) += tls_ciphers.o
+////kbuild:lib-$(CONFIG_TLS) += tls_aes.o
+////kbuild:lib-$(CONFIG_TLS) += tls_aes_gcm.o
+
+//usage:#define tls_trivial_usage
+//usage:       "HOST[:PORT]"
+//usage:#define tls_full_usage "\n\n"
+
+#include "libbb.h"
+//#include "tls_cryptoapi.h"
+//#include "tls_ciphers.h"
+
+#if 1
+# define dbg(...) fprintf(stderr, __VA_ARGS__)
+#else
+# define dbg(...) ((void)0)
+#endif
+
+#define RECORD_TYPE_CHANGE_CIPHER_SPEC 20
+#define RECORD_TYPE_ALERT              21
+#define RECORD_TYPE_HANDSHAKE          22
+#define RECORD_TYPE_APPLICATION_DATA   23
+
+#define HANDSHAKE_HELLO_REQUEST        0
+#define HANDSHAKE_CLIENT_HELLO         1
+#define HANDSHAKE_SERVER_HELLO         2
+#define HANDSHAKE_HELLO_VERIFY_REQUEST 3
+#define HANDSHAKE_NEW_SESSION_TICKET   4
+#define HANDSHAKE_CERTIFICATE          11
+#define HANDSHAKE_SERVER_KEY_EXCHANGE  12
+#define HANDSHAKE_CERTIFICATE_REQUEST  13
+#define HANDSHAKE_SERVER_HELLO_DONE    14
+#define HANDSHAKE_CERTIFICATE_VERIFY   15
+#define HANDSHAKE_CLIENT_KEY_EXCHANGE  16
+#define HANDSHAKE_FINISHED             20
+
+#define SSL_NULL_WITH_NULL_NULL                 0x0000
+#define SSL_RSA_WITH_NULL_MD5                   0x0001
+#define SSL_RSA_WITH_NULL_SHA                   0x0002
+#define SSL_RSA_WITH_RC4_128_MD5                0x0004
+#define SSL_RSA_WITH_RC4_128_SHA                0x0005
+#define SSL_RSA_WITH_3DES_EDE_CBC_SHA           0x000A  /* 10 */
+#define TLS_RSA_WITH_AES_128_CBC_SHA            0x002F  /* 47 */
+#define TLS_RSA_WITH_AES_256_CBC_SHA            0x0035  /* 53 */
+#define TLS_EMPTY_RENEGOTIATION_INFO_SCSV       0x00FF
+
+#define TLS_RSA_WITH_IDEA_CBC_SHA               0x0007  /* 7 */
+#define SSL_DHE_RSA_WITH_3DES_EDE_CBC_SHA       0x0016  /* 22 */
+#define SSL_DH_anon_WITH_RC4_128_MD5            0x0018  /* 24 */
+#define SSL_DH_anon_WITH_3DES_EDE_CBC_SHA       0x001B  /* 27 */
+#define TLS_DHE_RSA_WITH_AES_128_CBC_SHA        0x0033  /* 51 */
+#define TLS_DHE_RSA_WITH_AES_256_CBC_SHA        0x0039  /* 57 */
+#define TLS_DHE_RSA_WITH_AES_128_CBC_SHA256     0x0067  /* 103 */
+#define TLS_DHE_RSA_WITH_AES_256_CBC_SHA256     0x006B  /* 107 */
+#define TLS_DH_anon_WITH_AES_128_CBC_SHA        0x0034  /* 52 */
+#define TLS_DH_anon_WITH_AES_256_CBC_SHA        0x003A  /* 58 */
+#define TLS_RSA_WITH_AES_128_CBC_SHA256         0x003C  /* 60 */
+#define TLS_RSA_WITH_AES_256_CBC_SHA256         0x003D  /* 61 */
+#define TLS_RSA_WITH_SEED_CBC_SHA               0x0096  /* 150 */
+#define TLS_PSK_WITH_AES_128_CBC_SHA            0x008C  /* 140 */
+#define TLS_PSK_WITH_AES_128_CBC_SHA256         0x00AE  /* 174 */
+#define TLS_PSK_WITH_AES_256_CBC_SHA384         0x00AF  /* 175 */
+#define TLS_PSK_WITH_AES_256_CBC_SHA            0x008D  /* 141 */
+#define TLS_DHE_PSK_WITH_AES_128_CBC_SHA        0x0090  /* 144 */
+#define TLS_DHE_PSK_WITH_AES_256_CBC_SHA        0x0091  /* 145 */
+#define TLS_ECDH_ECDSA_WITH_AES_128_CBC_SHA     0xC004  /* 49156 */
+#define TLS_ECDH_ECDSA_WITH_AES_256_CBC_SHA     0xC005  /* 49157 */
+#define TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA    0xC009  /* 49161 */
+#define TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA    0xC00A  /* 49162 */
+#define TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA     0xC012  /* 49170 */
+#define TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA      0xC013  /* 49171 */
+#define TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA      0xC014  /* 49172 */
+#define TLS_ECDH_RSA_WITH_AES_128_CBC_SHA       0xC00E  /* 49166 */
+#define TLS_ECDH_RSA_WITH_AES_256_CBC_SHA       0xC00F  /* 49167 */
+#define TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256 0xC023  /* 49187 */
+#define TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384 0xC024  /* 49188 */
+#define TLS_ECDH_ECDSA_WITH_AES_128_CBC_SHA256  0xC025  /* 49189 */
+#define TLS_ECDH_ECDSA_WITH_AES_256_CBC_SHA384  0xC026  /* 49190 */
+#define TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256   0xC027  /* 49191 */
+#define TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384   0xC028  /* 49192 */
+#define TLS_ECDH_RSA_WITH_AES_128_CBC_SHA256    0xC029  /* 49193 */
+#define TLS_ECDH_RSA_WITH_AES_256_CBC_SHA384    0xC02A  /* 49194 */
+
+#define TLS_RSA_WITH_AES_128_GCM_SHA256         0x009C  /* 156 */
+#define TLS_RSA_WITH_AES_256_GCM_SHA384         0x009D  /* 157 */
+#define TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 0xC02B  /* 49195 */
+#define TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 0xC02C  /* 49196 */
+#define TLS_ECDH_ECDSA_WITH_AES_128_GCM_SHA256  0xC02D  /* 49197 */
+#define TLS_ECDH_ECDSA_WITH_AES_256_GCM_SHA384  0xC02E  /* 49198 */
+#define TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256   0xC02F  /* 49199 */
+#define TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384   0xC030  /* 49200 */
+#define TLS_ECDH_RSA_WITH_AES_128_GCM_SHA256    0xC031  /* 49201 */
+#define TLS_ECDH_RSA_WITH_AES_256_GCM_SHA384    0xC032  /* 49202 */
+
+//Tested against kernel.org:
+//TLS 1.1
+//#define TLS_MAJ 3
+//#define TLS_MIN 2
+//#define CIPHER_ID TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA // ok, recvs SERVER_KEY_EXCHANGE
+//TLS 1.2
+#define TLS_MAJ 3
+#define TLS_MIN 3
+//#define CIPHER_ID TLS_RSA_WITH_AES_256_CBC_SHA256 // ok, no SERVER_KEY_EXCHANGE
+// All GCMs:
+//#define CIPHER_ID TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 // SSL_ALERT_HANDSHAKE_FAILURE
+//#define CIPHER_ID TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 // SSL_ALERT_HANDSHAKE_FAILURE
+//#define CIPHER_ID TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 // ok, recvs SERVER_KEY_EXCHANGE
+//#define CIPHER_ID TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
+//#define CIPHER_ID TLS_ECDH_ECDSA_WITH_AES_256_GCM_SHA384
+//#define CIPHER_ID TLS_ECDH_ECDSA_WITH_AES_128_GCM_SHA256 // SSL_ALERT_HANDSHAKE_FAILURE
+//#define CIPHER_ID TLS_ECDH_RSA_WITH_AES_256_GCM_SHA384
+//#define CIPHER_ID TLS_ECDH_RSA_WITH_AES_128_GCM_SHA256 // SSL_ALERT_HANDSHAKE_FAILURE
+//#define CIPHER_ID TLS_RSA_WITH_AES_256_GCM_SHA384 // ok, no SERVER_KEY_EXCHANGE
+#define CIPHER_ID TLS_RSA_WITH_AES_128_GCM_SHA256 // ok, no SERVER_KEY_EXCHANGE
+//#define CIPHER_ID TLS_DH_anon_WITH_AES_256_CBC_SHA // SSL_ALERT_HANDSHAKE_FAILURE
+// (tested b/c this one doesn't req server certs... no luck)
+//test TLS_RSA_WITH_AES_128_CBC_SHA, in tls 1.2 it's mandated to be always supported
+
+struct transport_hdr {
+	uint8_t type;
+	uint8_t proto_maj, proto_min;
+	uint8_t len16_hi, len16_lo;
+};
+
+typedef struct tls_state {
+	int fd;
+
+	uint8_t *pubkey;
+	int pubkey_len;
+
+	int insize;
+	int tail;
+	// RFC 5246
+	// |6.2.1. Fragmentation
+	// |  The record layer fragments information blocks into TLSPlaintext
+	// |  records carrying data in chunks of 2^14 bytes or less.  Client
+	// |  message boundaries are not preserved in the record layer (i.e.,
+	// |  multiple client messages of the same ContentType MAY be coalesced
+	// |  into a single TLSPlaintext record, or a single message MAY be
+	// |  fragmented across several records)
+	// |...
+	// |  length
+	// |    The length (in bytes) of the following TLSPlaintext.fragment.
+	// |    The length MUST NOT exceed 2^14.
+	// |...
+	// | 6.2.2. Record Compression and Decompression
+	// |...
+	// |  Compression must be lossless and may not increase the content length
+	// |  by more than 1024 bytes.  If the decompression function encounters a
+	// |  TLSCompressed.fragment that would decompress to a length in excess of
+	// |  2^14 bytes, it MUST report a fatal decompression failure error.
+	// |...
+	// |  length
+	// |    The length (in bytes) of the following TLSCompressed.fragment.
+	// |    The length MUST NOT exceed 2^14 + 1024.
+	//
+	// Since our buffer also contains 5-byte headers, make it a bit bigger:
+	uint8_t inbuf[18*1024];
+} tls_state_t;
+
+static
+tls_state_t *new_tls_state(void)
+{
+	tls_state_t *tls = xzalloc(sizeof(*tls));
+	tls->fd = -1;
+	return tls;
+}
+
+static unsigned get24be(const uint8_t *p)
+{
+	return 0x100*(0x100*p[0] + p[1]) + p[2];
+}
+
+static void dump(const void *vp, int len)
+{
+	char hexbuf[32 * 1024 + 4];
+	const uint8_t *p = vp;
+
+	while (len > 0) {
+		unsigned xhdr_len;
+		if (len < 5) {
+			bin2hex(hexbuf, (void*)p, len)[0] = '\0';
+			dbg("< |%s|\n", hexbuf);
+			return;
+		}
+		xhdr_len = 0x100*p[3] + p[4];
+		dbg("< hdr_type:%u ver:%u.%u len:%u", p[0], p[1], p[2], xhdr_len);
+		p += 5;
+		len -= 5;
+		if (len >= 4 && p[-5] == RECORD_TYPE_HANDSHAKE) {
+			unsigned len24 = get24be(p + 1);
+			dbg(" type:%u len24:%u", p[0], len24);
+		}
+		if (xhdr_len > len)
+			xhdr_len = len;
+		bin2hex(hexbuf, (void*)p, xhdr_len)[0] = '\0';
+		dbg(" |%s|\n", hexbuf);
+		p += xhdr_len;
+		len -= xhdr_len;
+	}
+}
+
+static void tls_error_die(tls_state_t *tls)
+{
+	dump(tls->inbuf, tls->insize + tls->tail);
+	xfunc_die();
+}
+
+static int xread_tls_block(tls_state_t *tls)
+{
+	int len;
+	int total;
+	int target;
+
+	dbg("insize:%u tail:%u\n", tls->insize, tls->tail);
+	memmove(tls->inbuf, tls->inbuf + tls->insize, tls->tail);
+	errno = 0;
+	total = tls->tail;
+	target = sizeof(tls->inbuf);
+	for (;;) {
+		if (total >= sizeof(struct transport_hdr) && target == sizeof(tls->inbuf)) {
+			struct transport_hdr *xhdr = (void*)tls->inbuf;
+			target = sizeof(*xhdr) + (0x100 * xhdr->len16_hi + xhdr->len16_lo);
+		}
+		/* if total >= target, we have a full packet (and possibly more)... */
+		if (target - total <= 0)
+			break;
+		len = safe_read(tls->fd, tls->inbuf + total, sizeof(tls->inbuf) - total);
+		if (len <= 0)
+			bb_perror_msg_and_die("short read");
+		total += len;
+	}
+	tls->tail = -(target - total);
+	tls->insize = target;
+	target -= sizeof(struct transport_hdr);
+	dbg("got block len:%u\n", target);
+	return target;
+}
+
+static void send_client_hello(tls_state_t *tls)
+{
+	struct client_hello {
+		struct transport_hdr xhdr;
+		uint8_t type;
+		uint8_t len24_hi, len24_mid, len24_lo;
+		uint8_t proto_maj, proto_min;
+		uint8_t rand32[32];
+		uint8_t session_id_len;
+		/* uint8_t session_id[]; */
+		uint8_t cipherid_len16_hi, cipherid_len16_lo;
+		uint8_t cipherid[2 * 1]; /* actually variable */
+		uint8_t comprtypes_len;
+		uint8_t comprtypes[1]; /* actually variable */
+	};
+	struct client_hello hello;
+
+	memset(&hello, 0, sizeof(hello));
+	hello.xhdr.type = RECORD_TYPE_HANDSHAKE;
+	hello.xhdr.proto_maj = TLS_MAJ;
+	hello.xhdr.proto_min = TLS_MIN;
+	hello.xhdr.len16_hi = (sizeof(hello) - sizeof(hello.xhdr)) >> 8;
+	hello.xhdr.len16_lo = (sizeof(hello) - sizeof(hello.xhdr));
+	hello.type = HANDSHAKE_CLIENT_HELLO;
+	hello.len24_mid = (sizeof(hello) - sizeof(hello.xhdr) - 4) >> 8;
+	hello.len24_lo  = (sizeof(hello) - sizeof(hello.xhdr) - 4);
+	hello.proto_maj = TLS_MAJ;
+	hello.proto_min = TLS_MIN;
+	//fillrand(hello.rand32, sizeof(hello.rand32));
+	open_read_close("/dev/urandom", hello.rand32, sizeof(hello.rand32));
+	//hello.session_id_len = 0;
+	//hello.cipherid_len16_hi = 0;
+	hello.cipherid_len16_lo = 2;
+	hello.cipherid[0] = CIPHER_ID >> 8;
+	hello.cipherid[1] = CIPHER_ID & 0xff;
+	hello.comprtypes_len = 1;
+	//hello.comprtypes[0] = 0;
+
+	xwrite(tls->fd, &hello, sizeof(hello));
+}
+
+static void get_server_hello_or_die(tls_state_t *tls)
+{
+	struct server_hello {
+		struct transport_hdr xhdr;
+		uint8_t type;
+		uint8_t len24_hi, len24_mid, len24_lo;
+		uint8_t proto_maj, proto_min;
+		uint8_t rand32[32]; /* first 4 bytes are unix time in BE format */
+		uint8_t session_id_len;
+		uint8_t session_id[32];
+		uint8_t cipherid_hi, cipherid_lo;
+		uint8_t comprtype;
+		/* extensions may follow, but only those which client offered in its Hello */
+	};
+	struct server_hello *hp;
+	int len;
+
+	len = xread_tls_block(tls);
+
+	hp = (void*)tls->inbuf;
+	if (len != 74 /* TODO: if we accept extensions, should be < instead of != */
+	 || hp->xhdr.type != RECORD_TYPE_HANDSHAKE
+	 || hp->xhdr.proto_maj != TLS_MAJ
+	 || hp->xhdr.proto_min != TLS_MIN
+	) {
+		/* example: RECORD_TYPE_ALERT if server can't support our ciphers */
+		tls_error_die(tls);
+	}
+	dbg("got HANDSHAKE\n");
+	// 02   000046 03|03   58|78|cf|c1 50|a5|49|ee|7e|29|48|71|fe|97|fa|e8|2d|19|87|72|90|84|9d|37|a3|f0|cb|6f|5f|e3|3c|2f |20  |d8|1a|78|96|52|d6|91|01|24|b3|d6|5b|b7|d0|6c|b3|e1|78|4e|3c|95|de|74|a0|ba|eb|a7|3a|ff|bd|a2|bf |00|9c |00|
+	// SvHl len=70 maj.min unixtime^^^ 28randbytes^^^^^^^^^^^^^^^^^^^^^^^^^^^^_^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^_^^^ slen sid32bytes^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ cipSel comprSel
+	if (hp->type != HANDSHAKE_SERVER_HELLO
+	 || hp->len24_hi  != 0
+	 || hp->len24_mid != 0
+	 || hp->len24_lo  != 70
+	 || hp->proto_maj != TLS_MAJ
+	 || hp->proto_min != TLS_MIN
+	 || hp->session_id_len != 32
+	 || hp->cipherid_hi != (CIPHER_ID >> 8)
+	 || hp->cipherid_lo != (CIPHER_ID & 0xff)
+	 || hp->comprtype != 0
+	) {
+		tls_error_die(tls);
+	}
+	dbg("got SERVER_HELLO\n");
+}
+
+static unsigned get_der_len(uint8_t **bodyp, uint8_t *der, uint8_t *end)
+{
+	unsigned len;
+
+	if (end - der < 2)
+		xfunc_die();
+//	if ((der[0] & 0x1f) == 0x1f) /* not single-byte item code? */
+//		xfunc_die();
+
+	len = der[1]; /* maybe it's short len */
+	if (len >= 0x80) {
+		/* no */
+		if (len != 0x82) {
+			/* 0x80 is "0 bytes of len", invalid DER: must use short len if can */
+			/* 0x81 is "1 byte of len", invalid DER */
+			/* >0x82 is "3+ bytes of len", should not happen realistically */
+			xfunc_die();
+		}
+		if (end - der < 4)
+			xfunc_die();
+		/* it's "ii 82 xx yy" */
+		len = 0x100*der[2] + der[3];
+		if (len < 0x80)
+			xfunc_die(); /* invalid DER: must use short len if can */
+
+		der += 2; /* skip [code]+[82]+[2byte_len] */
+	}
+	der += 2; /* skip [code]+[1byte_len] */
+
+	if (end - der < len)
+		xfunc_die();
+	*bodyp = der;
+
+	return len;
+}
+
+static uint8_t *enter_der_item(uint8_t *der, uint8_t **endp)
+{
+	uint8_t *new_der;
+	unsigned len = get_der_len(&new_der, der, *endp);
+	dbg("entered der @%p:0x%02x len:%u inner_byte @%p:0x%02x\n", der, der[0], len, new_der, new_der[0]);
+	/* Move "end" position to cover only this item */
+	*endp = new_der + len;
+	return new_der;
+}
+
+static uint8_t *skip_der_item(uint8_t *der, uint8_t *end)
+{
+	uint8_t *new_der;
+	unsigned len = get_der_len(&new_der, der, end);
+	/* Skip body */
+	new_der += len;
+	dbg("skipped der 0x%02x, next byte 0x%02x\n", der[0], new_der[0]);
+	return new_der;
+}
+
+static void *find_key_in_der_cert(int *key_len, uint8_t *der, int len)
+{
+/* Example: partial decode of kernel.org certificate in DER format.
+ *  SEQ 0x05ac/1452 bytes (Certificate): 308205ac
+ *    SEQ 0x0494/1172 bytes (tbsCertificate): 30820494
+ *      [ASN_CONTEXT_SPECIFIC | ASN_CONSTRUCTED | 0] 3 bytes: a003
+ *        INTEGER (version): 0201 02
+ *      INTEGER 0x11 bytes (serialNumber): 0211 00 9f85bf664b0cddafca508679501b2be4
+ *      //^^^^^^note: matrixSSL also allows [ASN_CONTEXT_SPECIFIC | ASN_PRIMITIVE | 2] = 0x82 type
+ *      SEQ 0x0d bytes (signatureAlgo): 300d
+ *        OID 9 bytes: 0609 2a864886f70d01010b (OID_SHA256_RSA_SIG 42.134.72.134.247.13.1.1.11)
+ *        NULL: 0500
+ *      SEQ 0x5f bytes (issuer): 305f
+ *        SET 11 bytes: 310b
+ *          SEQ 9 bytes: 3009
+ *            OID 3 bytes: 0603 550406
+ *            Printable string "FR": 1302 4652
+ *        SET 14 bytes: 310e
+ *          SEQ 12 bytes: 300c
+ *            OID 3 bytes: 0603 550408
+ *            Printable string "Paris": 1305 5061726973
+ *        SET 14 bytes: 310e
+ *          SEQ 12 bytes: 300c
+ *            OID 3 bytes: 0603 550407
+ *            Printable string "Paris": 1305 5061726973
+ *        SET 14 bytes: 310e
+ *          SEQ 12 bytes: 300c
+ *            OID 3 bytes: 0603 55040a
+ *            Printable string "Gandi": 1305 47616e6469
+ *        SET 32 bytes: 3120
+ *          SEQ 30 bytes: 301e
+ *            OID 3 bytes: 0603 550403
+ *            Printable string "Gandi Standard SSL CA 2": 1317
+ *                              47616e6469205374616e646172642053534c2043412032
+ *      SEQ 30 bytes (validity): 301e
+ *        TIME "161011000000Z": 170d 3136313031313030303030305a
+ *        TIME "191011235959Z": 170d 3139313031313233353935395a
+ *      SEQ 0x5b/91 bytes (subject): 305b //I did not decode this
+ *          3121301f060355040b1318446f6d61696e20436f
+ *          6e74726f6c2056616c6964617465643121301f06
+ *          0355040b1318506f73697469766553534c204d75
+ *          6c74692d446f6d61696e31133011060355040313
+ *          0a6b65726e656c2e6f7267
+ *      SEQ 0x01a2/418 bytes (subjectPublicKeyInfo): 308201a2
+ *        SEQ 13 bytes (algorithm): 300d
+ *          OID 9 bytes: 0609 2a864886f70d010101 (OID_RSA_KEY_ALG 42.134.72.134.247.13.1.1.1)
+ *          NULL: 0500
+ *        BITSTRING 0x018f/399 bytes (publicKey): 0382018f
+ *          ????: 00
+ *          //after the zero byte, it appears key itself uses DER encoding:
+ *          SEQ 0x018a/394 bytes: 3082018a
+ *            INTEGER 0x0181/385 bytes (modulus): 02820181
+ *                  00b1ab2fc727a3bef76780c9349bf3
+ *                  ...24 more blocks of 15 bytes each...
+ *                  90e895291c6bc8693b65
+ *            INTEGER 3 bytes (exponent): 0203 010001
+ *      [ASN_CONTEXT_SPECIFIC | ASN_CONSTRUCTED | 0x3] 0x01e5 bytes (X509v3 extensions): a38201e5
+ *        SEQ 0x01e1 bytes: 308201e1
+ *        ...
+ * Certificate is a DER-encoded data structure. Each DER element has a length,
+ * which makes it easy to skip over large compound elements of any complexity
+ * without parsing them.
+ *
+ * Certificate is a sequence of three elements:
+ *	tbsCertificate (SEQ)
+ *	signatureAlgorithm (AlgorithmIdentifier)
+ *	signatureValue (BIT STRING)
+ *
+ * In turn, tbsCertificate is a sequence of:
+ *	version
+ *	serialNumber
+ *	signatureAlgo (AlgorithmIdentifier)
+ *	issuer (Name, has complex structure)
+ *	validity (Validity, SEQ of two Times)
+ *	subject (Name)
+ *	subjectPublicKeyInfo (SEQ)
+ *	...
+ *
+ * subjectPublicKeyInfo is a sequence of:
+ *	algorithm (AlgorithmIdentifier)
+ *	publicKey (BIT STRING)
+ *
+ * Essentially, we want subjectPublicKeyInfo.publicKey
+ */
+	uint8_t *end = der + len;
+
+	/* enter "Certificate" item: [der, end) will be only Cert */
+	der = enter_der_item(der, &end);
+
+	/* enter "tbsCertificate" item: [der, end) will be only tbsCert */
+	der = enter_der_item(der, &end);
+
+	/* skip up to subjectPublicKeyInfo */
+	der = skip_der_item(der, end); /* version */
+	der = skip_der_item(der, end); /* serialNumber */
+	der = skip_der_item(der, end); /* signatureAlgo */
+	der = skip_der_item(der, end); /* issuer */
+	der = skip_der_item(der, end); /* validity */
+	der = skip_der_item(der, end); /* subject */
+
+	/* enter "subjectPublicKeyInfo" */
+	der = enter_der_item(der, &end);
+
+	/* skip "subjectPublicKeyInfo.algorithm" */
+	der = skip_der_item(der, end);
+	/* enter "subjectPublicKeyInfo.publicKey" */
+//	die_if_not_this_der_type(der, end, 0x03); /* must be BITSTRING */
+	der = enter_der_item(der, &end);
+
+	/* return a copy */
+	*key_len = end - der;
+	dbg("copying key bytes:%u, first:0x%02x\n", *key_len, der[0]);
+	return xmemdup(der, *key_len);
+}
+
+static void get_server_cert_or_die(tls_state_t *tls)
+{
+	struct transport_hdr *xhdr;
+	uint8_t *certbuf;
+	int len, len1;
+
+	len = xread_tls_block(tls);
+	xhdr = (void*)tls->inbuf;
+	if (len < sizeof(*xhdr) + 10
+	 || xhdr->type != RECORD_TYPE_HANDSHAKE
+	 || xhdr->proto_maj != TLS_MAJ
+	 || xhdr->proto_min != TLS_MIN
+	) {
+		tls_error_die(tls);
+	}
+	dbg("got HANDSHAKE\n");
+	certbuf = (void*)(xhdr + 1);
+	if (certbuf[0] != HANDSHAKE_CERTIFICATE)
+		tls_error_die(tls);
+	dbg("got CERTIFICATE\n");
+	// 0b   00|11|24 00|11|21 00|05|b0 30|82|05|ac|30|82|04|94|a0|03|02|01|02|02|11|00|9f|85|bf|66|4b|0c|dd|af|ca|50|86|79|50|1b|2b|e4|30|0d... (4392 bytes)
+	// Cert len=4388 ChainLen CertLen^ DER encoded X509 starts here. openssl x509 -in FILE -inform DER -noout -text
+	len1 = get24be(certbuf + 1);
+	if (len1 > len - 4) tls_error_die(tls);
+	len = len1;
+
+	len1 = get24be(certbuf + 4);
+	if (len1 > len - 3) tls_error_die(tls);
+	len = len1;
+
+	len1 = get24be(certbuf + 7);
+	if (len1 > len - 3) tls_error_die(tls);
+	len = len1;
+
+	if (len)
+		tls->pubkey = find_key_in_der_cert(&tls->pubkey_len, certbuf + 10, len);
+}
+
+static void tls_handshake(tls_state_t *tls)
+{
+	// Client              RFC 5246                Server
+	// (*) - optional messages, not always sent
+	//
+	// ClientHello          ------->
+	//                                        ServerHello
+	//                                       Certificate*
+	//                                 ServerKeyExchange*
+	//                                CertificateRequest*
+	//                      <-------      ServerHelloDone
+	// Certificate*
+	// ClientKeyExchange
+	// CertificateVerify*
+	// [ChangeCipherSpec]
+	// Finished             ------->
+	//                                 [ChangeCipherSpec]
+	//                      <-------             Finished
+	// Application Data     <------>     Application Data
+	int len;
+
+	send_client_hello(tls);
+#if 0 /* dump */
+	for (;;) {
+		uint8_t buf[16*1024];
+		sleep(2);
+		len = recv(tls->fd, buf, sizeof(buf), 0); //MSG_DONTWAIT);
+		if (len < 0) {
+			if (errno == EAGAIN)
+				continue;
+			bb_perror_msg_and_die("recv");
+		}
+		if (len == 0)
+			break;
+		dump(buf, len);
+	}
+#endif
+
+	get_server_hello_or_die(tls);
+
+	//RFC 5246
+	// The server MUST send a Certificate message whenever the agreed-
+	// upon key exchange method uses certificates for authentication
+	// (this includes all key exchange methods defined in this document
+	// except DH_anon).  This message will always immediately follow the
+	// ServerHello message.
+	//
+	// IOW: in practice, Certificate *always* follows.
+	// (for example, kernel.org does not even accept DH_anon cipher id)
+	get_server_cert_or_die(tls);
+
+	len = xread_tls_block(tls);
+	/* Next handshake type is not predetermined */
+	switch (tls->inbuf[5]) {
+	case HANDSHAKE_SERVER_KEY_EXCHANGE:
+		//0c    0001c7 03|00|17|41|04|87|94|2e|2f|68|d0|c9|f4|97|a8|2d|ef|ed|67|ea|c6|f3|b3|56|47|5d|27|b6|bd|ee|70|25|30|5e|b0|8e|f6|21|5a... 459 bytes
+		//SvKey len^^^
+		dbg("got SERVER_KEY_EXCHANGE\n");
+		len = xread_tls_block(tls);
+		break;
+	case HANDSHAKE_CERTIFICATE_REQUEST:
+		dbg("got CERTIFICATE_REQUEST\n");
+		len = xread_tls_block(tls);
+		break;
+	case HANDSHAKE_SERVER_HELLO_DONE:
+		// 0e 000000 (len:0)
+		dbg("got SERVER_HELLO_DONE\n");
+		break;
+	default:
+		tls_error_die(tls);
+	}
+}
+
+int tls_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
+int tls_main(int argc UNUSED_PARAM, char **argv)
+{
+	tls_state_t *tls;
+	len_and_sockaddr *lsa;
+	int fd;
+
+	// INIT_G();
+	// getopt32(argv, "myopts")
+
+	if (!argv[1])
+		bb_show_usage();
+
+	lsa = xhost2sockaddr(argv[1], 443);
+	fd = xconnect_stream(lsa);
+
+	tls = new_tls_state();
+	tls->fd = fd;
+	tls_handshake(tls);
+
+	return EXIT_SUCCESS;
+}