1 /* $NetBSD: netstring.c,v 1.3 2020/03/18 19:05:21 christos Exp $ */ 2 3 /*++ 4 /* NAME 5 /* netstring 3 6 /* SUMMARY 7 /* netstring stream I/O support 8 /* SYNOPSIS 9 /* #include <netstring.h> 10 /* 11 /* void netstring_setup(stream, timeout) 12 /* VSTREAM *stream; 13 /* int timeout; 14 /* 15 /* void netstring_except(stream, exception) 16 /* VSTREAM *stream; 17 /* int exception; 18 /* 19 /* const char *netstring_strerror(err) 20 /* int err; 21 /* 22 /* VSTRING *netstring_get(stream, buf, limit) 23 /* VSTREAM *stream; 24 /* VSTRING *buf; 25 /* ssize_t limit; 26 /* 27 /* void netstring_put(stream, data, len) 28 /* VSTREAM *stream; 29 /* const char *data; 30 /* ssize_t len; 31 /* 32 /* void netstring_put_multi(stream, data, len, data, len, ..., 0) 33 /* VSTREAM *stream; 34 /* const char *data; 35 /* ssize_t len; 36 /* 37 /* void NETSTRING_PUT_BUF(stream, buf) 38 /* VSTREAM *stream; 39 /* VSTRING *buf; 40 /* 41 /* void netstring_fflush(stream) 42 /* VSTREAM *stream; 43 /* 44 /* VSTRING *netstring_memcpy(buf, data, len) 45 /* VSTRING *buf; 46 /* const char *data; 47 /* ssize_t len; 48 /* 49 /* VSTRING *netstring_memcat(buf, data, len) 50 /* VSTRING *buf; 51 /* const char *src; 52 /* ssize_t len; 53 /* AUXILIARY ROUTINES 54 /* ssize_t netstring_get_length(stream) 55 /* VSTREAM *stream; 56 /* 57 /* VSTRING *netstring_get_data(stream, buf, len) 58 /* VSTREAM *stream; 59 /* VSTRING *buf; 60 /* ssize_t len; 61 /* 62 /* void netstring_get_terminator(stream) 63 /* VSTREAM *stream; 64 /* DESCRIPTION 65 /* This module reads and writes netstrings with error detection: 66 /* timeouts, unexpected end-of-file, or format errors. Netstring 67 /* is a data format designed by Daniel Bernstein. 68 /* 69 /* netstring_setup() arranges for a time limit on the netstring 70 /* read and write operations described below. 71 /* This routine alters the behavior of streams as follows: 72 /* .IP \(bu 73 /* The read/write timeout is set to the specified value. 74 /* .IP \(bu 75 /* The stream is configured to enable exception handling. 76 /* .PP 77 /* netstring_except() raises the specified exception on the 78 /* named stream. See the DIAGNOSTICS section below. 79 /* 80 /* netstring_strerror() converts an exception number to string. 81 /* 82 /* netstring_get() reads a netstring from the specified stream 83 /* and extracts its content. The limit specifies a maximal size. 84 /* Specify zero to disable the size limit. The result is not null 85 /* terminated. The result value is the buf argument. 86 /* 87 /* netstring_put() encapsulates the specified string as a netstring 88 /* and sends the result to the specified stream. 89 /* The stream output buffer is not flushed. 90 /* 91 /* netstring_put_multi() encapsulates the content of multiple strings 92 /* as one netstring and sends the result to the specified stream. The 93 /* argument list must be terminated with a null data pointer. 94 /* The stream output buffer is not flushed. 95 /* 96 /* NETSTRING_PUT_BUF() is a macro that provides a VSTRING-based 97 /* wrapper for the netstring_put() routine. 98 /* 99 /* netstring_fflush() flushes the output buffer of the specified 100 /* stream and handles any errors. 101 /* 102 /* netstring_memcpy() encapsulates the specified data as a netstring 103 /* and copies the result over the specified buffer. The result 104 /* value is the buffer. 105 /* 106 /* netstring_memcat() encapsulates the specified data as a netstring 107 /* and appends the result to the specified buffer. The result 108 /* value is the buffer. 109 /* 110 /* The following routines provide low-level access to a netstring 111 /* stream. 112 /* 113 /* netstring_get_length() reads a length field from the specified 114 /* stream, and absorbs the netstring length field terminator. 115 /* 116 /* netstring_get_data() reads the specified number of bytes from the 117 /* specified stream into the specified buffer, and absorbs the 118 /* netstring terminator. The result value is the buf argument. 119 /* 120 /* netstring_get_terminator() reads the netstring terminator from 121 /* the specified stream. 122 /* DIAGNOSTICS 123 /* .fi 124 /* .ad 125 /* In case of error, a vstream_longjmp() call is performed to the 126 /* caller-provided context specified with vstream_setjmp(). 127 /* Error codes passed along with vstream_longjmp() are: 128 /* .IP NETSTRING_ERR_EOF 129 /* An I/O error happened, or the peer has disconnected unexpectedly. 130 /* .IP NETSTRING_ERR_TIME 131 /* The time limit specified to netstring_setup() was exceeded. 132 /* .IP NETSTRING_ERR_FORMAT 133 /* The input contains an unexpected character value. 134 /* .IP NETSTRING_ERR_SIZE 135 /* The input is larger than acceptable. 136 /* BUGS 137 /* The timeout deadline affects all I/O on the named stream, not 138 /* just the I/O done on behalf of this module. 139 /* 140 /* The timeout deadline overwrites any previously set up state on 141 /* the named stream. 142 /* 143 /* netstrings are not null terminated, which makes printing them 144 /* a bit awkward. 145 /* LICENSE 146 /* .ad 147 /* .fi 148 /* The Secure Mailer license must be distributed with this software. 149 /* SEE ALSO 150 /* http://cr.yp.to/proto/netstrings.txt, netstring definition 151 /* AUTHOR(S) 152 /* Wietse Venema 153 /* IBM T.J. Watson Research 154 /* P.O. Box 704 155 /* Yorktown Heights, NY 10598, USA 156 /* 157 /* Wietse Venema 158 /* Google, Inc. 159 /* 111 8th Avenue 160 /* New York, NY 10011, USA 161 /*--*/ 162 163 /* System library. */ 164 165 #include <sys_defs.h> 166 #include <stdarg.h> 167 #include <ctype.h> 168 169 /* Utility library. */ 170 171 #include <msg.h> 172 #include <vstream.h> 173 #include <vstring.h> 174 #include <compat_va_copy.h> 175 #include <netstring.h> 176 177 /* Application-specific. */ 178 179 #define STR(x) vstring_str(x) 180 #define LEN(x) VSTRING_LEN(x) 181 182 /* netstring_setup - initialize netstring stream */ 183 184 void netstring_setup(VSTREAM *stream, int timeout) 185 { 186 vstream_control(stream, 187 CA_VSTREAM_CTL_TIMEOUT(timeout), 188 CA_VSTREAM_CTL_EXCEPT, 189 CA_VSTREAM_CTL_END); 190 } 191 192 /* netstring_except - process netstring stream exception */ 193 194 void netstring_except(VSTREAM *stream, int exception) 195 { 196 vstream_longjmp(stream, exception); 197 } 198 199 /* netstring_get_length - read netstring length + terminator */ 200 201 ssize_t netstring_get_length(VSTREAM *stream) 202 { 203 const char *myname = "netstring_get_length"; 204 ssize_t len = 0; 205 int ch; 206 int digit; 207 208 for (;;) { 209 switch (ch = VSTREAM_GETC(stream)) { 210 case VSTREAM_EOF: 211 netstring_except(stream, vstream_ftimeout(stream) ? 212 NETSTRING_ERR_TIME : NETSTRING_ERR_EOF); 213 case ':': 214 if (msg_verbose > 1) 215 msg_info("%s: read netstring length %ld", myname, (long) len); 216 return (len); 217 default: 218 if (!ISDIGIT(ch)) 219 netstring_except(stream, NETSTRING_ERR_FORMAT); 220 digit = ch - '0'; 221 if (len > SSIZE_T_MAX / 10 222 || (len *= 10) > SSIZE_T_MAX - digit) 223 netstring_except(stream, NETSTRING_ERR_SIZE); 224 len += digit; 225 break; 226 } 227 } 228 } 229 230 /* netstring_get_data - read netstring payload + terminator */ 231 232 VSTRING *netstring_get_data(VSTREAM *stream, VSTRING *buf, ssize_t len) 233 { 234 const char *myname = "netstring_get_data"; 235 236 /* 237 * Read the payload and absorb the terminator. 238 */ 239 if (vstream_fread_buf(stream, buf, len) != len) 240 netstring_except(stream, vstream_ftimeout(stream) ? 241 NETSTRING_ERR_TIME : NETSTRING_ERR_EOF); 242 if (msg_verbose > 1) 243 msg_info("%s: read netstring data %.*s", 244 myname, (int) (len < 30 ? len : 30), STR(buf)); 245 netstring_get_terminator(stream); 246 247 /* 248 * Return the buffer. 249 */ 250 return (buf); 251 } 252 253 /* netstring_get_terminator - absorb netstring terminator */ 254 255 void netstring_get_terminator(VSTREAM *stream) 256 { 257 if (VSTREAM_GETC(stream) != ',') 258 netstring_except(stream, NETSTRING_ERR_FORMAT); 259 } 260 261 /* netstring_get - read string from netstring stream */ 262 263 VSTRING *netstring_get(VSTREAM *stream, VSTRING *buf, ssize_t limit) 264 { 265 ssize_t len; 266 267 len = netstring_get_length(stream); 268 if (ENFORCING_SIZE_LIMIT(limit) && len > limit) 269 netstring_except(stream, NETSTRING_ERR_SIZE); 270 netstring_get_data(stream, buf, len); 271 return (buf); 272 } 273 274 /* netstring_put - send string as netstring */ 275 276 void netstring_put(VSTREAM *stream, const char *data, ssize_t len) 277 { 278 const char *myname = "netstring_put"; 279 280 if (msg_verbose > 1) 281 msg_info("%s: write netstring len %ld data %.*s", 282 myname, (long) len, (int) (len < 30 ? len : 30), data); 283 vstream_fprintf(stream, "%ld:", (long) len); 284 vstream_fwrite(stream, data, len); 285 VSTREAM_PUTC(',', stream); 286 } 287 288 /* netstring_put_multi - send multiple strings as one netstring */ 289 290 void netstring_put_multi(VSTREAM *stream,...) 291 { 292 const char *myname = "netstring_put_multi"; 293 ssize_t total; 294 char *data; 295 ssize_t data_len; 296 va_list ap; 297 va_list ap2; 298 299 /* 300 * Initialize argument lists. 301 */ 302 va_start(ap, stream); 303 VA_COPY(ap2, ap); 304 305 /* 306 * Figure out the total result size. 307 */ 308 for (total = 0; (data = va_arg(ap, char *)) != 0; total += data_len) 309 if ((data_len = va_arg(ap, ssize_t)) < 0) 310 msg_panic("%s: bad data length %ld", myname, (long) data_len); 311 va_end(ap); 312 if (total < 0) 313 msg_panic("%s: bad total length %ld", myname, (long) total); 314 if (msg_verbose > 1) 315 msg_info("%s: write total length %ld", myname, (long) total); 316 317 /* 318 * Send the length, content and terminator. 319 */ 320 vstream_fprintf(stream, "%ld:", (long) total); 321 while ((data = va_arg(ap2, char *)) != 0) { 322 data_len = va_arg(ap2, ssize_t); 323 if (msg_verbose > 1) 324 msg_info("%s: write netstring len %ld data %.*s", 325 myname, (long) data_len, 326 (int) (data_len < 30 ? data_len : 30), data); 327 if (vstream_fwrite(stream, data, data_len) != data_len) 328 netstring_except(stream, vstream_ftimeout(stream) ? 329 NETSTRING_ERR_TIME : NETSTRING_ERR_EOF); 330 } 331 va_end(ap2); 332 vstream_fwrite(stream, ",", 1); 333 } 334 335 /* netstring_fflush - flush netstring stream */ 336 337 void netstring_fflush(VSTREAM *stream) 338 { 339 if (vstream_fflush(stream) == VSTREAM_EOF) 340 netstring_except(stream, vstream_ftimeout(stream) ? 341 NETSTRING_ERR_TIME : NETSTRING_ERR_EOF); 342 } 343 344 /* netstring_memcpy - copy data as in-memory netstring */ 345 346 VSTRING *netstring_memcpy(VSTRING *buf, const char *src, ssize_t len) 347 { 348 vstring_sprintf(buf, "%ld:", (long) len); 349 vstring_memcat(buf, src, len); 350 VSTRING_ADDCH(buf, ','); 351 return (buf); 352 } 353 354 /* netstring_memcat - append data as in-memory netstring */ 355 356 VSTRING *netstring_memcat(VSTRING *buf, const char *src, ssize_t len) 357 { 358 vstring_sprintf_append(buf, "%ld:", (long) len); 359 vstring_memcat(buf, src, len); 360 VSTRING_ADDCH(buf, ','); 361 return (buf); 362 } 363 364 /* netstring_strerror - convert error number to string */ 365 366 const char *netstring_strerror(int err) 367 { 368 switch (err) { 369 case NETSTRING_ERR_EOF: 370 return ("unexpected disconnect"); 371 case NETSTRING_ERR_TIME: 372 return ("time limit exceeded"); 373 case NETSTRING_ERR_FORMAT: 374 return ("input format error"); 375 case NETSTRING_ERR_SIZE: 376 return ("input exceeds size limit"); 377 default: 378 return ("unknown netstring error"); 379 } 380 } 381 382 /* 383 * Proof-of-concept netstring encoder/decoder. 384 * 385 * Usage: netstring command... 386 * 387 * Run the command as a child process. Then, convert between plain strings on 388 * our own stdin/stdout, and netstrings on the child program's stdin/stdout. 389 * 390 * Example (socketmap test server): netstring nc -l 9999 391 */ 392 #ifdef TEST 393 #include <unistd.h> 394 #include <stdlib.h> 395 #include <events.h> 396 397 static VSTRING *stdin_read_buf; /* stdin line buffer */ 398 static VSTRING *child_read_buf; /* child read buffer */ 399 static VSTREAM *child_stream; /* child stream (full-duplex) */ 400 401 /* stdin_read_event - line-oriented event handler */ 402 403 static void stdin_read_event(int event, void *context) 404 { 405 int ch; 406 407 /* 408 * Send a netstring to the child when we have accumulated an entire line 409 * of input. 410 * 411 * Note: the first VSTREAM_GETCHAR() call implicitly fills the VSTREAM 412 * buffer. We must drain the entire VSTREAM buffer before requesting the 413 * next read(2) event. 414 */ 415 do { 416 ch = VSTREAM_GETCHAR(); 417 switch (ch) { 418 default: 419 VSTRING_ADDCH(stdin_read_buf, ch); 420 break; 421 case '\n': 422 NETSTRING_PUT_BUF(child_stream, stdin_read_buf); 423 vstream_fflush(child_stream); 424 VSTRING_RESET(stdin_read_buf); 425 break; 426 case VSTREAM_EOF: 427 /* Better: wait for child to terminate. */ 428 sleep(1); 429 exit(0); 430 } 431 } while (vstream_peek(VSTREAM_IN) > 0); 432 } 433 434 /* child_read_event - netstring-oriented event handler */ 435 436 static void child_read_event(int event, void *context) 437 { 438 439 /* 440 * Read an entire netstring from the child and send the result to stdout. 441 * 442 * This is a simplistic implementation that assumes a server will not 443 * trickle its data. 444 * 445 * Note: the first netstring_get() call implicitly fills the VSTREAM buffer. 446 * We must drain the entire VSTREAM buffer before requesting the next 447 * read(2) event. 448 */ 449 do { 450 netstring_get(child_stream, child_read_buf, 10000); 451 vstream_fwrite(VSTREAM_OUT, STR(child_read_buf), LEN(child_read_buf)); 452 VSTREAM_PUTC('\n', VSTREAM_OUT); 453 vstream_fflush(VSTREAM_OUT); 454 } while (vstream_peek(child_stream) > 0); 455 } 456 457 int main(int argc, char **argv) 458 { 459 int err; 460 461 /* 462 * Sanity check. 463 */ 464 if (argv[1] == 0) 465 msg_fatal("usage: %s command...", argv[0]); 466 467 /* 468 * Run the specified command as a child process with stdin and stdout 469 * connected to us. 470 */ 471 child_stream = vstream_popen(O_RDWR, CA_VSTREAM_POPEN_ARGV(argv + 1), 472 CA_VSTREAM_POPEN_END); 473 vstream_control(child_stream, CA_VSTREAM_CTL_DOUBLE, CA_VSTREAM_CTL_END); 474 netstring_setup(child_stream, 10); 475 476 /* 477 * Buffer plumbing. 478 */ 479 stdin_read_buf = vstring_alloc(100); 480 child_read_buf = vstring_alloc(100); 481 482 /* 483 * Monitor both the child's stdout stream and our own stdin stream. If 484 * there is activity on the child stdout stream, read an entire netstring 485 * or EOF. If there is activity on stdin, send a netstring to the child 486 * when we have read an entire line, or terminate in case of EOF. 487 */ 488 event_enable_read(vstream_fileno(VSTREAM_IN), stdin_read_event, (void *) 0); 489 event_enable_read(vstream_fileno(child_stream), child_read_event, 490 (void *) 0); 491 492 if ((err = vstream_setjmp(child_stream)) == 0) { 493 for (;;) 494 event_loop(-1); 495 } else { 496 msg_fatal("%s: %s", argv[1], netstring_strerror(err)); 497 } 498 } 499 500 #endif 501