mime_cte.c

   1 /*@ S-nail - a mail user agent derived from Berkeley Mail.
   2  *@ Content-Transfer-Encodings as defined in RFC 2045:
   3  *@ - Quoted-Printable, section 6.7
   4  *@ - Base64, section 6.8
   5  *
   6  * Copyright (c) 2000-2004 Gunnar Ritter, Freiburg i. Br., Germany.
   7  * Copyright (c) 2012 - 2013 Steffen "Daode" Nurpmeso <sdaoden@users.sf.net>.
   8  */
   9 /* QP quoting idea, _b64_decode(), b64_encode() taken from NetBSDs mailx(1): */
  10 /*      $NetBSD: mime_codecs.c,v 1.9 2009/04/10 13:08:25 christos Exp $ */
  11 /*
  12  * Copyright (c) 2006 The NetBSD Foundation, Inc.
  13  * All rights reserved.
  14  *
  15  * This code is derived from software contributed to The NetBSD Foundation
  16  * by Anon Ymous.
  17  *
  18  * Redistribution and use in source and binary forms, with or without
  19  * modification, are permitted provided that the following conditions
  20  * are met:
  21  * 1. Redistributions of source code must retain the above copyright
  22  *    notice, this list of conditions and the following disclaimer.
  23  * 2. Redistributions in binary form must reproduce the above copyright
  24  *    notice, this list of conditions and the following disclaimer in the
  25  *    documentation and/or other materials provided with the distribution.
  26  *
  27  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
  28  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
  29  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  30  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
  31  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  32  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  33  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  34  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  35  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  36  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  37  * POSSIBILITY OF SUCH DAMAGE.
  38  */
  39
  40 #include "rcv.h"
  41 #include "extern.h"
  42
  43 enum _qact {
  44          N =   0,       /* Do not quote */
  45          Q =   1,       /* Must quote */
  46         SP =   2,       /* sp */
  47         XF =   3,       /* Special character 'F' - maybe quoted */
  48         XD =   4,       /* Special character '.' - maybe quoted */
  49         US = '_',       /* In header, special character ' ' quoted as '_' */
  50         QM = '?',       /* In header, special character ? not always quoted */
  51         EQ =   Q,       /* '=' must be quoted */
  52         TB =  SP,       /* Treat '\t' as a space */
  53         NL =   N,       /* Don't quote '\n' (NL) */
  54         CR =   Q        /* Always quote a '\r' (CR) */
  55 };
  56
  57 /* Lookup tables to decide wether a character must be encoded or not.
  58  * Email header differences according to RFC 2047, section 4.2:
  59  * - also quote SP (as the underscore _), TAB, ?, _, CR, LF
  60  * - don't care about the special ^F[rom] and ^.$ */
  61 static uc_it const      _qtab_body[] = {
  62                  Q, Q, Q, Q,  Q, Q, Q, Q,  Q,TB,NL, Q,  Q,CR, Q, Q,
  63                  Q, Q, Q, Q,  Q, Q, Q, Q,  Q, Q, Q, Q,  Q, Q, Q, Q,
  64                 SP, N, N, N,  N, N, N, N,  N, N, N, N,  N, N,XD, N,
  65                  N, N, N, N,  N, N, N, N,  N, N, N, N,  N,EQ, N, N,
  66
  67                  N, N, N, N,  N, N,XF, N,  N, N, N, N,  N, N, N, N,
  68                  N, N, N, N,  N, N, N, N,  N, N, N, N,  N, N, N, N,
  69                  N, N, N, N,  N, N, N, N,  N, N, N, N,  N, N, N, N,
  70                  N, N, N, N,  N, N, N, N,  N, N, N, N,  N, N, N, Q,
  71         },
  72                         _qtab_head[] = {
  73                  Q, Q, Q, Q,  Q, Q, Q, Q,  Q, Q, Q, Q,  Q, Q, Q, Q,
  74                  Q, Q, Q, Q,  Q, Q, Q, Q,  Q, Q, Q, Q,  Q, Q, Q, Q,
  75                 US, N, N, N,  N, N, N, N,  N, N, N, N,  N, N, N, N,
  76                  N, N, N, N,  N, N, N, N,  N, N, N, N,  N,EQ, N,QM,
  77
  78                  N, N, N, N,  N, N, N, N,  N, N, N, N,  N, N, N, N,
  79                  N, N, N, N,  N, N, N, N,  N, N, N, N,  N, N, N, Q,
  80                  N, N, N, N,  N, N, N, N,  N, N, N, N,  N, N, N, N,
  81                  N, N, N, N,  N, N, N, N,  N, N, N, N,  N, N, N, Q,
  82         };
  83
  84 /* Check wether **s* must be quoted according to *ishead*, else body rules;
  85  * *sol* indicates wether we are at the first character of a line/field */
  86 SINLINE enum _qact      _mustquote(char const *s, char const *e, bool_t sol,
  87                                 bool_t ishead);
  88
  89 /* Convert c to/from a hexadecimal character string */
  90 SINLINE char *          _qp_ctohex(char *store, char c);
  91 SINLINE si_it           _qp_cfromhex(char const *hex);
  92
  93 /* Trim WS and make *work* point to the decodable range of *in*.
  94  * Return the amount of bytes a b64_decode operation on that buffer requires */
  95 static size_t           _b64_decode_prepare(struct str *work,
  96                                 struct str const *in);
  97
  98 /* Perform b64_decode on sufficiently spaced & multiple-of-4 base *in*put.
  99  * Return number of useful bytes in *out* or -1 on error */
 100 static ssize_t          _b64_decode(struct str *out, struct str *in);
 101
 102 SINLINE enum _qact
 103 _mustquote(char const *s, char const *e, bool_t sol, bool_t ishead)
 104 {
 105         uc_it const *qtab = ishead ? _qtab_head : _qtab_body;
 106         enum _qact a = ((uc_it)*s > 0x7F) ? Q : qtab[(uc_it)*s], r;
 107
 108         if ((r = a) == N || (r = a) == Q)
 109                 goto jleave;
 110         r = Q;
 111
 112         /* Special header fields */
 113         if (ishead) {
 114                 /* ' ' -> '_' */
 115                 if (a == US) {
 116                         r = US;
 117                         goto jleave;
 118                 }
 119                 /* Treat '?' only special if part of '=?' and '?=' (still to
 120                  * much quoting since it's '=?CHARSET?CTE?stuff?=', and
 121                  * especially the trailing ?= should be hard too match ,) */
 122                 if (a == QM && ((! sol && s[-1] == '=') ||
 123                                 (s < e && s[1] == '=')))
 124                         goto jleave;
 125                 goto jnquote;
 126         }
 127
 128         /* Body-only */
 129
 130         if (a == SP) {
 131                 /* WS only if trailing white space */
 132                 if (s + 1 == e || s[1] == '\n')
 133                         goto jleave;
 134                 goto jnquote;
 135         }
 136
 137         /* Rest are special begin-of-line cases */
 138         if (! sol)
 139                 goto jnquote;
 140
 141         /* ^From */
 142         if (a == XF) {
 143                 if (s + 4 < e && s[1] == 'r' && s[2] == 'o' && s[3] == 'm')
 144                         goto jleave;
 145                 goto jnquote;
 146         }
 147         /* ^.$ */
 148         if (a == XD && (s + 1 == e || s[1] == '\n'))
 149                 goto jleave;
 150 jnquote:
 151         r = N;
 152 jleave:
 153         return r;
 154 }
 155
 156 SINLINE char *
 157 _qp_ctohex(char *store, char c)
 158 {
 159         static char const hexmap[] = "0123456789ABCDEF";
 160
 161         store[2] = '\0';
 162         store[1] = hexmap[(uc_it)c & 0x0F];
 163         c = ((uc_it)c >> 4) & 0x0F;
 164         store[0] = hexmap[(uc_it)c];
 165         return store;
 166 }
 167
 168 SINLINE si_it
 169 _qp_cfromhex(char const *hex)
 170 {
 171         /* Be robust, allow lowercase hexadecimal letters, too */
 172         static uc_it const atoi16[] = {
 173                 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, /* 0x30-0x37 */
 174                 0x08, 0x09, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, /* 0x38-0x3F */
 175                 0xFF, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F, 0xFF, /* 0x40-0x47 */
 176                 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, /* 0x48-0x4f */
 177                 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, /* 0x50-0x57 */
 178                 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, /* 0x58-0x5f */
 179                 0xFF, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F, 0xFF  /* 0x60-0x67 */
 180         };
 181         uc_it i1, i2;
 182         si_it r;
 183
 184         if ((i1 = (uc_it)hex[0] - '0') >= ARRAY_COUNT(atoi16) ||
 185                         (i2 = (uc_it)hex[1] - '0') >= ARRAY_COUNT(atoi16))
 186                 goto jerr;
 187         i1 = atoi16[i1];
 188         i2 = atoi16[i2];
 189         if ((i1 | i2) & 0xF0)
 190                 goto jerr;
 191         r = i1;
 192         r <<= 4;
 193         r += i2;
 194 jleave:
 195         return r;
 196 jerr:
 197         r = -1;
 198         goto jleave;
 199 }
 200
 201 static size_t
 202 _b64_decode_prepare(struct str *work, struct str const *in)
 203 {
 204         char *cp = in->s;
 205         size_t cp_len = in->l;
 206
 207         while (cp_len > 0 && spacechar(*cp))
 208                 ++cp, --cp_len;
 209         work->s = cp;
 210
 211         for (cp += cp_len; cp_len > 0; --cp_len) {
 212                 char c = *--cp;
 213                 if (! spacechar(c))
 214                         break;
 215         }
 216         work->l = cp_len;
 217
 218         if (cp_len > 16)
 219                 cp_len = ((cp_len * 3) >> 2) + (cp_len >> 3);
 220         return cp_len;
 221 }
 222
 223 static ssize_t
 224 _b64_decode(struct str *out, struct str *in)
 225 {
 226         static signed char const b64index[] = {
 227                 -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
 228                 -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
 229                 -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,62, -1,-1,-1,63,
 230                 52,53,54,55, 56,57,58,59, 60,61,-1,-1, -1,-2,-1,-1,
 231                 -1, 0, 1, 2,  3, 4, 5, 6,  7, 8, 9,10, 11,12,13,14,
 232                 15,16,17,18, 19,20,21,22, 23,24,25,-1, -1,-1,-1,-1,
 233                 -1,26,27,28, 29,30,31,32, 33,34,35,36, 37,38,39,40,
 234                 41,42,43,44, 45,46,47,48, 49,50,51,-1, -1,-1,-1,-1
 235         };
 236 #define EQU             (ui_it)-2
 237 #define BAD             (ui_it)-1
 238 #define uchar64(c)      ((c) >= sizeof(b64index) ? BAD : (ui_it)b64index[(c)])
 239
 240         ssize_t ret = -1;
 241         uc_it *p = (uc_it*)out->s;
 242         uc_it const *q = (uc_it const*)in->s, *end;
 243
 244         out->l = 0;
 245
 246         for (end = q + in->l; q + 4 <= end; q += 4) {
 247                 ui_it a = uchar64(q[0]), b = uchar64(q[1]), c = uchar64(q[2]),
 248                         d = uchar64(q[3]);
 249
 250                 if (a >= EQU || b >= EQU || c == BAD || d == BAD)
 251                         goto jleave;
 252
 253                 *p++ = ((a << 2) | ((b & 0x30) >> 4));
 254                 if (c == EQU)   { /* got '=' */
 255                         if (d != EQU)
 256                                 goto jleave;
 257                         break;
 258                 }
 259                 *p++ = (((b & 0x0f) << 4) | ((c & 0x3c) >> 2));
 260                 if (d == EQU) /* got '=' */
 261                         break;
 262                 *p++ = (((c & 0x03) << 6) | d);
 263         }
 264 #undef uchar64
 265 #undef EQU
 266 #undef BAD
 267
 268         ret = (size_t)((char*)p - out->s);
 269         out->l = (size_t)ret;
 270 jleave:
 271         in->l -= (size_t)((char*)UNCONST(q) - in->s);
 272         in->s = UNCONST(q);
 273         return ret;
 274 }
 275
 276 size_t
 277 mime_cte_mustquote(char const *ln, size_t lnlen, bool_t ishead)
 278 {
 279         size_t ret;
 280         bool_t sol;
 281
 282         for (ret = 0, sol = TRU1; lnlen > 0; sol = FAL0, ++ln, --lnlen)
 283                 ret += (_mustquote(ln, ln + lnlen, sol, ishead) != N);
 284         return ret;
 285 }
 286
 287 size_t
 288 qp_encode_calc_size(size_t len)
 289 {
 290         /* Worst case: 'CRLF' -> '=0D=0A=' */
 291         len = len * 3 + (len >> 1) + 1;
 292         return len;
 293 }
 294
 295 struct str *
 296 qp_encode_cp(struct str *out, char const *cp, enum qpflags flags)
 297 {
 298         struct str in;
 299         in.s = UNCONST(cp);
 300         in.l = strlen(cp);
 301         return qp_encode(out, &in, flags);
 302 }
 303
 304 struct str *
 305 qp_encode_buf(struct str *out, void const *vp, size_t vp_len,
 306         enum qpflags flags)
 307 {
 308         struct str in;
 309         in.s = UNCONST(vp);
 310         in.l = vp_len;
 311         return qp_encode(out, &in, flags);
 312 }
 313
 314 struct str *
 315 qp_encode(struct str *out, struct str const *in, enum qpflags flags)
 316 {
 317         bool_t sol = (flags & QP_ISHEAD ? FAL0 : TRU1), seenx;
 318         ssize_t lnlen;
 319         char *qp;
 320         char const *is, *ie;
 321
 322         if ((flags & QP_BUF) == 0) {
 323                 lnlen = qp_encode_calc_size(in->l);
 324                 out->s = (flags & QP_SALLOC) ? salloc(lnlen)
 325                                 : srealloc(out->s, lnlen);
 326         }
 327         qp = out->s;
 328         is = in->s;
 329         ie = is + in->l;
 330
 331         /* QP_ISHEAD? */
 332         if (! sol) {
 333                 for (seenx = FAL0, sol = TRU1; is < ie; sol = FAL0, ++qp) {
 334                         enum _qact mq = _mustquote(is, ie, sol, TRU1);
 335                         char c = *is++;
 336
 337                         if (mq == N) {
 338                                 /* We convert into a single *encoded-word*,
 339                                  * that'll end up in =?C?Q??=; quote '?' from
 340                                  * the moment when we're inside there on */
 341                                 if (seenx && c == '?')
 342                                         goto jheadq;
 343                                 *qp = c;
 344                         } else if (mq == US)
 345                                 *qp = US;
 346                         else {
 347                                 seenx = TRU1;
 348 jheadq:
 349                                 *qp++ = '=';
 350                                 qp = _qp_ctohex(qp, c) + 1;
 351                         }
 352                 }
 353                 goto jleave;
 354         }
 355
 356         /* The body needs to take care for soft line breaks etc. */
 357         for (lnlen = 0, seenx = FAL0; is < ie; sol = FAL0) {
 358                 enum _qact mq = _mustquote(is, ie, sol, FAL0);
 359                 char c = *is++;
 360
 361                 if (mq == N && (c != '\n' || ! seenx)) {
 362                         *qp++ = c;
 363                         if (++lnlen < QP_LINESIZE - 1 -1)
 364                                 continue;
 365                         /* Don't write a soft line break when we're in the last
 366                          * possible column and either an LF has been written or
 367                          * only an LF follows, as that'll end the line anyway */
 368                         /* XXX but - ensure is+1>=ie, then??
 369                          * xxx and/or - what about resetting lnlen; that contra
 370                          * xxx dicts input==1 input line assertion, though */
 371                         if (c == '\n' || is == ie || *is == '\n')
 372                                 continue;
 373 jsoftnl:
 374                         qp[0] = '=';
 375                         qp[1] = '\n';
 376                         qp += 2;
 377                         lnlen = 0;
 378                         continue;
 379                 }
 380
 381                 if (lnlen > QP_LINESIZE - 3 - 1 -1) {
 382                         qp[0] = '=';
 383                         qp[1] = '\n';
 384                         qp += 2;
 385                         lnlen = 0;
 386                 }
 387                 *qp++ = '=';
 388                 qp = _qp_ctohex(qp, c);
 389                 qp += 2;
 390                 lnlen += 3;
 391                 if (c != '\n' || ! seenx)
 392                         seenx = (c == '\r');
 393                 else {
 394                         seenx = FAL0;
 395                         goto jsoftnl;
 396                 }
 397         }
 398
 399         /* Enforce soft line break if we haven't seen LF */
 400         if (in->l > 0 && *--is != '\n') {
 401                 qp[0] = '=';
 402                 qp[1] = '\n';
 403                 qp += 2;
 404         }
 405 jleave:
 406         out->l = (size_t)(qp - out->s);
 407         out->s[out->l] = '\0';
 408         return out;
 409 }
 410
 411 int
 412 qp_decode(struct str *out, struct str const *in, struct str *rest)
 413 {
 414         int ret = STOP;
 415         char *os, *oc;
 416         char const *is, *ie;
 417
 418         if (rest != NULL && rest->l != 0) {
 419                 os = out->s;
 420                 *out = *rest;
 421                 rest->s = os;
 422                 rest->l = 0;
 423         }
 424
 425         oc = os =
 426         out->s = srealloc(out->s, out->l + in->l + 3);
 427         oc += out->l;
 428         is = in->s;
 429         ie = is + in->l;
 430
 431         /* Decoding encoded-word (RFC 2049) in a header field? */
 432         if (rest == NULL) {
 433                 while (is < ie) {
 434                         si_it c = *is++;
 435                         if (c == '=') {
 436                                 if (is + 1 >= ie) {
 437                                         ++is;
 438                                         goto jehead;
 439                                 }
 440                                 c = _qp_cfromhex(is);
 441                                 is += 2;
 442                                 if (c >= 0)
 443                                         *oc++ = (char)c;
 444                                 else {
 445                                         /* Illegal according to RFC 2045,
 446                                          * section 6.7.  Almost follow it */
 447 jehead:
 448                                         oc[0] = '['; oc[1] = '?'; oc[2] = ']';
 449                                         oc += 3;
 450                                 }
 451                         } else
 452                                 *oc++ = (c == '_') ? ' ' : (char)c;
 453                 }
 454                 goto jleave; /* XXX QP decode, header: errors not reported */
 455         }
 456
 457         /* Decoding a complete message/mimepart body line */
 458         while (is < ie) {
 459                 si_it c = *is++;
 460                 if (c != '=') {
 461                         *oc++ = (char)c;
 462                         continue;
 463                 }
 464
 465                 /*
 466                  * RFC 2045, 6.7:
 467                  *   Therefore, when decoding a Quoted-Printable body, any
 468                  *   trailing white space on a line must be deleted, as it will
 469                  *   necessarily have been added by intermediate transport
 470                  *   agents.
 471                  */
 472                 for (; is < ie && blankchar(*is); ++is)
 473                         ;
 474                 if (is + 1 >= ie) {
 475                         /* Soft line break? */
 476                         if (*is == '\n')
 477                                 goto jsoftnl;
 478                         ++is;
 479                         goto jebody;
 480                 }
 481
 482                 /* Not a soft line break? */
 483                 if (*is != '\n') {
 484                         c = _qp_cfromhex(is);
 485                         is += 2;
 486                         if (c >= 0)
 487                                 *oc++ = (char)c;
 488                         else {
 489                                 /* Illegal according to RFC 2045, section 6.7.
 490                                  * Rather follow it and include the = and the
 491                                  * follow char */
 492 jebody:
 493                                 oc[0] = '['; oc[1] = '?'; oc[2] = ']';
 494                                 oc += 3;
 495                         }
 496                         continue;
 497                 }
 498
 499                 /* CRLF line endings are encoded as QP, followed by a soft line
 500                  * break, so check for this special case, and simply forget we
 501                  * have seen one, so as not to end up with the entire DOS file
 502                  * in a contiguous buffer */
 503 jsoftnl:
 504                 if (oc > os && oc[-1] == '\n') {
 505 #if 0                   /* TODO qp_decode() we do not normalize CRLF
 506                          * TODO to LF because for that we would need
 507                          * TODO to know if we are about to write to
 508                          * TODO the display or do save the file!
 509                          * TODO 'hope the MIME/send layer rewrite will
 510                          * TODO offer the possibility to DTRT */
 511                         if (oc - 1 > os && oc[-2] == '\r') {
 512                                 --oc;
 513                                 oc[-1] = '\n';
 514                         }
 515 #endif
 516                         break;
 517                 }
 518                 out->l = (size_t)(oc - os);
 519                 rest->s = srealloc(rest->s, rest->l + out->l);
 520                 memcpy(rest->s + rest->l, out->s, out->l);
 521                 rest->l += out->l;
 522                 oc = os;
 523                 break;
 524         }
 525         /* XXX RFC: QP decode should check no trailing WS on line */
 526 jleave:
 527         out->l = (size_t)(oc - os);
 528         ret = OKAY;
 529         return ret;
 530 }
 531
 532 size_t
 533 b64_encode_calc_size(size_t len)
 534 {
 535         len = (len * 4) / 3;
 536         len += (((len / B64_ENCODE_INPUT_PER_LINE) + 1) * 3);
 537         ++len;
 538         return len;
 539 }
 540
 541 struct str *
 542 b64_encode(struct str *out, struct str const *in, enum b64flags flags)
 543 {
 544         static char const b64table[] =
 545             "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
 546         uc_it const *p = (uc_it const*)in->s;
 547         ssize_t i = b64_encode_calc_size(in->l), lnlen;
 548         char *b64;
 549
 550         if ((flags & B64_BUF) == 0)
 551                 out->s = (flags & B64_SALLOC) ? salloc(i) : srealloc(out->s, i);
 552         b64 = out->s;
 553
 554         if (! (flags & (B64_CRLF|B64_LF)))
 555                 flags &= ~B64_MULTILINE;
 556
 557         for (lnlen = 0, i = (ssize_t)in->l; i > 0; p += 3, i -= 3) {
 558                 ui_it a = p[0], b, c;
 559
 560                 b64[0] = b64table[a >> 2];
 561                 switch (i) {
 562                 case 1:
 563                         b64[1] = b64table[((a & 0x3) << 4)];
 564                         b64[2] =
 565                         b64[3] = '=';
 566                         break;
 567                 case 2:
 568                         b = p[1];
 569                         b64[1] = b64table[((a & 0x3) << 4) | ((b & 0xf0) >> 4)];
 570                         b64[2] = b64table[((b & 0xf) << 2)];
 571                         b64[3] = '=';
 572                         break;
 573                 default:
 574                         b = p[1];
 575                         c = p[2];
 576                         b64[1] = b64table[((a & 0x3) << 4) | ((b & 0xf0) >> 4)];
 577                         b64[2] = b64table[((b & 0xf) << 2) | ((c & 0xc0) >> 6)];
 578                         b64[3] = b64table[c & 0x3f];
 579                         break;
 580                 }
 581
 582                 b64 += 4;
 583                 if (! (flags & B64_MULTILINE))
 584                         continue;
 585                 lnlen += 4;
 586                 if (lnlen < B64_LINESIZE - 1)
 587                         continue;
 588
 589                 lnlen = 0;
 590                 if (flags & B64_CRLF)
 591                         *b64++ = '\r';
 592                 if (flags & (B64_CRLF|B64_LF))
 593                         *b64++ = '\n';
 594         }
 595
 596         if ((flags & (B64_CRLF|B64_LF)) != 0 &&
 597                         ((flags & B64_MULTILINE) == 0 || lnlen != 0)) {
 598                 if (flags & B64_CRLF)
 599                         *b64++ = '\r';
 600                 if (flags & (B64_CRLF|B64_LF))
 601                         *b64++ = '\n';
 602         }
 603         out->l = (size_t)(b64 - out->s);
 604         out->s[out->l] = '\0';
 605         return out;
 606 }
 607
 608 struct str *
 609 b64_encode_cp(struct str *out, char const *cp, enum b64flags flags)
 610 {
 611         struct str in;
 612         in.s = UNCONST(cp);
 613         in.l = strlen(cp);
 614         return b64_encode(out, &in, flags);
 615 }
 616
 617 struct str *
 618 b64_encode_buf(struct str *out, void const *vp, size_t vp_len,
 619         enum b64flags flags)
 620 {
 621         struct str in;
 622         in.s = UNCONST(vp);
 623         in.l = vp_len;
 624         return b64_encode(out, &in, flags);
 625 }
 626
 627 int
 628 b64_decode(struct str *out, struct str const *in, struct str *rest)
 629 {
 630         struct str work;
 631         char *x;
 632         int ret = STOP;
 633         size_t len = _b64_decode_prepare(&work, in);
 634
 635         /* Ignore an empty input, as may happen for an empty final line */
 636         if (work.l == 0) {
 637                 /* In B64_T cases there may be leftover decoded data for
 638                  * iconv(3) though, even if that means it's incomplete
 639                  * multibyte character we have to copy over */
 640                 /* XXX strictly speaking this should not be handled in here,
 641                  * XXX since its leftover decoded data from an iconv(3);
 642                  * XXX like this we shared the prototype with QP, though?? */
 643                 if (rest != NULL && rest->l > 0) {
 644                         x = out->s;
 645                         *out = *rest;
 646                         rest->s = x;
 647                         rest->l = 0;
 648                 } else
 649                         out->l = 0;
 650                 ret = OKAY;
 651                 goto jleave;
 652         }
 653         if (work.l >= 4 && (work.l & 3) == 0) {
 654                 out->s = srealloc(out->s, len);
 655                 ret = OKAY;
 656         }
 657         if (ret != OKAY || (ssize_t)(len = _b64_decode(out, &work)) < 0)
 658                 goto jerr;
 659 jleave:
 660         return ret;
 661
 662 jerr:   {
 663         char const *err = tr(15, "[Invalid Base64 encoding ignored]\n");
 664         len = strlen(err);
 665         x = out->s = srealloc(out->s, len + 2);
 666         if (rest != NULL && rest->l)
 667                 *x++ = '\n';
 668         memcpy(x, err, len);
 669         x += len;
 670         *x = '\0';
 671         out->l = (size_t)(x - out->s);
 672         if (rest != NULL)
 673                 rest->l = 0;
 674         ret = STOP;
 675         goto jleave;
 676         }
 677 }