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 #ifndef HAVE_AMALGAMATION
  41 # include "nail.h"
  42 #endif
  43
  44 enum _qact {
  45          N =   0,       /* Do not quote */
  46          Q =   1,       /* Must quote */
  47         SP =   2,       /* sp */
  48         XF =   3,       /* Special character 'F' - maybe quoted */
  49         XD =   4,       /* Special character '.' - maybe quoted */
  50         US = '_',       /* In header, special character ' ' quoted as '_' */
  51         QM = '?',       /* In header, special character ? not always quoted */
  52         EQ =   Q,       /* '=' must be quoted */
  53         TB =  SP,       /* Treat '\t' as a space */
  54         NL =   N,       /* Don't quote '\n' (NL) */
  55         CR =   Q        /* Always quote a '\r' (CR) */
  56 };
  57
  58 /* Lookup tables to decide wether a character must be encoded or not.
  59  * Email header differences according to RFC 2047, section 4.2:
  60  * - also quote SP (as the underscore _), TAB, ?, _, CR, LF
  61  * - don't care about the special ^F[rom] and ^.$ */
  62 static uc_it const      _qtab_body[] = {
  63                  Q, Q, Q, Q,  Q, Q, Q, Q,  Q,TB,NL, Q,  Q,CR, Q, Q,
  64                  Q, Q, Q, Q,  Q, Q, Q, Q,  Q, Q, Q, Q,  Q, Q, Q, Q,
  65                 SP, N, N, N,  N, N, N, N,  N, N, N, N,  N, N,XD, N,
  66                  N, N, N, N,  N, N, N, N,  N, N, N, N,  N,EQ, N, N,
  67
  68                  N, N, N, N,  N, N,XF, 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, N,
  71                  N, N, N, N,  N, N, N, N,  N, N, N, N,  N, N, N, Q,
  72         },
  73                         _qtab_head[] = {
  74                  Q, Q, Q, Q,  Q, Q, Q, Q,  Q, Q, Q, Q,  Q, Q, Q, Q,
  75                  Q, Q, Q, Q,  Q, Q, Q, Q,  Q, Q, Q, Q,  Q, Q, Q, Q,
  76                 US, N, N, N,  N, N, N, N,  N, N, N, N,  N, N, N, N,
  77                  N, N, N, N,  N, N, N, N,  N, N, N, N,  N,EQ, N,QM,
  78
  79                  N, N, N, N,  N, N, N, N,  N, N, N, N,  N, N, N, N,
  80                  N, N, N, N,  N, N, N, N,  N, N, N, N,  N, N, N, Q,
  81                  N, N, N, N,  N, N, N, N,  N, N, N, N,  N, N, N, N,
  82                  N, N, N, N,  N, N, N, N,  N, N, N, N,  N, N, N, Q,
  83         };
  84
  85 /* Check wether **s* must be quoted according to *ishead*, else body rules;
  86  * *sol* indicates wether we are at the first character of a line/field */
  87 SINLINE enum _qact      _mustquote(char const *s, char const *e, bool_t sol,
  88                                 bool_t ishead);
  89
  90 /* Convert c to/from a hexadecimal character string */
  91 SINLINE char *          _qp_ctohex(char *store, char c);
  92 SINLINE si_it           _qp_cfromhex(char const *hex);
  93
  94 /* Trim WS and make *work* point to the decodable range of *in*.
  95  * Return the amount of bytes a b64_decode operation on that buffer requires */
  96 static size_t           _b64_decode_prepare(struct str *work,
  97                                 struct str const *in);
  98
  99 /* Perform b64_decode on sufficiently spaced & multiple-of-4 base *in*put.
 100  * Return number of useful bytes in *out* or -1 on error */
 101 static ssize_t          _b64_decode(struct str *out, struct str *in);
 102
 103 SINLINE enum _qact
 104 _mustquote(char const *s, char const *e, bool_t sol, bool_t ishead)
 105 {
 106         uc_it const *qtab = ishead ? _qtab_head : _qtab_body;
 107         enum _qact a = ((uc_it)*s > 0x7F) ? Q : qtab[(uc_it)*s], r;
 108
 109         if ((r = a) == N || (r = a) == Q)
 110                 goto jleave;
 111         r = Q;
 112
 113         /* Special header fields */
 114         if (ishead) {
 115                 /* ' ' -> '_' */
 116                 if (a == US) {
 117                         r = US;
 118                         goto jleave;
 119                 }
 120                 /* Treat '?' only special if part of '=?' and '?=' (still to
 121                  * much quoting since it's '=?CHARSET?CTE?stuff?=', and
 122                  * especially the trailing ?= should be hard too match ,) */
 123                 if (a == QM && ((! sol && s[-1] == '=') ||
 124                                 (s < e && s[1] == '=')))
 125                         goto jleave;
 126                 goto jnquote;
 127         }
 128
 129         /* Body-only */
 130
 131         if (a == SP) {
 132                 /* WS only if trailing white space */
 133                 if (s + 1 == e || s[1] == '\n')
 134                         goto jleave;
 135                 goto jnquote;
 136         }
 137
 138         /* Rest are special begin-of-line cases */
 139         if (! sol)
 140                 goto jnquote;
 141
 142         /* ^From */
 143         if (a == XF) {
 144                 if (s + 4 < e && s[1] == 'r' && s[2] == 'o' && s[3] == 'm')
 145                         goto jleave;
 146                 goto jnquote;
 147         }
 148         /* ^.$ */
 149         if (a == XD && (s + 1 == e || s[1] == '\n'))
 150                 goto jleave;
 151 jnquote:
 152         r = N;
 153 jleave:
 154         return r;
 155 }
 156
 157 SINLINE char *
 158 _qp_ctohex(char *store, char c)
 159 {
 160         static char const hexmap[] = "0123456789ABCDEF";
 161
 162         store[2] = '\0';
 163         store[1] = hexmap[(uc_it)c & 0x0F];
 164         c = ((uc_it)c >> 4) & 0x0F;
 165         store[0] = hexmap[(uc_it)c];
 166         return store;
 167 }
 168
 169 SINLINE si_it
 170 _qp_cfromhex(char const *hex)
 171 {
 172         /* Be robust, allow lowercase hexadecimal letters, too */
 173         static uc_it const atoi16[] = {
 174                 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, /* 0x30-0x37 */
 175                 0x08, 0x09, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, /* 0x38-0x3F */
 176                 0xFF, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F, 0xFF, /* 0x40-0x47 */
 177                 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, /* 0x48-0x4f */
 178                 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, /* 0x50-0x57 */
 179                 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, /* 0x58-0x5f */
 180                 0xFF, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F, 0xFF  /* 0x60-0x67 */
 181         };
 182         uc_it i1, i2;
 183         si_it r;
 184
 185         if ((i1 = (uc_it)hex[0] - '0') >= NELEM(atoi16) ||
 186                         (i2 = (uc_it)hex[1] - '0') >= NELEM(atoi16))
 187                 goto jerr;
 188         i1 = atoi16[i1];
 189         i2 = atoi16[i2];
 190         if ((i1 | i2) & 0xF0)
 191                 goto jerr;
 192         r = i1;
 193         r <<= 4;
 194         r += i2;
 195 jleave:
 196         return r;
 197 jerr:
 198         r = -1;
 199         goto jleave;
 200 }
 201
 202 static size_t
 203 _b64_decode_prepare(struct str *work, struct str const *in)
 204 {
 205         char *cp = in->s;
 206         size_t cp_len = in->l;
 207
 208         while (cp_len > 0 && spacechar(*cp))
 209                 ++cp, --cp_len;
 210         work->s = cp;
 211
 212         for (cp += cp_len; cp_len > 0; --cp_len) {
 213                 char c = *--cp;
 214                 if (! spacechar(c))
 215                         break;
 216         }
 217         work->l = cp_len;
 218
 219         if (cp_len > 16)
 220                 cp_len = ((cp_len * 3) >> 2) + (cp_len >> 3);
 221         return cp_len;
 222 }
 223
 224 static ssize_t
 225 _b64_decode(struct str *out, struct str *in)
 226 {
 227         static signed char const b64index[] = {
 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,-1, -1,-1,-1,-1,
 230                 -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,62, -1,-1,-1,63,
 231                 52,53,54,55, 56,57,58,59, 60,61,-1,-1, -1,-2,-1,-1,
 232                 -1, 0, 1, 2,  3, 4, 5, 6,  7, 8, 9,10, 11,12,13,14,
 233                 15,16,17,18, 19,20,21,22, 23,24,25,-1, -1,-1,-1,-1,
 234                 -1,26,27,28, 29,30,31,32, 33,34,35,36, 37,38,39,40,
 235                 41,42,43,44, 45,46,47,48, 49,50,51,-1, -1,-1,-1,-1
 236         };
 237 #define EQU             (ui_it)-2
 238 #define BAD             (ui_it)-1
 239 #define uchar64(c)      ((c) >= sizeof(b64index) ? BAD : (ui_it)b64index[(c)])
 240
 241         ssize_t ret = -1;
 242         uc_it *p = (uc_it*)out->s;
 243         uc_it const *q = (uc_it const*)in->s, *end;
 244
 245         out->l = 0;
 246
 247         for (end = q + in->l; q + 4 <= end; q += 4) {
 248                 ui_it a = uchar64(q[0]), b = uchar64(q[1]), c = uchar64(q[2]),
 249                         d = uchar64(q[3]);
 250
 251                 if (a >= EQU || b >= EQU || c == BAD || d == BAD)
 252                         goto jleave;
 253
 254                 *p++ = ((a << 2) | ((b & 0x30) >> 4));
 255                 if (c == EQU)   { /* got '=' */
 256                         if (d != EQU)
 257                                 goto jleave;
 258                         break;
 259                 }
 260                 *p++ = (((b & 0x0f) << 4) | ((c & 0x3c) >> 2));
 261                 if (d == EQU) /* got '=' */
 262                         break;
 263                 *p++ = (((c & 0x03) << 6) | d);
 264         }
 265 #undef uchar64
 266 #undef EQU
 267 #undef BAD
 268
 269         ret = (size_t)((char*)p - out->s);
 270         out->l = (size_t)ret;
 271 jleave:
 272         in->l -= (size_t)((char*)UNCONST(q) - in->s);
 273         in->s = UNCONST(q);
 274         return ret;
 275 }
 276
 277 FL size_t
 278 mime_cte_mustquote(char const *ln, size_t lnlen, bool_t ishead)
 279 {
 280         size_t ret;
 281         bool_t sol;
 282
 283         for (ret = 0, sol = TRU1; lnlen > 0; sol = FAL0, ++ln, --lnlen)
 284                 ret += (_mustquote(ln, ln + lnlen, sol, ishead) != N);
 285         return ret;
 286 }
 287
 288 FL size_t
 289 qp_encode_calc_size(size_t len)
 290 {
 291         /* Worst case: 'CRLF' -> '=0D=0A=' */
 292         len = len * 3 + (len >> 1) + 1;
 293         return len;
 294 }
 295
 296 #ifdef notyet
 297 FL struct str *
 298 qp_encode_cp(struct str *out, char const *cp, enum qpflags flags)
 299 {
 300         struct str in;
 301         in.s = UNCONST(cp);
 302         in.l = strlen(cp);
 303         return qp_encode(out, &in, flags);
 304 }
 305
 306 FL struct str *
 307 qp_encode_buf(struct str *out, void const *vp, size_t vp_len,
 308         enum qpflags flags)
 309 {
 310         struct str in;
 311         in.s = UNCONST(vp);
 312         in.l = vp_len;
 313         return qp_encode(out, &in, flags);
 314 }
 315 #endif /* notyet */
 316
 317 FL struct str *
 318 qp_encode(struct str *out, struct str const *in, enum qpflags flags)
 319 {
 320         bool_t sol = (flags & QP_ISHEAD ? FAL0 : TRU1), seenx;
 321         ssize_t lnlen;
 322         char *qp;
 323         char const *is, *ie;
 324
 325         if ((flags & QP_BUF) == 0) {
 326                 lnlen = qp_encode_calc_size(in->l);
 327                 out->s = (flags & QP_SALLOC) ? salloc(lnlen)
 328                                 : srealloc(out->s, lnlen);
 329         }
 330         qp = out->s;
 331         is = in->s;
 332         ie = is + in->l;
 333
 334         /* QP_ISHEAD? */
 335         if (! sol) {
 336                 for (seenx = FAL0, sol = TRU1; is < ie; sol = FAL0, ++qp) {
 337                         enum _qact mq = _mustquote(is, ie, sol, TRU1);
 338                         char c = *is++;
 339
 340                         if (mq == N) {
 341                                 /* We convert into a single *encoded-word*,
 342                                  * that'll end up in =?C?Q??=; quote '?' from
 343                                  * the moment when we're inside there on */
 344                                 if (seenx && c == '?')
 345                                         goto jheadq;
 346                                 *qp = c;
 347                         } else if (mq == US)
 348                                 *qp = US;
 349                         else {
 350                                 seenx = TRU1;
 351 jheadq:
 352                                 *qp++ = '=';
 353                                 qp = _qp_ctohex(qp, c) + 1;
 354                         }
 355                 }
 356                 goto jleave;
 357         }
 358
 359         /* The body needs to take care for soft line breaks etc. */
 360         for (lnlen = 0, seenx = FAL0; is < ie; sol = FAL0) {
 361                 enum _qact mq = _mustquote(is, ie, sol, FAL0);
 362                 char c = *is++;
 363
 364                 if (mq == N && (c != '\n' || ! seenx)) {
 365                         *qp++ = c;
 366                         if (++lnlen < QP_LINESIZE - 1 -1)
 367                                 continue;
 368                         /* Don't write a soft line break when we're in the last
 369                          * possible column and either an LF has been written or
 370                          * only an LF follows, as that'll end the line anyway */
 371                         /* XXX but - ensure is+1>=ie, then??
 372                          * xxx and/or - what about resetting lnlen; that contra
 373                          * xxx dicts input==1 input line assertion, though */
 374                         if (c == '\n' || is == ie || *is == '\n')
 375                                 continue;
 376 jsoftnl:
 377                         qp[0] = '=';
 378                         qp[1] = '\n';
 379                         qp += 2;
 380                         lnlen = 0;
 381                         continue;
 382                 }
 383
 384                 if (lnlen > QP_LINESIZE - 3 - 1 -1) {
 385                         qp[0] = '=';
 386                         qp[1] = '\n';
 387                         qp += 2;
 388                         lnlen = 0;
 389                 }
 390                 *qp++ = '=';
 391                 qp = _qp_ctohex(qp, c);
 392                 qp += 2;
 393                 lnlen += 3;
 394                 if (c != '\n' || ! seenx)
 395                         seenx = (c == '\r');
 396                 else {
 397                         seenx = FAL0;
 398                         goto jsoftnl;
 399                 }
 400         }
 401
 402         /* Enforce soft line break if we haven't seen LF */
 403         if (in->l > 0 && *--is != '\n') {
 404                 qp[0] = '=';
 405                 qp[1] = '\n';
 406                 qp += 2;
 407         }
 408 jleave:
 409         out->l = (size_t)(qp - out->s);
 410         out->s[out->l] = '\0';
 411         return out;
 412 }
 413
 414 FL int
 415 qp_decode(struct str *out, struct str const *in, struct str *rest)
 416 {
 417         int ret = STOP;
 418         char *os, *oc;
 419         char const *is, *ie;
 420
 421         if (rest != NULL && rest->l != 0) {
 422                 os = out->s;
 423                 *out = *rest;
 424                 rest->s = os;
 425                 rest->l = 0;
 426         }
 427
 428         oc = os =
 429         out->s = srealloc(out->s, out->l + in->l + 3);
 430         oc += out->l;
 431         is = in->s;
 432         ie = is + in->l;
 433
 434         /* Decoding encoded-word (RFC 2049) in a header field? */
 435         if (rest == NULL) {
 436                 while (is < ie) {
 437                         si_it c = *is++;
 438                         if (c == '=') {
 439                                 if (is + 1 >= ie) {
 440                                         ++is;
 441                                         goto jehead;
 442                                 }
 443                                 c = _qp_cfromhex(is);
 444                                 is += 2;
 445                                 if (c >= 0)
 446                                         *oc++ = (char)c;
 447                                 else {
 448                                         /* Illegal according to RFC 2045,
 449                                          * section 6.7.  Almost follow it */
 450 jehead:
 451                                         /* TODO 0xFFFD
 452                                         *oc[0] = '['; oc[1] = '?'; oc[2] = ']';
 453                                         *oc += 3; 0xFFFD TODO
 454                                         */ *oc++ = '?';
 455                                 }
 456                         } else
 457                                 *oc++ = (c == '_') ? ' ' : (char)c;
 458                 }
 459                 goto jleave; /* XXX QP decode, header: errors not reported */
 460         }
 461
 462         /* Decoding a complete message/mimepart body line */
 463         while (is < ie) {
 464                 si_it c = *is++;
 465                 if (c != '=') {
 466                         *oc++ = (char)c;
 467                         continue;
 468                 }
 469
 470                 /*
 471                  * RFC 2045, 6.7:
 472                  *   Therefore, when decoding a Quoted-Printable body, any
 473                  *   trailing white space on a line must be deleted, as it will
 474                  *   necessarily have been added by intermediate transport
 475                  *   agents.
 476                  */
 477                 for (; is < ie && blankchar(*is); ++is)
 478                         ;
 479                 if (is + 1 >= ie) {
 480                         /* Soft line break? */
 481                         if (*is == '\n')
 482                                 goto jsoftnl;
 483                         ++is;
 484                         goto jebody;
 485                 }
 486
 487                 /* Not a soft line break? */
 488                 if (*is != '\n') {
 489                         c = _qp_cfromhex(is);
 490                         is += 2;
 491                         if (c >= 0)
 492                                 *oc++ = (char)c;
 493                         else {
 494                                 /* Illegal according to RFC 2045, section 6.7.
 495                                  * Rather follow it and include the = and the
 496                                  * follow char */
 497 jebody:
 498                                 /* TODO 0xFFFD
 499                                 *oc[0] = '['; oc[1] = '?'; oc[2] = ']';
 500                                 *oc += 3; 0xFFFD TODO
 501                                 */ *oc++ = '?';
 502                         }
 503                         continue;
 504                 }
 505
 506                 /* CRLF line endings are encoded as QP, followed by a soft line
 507                  * break, so check for this special case, and simply forget we
 508                  * have seen one, so as not to end up with the entire DOS file
 509                  * in a contiguous buffer */
 510 jsoftnl:
 511                 if (oc > os && oc[-1] == '\n') {
 512 #if 0                   /* TODO qp_decode() we do not normalize CRLF
 513                          * TODO to LF because for that we would need
 514                          * TODO to know if we are about to write to
 515                          * TODO the display or do save the file!
 516                          * TODO 'hope the MIME/send layer rewrite will
 517                          * TODO offer the possibility to DTRT */
 518                         if (oc - 1 > os && oc[-2] == '\r') {
 519                                 --oc;
 520                                 oc[-1] = '\n';
 521                         }
 522 #endif
 523                         break;
 524                 }
 525                 out->l = (size_t)(oc - os);
 526                 rest->s = srealloc(rest->s, rest->l + out->l);
 527                 memcpy(rest->s + rest->l, out->s, out->l);
 528                 rest->l += out->l;
 529                 oc = os;
 530                 break;
 531         }
 532         /* XXX RFC: QP decode should check no trailing WS on line */
 533 jleave:
 534         out->l = (size_t)(oc - os);
 535         ret = OKAY;
 536         return ret;
 537 }
 538
 539 FL size_t
 540 b64_encode_calc_size(size_t len)
 541 {
 542         len = (len * 4) / 3;
 543         len += (((len / B64_ENCODE_INPUT_PER_LINE) + 1) * 3);
 544         ++len;
 545         return len;
 546 }
 547
 548 FL struct str *
 549 b64_encode(struct str *out, struct str const *in, enum b64flags flags)
 550 {
 551         static char const b64table[] =
 552             "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
 553         uc_it const *p = (uc_it const*)in->s;
 554         ssize_t i = b64_encode_calc_size(in->l), lnlen;
 555         char *b64;
 556
 557         if ((flags & B64_BUF) == 0)
 558                 out->s = (flags & B64_SALLOC) ? salloc(i) : srealloc(out->s, i);
 559         b64 = out->s;
 560
 561         if (! (flags & (B64_CRLF|B64_LF)))
 562                 flags &= ~B64_MULTILINE;
 563
 564         for (lnlen = 0, i = (ssize_t)in->l; i > 0; p += 3, i -= 3) {
 565                 ui_it a = p[0], b, c;
 566
 567                 b64[0] = b64table[a >> 2];
 568                 switch (i) {
 569                 case 1:
 570                         b64[1] = b64table[((a & 0x3) << 4)];
 571                         b64[2] =
 572                         b64[3] = '=';
 573                         break;
 574                 case 2:
 575                         b = p[1];
 576                         b64[1] = b64table[((a & 0x3) << 4) | ((b & 0xf0) >> 4)];
 577                         b64[2] = b64table[((b & 0xf) << 2)];
 578                         b64[3] = '=';
 579                         break;
 580                 default:
 581                         b = p[1];
 582                         c = p[2];
 583                         b64[1] = b64table[((a & 0x3) << 4) | ((b & 0xf0) >> 4)];
 584                         b64[2] = b64table[((b & 0xf) << 2) | ((c & 0xc0) >> 6)];
 585                         b64[3] = b64table[c & 0x3f];
 586                         break;
 587                 }
 588
 589                 b64 += 4;
 590                 if (! (flags & B64_MULTILINE))
 591                         continue;
 592                 lnlen += 4;
 593                 if (lnlen < B64_LINESIZE - 1)
 594                         continue;
 595
 596                 lnlen = 0;
 597                 if (flags & B64_CRLF)
 598                         *b64++ = '\r';
 599                 if (flags & (B64_CRLF|B64_LF))
 600                         *b64++ = '\n';
 601         }
 602
 603         if ((flags & (B64_CRLF|B64_LF)) != 0 &&
 604                         ((flags & B64_MULTILINE) == 0 || lnlen != 0)) {
 605                 if (flags & B64_CRLF)
 606                         *b64++ = '\r';
 607                 if (flags & (B64_CRLF|B64_LF))
 608                         *b64++ = '\n';
 609         }
 610         out->l = (size_t)(b64 - out->s);
 611         out->s[out->l] = '\0';
 612         return out;
 613 }
 614
 615 FL struct str *
 616 b64_encode_cp(struct str *out, char const *cp, enum b64flags flags)
 617 {
 618         struct str in;
 619         in.s = UNCONST(cp);
 620         in.l = strlen(cp);
 621         return b64_encode(out, &in, flags);
 622 }
 623
 624 FL struct str *
 625 b64_encode_buf(struct str *out, void const *vp, size_t vp_len,
 626         enum b64flags flags)
 627 {
 628         struct str in;
 629         in.s = UNCONST(vp);
 630         in.l = vp_len;
 631         return b64_encode(out, &in, flags);
 632 }
 633
 634 FL int
 635 b64_decode(struct str *out, struct str const *in, struct str *rest)
 636 {
 637         struct str work;
 638         char *x;
 639         int ret = STOP;
 640         size_t len = _b64_decode_prepare(&work, in);
 641
 642         /* Ignore an empty input, as may happen for an empty final line */
 643         if (work.l == 0) {
 644                 /* In B64_T cases there may be leftover decoded data for
 645                  * iconv(3) though, even if that means it's incomplete
 646                  * multibyte character we have to copy over */
 647                 /* XXX strictly speaking this should not be handled in here,
 648                  * XXX since its leftover decoded data from an iconv(3);
 649                  * XXX like this we shared the prototype with QP, though?? */
 650                 if (rest != NULL && rest->l > 0) {
 651                         x = out->s;
 652                         *out = *rest;
 653                         rest->s = x;
 654                         rest->l = 0;
 655                 } else
 656                         out->l = 0;
 657                 ret = OKAY;
 658                 goto jleave;
 659         }
 660         if (work.l >= 4 && (work.l & 3) == 0) {
 661                 out->s = srealloc(out->s, len);
 662                 ret = OKAY;
 663         }
 664         if (ret != OKAY || (ssize_t)(len = _b64_decode(out, &work)) < 0)
 665                 goto jerr;
 666 jleave:
 667         return ret;
 668
 669 jerr:   {
 670         char const *err = tr(15, "[Invalid Base64 encoding ignored]\n");
 671         len = strlen(err);
 672         x = out->s = srealloc(out->s, len + 2);
 673         if (rest != NULL && rest->l)
 674                 *x++ = '\n';
 675         memcpy(x, err, len);
 676         x += len;
 677         *x = '\0';
 678         out->l = (size_t)(x - out->s);
 679         if (rest != NULL)
 680                 rest->l = 0;
 681         ret = STOP;
 682         goto jleave;
 683         }
 684 }