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 - 2014 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  45     N =   0,   /* Do not quote */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 ui8_t 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 si32_t       _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    ui8_t const *qtab;
 107    enum _qact a, r;
 108    NYD_ENTER;
 109
 110    qtab = ishead ? _qtab_head : _qtab_body;
 111    a = ((ui8_t)*s > 0x7F) ? Q : qtab[(ui8_t)*s];
 112
 113    if ((r = a) == N || (r = a) == Q)
 114       goto jleave;
 115    r = Q;
 116
 117    /* Special header fields */
 118    if (ishead) {
 119       /* ' ' -> '_' */
 120       if (a == US) {
 121          r = US;
 122          goto jleave;
 123       }
 124       /* Treat '?' only special if part of '=?' .. '?=' (still too much quoting
 125        * since it's '=?CHARSET?CTE?stuff?=', and especially the trailing ?=
 126        * should be hard too match */
 127       if (a == QM && ((!sol && s[-1] == '=') || (s < e && s[1] == '=')))
 128          goto jleave;
 129       goto jnquote;
 130    }
 131
 132    /* Body-only */
 133
 134    if (a == SP) {
 135       /* WS only if trailing white space */
 136       if (PTRCMP(s + 1, ==, e) || s[1] == '\n')
 137          goto jleave;
 138       goto jnquote;
 139    }
 140
 141    /* Rest are special begin-of-line cases */
 142    if (!sol)
 143       goto jnquote;
 144
 145    /* ^From */
 146    if (a == XF) {
 147       if (PTRCMP(s + 4, <, e) && s[1] == 'r' && s[2] == 'o' && s[3] == 'm')
 148          goto jleave;
 149       goto jnquote;
 150    }
 151    /* ^.$ */
 152    if (a == XD && (PTRCMP(s + 1, ==, e) || s[1] == '\n'))
 153       goto jleave;
 154 jnquote:
 155    r = N;
 156 jleave:
 157    NYD_LEAVE;
 158    return r;
 159 }
 160
 161 SINLINE char *
 162 _qp_ctohex(char *store, char c)
 163 {
 164    static char const hexmap[] = "0123456789ABCDEF";
 165    NYD_ENTER;
 166
 167    store[2] = '\0';
 168    store[1] = hexmap[(ui8_t)c & 0x0F];
 169    c = ((ui8_t)c >> 4) & 0x0F;
 170    store[0] = hexmap[(ui8_t)c];
 171    NYD_LEAVE;
 172    return store;
 173 }
 174
 175 SINLINE si32_t
 176 _qp_cfromhex(char const *hex)
 177 {
 178    /* Be robust, allow lowercase hexadecimal letters, too */
 179    static ui8_t const atoi16[] = {
 180       0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, /* 0x30-0x37 */
 181       0x08, 0x09, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, /* 0x38-0x3F */
 182       0xFF, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F, 0xFF, /* 0x40-0x47 */
 183       0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, /* 0x48-0x4f */
 184       0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, /* 0x50-0x57 */
 185       0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, /* 0x58-0x5f */
 186       0xFF, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F, 0xFF  /* 0x60-0x67 */
 187    };
 188
 189    ui8_t i1, i2;
 190    si32_t r;
 191    NYD_ENTER;
 192
 193    if ((i1 = (ui8_t)hex[0] - '0') >= NELEM(atoi16) ||
 194          (i2 = (ui8_t)hex[1] - '0') >= NELEM(atoi16))
 195       goto jerr;
 196    i1 = atoi16[i1];
 197    i2 = atoi16[i2];
 198    if ((i1 | i2) & 0xF0u)
 199       goto jerr;
 200    r = i1;
 201    r <<= 4;
 202    r += i2;
 203 jleave:
 204    NYD_LEAVE;
 205    return r;
 206 jerr:
 207    r = -1;
 208    goto jleave;
 209 }
 210
 211 static size_t
 212 _b64_decode_prepare(struct str *work, struct str const *in)
 213 {
 214    char *cp;
 215    size_t cp_len;
 216    NYD_ENTER;
 217
 218    cp = in->s;
 219    cp_len = in->l;
 220
 221    while (cp_len > 0 && spacechar(*cp))
 222       ++cp, --cp_len;
 223    work->s = cp;
 224
 225    for (cp += cp_len; cp_len > 0; --cp_len) {
 226       char c = *--cp;
 227       if (!spacechar(c))
 228          break;
 229    }
 230    work->l = cp_len;
 231
 232    if (cp_len > 16)
 233       cp_len = ((cp_len * 3) >> 2) + (cp_len >> 3);
 234    NYD_LEAVE;
 235    return cp_len;
 236 }
 237
 238 static ssize_t
 239 _b64_decode(struct str *out, struct str *in)
 240 {
 241    static signed char const b64index[] = {
 242       -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
 243       -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
 244       -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,62, -1,-1,-1,63,
 245       52,53,54,55, 56,57,58,59, 60,61,-1,-1, -1,-2,-1,-1,
 246       -1, 0, 1, 2,  3, 4, 5, 6,  7, 8, 9,10, 11,12,13,14,
 247       15,16,17,18, 19,20,21,22, 23,24,25,-1, -1,-1,-1,-1,
 248       -1,26,27,28, 29,30,31,32, 33,34,35,36, 37,38,39,40,
 249       41,42,43,44, 45,46,47,48, 49,50,51,-1, -1,-1,-1,-1
 250    };
 251 #define EQU          (ui32_t)-2
 252 #define BAD          (ui32_t)-1
 253 #define uchar64(c)   ((c) >= sizeof(b64index) ? BAD : (ui32_t)b64index[(c)])
 254
 255    ssize_t ret = -1;
 256    ui8_t *p;
 257    ui8_t const *q, *end;
 258    NYD_ENTER;
 259
 260    p = (ui8_t*)out->s;
 261    q = (ui8_t const*)in->s;
 262    out->l = 0;
 263
 264    for (end = q + in->l; PTRCMP(q + 4, <=, end); q += 4) {
 265       ui32_t a = uchar64(q[0]), b = uchar64(q[1]), c = uchar64(q[2]),
 266          d = uchar64(q[3]);
 267
 268       if (a >= EQU || b >= EQU || c == BAD || d == BAD)
 269          goto jleave;
 270
 271       *p++ = ((a << 2) | ((b & 0x30) >> 4));
 272       if (c == EQU)  { /* got '=' */
 273          if (d != EQU)
 274             goto jleave;
 275          break;
 276       }
 277       *p++ = (((b & 0x0F) << 4) | ((c & 0x3C) >> 2));
 278       if (d == EQU) /* got '=' */
 279          break;
 280       *p++ = (((c & 0x03) << 6) | d);
 281    }
 282 #undef uchar64
 283 #undef EQU
 284 #undef BAD
 285
 286    ret = PTR2SIZE((char*)p - out->s);
 287    out->l = (size_t)ret;
 288 jleave:
 289    in->l -= PTR2SIZE((char*)UNCONST(q) - in->s);
 290    in->s = UNCONST(q);
 291    NYD_LEAVE;
 292    return ret;
 293 }
 294
 295 FL size_t
 296 mime_cte_mustquote(char const *ln, size_t lnlen, bool_t ishead)
 297 {
 298    size_t ret;
 299    bool_t sol;
 300    NYD_ENTER;
 301
 302    for (ret = 0, sol = TRU1; lnlen > 0; sol = FAL0, ++ln, --lnlen)
 303       ret += (_mustquote(ln, ln + lnlen, sol, ishead) != N);
 304    NYD_LEAVE;
 305    return ret;
 306 }
 307
 308 FL size_t
 309 qp_encode_calc_size(size_t len)
 310 {
 311    NYD_ENTER;
 312    /* Worst case: 'CRLF' -> '=0D=0A=\n\0' */
 313    len = (len * 3) + 1/* soft NL */ + 1/* visual NL */ + 1/* NUL */;
 314    NYD_LEAVE;
 315    return len;
 316 }
 317
 318 #ifdef notyet
 319 FL struct str *
 320 qp_encode_cp(struct str *out, char const *cp, enum qpflags flags)
 321 {
 322    struct str in;
 323    NYD_ENTER;
 324
 325    in.s = UNCONST(cp);
 326    in.l = strlen(cp);
 327    out = qp_encode(out, &in, flags);
 328    NYD_LEAVE;
 329    return out;
 330 }
 331
 332 FL struct str *
 333 qp_encode_buf(struct str *out, void const *vp, size_t vp_len,
 334    enum qpflags flags)
 335 {
 336    struct str in;
 337    NYD_ENTER;
 338
 339    in.s = UNCONST(vp);
 340    in.l = vp_len;
 341    out = qp_encode(out, &in, flags);
 342    NYD_LEAVE;
 343    return out;
 344 }
 345 #endif /* notyet */
 346
 347 FL struct str *
 348 qp_encode(struct str *out, struct str const *in, enum qpflags flags)
 349 {
 350    bool_t sol = (flags & QP_ISHEAD ? FAL0 : TRU1), seenx;
 351    ssize_t lnlen;
 352    char *qp;
 353    char const *is, *ie;
 354    NYD_ENTER;
 355
 356    if (!(flags & QP_BUF)) {
 357       lnlen = qp_encode_calc_size(in->l);
 358       out->s = (flags & QP_SALLOC) ? salloc(lnlen) : srealloc(out->s, lnlen);
 359    }
 360    qp = out->s;
 361    is = in->s;
 362    ie = is + in->l;
 363
 364    /* QP_ISHEAD? */
 365    if (!sol) {
 366       for (seenx = FAL0, sol = TRU1; is < ie; sol = FAL0, ++qp) {
 367          enum _qact mq = _mustquote(is, ie, sol, TRU1);
 368          char c = *is++;
 369
 370          if (mq == N) {
 371             /* We convert into a single *encoded-word*, that'll end up in
 372              * =?C?Q??=; quote '?' from when we're inside there on */
 373             if (seenx && c == '?')
 374                goto jheadq;
 375             *qp = c;
 376          } else if (mq == US)
 377             *qp = US;
 378          else {
 379             seenx = TRU1;
 380 jheadq:
 381             *qp++ = '=';
 382             qp = _qp_ctohex(qp, c) + 1;
 383          }
 384       }
 385       goto jleave;
 386    }
 387
 388    /* The body needs to take care for soft line breaks etc. */
 389    for (lnlen = 0, seenx = FAL0; is < ie; sol = FAL0) {
 390       enum _qact mq = _mustquote(is, ie, sol, FAL0);
 391       char c = *is++;
 392
 393       if (mq == N && (c != '\n' || !seenx)) {
 394          *qp++ = c;
 395          if (++lnlen < QP_LINESIZE - 1)
 396             continue;
 397          /* Don't write a soft line break when we're in the last possible
 398           * column and either an LF has been written or only an LF follows, as
 399           * that'll end the line anyway */
 400          /* XXX but - ensure is+1>=ie, then??
 401           * xxx and/or - what about resetting lnlen; that contra
 402           * xxx dicts input==1 input line assertion, though */
 403          if (c == '\n' || is == ie || *is == '\n')
 404             continue;
 405 jsoftnl:
 406          qp[0] = '=';
 407          qp[1] = '\n';
 408          qp += 2;
 409          lnlen = 0;
 410          continue;
 411       }
 412
 413       if (lnlen > QP_LINESIZE - 3 - 1) {
 414          qp[0] = '=';
 415          qp[1] = '\n';
 416          qp += 2;
 417          lnlen = 0;
 418       }
 419       *qp++ = '=';
 420       qp = _qp_ctohex(qp, c);
 421       qp += 2;
 422       lnlen += 3;
 423       if (c != '\n' || !seenx)
 424          seenx = (c == '\r');
 425       else {
 426          seenx = FAL0;
 427          goto jsoftnl;
 428       }
 429    }
 430
 431    /* Enforce soft line break if we haven't seen LF */
 432    if (in->l > 0 && *--is != '\n') {
 433       qp[0] = '=';
 434       qp[1] = '\n';
 435       qp += 2;
 436    }
 437 jleave:
 438    out->l = PTR2SIZE(qp - out->s);
 439    out->s[out->l] = '\0';
 440    NYD_LEAVE;
 441    return out;
 442 }
 443
 444 FL int
 445 qp_decode(struct str *out, struct str const *in, struct str *rest)
 446 {
 447    int ret = STOP;
 448    char *os, *oc;
 449    char const *is, *ie;
 450    NYD_ENTER;
 451
 452    if (rest != NULL && rest->l != 0) {
 453       os = out->s;
 454       *out = *rest;
 455       rest->s = os;
 456       rest->l = 0;
 457    }
 458
 459    oc = os =
 460    out->s = srealloc(out->s, out->l + in->l + 3);
 461    oc += out->l;
 462    is = in->s;
 463    ie = is + in->l;
 464
 465    /* Decoding encoded-word (RFC 2049) in a header field? */
 466    if (rest == NULL) {
 467       while (is < ie) {
 468          si32_t c = *is++;
 469          if (c == '=') {
 470             if (PTRCMP(is + 1, >=, ie)) {
 471                ++is;
 472                goto jehead;
 473             }
 474             c = _qp_cfromhex(is);
 475             is += 2;
 476             if (c >= 0)
 477                *oc++ = (char)c;
 478             else {
 479                /* Illegal according to RFC 2045, section 6.7. Almost follow */
 480 jehead:
 481                /* TODO 0xFFFD
 482                *oc[0] = '['; oc[1] = '?'; oc[2] = ']';
 483                *oc += 3; 0xFFFD TODO
 484                */ *oc++ = '?';
 485             }
 486          } else
 487             *oc++ = (c == '_') ? ' ' : (char)c;
 488       }
 489       goto jleave; /* XXX QP decode, header: errors not reported */
 490    }
 491
 492    /* Decoding a complete message/mimepart body line */
 493    while (is < ie) {
 494       si32_t c = *is++;
 495       if (c != '=') {
 496          *oc++ = (char)c;
 497          continue;
 498       }
 499
 500       /* RFC 2045, 6.7:
 501        *   Therefore, when decoding a Quoted-Printable body, any
 502        *   trailing white space on a line must be deleted, as it will
 503        *   necessarily have been added by intermediate transport
 504        *   agents */
 505       for (; is < ie && blankchar(*is); ++is)
 506          ;
 507       if (PTRCMP(is + 1, >=, ie)) {
 508          /* Soft line break? */
 509          if (*is == '\n')
 510             goto jsoftnl;
 511          ++is;
 512          goto jebody;
 513       }
 514
 515       /* Not a soft line break? */
 516       if (*is != '\n') {
 517          c = _qp_cfromhex(is);
 518          is += 2;
 519          if (c >= 0)
 520             *oc++ = (char)c;
 521          else {
 522             /* Illegal according to RFC 2045, section 6.7.
 523              * Almost follow it and include the = and the follow char */
 524 jebody:
 525             /* TODO 0xFFFD
 526             *oc[0] = '['; oc[1] = '?'; oc[2] = ']';
 527             *oc += 3; 0xFFFD TODO
 528             */ *oc++ = '?';
 529          }
 530          continue;
 531       }
 532
 533       /* CRLF line endings are encoded as QP, followed by a soft line break, so
 534        * check for this special case, and simply forget we have seen one, so as
 535        * not to end up with the entire DOS file in a contiguous buffer */
 536 jsoftnl:
 537       if (oc > os && oc[-1] == '\n') {
 538 #if 0       /* TODO qp_decode() we do not normalize CRLF
 539           * TODO to LF because for that we would need
 540           * TODO to know if we are about to write to
 541           * TODO the display or do save the file!
 542           * TODO 'hope the MIME/send layer rewrite will
 543           * TODO offer the possibility to DTRT */
 544          if (oc - 1 > os && oc[-2] == '\r') {
 545             --oc;
 546             oc[-1] = '\n';
 547          }
 548 #endif
 549          break;
 550       }
 551       out->l = PTR2SIZE(oc - os);
 552       rest->s = srealloc(rest->s, rest->l + out->l);
 553       memcpy(rest->s + rest->l, out->s, out->l);
 554       rest->l += out->l;
 555       oc = os;
 556       break;
 557    }
 558    /* XXX RFC: QP decode should check no trailing WS on line */
 559 jleave:
 560    out->l = PTR2SIZE(oc - os);
 561    ret = OKAY;
 562    NYD_LEAVE;
 563    return ret;
 564 }
 565
 566 FL size_t
 567 b64_encode_calc_size(size_t len)
 568 {
 569    NYD_ENTER;
 570    len = (len * 4) / 3;
 571    len += (((len / B64_ENCODE_INPUT_PER_LINE) + 1) * 3);
 572    len += 2 + 1; /* CRLF, \0 */
 573    NYD_LEAVE;
 574    return len;
 575 }
 576
 577 FL struct str *
 578 b64_encode(struct str *out, struct str const *in, enum b64flags flags)
 579 {
 580    static char const b64table[] =
 581        "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
 582
 583    ui8_t const *p;
 584    ssize_t i, lnlen;
 585    char *b64;
 586    NYD_ENTER;
 587
 588    p = (ui8_t const*)in->s;
 589
 590    if (!(flags & B64_BUF)) {
 591       i = b64_encode_calc_size(in->l);
 592       out->s = (flags & B64_SALLOC) ? salloc(i) : srealloc(out->s, i);
 593    }
 594    b64 = out->s;
 595
 596    if (!(flags & (B64_CRLF | B64_LF)))
 597       flags &= ~B64_MULTILINE;
 598
 599    for (lnlen = 0, i = (ssize_t)in->l; i > 0; p += 3, i -= 3) {
 600       ui32_t a = p[0], b, c;
 601
 602       b64[0] = b64table[a >> 2];
 603       switch (i) {
 604       case 1:
 605          b64[1] = b64table[((a & 0x3) << 4)];
 606          b64[2] =
 607          b64[3] = '=';
 608          break;
 609       case 2:
 610          b = p[1];
 611          b64[1] = b64table[((a & 0x03) << 4) | ((b & 0xF0u) >> 4)];
 612          b64[2] = b64table[((b & 0x0F) << 2)];
 613          b64[3] = '=';
 614          break;
 615       default:
 616          b = p[1];
 617          c = p[2];
 618          b64[1] = b64table[((a & 0x03) << 4) | ((b & 0xF0u) >> 4)];
 619          b64[2] = b64table[((b & 0x0F) << 2) | ((c & 0xC0u) >> 6)];
 620          b64[3] = b64table[c & 0x3F];
 621          break;
 622       }
 623
 624       b64 += 4;
 625       if (!(flags & B64_MULTILINE))
 626          continue;
 627       lnlen += 4;
 628       if (lnlen < B64_LINESIZE)
 629          continue;
 630
 631       lnlen = 0;
 632       if (flags & B64_CRLF)
 633          *b64++ = '\r';
 634       if (flags & (B64_CRLF | B64_LF))
 635          *b64++ = '\n';
 636    }
 637
 638    if ((flags & (B64_CRLF | B64_LF)) &&
 639          (!(flags & B64_MULTILINE) || lnlen != 0)) {
 640       if (flags & B64_CRLF)
 641          *b64++ = '\r';
 642       if (flags & (B64_CRLF | B64_LF))
 643          *b64++ = '\n';
 644    }
 645    out->l = PTR2SIZE(b64 - out->s);
 646    out->s[out->l] = '\0';
 647    NYD_LEAVE;
 648    return out;
 649 }
 650
 651 FL struct str *
 652 b64_encode_cp(struct str *out, char const *cp, enum b64flags flags)
 653 {
 654    struct str in;
 655    NYD_ENTER;
 656
 657    in.s = UNCONST(cp);
 658    in.l = strlen(cp);
 659    out = b64_encode(out, &in, flags);
 660    NYD_LEAVE;
 661    return out;
 662 }
 663
 664 FL struct str *
 665 b64_encode_buf(struct str *out, void const *vp, size_t vp_len,
 666    enum b64flags flags)
 667 {
 668    struct str in;
 669    NYD_ENTER;
 670
 671    in.s = UNCONST(vp);
 672    in.l = vp_len;
 673    out = b64_encode(out, &in, flags);
 674    NYD_LEAVE;
 675    return out;
 676 }
 677
 678 FL int
 679 b64_decode(struct str *out, struct str const *in, struct str *rest)
 680 {
 681    struct str work;
 682    char *x;
 683    int ret = STOP;
 684    size_t len;
 685    NYD_ENTER;
 686
 687    len = _b64_decode_prepare(&work, in);
 688
 689    /* Ignore an empty input, as may happen for an empty final line */
 690    if (work.l == 0) {
 691       /* With B64_T there may be leftover decoded data for iconv(3), even if
 692        * that means it's incomplete multibyte character we have to copy over */
 693       /* XXX strictly speaking this should not be handled in here,
 694        * XXX since its leftover decoded data from an iconv(3);
 695        * XXX like this we shared the prototype with QP, though?? */
 696       if (rest != NULL && rest->l > 0) {
 697          x = out->s;
 698          *out = *rest;
 699          rest->s = x;
 700          rest->l = 0;
 701       } else
 702          out->l = 0;
 703       ret = OKAY;
 704       goto jleave;
 705    }
 706    if (work.l >= 4 && !(work.l & 3)) {
 707       out->s = srealloc(out->s, len);
 708       ret = OKAY;
 709    }
 710    if (ret != OKAY || (ssize_t)(len = _b64_decode(out, &work)) < 0)
 711       goto jerr;
 712 jleave:
 713    NYD_LEAVE;
 714    return ret;
 715
 716 jerr: {
 717    char const *err = tr(15, "[Invalid Base64 encoding ignored]\n");
 718    len = strlen(err);
 719    x = out->s = srealloc(out->s, len + 1 +1);
 720    if (rest != NULL && rest->l)
 721       *x++ = '\n';
 722    memcpy(x, err, len);
 723    x += len;
 724    *x = '\0';
 725    out->l = PTR2SIZE(x - out->s);
 726    if (rest != NULL)
 727       rest->l = 0;
 728    ret = STOP;
 729    goto jleave;
 730    }
 731 }
 732
 733 /* vim:set fenc=utf-8:s-it-mode */