src/src/imap_utf7.c

   1 /* Copyright (c) University of Cambridge 1995 - 2018 */
   2 /* See the file NOTICE for conditions of use and distribution. */
   3
   4 #include "exim.h"
   5
   6 #ifdef SUPPORT_I18N
   7
   8 uschar *
   9 imap_utf7_encode(uschar *string, const uschar *charset, uschar sep,
  10   uschar *specials, uschar **error)
  11 {
  12 static uschar encode_base64[64] =
  13   "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";
  14 size_t slen;
  15 uschar *sptr;
  16 gstring * yield = NULL;
  17 int i = 0;      /* compiler quietening */
  18 uschar c = 0;   /* compiler quietening */
  19 BOOL base64mode = FALSE;
  20 BOOL lastsep = FALSE;
  21 uschar utf16buf[256];
  22 uschar *utf16ptr;
  23 uschar *s;
  24 uschar outbuf[256];
  25 uschar *outptr = outbuf;
  26 #if HAVE_ICONV
  27 iconv_t icd;
  28 #endif
  29
  30 if (!specials) specials = US"";
  31
  32 /* Pass over the string. If it consists entirely of "normal" characters
  33    (possibly with leading seps), return it as is. */
  34 for (s = string; *s; s++)
  35   {
  36   if (s == string && *s == sep)
  37     string++;
  38   if (  *s >= 0x7f
  39      || *s < 0x20
  40      || strchr("./&", *s)
  41      || *s == sep
  42      || Ustrchr(specials, *s)
  43      )
  44     break;
  45   }
  46
  47 if (!*s)
  48   return string;
  49
  50 sptr = string;
  51 slen = Ustrlen(string);
  52
  53 #if HAVE_ICONV
  54 if ((icd = iconv_open("UTF-16BE", CCS charset)) == (iconv_t)-1)
  55   {
  56   *error = string_sprintf(
  57         "imapfolder: iconv_open(\"UTF-16BE\", \"%s\") failed: %s%s",
  58     charset, strerror(errno),
  59     errno == EINVAL ? " (maybe unsupported conversion)" : "");
  60   return NULL;
  61   }
  62 #endif
  63
  64 while (slen > 0)
  65   {
  66 #if HAVE_ICONV
  67   size_t left = sizeof(utf16buf);
  68   utf16ptr = utf16buf;
  69
  70   if (  iconv(icd, (ICONV_ARG2_TYPE)&sptr, &slen, CSS &utf16ptr, &left)
  71                 == (size_t)-1
  72      && errno != E2BIG
  73          )
  74     {
  75     *error = string_sprintf("imapfolder: iconv() failed to convert from %s: %s",
  76                               charset, strerror(errno));
  77     iconv_close(icd);
  78     return NULL;
  79     }
  80 #else
  81   for (utf16ptr = utf16buf;
  82        slen > 0 && (utf16ptr - utf16buf) < sizeof(utf16buf);
  83        utf16ptr += 2, slen--, sptr++)
  84     {
  85     *utf16ptr = *sptr;
  86     *(utf16ptr+1) = '\0';
  87     }
  88 #endif
  89
  90   s = utf16buf;
  91   while (s < utf16ptr)
  92     {
  93     /* Now encode utf16buf as modified UTF-7 */
  94     if (  s[0] != 0
  95        || s[1] >= 0x7f
  96        || s[1] < 0x20
  97        || (Ustrchr(specials, s[1]) && s[1] != sep)
  98        )
  99       {
 100       lastsep = FALSE;
 101       /* Encode as modified BASE64 */
 102       if (!base64mode)
 103         {
 104         *outptr++ = '&';
 105         base64mode = TRUE;
 106         i = 0;
 107         }
 108
 109       for (int j = 0; j < 2; j++, s++) switch (i++)
 110         {
 111         case 0:
 112           /* Top 6 bits of the first octet */
 113           *outptr++ = encode_base64[(*s >> 2) & 0x3F];
 114           c = (*s & 0x03); break;
 115         case 1:
 116           /* Bottom 2 bits of the first octet, and top 4 bits of the second */
 117           *outptr++ = encode_base64[(c << 4) | ((*s >> 4) & 0x0F)];
 118           c = (*s & 0x0F); break;
 119         case 2:
 120           /* Bottom 4 bits of the second octet and top 2 bits of the third */
 121           *outptr++ = encode_base64[(c << 2) | ((*s >> 6) & 0x03)];
 122           /* Bottom 6 bits of the third octet */
 123           *outptr++ = encode_base64[*s & 0x3F];
 124           i = 0;
 125         }
 126       }
 127
 128     else if (  (s[1] != '.' && s[1] != '/')
 129             || s[1] == sep
 130             )
 131       {
 132       /* Encode as self (almost) */
 133       if (base64mode)
 134         {
 135         switch (i)
 136           {
 137           case 1:
 138                 /* Remaining bottom 2 bits of the last octet */
 139                 *outptr++ = encode_base64[c << 4];
 140                 break;
 141           case 2:
 142                 /* Remaining bottom 4 bits of the last octet */
 143                 *outptr++ = encode_base64[c << 2];
 144           }
 145         *outptr++ = '-';
 146         base64mode = FALSE;
 147         }
 148
 149       if (*++s == sep)
 150         {
 151         if (!lastsep)
 152           {
 153           *outptr++ = '.';
 154           lastsep = TRUE;
 155           }
 156         }
 157       else
 158         {
 159         *outptr++ = *s;
 160         if (*s == '&')
 161           *outptr++ = '-';
 162         lastsep = FALSE;
 163         }
 164
 165       s++;
 166       }
 167     else
 168       {
 169       *error = string_sprintf("imapfolder: illegal character '%c'", s[1]);
 170       return NULL;
 171       }
 172
 173     if (outptr > outbuf + sizeof(outbuf) - 3)
 174       {
 175       yield = string_catn(yield, outbuf, outptr - outbuf);
 176       outptr = outbuf;
 177       }
 178
 179     }
 180   } /* End of input string */
 181
 182 if (base64mode)
 183   {
 184   switch (i)
 185     {
 186     case 1:
 187       /* Remaining bottom 2 bits of the last octet */
 188       *outptr++ = encode_base64[c << 4];
 189       break;
 190     case 2:
 191       /* Remaining bottom 4 bits of the last octet */
 192       *outptr++ = encode_base64[c << 2];
 193     }
 194   *outptr++ = '-';
 195   }
 196
 197 #if HAVE_ICONV
 198 iconv_close(icd);
 199 #endif
 200
 201 yield = string_catn(yield, outbuf, outptr - outbuf);
 202
 203 if (yield->s[yield->ptr-1] == '.')
 204   yield->ptr--;
 205
 206 return string_from_gstring(yield);
 207 }
 208
 209 #endif  /* whole file */
 210 /* vi: aw ai sw=2
 211 */