--- /dev/null
+/*
+ * Routines to encode message headers using RFC 2047-encoding.
+ *
+ * This code is Copyright (c) 2002, by the authors of nmh. See the
+ * COPYRIGHT file in the root directory of the nmh distribution for
+ * complete copyright information.
+ */
+
+#include <h/mh.h>
+#include <h/mhparse.h>
+#include <h/addrsbr.h>
+#include <h/utils.h>
+
+#include <ctype.h>
+
+/*
+ * List of headers that contain addresses and as a result require special
+ * handling
+ */
+
+static char *address_headers[] = {
+ "To",
+ "From",
+ "cc",
+ "Bcc",
+ "Reply-To",
+ "Sender",
+ "Resent-To",
+ "Resent-From",
+ "Resent-cc",
+ "Resent-Bcc",
+ "Resent-Reply-To",
+ "Resent-Sender",
+ NULL,
+};
+
+/*
+ * Macros we use for parsing headers
+ */
+
+#define is_fws(c) (c == '\t' || c == ' ' || c == '\n')
+
+#define qphrasevalid(c) ((c >= '0' && c <= '9') || (c >= 'A' && c <= 'Z') || \
+ (c >= 'a' && c <= 'z') || \
+ c == '!' || c == '*' || c == '+' || c == '-' || \
+ c == '/' || c == '=' || c == '_')
+#define qpspecial(c) (c < ' ' || c == '=' || c == '?' || c == '_')
+
+#define base64len(n) ((((n) + 2) / 3 ) * 4) /* String len to base64 len */
+#define strbase64(n) ((n) / 4 * 3) /* Chars that fit in base64 */
+
+#define ENCODELINELIMIT 76
+
+static void unfold_header(char **, int);
+static int field_encode_address(const char *, char **, const char *);
+static int field_encode_quoted(const char *, char **, const char *, int,
+ int, int);
+static int scanstring(const char *, int *, int *, int *);
+static int utf8len(const char *);
+/*static int pref_encoding(int, int, int);*/
+
+/*
+ * Encode a message header using RFC 2047 encoding. We make the assumption
+ * that all characters < 128 are ASCII and as a consequence don't need any
+ * encoding.
+ */
+
+int
+encode_rfc2047(const char *name, char **value, const char *charset)
+{
+ int i, asciicount = 0, eightbitcount = 0, qpspecialcount = 0;
+ char *p;
+
+ /*
+ * First, check to see if we even need to encode the header
+ */
+
+ for (p = *value; *p != '\0'; p++) {
+ if (isascii((unsigned char) *p)) {
+ asciicount++;
+ if (qpspecial((unsigned char) *p))
+ qpspecialcount++;
+ } else
+ eightbitcount++;
+ }
+
+ if (eightbitcount == 0)
+ return 0;
+
+ /*
+ * Some rules from RFC 2047:
+ *
+ * - Encoded words cannot be more than 75 characters long
+ * - Multiple "long" encoded words must be on new lines.
+ *
+ * Also, we're not permitted to encode email addresses, so
+ * we need to actually _parse_ email addresses and only encode
+ * the right bits.
+ */
+
+ /*
+ * If charset was NULL, then get the value from the locale. But
+ * we reject it if it returns US-ASCII
+ */
+
+ if (charset == NULL)
+ charset = write_charset_8bit();
+
+ if (strcasecmp(charset, "US-ASCII") == 0) {
+ advise(NULL, "Cannot use US-ASCII with 8 bit characters in header");
+ return 1;
+ }
+
+ /*
+ * If we have an address header, then we need to parse the addresses
+ * and only encode the names or comments. Otherwise, handle it normally.
+ */
+
+ for (i = 0; address_headers[i]; i++) {
+ if (strcasecmp(name, address_headers[i]) == 0) {
+ return field_encode_address(name, value, charset);
+ }
+ }
+
+ /*
+ * On the encoding we choose, and the specifics of encoding:
+ *
+ * - If a specified encoding is passed in, we use that.
+ * - Otherwise, pick which encoding is shorter.
+ *
+ * We don't quite handle continuation right here, but it should be
+ * pretty close.
+ */
+
+ unfold_header(value, asciicount + eightbitcount);
+
+ return field_encode_quoted(name, value, charset, asciicount,
+ eightbitcount + qpspecialcount, 0);
+}
+
+/*
+ * Encode our specified header (or field) using quoted-printable
+ */
+
+static int
+field_encode_quoted(const char *name, char **value, const char *charset,
+ int ascii, int encoded, int phraserules)
+{
+ int prefixlen = name ? strlen(name) + 2: 0, outlen = 0, column, newline = 1;
+ int charsetlen = strlen(charset), utf8;
+ char *output = NULL, *p, *q = NULL;
+
+ /*
+ * Right now we just encode the whole thing. Maybe later on we'll
+ * only encode things on a per-atom basis.
+ */
+
+ p = *value;
+
+ column = prefixlen + 2; /* Header name plus ": " */
+
+ utf8 = strcasecmp(charset, "UTF-8") == 0;
+
+ while (*p != '\0') {
+ /*
+ * Start a new line, if it's time
+ */
+ if (newline) {
+ /*
+ * If it's the start of the header, we don't need to pad it
+ *
+ * The length of the output string is ...
+ * =?charset?Q?...?= so that's 7+strlen(charset) + 2 for \n NUL
+ *
+ * plus 1 for every ASCII character and 3 for every eight bit
+ * or special character (eight bit characters are written as =XX).
+ *
+ */
+
+ int tokenlen;
+
+ outlen += 9 + charsetlen + ascii + 3 * encoded;
+
+ /*
+ * If output is set, then we're continuing the header. Otherwise
+ * do the initial allocation.
+ */
+
+ if (output) {
+ int curlen = q - output, i;
+ outlen += prefixlen + 1; /* Header plus \n ": " */
+ output = mh_xrealloc(output, outlen);
+ q = output + curlen;
+ *q++ = '?';
+ *q++ = '=';
+ *q++ = '\n';
+ for (i = 0; i < prefixlen; i++)
+ *q++ = ' ';
+ } else {
+ /*
+ * A bit of a hack here; the header can contain multiple
+ * spaces (probably at least one) until we get to the
+ * actual text. Copy until we get to a non-space.
+ */
+ output = mh_xmalloc(outlen);
+ q = output;
+ while (is_fws(*p))
+ *q++ = *p++;
+ }
+
+ tokenlen = snprintf(q, outlen - (q - output), "=?%s?Q?", charset);
+ q += tokenlen;
+ column = prefixlen + tokenlen;
+ newline = 0;
+ }
+
+ /*
+ * Process each character, encoding if necessary
+ *
+ * Note that we have a different set of rules if we're processing
+ * RFC 5322 'phrase' (something you'd see in an address header).
+ */
+
+ column++;
+
+ if (*p == ' ') {
+ *q++ = '_';
+ ascii--;
+ } else if (isascii((unsigned char) *p) &&
+ (phraserules ? qphrasevalid((unsigned char) *p) :
+ !qpspecial((unsigned char) *p))) {
+ *q++ = *p;
+ ascii--;
+ } else {
+ snprintf(q, outlen - (q - output), "=%02X", (unsigned char) *p);
+ q += 3;
+ column += 2; /* column already incremented by 1 above */
+ encoded--;
+ }
+
+ p++;
+
+ /*
+ * We're not allowed more than ENCODELINELIMIT characters per line,
+ * so reserve some room for the final ?=.
+ *
+ * If prefixlen == 0, we haven't been passed in a header name, so
+ * don't ever wrap the field (we're likely doing an address).
+ */
+
+ if (prefixlen == 0)
+ continue;
+
+ if (column >= ENCODELINELIMIT - 2) {
+ newline = 1;
+ } else if (utf8) {
+ /*
+ * Okay, this is a bit weird, but to explain a bit more ...
+ *
+ * RFC 2047 prohibits the splitting of multibyte characters
+ * across encoded words. Right now we only handle the case
+ * of UTF-8, the most common multibyte encoding.
+ *
+ * p is now pointing at the next input character. If we're
+ * using UTF-8 _and_ we'd go over ENCODELINELIMIT given the
+ * length of the complete character, then trigger a newline
+ * now. Note that we check the length * 3 since we have to
+ * allow for the encoded output.
+ */
+ if (column + (utf8len(p) * 3) > ENCODELINELIMIT - 2) {
+ newline = 1;
+ }
+ }
+ }
+
+ if (q == NULL) {
+ /* This should never happen, but just in case. Found by
+ clang static analyzer. */
+ admonish (NULL, "null output encoding for %s", *value);
+ return 1;
+ }
+ *q++ = '?';
+ *q++ = '=';
+
+ if (prefixlen)
+ *q++ = '\n';
+
+ *q = '\0';
+
+ free(*value);
+
+ *value = output;
+
+ return 0;
+}
+
+/*
+ * Calculate the length of a UTF-8 character.
+ *
+ * If it's not a UTF-8 character (or we're in the middle of a multibyte
+ * character) then simply return 0.
+ */
+
+static int
+utf8len(const char *p)
+{
+ int len = 1;
+
+ if (*p == '\0')
+ return 0;
+
+ if (isascii((unsigned char) *p) || (((unsigned char) *p) & 0xc0) == 0x80)
+ return 0;
+
+ p++;
+ while ((((unsigned char) *p++) & 0xc0) == 0x80)
+ len++;
+
+ return len;
+}
+
+/*
+ * "Unfold" a header, making it a single line (without continuation)
+ *
+ * We cheat a bit here; we never make the string longer, so using the
+ * original length here is fine.
+ */
+
+static void
+unfold_header(char **value, int len)
+{
+ char *str = mh_xmalloc(len + 1);
+ char *p = str, *q = *value;
+
+ while (*q != '\0') {
+ if (*q == '\n') {
+ /*
+ * When we get a newline, skip to the next non-whitespace
+ * character and add a space to replace all of the whitespace
+ *
+ * This has the side effect of stripping off the final newline
+ * for the header; we put it back in the encoding routine.
+ */
+ while (is_fws(*q))
+ q++;
+ if (*q == '\0')
+ break;
+
+ *p++ = ' ';
+ } else {
+ *p++ = *q++;
+ }
+ }
+
+ *p = '\0';
+
+ free(*value);
+ *value = str;
+}
+
+/*
+ * Decode a header containing addresses. This means we have to parse
+ * each address and only encode the display-name or comment field.
+ */
+
+static int
+field_encode_address(const char *name, char **value, const char *charset)
+{
+ int prefixlen = strlen(name) + 2, column = prefixlen, groupflag;
+ int asciichars, specialchars, eightbitchars, reformat = 0, errflag = 0;
+ size_t len;
+ char *mp, *cp = NULL, *output = NULL;
+ char *tmpbuf = NULL;
+ size_t tmpbufsize = 0;
+ struct mailname *mn;
+ char errbuf[BUFSIZ];
+
+ /*
+ * Because these are addresses, we need to handle them individually.
+ *
+ * Break them down and process them one by one. This means we have to
+ * rewrite the whole header, but that's unavoidable.
+ */
+
+ /*
+ * The output headers always have to start with a space first; this
+ * is just the way the API works right now.
+ */
+
+ output = add(" ", output);
+
+ for (groupflag = 0; (mp = getname(*value)); ) {
+ if ((mn = getm(mp, NULL, 0, AD_HOST, errbuf)) == NULL) {
+ advise(NULL, "%s: %s", errbuf, mp);
+ errflag++;
+ continue;
+ }
+
+ reformat = 0;
+
+ /*
+ * We only care if the phrase (m_pers) or any trailing comment
+ * (m_note) have 8-bit characters. If doing q-p, we also need
+ * to encode anything marked as qspecial(). Unquote it first
+ * so the specialchars count is right.
+ */
+
+ if (! mn->m_pers)
+ goto check_note;
+
+ if ((len = strlen(mn->m_pers)) + 1 > tmpbufsize) {
+ tmpbuf = mh_xrealloc(tmpbuf, tmpbufsize = len + 1);
+ }
+
+ unquote_string(mn->m_pers, tmpbuf);
+
+ if (scanstring(tmpbuf, &asciichars, &eightbitchars,
+ &specialchars)) {
+ /*
+ * If we have 8-bit characters, encode it.
+ */
+
+ /*
+ * This is okay, because the output of unquote_string will be either
+ * equal or shorter than the original.
+ */
+
+ strcpy(mn->m_pers, tmpbuf);
+
+ if (field_encode_quoted(NULL, &mn->m_pers, charset, asciichars,
+ eightbitchars + specialchars, 1)) {
+ errflag++;
+ goto out;
+ }
+
+ reformat++;
+ }
+
+ check_note:
+
+ /*
+ * The "note" field is generally a comment at the end of the address,
+ * at least as how it's implemented here. Notes are always surrounded
+ * by parenthesis (since they're comments). Strip them out and
+ * then put them back when we format the final field, but they do
+ * not get encoded.
+ */
+
+ if (! mn->m_note)
+ goto do_reformat;
+
+ if ((len = strlen(mn->m_note)) + 1 > tmpbufsize) {
+ tmpbuf = mh_xrealloc(tmpbuf, tmpbufsize = len + 1);
+ }
+
+ if (mn->m_note[0] != '(' || mn->m_note[len - 1] != ')') {
+ advise(NULL, "Internal error: Invalid note field \"%s\"",
+ mn->m_note);
+ errflag++;
+ goto out;
+ }
+
+ strncpy(tmpbuf, mn->m_note + 1, len - 1);
+ tmpbuf[len - 2] = '\0';
+
+ if (scanstring(tmpbuf, &asciichars, &eightbitchars,
+ &specialchars)) {
+ /*
+ * If we have 8-bit characters, encode it.
+ */
+
+ if (field_encode_quoted(NULL, &tmpbuf, charset, asciichars,
+ eightbitchars + specialchars, 1)) {
+ errflag++;
+ goto out;
+ }
+
+ reformat++;
+
+ /*
+ * Make sure the size of tmpbuf is correct (it always gets
+ * reallocated in the above functions).
+ */
+
+ tmpbufsize = strlen(tmpbuf) + 1;
+
+ /*
+ * Put the note field back surrounded by parenthesis.
+ */
+
+ mn->m_note = mh_xrealloc(mn->m_note, tmpbufsize + 2);
+
+ snprintf(mn->m_note, tmpbufsize + 2, "(%s)", tmpbuf);
+ }
+
+do_reformat:
+
+ /*
+ * So, some explanation is in order.
+ *
+ * We know we need to rewrite at least one address in the header,
+ * otherwise we wouldn't be here. If we had to reformat this
+ * particular address, then run it through adrformat(). Otherwise
+ * we can use m_text directly.
+ */
+
+ /*
+ * If we were in a group but are no longer, make sure we add a
+ * semicolon (which needs to be FIRST, as it needs to be at the end
+ * of the last address).
+ */
+
+ if (groupflag && ! mn->m_ingrp) {
+ output = add(";", output);
+ column += 1;
+ }
+
+ groupflag = mn->m_ingrp;
+
+ if (mn->m_gname) {
+ cp = add(mn->m_gname, NULL);
+ }
+
+ if (reformat) {
+ cp = add(adrformat(mn), cp);
+ } else {
+ cp = add(mn->m_text, cp);
+ }
+
+ len = strlen(cp);
+
+ /*
+ * If we're not at the beginning of the line, add a command and
+ * either a space or a newline.
+ */
+
+ if (column != prefixlen) {
+ if (len + column + 2 > OUTPUTLINELEN) {
+
+ if ((size_t) (prefixlen + 3) < tmpbufsize)
+ tmpbuf = mh_xrealloc(tmpbuf, tmpbufsize = prefixlen + 3);
+
+ snprintf(tmpbuf, tmpbufsize, ",\n%*s", column = prefixlen, "");
+ output = add(tmpbuf, output);
+ } else {
+ output = add(", ", output);
+ column += 2;
+ }
+ }
+
+ /*
+ * Finally add the address
+ */
+
+ output = add(cp, output);
+ column += len;
+ free(cp);
+ cp = NULL;
+ }
+
+ /*
+ * Just in case we're at the end of a list
+ */
+
+ if (groupflag) {
+ output = add(";", output);
+ }
+
+ output = add("\n", output);
+
+ free(*value);
+ *value = output;
+ output = NULL;
+
+out:
+
+ if (tmpbuf)
+ free(tmpbuf);
+ if (output)
+ free(output);
+
+ return errflag > 0;
+}
+
+/*
+ * Scan a string, check for characters that need to be encoded
+ */
+
+static int
+scanstring(const char *string, int *asciilen, int *eightbitchars,
+ int *specialchars)
+{
+ *asciilen = 0;
+ *eightbitchars = 0;
+ *specialchars = 0;
+
+ for (; *string != '\0'; string++) {
+ if ((isascii((unsigned char) *string))) {
+ (*asciilen)++;
+ /*
+ * So, a space is not a valid phrase character, but we're counting
+ * an exception here, because in q-p a space can be directly
+ * encoded as an underscore.
+ */
+ if (!qphrasevalid((unsigned char) *string) && *string != ' ')
+ (*specialchars)++;
+ } else {
+ (*eightbitchars)++;
+ }
+ }
+
+ return *eightbitchars > 0;
+}
+
+/*
+ * This function is to be used to decide which encoding algorithm we should
+ * use if one is not given. Basically, we pick whichever one is the shorter
+ * of the two.
+ *
+ * Arguments are:
+ *
+ * ascii - Number of ASCII characters in to-be-encoded string.
+ * specials - Number of ASCII characters in to-be-encoded string that
+ * still require encoding under quoted-printable. Note that
+ * these are included in the "ascii" total.
+ * eightbit - Eight-bit characters in the to-be-encoded string.
+ *
+ * Returns one of CE_BASE64 or CE_QUOTED.
+ */
+/*
+static int
+pref_encoding(int ascii, int specials, int eightbits)
+{ */
+ /*
+ * The length of the q-p encoding is:
+ *
+ * ascii - specials + (specials + eightbits) * 3.
+ *
+ * The length of the base64 encoding is:
+ *
+ * base64len(ascii + eightbits) (See macro for details)
+ */
+/*
+ return base64len(ascii + eightbits) < (ascii - specials +
+ (specials + eightbits) * 3) ? CE_BASE64 : CE_QUOTED;
+}*/
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