www.pudn.com > unmime.rar > UNMIME.C
/*
* MIME mail decoding.
*
* This module contains decoding routines for converting
* quoted-printable data into pure 8-bit data, in MIME
* formatted messages.
*
* By Henrik Storner
*
* Configuration file support for fetchmail 4.3.8 by
* Frank Damgaard
*
*/
#include "config.h"
#include
#include
#include
#include "fetchmail.h"
static unsigned char unhex(unsigned char c)
{
if ((c >= '0') && (c <= '9'))
return (c - '0');
else if ((c >= 'A') && (c <= 'F'))
return (c - 'A' + 10);
else if ((c >= 'a') && (c <= 'f'))
return (c - 'a' + 10);
else
return c;
}
static int qp_char(unsigned char c1, unsigned char c2, unsigned char *c_out)
{
c1 = unhex(c1);
c2 = unhex(c2);
if ((c1 > 15) || (c2 > 15))
return 1;
else {
*c_out = 16*c1+c2;
return 0;
}
}
/*
* Routines to decode MIME QP-encoded headers, as per RFC 2047.
*/
/* States of the decoding state machine */
#define S_COPY_PLAIN 0 /* Just copy, but watch for the QP flag */
#define S_SKIP_MIMEINIT 1 /* Get the encoding, and skip header */
#define S_COPY_MIME 2 /* Decode a sequence of coded characters */
static const char MIMEHDR_INIT[] = "=?"; /* Start of coded sequence */
static const char MIMEHDR_END[] = "?="; /* End of coded sequence */
void UnMimeHeader(unsigned char *hdr)
{
/* Decode a buffer containing data encoded according to RFC
* 2047. This only handles content-transfer-encoding; conversion
* between character sets is not implemented. In other words: We
* assume the charsets used can be displayed by your mail program
* without problems.
*/
/* Note: Decoding is done "in-situ", i.e. without using an
* additional buffer for temp. storage. This is possible, since the
* decoded string will always be shorter than the encoded string,
* due to the en- coding scheme.
*/
int state = S_COPY_PLAIN;
unsigned char *p_in, *p_out, *p;
unsigned char enc = '\0'; /* initialization pacifies -Wall */
int i;
/* Speed up in case this is not a MIME-encoded header */
p = strstr(hdr, MIMEHDR_INIT);
if (p == NULL)
return; /* No MIME header */
/* Loop through the buffer.
* p_in : Next char to be processed.
* p_out: Where to put the next processed char
* enc : Encoding used (usually, 'q' = quoted-printable)
*/
for (p_out = p_in = hdr; (*p_in); ) {
switch (state) {
case S_COPY_PLAIN:
p = strstr(p_in, MIMEHDR_INIT);
if (p == NULL) {
/*
* No more coded data in buffer,
* just move remainder into place.
*/
i = strlen(p_in); /* How much left */
memmove(p_out, p_in, i);
p_in += i; p_out += i;
}
else {
/* MIME header init found at location p */
if (p > p_in) {
/* There are some uncoded chars at the beginning. */
i = (p - p_in);
memmove(p_out, p_in, i);
p_out += i;
}
p_in = (p + 2);
state = S_SKIP_MIMEINIT;
}
break;
case S_SKIP_MIMEINIT:
/* Mime type definition: "charset?encoding?" */
p = strchr(p_in, '?');
if (p != NULL) {
/* p_in .. (p-1) holds the charset */
/* *(p+1) is the transfer encoding, *(p+2) must be a '?' */
if (*(p+2) == '?') {
enc = tolower(*(p+1));
p_in = p+3;
state = S_COPY_MIME;
}
else
state = S_COPY_PLAIN;
}
else
state = S_COPY_PLAIN; /* Invalid data */
break;
case S_COPY_MIME:
p = strstr(p_in, MIMEHDR_END); /* Find end of coded data */
if (p == NULL) p = p_in + strlen(p_in);
for (; (p_in < p); ) {
/* Decode all encoded data */
if (enc == 'q') {
if (*p_in == '=') {
/* Decode one char qp-coded at (p_in+1) and (p_in+2) */
if (qp_char(*(p_in+1), *(p_in+2), p_out) == 0)
p_in += 3;
else {
/* Invalid QP data - pass through unchanged. */
*p_out = *p_in;
p_in++;
}
}
else if (*p_in == '_') {
/*
* RFC 2047: '_' inside encoded word represents 0x20.
* NOT a space - always the value 0x20.
*/
*p_out = 0x20;
p_in++;
}
else {
/* Copy unchanged */
*p_out = *p_in;
p_in++;
}
p_out++;
}
else if (enc == 'b') {
/* Decode base64 encoded data */
char delimsave;
int decoded_count;
delimsave = *p; *p = '\r';
decoded_count = from64tobits(p_out, p_in);
*p = delimsave;
if (decoded_count > 0)
p_out += decoded_count;
p_in = p;
}
else {
/* Copy unchanged */
*p_out = *p_in;
p_in++;
p_out++;
}
}
if (*p_in)
p_in += 2; /* Skip the MIMEHDR_END delimiter */
/*
* We've completed decoding one encoded sequence. But another
* may follow immediately, in which case whitespace before the
* new MIMEHDR_INIT delimiter must be discarded.
* See if that is the case
*/
p = strstr(p_in, MIMEHDR_INIT);
state = S_COPY_PLAIN;
if (p != NULL) {
/*
* There is more MIME data later on. Is there
* whitespace only before the delimiter?
*/
unsigned char *q;
int wsp_only = 1;
for (q=p_in; (wsp_only && (q < p)); q++)
wsp_only = isspace(*q);
if (wsp_only) {
/*
* Whitespace-only before the MIME delimiter. OK,
* just advance p_in to past the new MIMEHDR_INIT,
* and prepare to process the new MIME charset/encoding
* header.
*/
p_in = p + strlen(MIMEHDR_INIT);
state = S_SKIP_MIMEINIT;
}
}
break;
}
}
*p_out = '\0';
}
/*
* Routines for decoding body-parts of a message.
*
* Since the "fetch" part of fetchmail gets a message body
* one line at a time, we need to maintain some state variables
* across multiple invokations of the UnMimeBodyline() routine.
* The driver routine should call MimeBodyType() when all
* headers have been received, and then UnMimeBodyline() for
* every line in the message body.
*
*/
#define S_BODY_DATA 0
#define S_BODY_HDR 1
/*
* Flag indicating if we are currently processing
* the headers or the body of a (multipart) message.
*/
static int BodyState = S_BODY_DATA;
/*
* Flag indicating if we are in the process of decoding
* a quoted-printable body part.
*/
static int CurrEncodingIsQP = 0;
/*
* Delimiter for multipart messages. RFC 2046 states that this must
* NEVER be longer than 70 characters. Add 3 for the two hyphens
* at the beginning, and a terminating null.
*/
#define MAX_DELIM_LEN 70
static unsigned char MultipartDelimiter[MAX_DELIM_LEN+3];
/* This string replaces the "Content-Transfer-Encoding: quoted-printable"
* string in all headers, including those in body-parts. The replacement
* must be no longer than the original string.
*/
static const char ENC8BIT[] = "Content-Transfer-Encoding: 8bit";
static void SetEncoding8bit(unsigned char *XferEncOfs)
{
unsigned char *p;
if (XferEncOfs != NULL) {
memcpy(XferEncOfs, ENC8BIT, strlen(ENC8BIT));
/* If anything left, in this header, replace with whitespace */
for (p=XferEncOfs+strlen(ENC8BIT); (*p >= ' '); p++) *p=' ';
}
}
static char *GetBoundary(char *CntType)
{
char *p1, *p2;
int flag;
/* Find the "boundary" delimiter. It must be preceded with a ';'
* and optionally some whitespace.
*/
p1 = CntType;
do {
p2 = strchr(p1, ';');
if (p2)
for (p2++; isspace(*p2); p2++);
p1 = p2;
} while ((p1) && (strncasecmp(p1, "boundary", 8) != 0));
if (p1 == NULL)
/* No boundary delimiter */
return NULL;
/* Skip "boundary", whitespace and '='; check that we do have a '=' */
for (p1+=8, flag=0; (isspace(*p1) || (*p1 == '=')); p1++)
flag |= (*p1 == '=');
if (!flag)
return NULL;
/* Find end of boundary delimiter string */
if (*p1 == '\"') {
/* The delimiter is inside quotes */
p1++;
p2 = strchr(p1, '\"');
if (p2 == NULL)
return NULL; /* No closing '"' !?! */
}
else {
/* There might be more text after the "boundary" string. */
p2 = strchr(p1, ';'); /* Safe - delimiter with ';' must be in quotes */
}
/* Zero-terminate the boundary string */
if (p2 != NULL)
*p2 = '\0';
return (p1 && strlen(p1)) ? p1 : NULL;
}
/*
* This routine does three things:
* 1) It determines - based on the message headers - whether the
* message body is a MIME message that may hold 8 bit data.
* - A message that has a "quoted-printable" or "8bit" transfer
* encoding is assumed to contain 8-bit data (when decoded).
* - A multipart message is assumed to contain 8-bit data
* when decoded (there might be quoted-printable body-parts).
* - All other messages are assumed NOT to include 8-bit data.
* 2) It determines the delimiter-string used in multi-part message
* bodies.
* 3) It sets the initial values of the CurrEncodingIsQP and BodyState
* variables, from the header contents.
*
* The return value is a bitmask.
*/
int MimeBodyType(unsigned char *hdrs, int WantDecode)
{
unsigned char *NxtHdr = hdrs;
unsigned char *XferEnc, *XferEncOfs, *CntType, *MimeVer, *p;
int HdrsFound = 0; /* We only look for three headers */
int BodyType; /* Return value */
/* Setup for a standard (no MIME, no QP, 7-bit US-ASCII) message */
MultipartDelimiter[0] = '\0';
CurrEncodingIsQP = 0;
BodyState = S_BODY_DATA;
BodyType = 0;
/* Just in case ... */
if (hdrs == NULL)
return BodyType;
XferEnc = XferEncOfs = CntType = MimeVer = NULL;
do {
if (strncasecmp("Content-Transfer-Encoding:", NxtHdr, 26) == 0) {
XferEncOfs = NxtHdr;
p = nxtaddr(NxtHdr);
if (p != NULL) {
xalloca(XferEnc, char *, strlen(p) + 1);
strcpy(XferEnc, p);
HdrsFound++;
}
}
else if (strncasecmp("Content-Type:", NxtHdr, 13) == 0) {
/*
* This one is difficult. We cannot use the standard
* nxtaddr() routine, since the boundary-delimiter is
* (probably) enclosed in quotes - and thus appears
* as an rfc822 comment, and nxtaddr() "eats" up any
* spaces in the delimiter. So, we have to do this
* by hand.
*/
/* Skip the "Content-Type:" part and whitespace after it */
for (NxtHdr += 13; ((*NxtHdr == ' ') || (*NxtHdr == '\t')); NxtHdr++);
/*
* Get the full value of the Content-Type header;
* it might span multiple lines. So search for
* a newline char, but ignore those that have a
* have a TAB or space just after the NL (continued
* lines).
*/
p = NxtHdr-1;
do {
p=strchr((p+1),'\n');
} while ( (p != NULL) && ((*(p+1) == '\t') || (*(p+1) == ' ')) );
if (p == NULL) p = NxtHdr + strlen(NxtHdr);
xalloca(CntType, char *, p-NxtHdr+2);
strncpy(CntType, NxtHdr, (p-NxtHdr));
*(CntType+(p-NxtHdr)) = '\0';
HdrsFound++;
}
else if (strncasecmp("MIME-Version:", NxtHdr, 13) == 0) {
p = nxtaddr(NxtHdr);
if (p != NULL) {
xalloca(MimeVer, char *, strlen(p) + 1);
strcpy(MimeVer, p);
HdrsFound++;
}
}
NxtHdr = (strchr(NxtHdr, '\n'));
if (NxtHdr != NULL) NxtHdr++;
} while ((NxtHdr != NULL) && (*NxtHdr) && (HdrsFound != 3));
/* Done looking through the headers, now check what they say */
if ((MimeVer != NULL) && (strcmp(MimeVer, "1.0") == 0)) {
/* Check Content-Type to see if this is a multipart message */
if ( (CntType != NULL) &&
((strncasecmp(CntType, "multipart/", 10) == 0) ||
(strncasecmp(CntType, "message/", 8) == 0)) ) {
char *p1 = GetBoundary(CntType);
if (p1 != NULL) {
/* The actual delimiter is "--" followed by
the boundary string */
strcpy(MultipartDelimiter, "--");
strncat(MultipartDelimiter, p1, MAX_DELIM_LEN);
BodyType = (MSG_IS_8BIT | MSG_NEEDS_DECODE);
}
}
/*
* Check Content-Transfer-Encoding, but
* ONLY for non-multipart messages (BodyType == 0).
*/
if ((XferEnc != NULL) && (BodyType == 0)) {
if (strcasecmp(XferEnc, "quoted-printable") == 0) {
CurrEncodingIsQP = 1;
BodyType = (MSG_IS_8BIT | MSG_NEEDS_DECODE);
if (WantDecode) {
SetEncoding8bit(XferEncOfs);
}
}
else if (strcasecmp(XferEnc, "7bit") == 0) {
CurrEncodingIsQP = 0;
BodyType = (MSG_IS_7BIT);
}
else if (strcasecmp(XferEnc, "8bit") == 0) {
CurrEncodingIsQP = 0;
BodyType = (MSG_IS_8BIT);
}
}
}
return BodyType;
}
/*
* Decode one line of data containing QP data.
* Return flag set if this line ends with a soft line-break.
* 'bufp' is modified to point to the end of the output buffer.
*/
static int DoOneQPLine(unsigned char **bufp, int collapsedoubledot)
{
unsigned char *buf = *bufp;
unsigned char *p_in, *p_out, *p;
int n;
int ret = 0;
p_in = buf;
if (collapsedoubledot && (strncmp(buf, "..", 2) == 0))
p_in++;
for (p_out = buf; (*p_in); ) {
p = strchr(p_in, '=');
if (p == NULL) {
/* No more QP data, just move remainder into place */
n = strlen(p_in);
memmove(p_out, p_in, n);
p_in += n; p_out += n;
}
else {
if (p > p_in) {
/* There are some uncoded chars at the beginning. */
n = (p - p_in);
memmove(p_out, p_in, n);
p_out += n;
}
switch (*(p+1)) {
case '\0': case '\r': case '\n':
/* Soft line break, skip '=' */
p_in = p+1;
if (*p_in == '\r') p_in++;
if (*p_in == '\n') p_in++;
ret = 1;
break;
default:
/* There is a QP encoded byte */
if (qp_char(*(p+1), *(p+2), p_out) == 0) {
p_in = p+3;
}
else {
/* Invalid QP data - pass through unchanged. */
*p_out = '=';
p_in = p+1;
}
p_out++;
break;
}
}
}
*p_out = '\0';
*bufp = p_out;
return ret;
}
/* This is called once per line in the message body. We need to scan
* all lines in the message body for the multipart delimiter string,
* and handle any body-part headers in such messages (these can toggle
* qp-decoding on and off).
*
* Note: Messages that are NOT multipart-messages go through this
* routine quickly, since BodyState will always be S_BODY_DATA,
* and MultipartDelimiter is NULL.
*
* Return flag set if this line ends with a soft line-break.
* 'bufp' is modified to point to the end of the output buffer.
*/
int UnMimeBodyline(unsigned char **bufp, int collapsedoubledot)
{
unsigned char *buf = *bufp;
int ret = 0;
switch (BodyState) {
case S_BODY_HDR:
UnMimeHeader(buf); /* Headers in body-parts can be encoded, too! */
if (strncasecmp("Content-Transfer-Encoding:", buf, 26) == 0) {
char *XferEnc;
XferEnc = nxtaddr(buf);
if ((XferEnc != NULL) && (strcasecmp(XferEnc, "quoted-printable") == 0)) {
CurrEncodingIsQP = 1;
SetEncoding8bit(buf);
}
}
else if ((*buf == '\0') || (*buf == '\n') || (strcmp(buf, "\r\n") == 0))
BodyState = S_BODY_DATA;
*bufp = (buf + strlen(buf));
break;
case S_BODY_DATA:
if ((*MultipartDelimiter) &&
(strncmp(buf, MultipartDelimiter, strlen(MultipartDelimiter)) == 0)) {
BodyState = S_BODY_HDR;
CurrEncodingIsQP = 0;
}
if (CurrEncodingIsQP)
ret = DoOneQPLine(bufp, collapsedoubledot);
else
*bufp = (buf + strlen(buf));
break;
}
return ret;
}
#ifdef STANDALONE
#include
#include
char *program_name = "unmime";
#define BUFSIZE_INCREMENT 4096
#ifdef DEBUG
#define DBG_FWRITE(B,L,BS,FD) fwrite(B, L, BS, FD)
#else
#define DBG_FWRITE(B,L,BS,FD)
#endif
int main(int argc, char *argv[])
{
unsigned int BufSize;
unsigned char *buffer, *buf_p;
int nl_count, i, bodytype;
#ifdef DEBUG
pid_t pid;
FILE *fd_orig, *fd_conv;
char fnam[100];
pid = getpid();
sprintf(fnam, "/tmp/i_unmime.%x", pid);
fd_orig = fopen(fnam, "w");
sprintf(fnam, "/tmp/o_unmime.%x", pid);
fd_conv = fopen(fnam, "w");
#endif
BufSize = BUFSIZE_INCREMENT; /* Initial size of buffer */
buf_p = buffer = (unsigned char *) xmalloc(BufSize);
nl_count = 0;
do {
i = fread(buf_p, 1, 1, stdin);
switch (*buf_p) {
case '\n':
nl_count++;
break;
case '\r':
break;
default:
nl_count = 0;
break;
}
buf_p++;
if ((buf_p - buffer) == BufSize) {
/* Buffer is full! Get more room. */
buffer = xrealloc(buffer, BufSize+BUFSIZE_INCREMENT);
buf_p = buffer + BufSize;
BufSize += BUFSIZE_INCREMENT;
}
} while ((i > 0) && (nl_count < 2));
*buf_p = '\0';
DBG_FWRITE(buffer, strlen(buffer), 1, fd_orig);
UnMimeHeader(buffer);
bodytype = MimeBodyType(buffer, 1);
i = strlen(buffer);
fwrite(buffer, i, 1, stdout);
DBG_FWRITE(buffer, i, 1, fd_conv);
do {
buf_p = (buffer - 1);
do {
buf_p++;
i = fread(buf_p, 1, 1, stdin);
} while ((i == 1) && (*buf_p != '\n'));
if (i == 1) buf_p++;
*buf_p = '\0';
DBG_FWRITE(buf, (buf_p - buffer), 1, fd_orig);
if (buf_p > buffer) {
if (bodytype & MSG_NEEDS_DECODE) {
buf_p = buffer;
UnMimeBodyline(&buf_p, 0);
}
fwrite(buffer, (buf_p - buffer), 1, stdout);
DBG_FWRITE(buffer, (buf_p - buffer), 1, fd_conv);
}
} while (buf_p > buffer);
free(buffer);
fflush(stdout);
#ifdef DEBUG
fclose(fd_orig);
fclose(fd_conv);
#endif
return 0;
}
#endif