/* $Cambridge: exim/exim-src/src/mime.c,v 1.15 2006/09/05 15:34:41 ph10 Exp $ */
/*************************************************
* Exim - an Internet mail transport agent *
*************************************************/
/* Copyright (c) Tom Kistner <tom@duncanthrax.net> 2004 */
/* License: GPL */
#include "exim.h"
#ifdef WITH_CONTENT_SCAN
#include "mime.h"
#include <sys/stat.h>
FILE *mime_stream = NULL;
uschar *mime_current_boundary = NULL;
/*************************************************
* set MIME anomaly level + text *
*************************************************/
/* Small wrapper to set the two expandables which
give info on detected "problems" in MIME
encodings. Those are defined in mime.h. */
void mime_set_anomaly(int level, char *text) {
mime_anomaly_level = level;
mime_anomaly_text = US text;
}
/*************************************************
* decode quoted-printable chars *
*************************************************/
/* gets called when we hit a =
returns: new pointer position
result code in c:
-2 - decode error
-1 - soft line break, no char
0-255 - char to write
*/
uschar *mime_decode_qp_char(uschar *qp_p, int *c) {
uschar *initial_pos = qp_p;
/* advance one char */
qp_p++;
/* Check for two hex digits and decode them */
if (isxdigit(*qp_p) && isxdigit(qp_p[1])) {
/* Do hex conversion */
if (isdigit(*qp_p)) {*c = *qp_p - '0';}
else {*c = toupper(*qp_p) - 'A' + 10;};
*c <<= 4;
if (isdigit(qp_p[1])) {*c |= qp_p[1] - '0';}
else {*c |= toupper(qp_p[1]) - 'A' + 10;};
return qp_p + 2;
};
/* tab or whitespace may follow just ignore it if it precedes \n */
while (*qp_p == '\t' || *qp_p == ' ' || *qp_p == '\r')
qp_p++;
if (*qp_p == '\n') {
/* hit soft line break */
*c = -1;
return qp_p;
};
/* illegal char here */
*c = -2;
return initial_pos;
}
uschar *mime_parse_line(uschar *buffer, uschar *data, uschar *encoding, int *num_decoded) {
if (encoding == NULL) {
/* no encoding type at all */
NO_DECODING:
memcpy(data, buffer, Ustrlen(buffer));
data[(Ustrlen(buffer))] = 0;
*num_decoded = Ustrlen(data);
return data;
}
else if (Ustrcmp(encoding,"base64") == 0) {
uschar *p = buffer;
int offset = 0;
/* ----- BASE64 ---------------------------------------------------- */
/* NULL out '\r' and '\n' chars */
while (Ustrrchr(p,'\r') != NULL) {
*(Ustrrchr(p,'\r')) = '\0';
};
while (Ustrrchr(p,'\n') != NULL) {
*(Ustrrchr(p,'\n')) = '\0';
};
while (*(p+offset) != '\0') {
/* hit illegal char ? */
if (mime_b64[*(p+offset)] == 128) {
mime_set_anomaly(MIME_ANOMALY_BROKEN_BASE64);
offset++;
}
else {
*p = mime_b64[*(p+offset)];
p++;
};
};
*p = 255;
/* line is translated, start bit shifting */
p = buffer;
*num_decoded = 0;
while(*p != 255) {
uschar tmp_c;
/* byte 0 ---------------------- */
if (*(p+1) == 255) {
break;
}
data[(*num_decoded)] = *p;
data[(*num_decoded)] <<= 2;
tmp_c = *(p+1);
tmp_c >>= 4;
data[(*num_decoded)] |= tmp_c;
(*num_decoded)++;
p++;
/* byte 1 ---------------------- */
if (*(p+1) == 255) {
break;
}
data[(*num_decoded)] = *p;
data[(*num_decoded)] <<= 4;
tmp_c = *(p+1);
tmp_c >>= 2;
data[(*num_decoded)] |= tmp_c;
(*num_decoded)++;
p++;
/* byte 2 ---------------------- */
if (*(p+1) == 255) {
break;
}
data[(*num_decoded)] = *p;
data[(*num_decoded)] <<= 6;
data[(*num_decoded)] |= *(p+1);
(*num_decoded)++;
p+=2;
};
return data;
/* ----------------------------------------------------------------- */
}
else if (Ustrcmp(encoding,"quoted-printable") == 0) {
uschar *p = buffer;
/* ----- QP -------------------------------------------------------- */
*num_decoded = 0;
while (*p != 0) {
if (*p == '=') {
int decode_qp_result;
p = mime_decode_qp_char(p,&decode_qp_result);
if (decode_qp_result == -2) {
/* Error from decoder. p is unchanged. */
mime_set_anomaly(MIME_ANOMALY_BROKEN_QP);
data[(*num_decoded)] = '=';
(*num_decoded)++;
p++;
}
else if (decode_qp_result == -1) {
break;
}
else if (decode_qp_result >= 0) {
data[(*num_decoded)] = decode_qp_result;
(*num_decoded)++;
};
}
else {
data[(*num_decoded)] = *p;
(*num_decoded)++;
p++;
};
};
return data;
/* ----------------------------------------------------------------- */
}
/* unknown encoding type, just dump as-is */
else goto NO_DECODING;
}
FILE *mime_get_decode_file(uschar *pname, uschar *fname) {
FILE *f = NULL;
uschar *filename;
filename = (uschar *)malloc(2048);
if ((pname != NULL) && (fname != NULL)) {
(void)string_format(filename, 2048, "%s/%s", pname, fname);
f = modefopen(filename,"wb+",SPOOL_MODE);
}
else if (pname == NULL) {
f = modefopen(fname,"wb+",SPOOL_MODE);
}
else if (fname == NULL) {
int file_nr = 0;
int result = 0;
/* must find first free sequential filename */
do {
struct stat mystat;
(void)string_format(filename,2048,"%s/%s-%05u", pname, message_id, file_nr);
file_nr++;
/* security break */
if (file_nr >= 1024)
break;
result = stat(CS filename,&mystat);
}
while(result != -1);
f = modefopen(filename,"wb+",SPOOL_MODE);
};
/* set expansion variable */
mime_decoded_filename = filename;
return f;
}
int mime_decode(uschar **listptr) {
int sep = 0;
uschar *list = *listptr;
uschar *option;
uschar option_buffer[1024];
uschar decode_path[1024];
FILE *decode_file = NULL;
uschar *buffer = NULL;
uschar *decode_buffer = NULL;
long f_pos = 0;
unsigned int size_counter = 0;
if (mime_stream == NULL)
return FAIL;
f_pos = ftell(mime_stream);
/* build default decode path (will exist since MBOX must be spooled up) */
(void)string_format(decode_path,1024,"%s/scan/%s",spool_directory,message_id);
/* reserve a line and decoder buffer to work in */
buffer = (uschar *)malloc(MIME_MAX_LINE_LENGTH+1);
if (buffer == NULL) {
log_write(0, LOG_PANIC,
"decode ACL condition: can't allocate %d bytes of memory.", MIME_MAX_LINE_LENGTH+1);
return DEFER;
};
decode_buffer = (uschar *)malloc(MIME_MAX_LINE_LENGTH+1);
if (decode_buffer == NULL) {
log_write(0, LOG_PANIC,
"decode ACL condition: can't allocate %d bytes of memory.", MIME_MAX_LINE_LENGTH+1);
return DEFER;
};
/* try to find 1st option */
if ((option = string_nextinlist(&list, &sep,
option_buffer,
sizeof(option_buffer))) != NULL) {
/* parse 1st option */
if ( (Ustrcmp(option,"false") == 0) || (Ustrcmp(option,"0") == 0) ) {
/* explicitly no decoding */
return FAIL;
};
if (Ustrcmp(option,"default") == 0) {
/* explicit default path + file names */
goto DEFAULT_PATH;
};
if (option[0] == '/') {
struct stat statbuf;
memset(&statbuf,0,sizeof(statbuf));
/* assume either path or path+file name */
if ( (stat(CS option, &statbuf) == 0) && S_ISDIR(statbuf.st_mode) )
/* is directory, use it as decode_path */
decode_file = mime_get_decode_file(option, NULL);
else
/* does not exist or is a file, use as full file name */
decode_file = mime_get_decode_file(NULL, option);
}
else
/* assume file name only, use default path */
decode_file = mime_get_decode_file(decode_path, option);
}
else
/* no option? patch default path */
DEFAULT_PATH: decode_file = mime_get_decode_file(decode_path, NULL);
if (decode_file == NULL)
return DEFER;
/* read data linewise and dump it to the file,
while looking for the current boundary */
while(fgets(CS buffer, MIME_MAX_LINE_LENGTH, mime_stream) != NULL) {
uschar *decoded_line = NULL;
int decoded_line_length = 0;
if (mime_current_boundary != NULL) {
/* boundary line must start with 2 dashes */
if (Ustrncmp(buffer,"--",2) == 0) {
if (Ustrncmp((buffer+2),mime_current_boundary,Ustrlen(mime_current_boundary)) == 0)
break;
};
};
decoded_line = mime_parse_line(buffer, decode_buffer, mime_content_transfer_encoding, &decoded_line_length);
/* write line to decode file */
if (fwrite(decoded_line, 1, decoded_line_length, decode_file) < decoded_line_length) {
/* error/short write */
clearerr(mime_stream);
fseek(mime_stream,f_pos,SEEK_SET);
return DEFER;
};
size_counter += decoded_line_length;
if (size_counter > 1023) {
if ((mime_content_size + (size_counter / 1024)) < 65535)
mime_content_size += (size_counter / 1024);
else
mime_content_size = 65535;
size_counter = (size_counter % 1024);
};
}
(void)fclose(decode_file);
clearerr(mime_stream);
fseek(mime_stream,f_pos,SEEK_SET);
/* round up remaining size bytes to one k */
if (size_counter) {
mime_content_size++;
};
return OK;
}
int mime_get_header(FILE *f, uschar *header) {
int c = EOF;
int done = 0;
int header_value_mode = 0;
int header_open_brackets = 0;
int num_copied = 0;
while(!done) {
c = fgetc(f);
if (c == EOF) break;
/* always skip CRs */
if (c == '\r') continue;
if (c == '\n') {
if (num_copied > 0) {
/* look if next char is '\t' or ' ' */
c = fgetc(f);
if (c == EOF) break;
if ( (c == '\t') || (c == ' ') ) continue;
(void)ungetc(c,f);
};
/* end of the header, terminate with ';' */
c = ';';
done = 1;
};
/* skip control characters */
if (c < 32) continue;
if (header_value_mode) {
/* --------- value mode ----------- */
/* skip leading whitespace */
if ( ((c == '\t') || (c == ' ')) && (header_value_mode == 1) )
continue;
/* we have hit a non-whitespace char, start copying value data */
header_value_mode = 2;
/* skip quotes */
if (c == '"') continue;
/* leave value mode on ';' */
if (c == ';') {
header_value_mode = 0;
};
/* -------------------------------- */
}
else {
/* -------- non-value mode -------- */
/* skip whitespace + tabs */
if ( (c == ' ') || (c == '\t') )
continue;
if (c == '\\') {
/* quote next char. can be used
to escape brackets. */
c = fgetc(f);
if (c == EOF) break;
}
else if (c == '(') {
header_open_brackets++;
continue;
}
else if ((c == ')') && header_open_brackets) {
header_open_brackets--;
continue;
}
else if ( (c == '=') && !header_open_brackets ) {
/* enter value mode */
header_value_mode = 1;
};
/* skip chars while we are in a comment */
if (header_open_brackets > 0)
continue;
/* -------------------------------- */
};
/* copy the char to the buffer */
header[num_copied] = (uschar)c;
/* raise counter */
num_copied++;
/* break if header buffer is full */
if (num_copied > MIME_MAX_HEADER_SIZE-1) {
done = 1;
};
};
if ((num_copied > 0) && (header[num_copied-1] != ';')) {
header[num_copied-1] = ';';
};
/* 0-terminate */
header[num_copied] = '\0';
/* return 0 for EOF or empty line */
if ((c == EOF) || (num_copied == 1))
return 0;
else
return 1;
}
int mime_acl_check(uschar *acl, FILE *f, struct mime_boundary_context *context,
uschar **user_msgptr, uschar **log_msgptr) {
int rc = OK;
uschar *header = NULL;
struct mime_boundary_context nested_context;
/* reserve a line buffer to work in */
header = (uschar *)malloc(MIME_MAX_HEADER_SIZE+1);
if (header == NULL) {
log_write(0, LOG_PANIC,
"MIME ACL: can't allocate %d bytes of memory.", MIME_MAX_HEADER_SIZE+1);
return DEFER;
};
/* Not actually used at the moment, but will be vital to fixing
* some RFC 2046 nonconformance later... */
nested_context.parent = context;
/* loop through parts */
while(1) {
/* reset all per-part mime variables */
mime_anomaly_level = 0;
mime_anomaly_text = NULL;
mime_boundary = NULL;
mime_charset = NULL;
mime_decoded_filename = NULL;
mime_filename = NULL;
mime_content_description = NULL;
mime_content_disposition = NULL;
mime_content_id = NULL;
mime_content_transfer_encoding = NULL;
mime_content_type = NULL;
mime_is_multipart = 0;
mime_content_size = 0;
/*
If boundary is null, we assume that *f is positioned on the start of headers (for example,
at the very beginning of a message.
If a boundary is given, we must first advance to it to reach the start of the next header
block.
*/
/* NOTE -- there's an error here -- RFC2046 specifically says to
* check for outer boundaries. This code doesn't do that, and
* I haven't fixed this.
*
* (I have moved partway towards adding support, however, by adding
* a "parent" field to my new boundary-context structure.)
*/
if (context != NULL) {
while(fgets(CS header, MIME_MAX_HEADER_SIZE, f) != NULL) {
/* boundary line must start with 2 dashes */
if (Ustrncmp(header,"--",2) == 0) {
if (Ustrncmp((header+2),context->boundary,Ustrlen(context->boundary)) == 0) {
/* found boundary */
if (Ustrncmp((header+2+Ustrlen(context->boundary)),"--",2) == 0) {
/* END boundary found */
debug_printf("End boundary found %s\n", context->boundary);
return rc;
}
else {
debug_printf("Next part with boundary %s\n", context->boundary);
};
/* can't use break here */
goto DECODE_HEADERS;
}
};
}
/* Hit EOF or read error. Ugh. */
debug_printf("Hit EOF ...\n");
return rc;
};
DECODE_HEADERS:
/* parse headers, set up expansion variables */
while(mime_get_header(f,header)) {
int i;
/* loop through header list */
for (i = 0; i < mime_header_list_size; i++) {
uschar *header_value = NULL;
int header_value_len = 0;
/* found an interesting header? */
if (strncmpic(mime_header_list[i].name,header,mime_header_list[i].namelen) == 0) {
uschar *p = header + mime_header_list[i].namelen;
/* yes, grab the value (normalize to lower case)
and copy to its corresponding expansion variable */
while(*p != ';') {
*p = tolower(*p);
p++;
};
header_value_len = (p - (header + mime_header_list[i].namelen));
header_value = (uschar *)malloc(header_value_len+1);
memset(header_value,0,header_value_len+1);
p = header + mime_header_list[i].namelen;
Ustrncpy(header_value, p, header_value_len);
debug_printf("Found %s MIME header, value is '%s'\n", mime_header_list[i].name, header_value);
*((uschar **)(mime_header_list[i].value)) = header_value;
/* make p point to the next character after the closing ';' */
p += (header_value_len+1);
/* grab all param=value tags on the remaining line, check if they are interesting */
NEXT_PARAM_SEARCH: while (*p != 0) {
int j;
for (j = 0; j < mime_parameter_list_size; j++) {
uschar *param_value = NULL;
int param_value_len = 0;
/* found an interesting parameter? */
if (strncmpic(mime_parameter_list[j].name,p,mime_parameter_list[j].namelen) == 0) {
uschar *q = p + mime_parameter_list[j].namelen;
/* yes, grab the value and copy to its corresponding expansion variable */
while(*q != ';') q++;
param_value_len = (q - (p + mime_parameter_list[j].namelen));
param_value = (uschar *)malloc(param_value_len+1);
memset(param_value,0,param_value_len+1);
q = p + mime_parameter_list[j].namelen;
Ustrncpy(param_value, q, param_value_len);
param_value = rfc2047_decode(param_value, check_rfc2047_length, NULL, 32, ¶m_value_len, &q);
debug_printf("Found %s MIME parameter in %s header, value is '%s'\n", mime_parameter_list[j].name, mime_header_list[i].name, param_value);
*((uschar **)(mime_parameter_list[j].value)) = param_value;
p += (mime_parameter_list[j].namelen + param_value_len + 1);
goto NEXT_PARAM_SEARCH;
};
}
/* There is something, but not one of our interesting parameters.
Advance to the next semicolon */
while(*p != ';') p++;
p++;
};
};
};
};
/* set additional flag variables (easier access) */
if ( (mime_content_type != NULL) &&
(Ustrncmp(mime_content_type,"multipart",9) == 0) )
mime_is_multipart = 1;
/* Make a copy of the boundary pointer.
Required since mime_boundary is global
and can be overwritten further down in recursion */
nested_context.boundary = mime_boundary;
/* raise global counter */
mime_part_count++;
/* copy current file handle to global variable */
mime_stream = f;
mime_current_boundary = context ? context->boundary : 0;
/* Note the context */
mime_is_coverletter = !(context && context->context == MBC_ATTACHMENT);
/* call ACL handling function */
rc = acl_check(ACL_WHERE_MIME, NULL, acl, user_msgptr, log_msgptr);
mime_stream = NULL;
mime_current_boundary = NULL;
if (rc != OK) break;
/* If we have a multipart entity and a boundary, go recursive */
if ( (mime_content_type != NULL) &&
(nested_context.boundary != NULL) &&
(Ustrncmp(mime_content_type,"multipart",9) == 0) ) {
debug_printf("Entering multipart recursion, boundary '%s'\n", nested_context.boundary);
if (context && context->context == MBC_ATTACHMENT)
nested_context.context = MBC_ATTACHMENT;
else if (!Ustrcmp(mime_content_type,"multipart/alternative")
|| !Ustrcmp(mime_content_type,"multipart/related"))
nested_context.context = MBC_COVERLETTER_ALL;
else
nested_context.context = MBC_COVERLETTER_ONESHOT;
rc = mime_acl_check(acl, f, &nested_context, user_msgptr, log_msgptr);
if (rc != OK) break;
}
else if ( (mime_content_type != NULL) &&
(Ustrncmp(mime_content_type,"message/rfc822",14) == 0) ) {
uschar *rfc822name = NULL;
uschar filename[2048];
int file_nr = 0;
int result = 0;
/* must find first free sequential filename */
do {
struct stat mystat;
(void)string_format(filename,2048,"%s/scan/%s/__rfc822_%05u", spool_directory, message_id, file_nr);
file_nr++;
/* security break */
if (file_nr >= 128)
goto NO_RFC822;
result = stat(CS filename,&mystat);
}
while(result != -1);
rfc822name = filename;
/* decode RFC822 attachment */
mime_decoded_filename = NULL;
mime_stream = f;
mime_current_boundary = context ? context->boundary : NULL;
mime_decode(&rfc822name);
mime_stream = NULL;
mime_current_boundary = NULL;
if (mime_decoded_filename == NULL) {
/* decoding failed */
log_write(0, LOG_MAIN,
"mime_regex acl condition warning - could not decode RFC822 MIME part to file.");
return DEFER;
};
mime_decoded_filename = NULL;
};
NO_RFC822:
/* If the boundary of this instance is NULL, we are finished here */
if (context == NULL) break;
if (context->context == MBC_COVERLETTER_ONESHOT)
context->context = MBC_ATTACHMENT;
};
return rc;
}
#endif
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