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Diffstat (limited to 'src/global/mime_state.c')
| -rw-r--r-- | src/global/mime_state.c | 1300 |
1 files changed, 1300 insertions, 0 deletions
diff --git a/src/global/mime_state.c b/src/global/mime_state.c new file mode 100644 index 0000000..e1b6a65 --- /dev/null +++ b/src/global/mime_state.c @@ -0,0 +1,1300 @@ +/*++ +/* NAME +/* mime_state 3 +/* SUMMARY +/* MIME parser state machine +/* SYNOPSIS +/* #include <mime_state.h> +/* +/* MIME_STATE *mime_state_alloc(flags, head_out, head_end, +/* body_out, body_end, +/* err_print, context) +/* int flags; +/* void (*head_out)(void *ptr, int header_class, +/* const HEADER_OPTS *header_info, +/* VSTRING *buf, off_t offset); +/* void (*head_end)(void *ptr); +/* void (*body_out)(void *ptr, int rec_type, +/* const char *buf, ssize_t len, +/* off_t offset); +/* void (*body_end)(void *ptr); +/* void (*err_print)(void *ptr, int err_flag, const char *text) +/* void *context; +/* +/* int mime_state_update(state, rec_type, buf, len) +/* MIME_STATE *state; +/* int rec_type; +/* const char *buf; +/* ssize_t len; +/* +/* MIME_STATE *mime_state_free(state) +/* MIME_STATE *state; +/* +/* const char *mime_state_error(error_code) +/* int error_code; +/* +/* typedef struct { +/* .in +4 +/* const int code; /* internal error code */ +/* const char *dsn; /* RFC 3463 */ +/* const char *text; /* descriptive text */ +/* .in -4 +/* } MIME_STATE_DETAIL; +/* +/* const MIME_STATE_DETAIL *mime_state_detail(error_code) +/* int error_code; +/* DESCRIPTION +/* This module implements a one-pass MIME processor with optional +/* 8-bit to quoted-printable conversion. +/* +/* In order to fend off denial of service attacks, message headers +/* are truncated at or above var_header_limit bytes, message boundary +/* strings are truncated at var_mime_bound_len bytes, and the multipart +/* nesting level is limited to var_mime_maxdepth levels. +/* +/* mime_state_alloc() creates a MIME state machine. The machine +/* is delivered in its initial state, expecting content type +/* text/plain, 7-bit data. +/* +/* mime_state_update() updates the MIME state machine according +/* to the input record type and the record content. +/* The result value is the bit-wise OR of zero or more of the following: +/* .IP MIME_ERR_TRUNC_HEADER +/* A message header was longer than var_header_limit bytes. +/* .IP MIME_ERR_NESTING +/* The MIME structure was nested more than var_mime_maxdepth levels. +/* .IP MIME_ERR_8BIT_IN_HEADER +/* A message header contains 8-bit data. This is always illegal. +/* .IP MIME_ERR_8BIT_IN_7BIT_BODY +/* A MIME header specifies (or defaults to) 7-bit content, but the +/* corresponding message body or body parts contain 8-bit content. +/* .IP MIME_ERR_ENCODING_DOMAIN +/* An entity of type "message" or "multipart" specifies the wrong +/* content transfer encoding domain, or specifies a transformation +/* (quoted-printable, base64) instead of a domain (7bit, 8bit, +/* or binary). +/* .PP +/* mime_state_free() releases storage for a MIME state machine, +/* and conveniently returns a null pointer. +/* +/* mime_state_error() returns a string representation for the +/* specified error code. When multiple errors are specified it +/* reports what it deems the most serious one. +/* +/* mime_state_detail() returns a table entry with error +/* information for the specified error code. When multiple +/* errors are specified it reports what it deems the most +/* serious one. +/* +/* Arguments: +/* .IP body_out +/* The output routine for body lines. It receives unmodified input +/* records, or the result of 8-bit -> 7-bit conversion. +/* .IP body_end +/* A null pointer, or a pointer to a routine that is called after +/* the last input record is processed. +/* .IP buf +/* Buffer with the content of a logical or physical message record. +/* .IP context +/* Caller context that is passed on to the head_out and body_out +/* routines. +/* .IP enc_type +/* The content encoding: MIME_ENC_7BIT or MIME_ENC_8BIT. +/* .IP err_print +/* Null pointer, or pointer to a function that is called with +/* arguments: the application context, the error type, and the +/* offending input. Only one instance per error type is reported. +/* .IP flags +/* Special processing options. Specify the bit-wise OR of zero or +/* more of the following: +/* .RS +/* .IP MIME_OPT_DISABLE_MIME +/* Pay no attention to Content-* message headers, and switch to +/* message body state at the end of the primary message headers. +/* .IP MIME_OPT_REPORT_TRUNC_HEADER +/* Report errors that set the MIME_ERR_TRUNC_HEADER error flag +/* (see above). +/* .IP MIME_OPT_REPORT_8BIT_IN_HEADER +/* Report errors that set the MIME_ERR_8BIT_IN_HEADER error +/* flag (see above). This rarely stops legitimate mail. +/* .IP MIME_OPT_REPORT_8BIT_IN_7BIT_BODY +/* Report errors that set the MIME_ERR_8BIT_IN_7BIT_BODY error +/* flag (see above). This currently breaks Majordomo mail that is +/* forwarded for approval, because Majordomo does not propagate +/* MIME type information from the enclosed message to the message +/* headers of the request for approval. +/* .IP MIME_OPT_REPORT_ENCODING_DOMAIN +/* Report errors that set the MIME_ERR_ENCODING_DOMAIN error +/* flag (see above). +/* .IP MIME_OPT_REPORT_NESTING +/* Report errors that set the MIME_ERR_NESTING error flag +/* (see above). +/* .IP MIME_OPT_DOWNGRADE +/* Transform content that claims to be 8-bit into quoted-printable. +/* Where appropriate, update Content-Transfer-Encoding: message +/* headers. +/* .RE +/* .sp +/* For convenience, MIME_OPT_NONE requests no special processing. +/* .IP header_class +/* Specifies where a message header is located. +/* .RS +/* .IP MIME_HDR_PRIMARY +/* In the primary message header section. +/* .IP MIME_HDR_MULTIPART +/* In the header section after a multipart boundary string. +/* .IP MIME_HDR_NESTED +/* At the start of a nested (e.g., message/rfc822) message. +/* .RE +/* .sp +/* For convenience, the macros MIME_HDR_FIRST and MIME_HDR_LAST +/* specify the range of MIME_HDR_MUMBLE macros. +/* .sp +/* To find out if something is a MIME header at the beginning +/* of an RFC 822 message or an attached message, look at the +/* header_info argument. +/* .IP header_info +/* Null pointer or information about the message header, see +/* header_opts(3). +/* .IP head_out +/* The output routine that is invoked for outputting a message header. +/* A multi-line header is passed as one chunk of text with embedded +/* newlines. +/* It is the responsibility of the output routine to break the text +/* at embedded newlines, and to break up long text between newlines +/* into multiple output records. +/* Note: an output routine is explicitly allowed to modify the text. +/* .IP head_end +/* A null pointer, or a pointer to a routine that is called after +/* the last message header in the first header block is processed. +/* .IP len +/* Length of non-VSTRING input buffer. +/* .IP offset +/* The offset in bytes from the start of the current block of message +/* headers or body lines. Line boundaries are counted as one byte. +/* .IP rec_type +/* The input record type as defined in rec_type(3h). State is +/* updated for text records (REC_TYPE_NORM or REC_TYPE_CONT). +/* Some input records are stored internally in order to reconstruct +/* multi-line input. Upon receipt of any non-text record type, all +/* stored input is flushed and the state is set to "body". +/* .IP state +/* MIME parser state created with mime_state_alloc(). +/* BUGS +/* NOTE: when the end of headers is reached, mime_state_update() +/* may execute up to three call-backs before returning to the +/* caller: head_out(), head_end(), and body_out() or body_end(). +/* As long as call-backs return no result, it is up to the +/* call-back routines to check if a previous call-back experienced +/* an error. +/* +/* Different mail user agents treat malformed message boundary +/* strings in different ways. The Postfix MIME processor cannot +/* be bug-compatible with everything. +/* +/* This module will not glue together multipart boundary strings that +/* span multiple input records. +/* +/* This module will not glue together RFC 2231 formatted (boundary) +/* parameter values. RFC 2231 claims compatibility with existing +/* MIME processors. Splitting boundary strings is not backwards +/* compatible. +/* +/* The "8-bit data inside 7-bit body" test is myopic. It is not aware +/* of any enclosing (message or multipart) encoding information. +/* +/* If the input ends in data other than a hard line break, this module +/* will add a hard line break of its own. No line break is added to +/* empty input. +/* +/* This code recognizes the obsolete form "headername :" but will +/* normalize it to the canonical form "headername:". Leaving the +/* obsolete form alone would cause too much trouble with existing code +/* that expects only the normalized form. +/* SEE ALSO +/* msg(3) diagnostics interface +/* header_opts(3) header information lookup +/* RFC 822 (ARPA Internet Text Messages) +/* RFC 2045 (MIME: Format of internet message bodies) +/* RFC 2046 (MIME: Media types) +/* DIAGNOSTICS +/* Fatal errors: memory allocation problem. +/* LICENSE +/* .ad +/* .fi +/* The Secure Mailer license must be distributed with this software. +/* HISTORY +/* .ad +/* .fi +/* This code was implemented from scratch after reading the RFC +/* documents. This was a relatively straightforward effort with +/* few if any surprises. Victor Duchovni of Morgan Stanley shared +/* his experiences with ambiguities in real-life MIME implementations. +/* Liviu Daia of the Romanian Academy shared his insights in some +/* of the darker corners. +/* AUTHOR(S) +/* Wietse Venema +/* IBM T.J. Watson Research +/* P.O. Box 704 +/* Yorktown Heights, NY 10598, USA +/* +/* Wietse Venema +/* Google, Inc. +/* 111 8th Avenue +/* New York, NY 10011, USA +/*--*/ + +/* System library. */ + +#include <sys_defs.h> +#include <stdarg.h> +#include <ctype.h> +#include <string.h> + +#ifdef STRCASECMP_IN_STRINGS_H +#include <strings.h> +#endif + +/* Utility library. */ + +#include <mymalloc.h> +#include <msg.h> +#include <vstring.h> + +/* Global library. */ + +#include <rec_type.h> +#include <is_header.h> +#include <header_opts.h> +#include <mail_params.h> +#include <header_token.h> +#include <lex_822.h> +#include <mime_state.h> + +/* Application-specific. */ + + /* + * Mime parser stack element for multipart content. + */ +typedef struct MIME_STACK { + int def_ctype; /* default content type */ + int def_stype; /* default content subtype */ + char *boundary; /* boundary string */ + ssize_t bound_len; /* boundary length */ + struct MIME_STACK *next; /* linkage */ +} MIME_STACK; + + /* + * Mime parser state. + */ +#define MIME_MAX_TOKEN 3 /* tokens per attribute */ + +struct MIME_STATE { + + /* + * Volatile members. + */ + int curr_state; /* header/body state */ + int curr_ctype; /* last or default content type */ + int curr_stype; /* last or default content subtype */ + int curr_encoding; /* last or default content encoding */ + int curr_domain; /* last or default encoding unit */ + VSTRING *output_buffer; /* headers, quoted-printable body */ + int prev_rec_type; /* previous input record type */ + int nesting_level; /* safety */ + MIME_STACK *stack; /* for composite types */ + HEADER_TOKEN token[MIME_MAX_TOKEN]; /* header token array */ + VSTRING *token_buffer; /* header parser scratch buffer */ + int err_flags; /* processing errors */ + off_t head_offset; /* offset in header block */ + off_t body_offset; /* offset in body block */ + + /* + * Static members. + */ + int static_flags; /* static processing options */ + MIME_STATE_HEAD_OUT head_out; /* header output routine */ + MIME_STATE_ANY_END head_end; /* end of primary header routine */ + MIME_STATE_BODY_OUT body_out; /* body output routine */ + MIME_STATE_ANY_END body_end; /* end of body output routine */ + MIME_STATE_ERR_PRINT err_print; /* error report */ + void *app_context; /* application context */ +}; + + /* + * Content types and subtypes that we care about, either because we have to, + * or because we want to filter out broken MIME messages. + */ +#define MIME_CTYPE_OTHER 0 +#define MIME_CTYPE_TEXT 1 +#define MIME_CTYPE_MESSAGE 2 +#define MIME_CTYPE_MULTIPART 3 + +#define MIME_STYPE_OTHER 0 +#define MIME_STYPE_PLAIN 1 +#define MIME_STYPE_RFC822 2 +#define MIME_STYPE_PARTIAL 3 +#define MIME_STYPE_EXTERN_BODY 4 +#define MIME_STYPE_GLOBAL 5 + + /* + * MIME parser states. We steal from the public interface. + */ +#define MIME_STATE_PRIMARY MIME_HDR_PRIMARY /* primary headers */ +#define MIME_STATE_MULTIPART MIME_HDR_MULTIPART /* after --boundary */ +#define MIME_STATE_NESTED MIME_HDR_NESTED /* message/rfc822 */ +#define MIME_STATE_BODY (MIME_HDR_NESTED + 1) + +#define SET_MIME_STATE(ptr, state, ctype, stype, encoding, domain) do { \ + (ptr)->curr_state = (state); \ + (ptr)->curr_ctype = (ctype); \ + (ptr)->curr_stype = (stype); \ + (ptr)->curr_encoding = (encoding); \ + (ptr)->curr_domain = (domain); \ + if ((state) == MIME_STATE_BODY) \ + (ptr)->body_offset = 0; \ + else \ + (ptr)->head_offset = 0; \ + } while (0) + +#define SET_CURR_STATE(ptr, state) do { \ + (ptr)->curr_state = (state); \ + if ((state) == MIME_STATE_BODY) \ + (ptr)->body_offset = 0; \ + else \ + (ptr)->head_offset = 0; \ + } while (0) + + /* + * MIME encodings and domains. We intentionally use the same codes for + * encodings and domains, so that we can easily find out whether a content + * transfer encoding header specifies a domain or whether it specifies + * domain+encoding, which is illegal for multipart/any and message/any. + */ +typedef struct MIME_ENCODING { + const char *name; /* external representation */ + int encoding; /* internal representation */ + int domain; /* subset of encoding */ +} MIME_ENCODING; + +#define MIME_ENC_QP 1 /* encoding + domain */ +#define MIME_ENC_BASE64 2 /* encoding + domain */ + /* These are defined in mime_state.h as part of the external interface. */ +#ifndef MIME_ENC_7BIT +#define MIME_ENC_7BIT 7 /* domain only */ +#define MIME_ENC_8BIT 8 /* domain only */ +#define MIME_ENC_BINARY 9 /* domain only */ +#endif + +static const MIME_ENCODING mime_encoding_map[] = { /* RFC 2045 */ + "7bit", MIME_ENC_7BIT, MIME_ENC_7BIT, /* domain */ + "8bit", MIME_ENC_8BIT, MIME_ENC_8BIT, /* domain */ + "binary", MIME_ENC_BINARY, MIME_ENC_BINARY, /* domain */ + "base64", MIME_ENC_BASE64, MIME_ENC_7BIT, /* encoding */ + "quoted-printable", MIME_ENC_QP, MIME_ENC_7BIT, /* encoding */ + 0, +}; + + /* + * Silly Little Macros. + */ +#define STR(x) vstring_str(x) +#define LEN(x) VSTRING_LEN(x) +#define END(x) vstring_end(x) +#define CU_CHAR_PTR(x) ((const unsigned char *) (x)) + +#define REPORT_ERROR_LEN(state, err_type, text, len) do { \ + if ((state->err_flags & err_type) == 0) { \ + if (state->err_print != 0) \ + state->err_print(state->app_context, err_type, text, len); \ + state->err_flags |= err_type; \ + } \ + } while (0) + +#define REPORT_ERROR(state, err_type, text) do { \ + const char *_text = text; \ + ssize_t _len = strlen(text); \ + REPORT_ERROR_LEN(state, err_type, _text, _len); \ + } while (0) + +#define REPORT_ERROR_BUF(state, err_type, buf) \ + REPORT_ERROR_LEN(state, err_type, STR(buf), LEN(buf)) + + + /* + * Outputs and state changes are interleaved, so we must maintain separate + * offsets for header and body segments. + */ +#define HEAD_OUT(ptr, info, len) do { \ + if ((ptr)->head_out) { \ + (ptr)->head_out((ptr)->app_context, (ptr)->curr_state, \ + (info), (ptr)->output_buffer, (ptr)->head_offset); \ + (ptr)->head_offset += (len) + 1; \ + } \ + } while(0) + +#define BODY_OUT(ptr, rec_type, text, len) do { \ + if ((ptr)->body_out) { \ + (ptr)->body_out((ptr)->app_context, (rec_type), \ + (text), (len), (ptr)->body_offset); \ + (ptr)->body_offset += (len) + 1; \ + } \ + } while(0) + +/* mime_state_push - push boundary onto stack */ + +static void mime_state_push(MIME_STATE *state, int def_ctype, int def_stype, + const char *boundary) +{ + MIME_STACK *stack; + + /* + * RFC 2046 mandates that a boundary string be up to 70 characters long. + * Some MTAs, including Postfix, include the fully-qualified MTA name + * which can be longer, so we are willing to handle boundary strings that + * exceed the RFC specification. We allow for message headers of up to + * var_header_limit characters. In order to avoid denial of service, we + * have to impose a configurable limit on the amount of text that we are + * willing to store as a boundary string. Despite this truncation way we + * will still correctly detect all intermediate boundaries and all the + * message headers that follow those boundaries. + */ + state->nesting_level += 1; + stack = (MIME_STACK *) mymalloc(sizeof(*stack)); + stack->def_ctype = def_ctype; + stack->def_stype = def_stype; + if ((stack->bound_len = strlen(boundary)) > var_mime_bound_len) + stack->bound_len = var_mime_bound_len; + stack->boundary = mystrndup(boundary, stack->bound_len); + stack->next = state->stack; + state->stack = stack; + if (msg_verbose) + msg_info("PUSH boundary %s", stack->boundary); +} + +/* mime_state_pop - pop boundary from stack */ + +static void mime_state_pop(MIME_STATE *state) +{ + MIME_STACK *stack; + + if ((stack = state->stack) == 0) + msg_panic("mime_state_pop: there is no stack"); + if (msg_verbose) + msg_info("POP boundary %s", stack->boundary); + state->nesting_level -= 1; + state->stack = stack->next; + myfree(stack->boundary); + myfree((void *) stack); +} + +/* mime_state_alloc - create MIME state machine */ + +MIME_STATE *mime_state_alloc(int flags, + MIME_STATE_HEAD_OUT head_out, + MIME_STATE_ANY_END head_end, + MIME_STATE_BODY_OUT body_out, + MIME_STATE_ANY_END body_end, + MIME_STATE_ERR_PRINT err_print, + void *context) +{ + MIME_STATE *state; + + state = (MIME_STATE *) mymalloc(sizeof(*state)); + + /* Volatile members. */ + state->err_flags = 0; + state->body_offset = 0; /* XXX */ + SET_MIME_STATE(state, MIME_STATE_PRIMARY, + MIME_CTYPE_TEXT, MIME_STYPE_PLAIN, + MIME_ENC_7BIT, MIME_ENC_7BIT); + state->output_buffer = vstring_alloc(100); + state->prev_rec_type = 0; + state->stack = 0; + state->token_buffer = vstring_alloc(1); + state->nesting_level = -1; /* BC Fix 20170512 */ + + /* Static members. */ + state->static_flags = flags; + state->head_out = head_out; + state->head_end = head_end; + state->body_out = body_out; + state->body_end = body_end; + state->err_print = err_print; + state->app_context = context; + return (state); +} + +/* mime_state_free - destroy MIME state machine */ + +MIME_STATE *mime_state_free(MIME_STATE *state) +{ + vstring_free(state->output_buffer); + while (state->stack) + mime_state_pop(state); + if (state->token_buffer) + vstring_free(state->token_buffer); + myfree((void *) state); + return (0); +} + +/* mime_state_content_type - process content-type header */ + +static void mime_state_content_type(MIME_STATE *state, + const HEADER_OPTS *header_info) +{ + const char *cp; + ssize_t tok_count; + int def_ctype; + int def_stype; + +#define TOKEN_MATCH(tok, text) \ + ((tok).type == HEADER_TOK_TOKEN && strcasecmp((tok).u.value, (text)) == 0) + +#define RFC2045_TSPECIALS "()<>@,;:\\\"/[]?=" + +#define PARSE_CONTENT_TYPE_HEADER(state, ptr) \ + header_token(state->token, MIME_MAX_TOKEN, \ + state->token_buffer, ptr, RFC2045_TSPECIALS, ';') + + cp = STR(state->output_buffer) + strlen(header_info->name) + 1; + if ((tok_count = PARSE_CONTENT_TYPE_HEADER(state, &cp)) > 0) { + + /* + * text/whatever. Right now we don't really care if it is plain or + * not, but we may want to recognize subtypes later, and then this + * code can serve as an example. + */ + if (TOKEN_MATCH(state->token[0], "text")) { + state->curr_ctype = MIME_CTYPE_TEXT; + if (tok_count >= 3 + && state->token[1].type == '/' + && TOKEN_MATCH(state->token[2], "plain")) + state->curr_stype = MIME_STYPE_PLAIN; + else + state->curr_stype = MIME_STYPE_OTHER; + return; + } + + /* + * message/whatever body parts start with another block of message + * headers that we may want to look at. The partial and external-body + * subtypes cannot be subjected to 8-bit -> 7-bit conversion, so we + * must properly recognize them. + */ + if (TOKEN_MATCH(state->token[0], "message")) { + state->curr_ctype = MIME_CTYPE_MESSAGE; + state->curr_stype = MIME_STYPE_OTHER; + if (tok_count >= 3 + && state->token[1].type == '/') { + if (TOKEN_MATCH(state->token[2], "rfc822")) + state->curr_stype = MIME_STYPE_RFC822; + else if (TOKEN_MATCH(state->token[2], "partial")) + state->curr_stype = MIME_STYPE_PARTIAL; + else if (TOKEN_MATCH(state->token[2], "external-body")) + state->curr_stype = MIME_STYPE_EXTERN_BODY; + else if (TOKEN_MATCH(state->token[2], "global")) + state->curr_stype = MIME_STYPE_GLOBAL; + } + return; + } + + /* + * multipart/digest has default content type message/rfc822, + * multipart/whatever has default content type text/plain. + */ + if (TOKEN_MATCH(state->token[0], "multipart")) { + state->curr_ctype = MIME_CTYPE_MULTIPART; + if (tok_count >= 3 + && state->token[1].type == '/' + && TOKEN_MATCH(state->token[2], "digest")) { + def_ctype = MIME_CTYPE_MESSAGE; + def_stype = MIME_STYPE_RFC822; + } else { + def_ctype = MIME_CTYPE_TEXT; + def_stype = MIME_STYPE_PLAIN; + } + + /* + * Yes, this is supposed to capture multiple boundary strings, + * which are illegal and which could be used to hide content in + * an implementation dependent manner. The code below allows us + * to find embedded message headers as long as the sender uses + * only one of these same-level boundary strings. + * + * Yes, this is supposed to ignore the boundary value type. + */ + while ((tok_count = PARSE_CONTENT_TYPE_HEADER(state, &cp)) >= 0) { + if (tok_count >= 3 + && TOKEN_MATCH(state->token[0], "boundary") + && state->token[1].type == '=') { + if (state->nesting_level > var_mime_maxdepth) { + if (state->static_flags & MIME_OPT_REPORT_NESTING) + REPORT_ERROR_BUF(state, MIME_ERR_NESTING, + state->output_buffer); + } else { + mime_state_push(state, def_ctype, def_stype, + state->token[2].u.value); + } + } + } + } + return; + } + + /* + * other/whatever. + */ + else { + state->curr_ctype = MIME_CTYPE_OTHER; + return; + } +} + +/* mime_state_content_encoding - process content-transfer-encoding header */ + +static void mime_state_content_encoding(MIME_STATE *state, + const HEADER_OPTS *header_info) +{ + const char *cp; + const MIME_ENCODING *cmp; + +#define PARSE_CONTENT_ENCODING_HEADER(state, ptr) \ + header_token(state->token, 1, state->token_buffer, ptr, (char *) 0, 0) + + /* + * Do content-transfer-encoding header. Never set the encoding domain to + * something other than 7bit, 8bit or binary, even if we don't recognize + * the input. + */ + cp = STR(state->output_buffer) + strlen(header_info->name) + 1; + if (PARSE_CONTENT_ENCODING_HEADER(state, &cp) > 0 + && state->token[0].type == HEADER_TOK_TOKEN) { + for (cmp = mime_encoding_map; cmp->name != 0; cmp++) { + if (strcasecmp(state->token[0].u.value, cmp->name) == 0) { + state->curr_encoding = cmp->encoding; + state->curr_domain = cmp->domain; + break; + } + } + } +} + +/* mime_state_enc_name - encoding to printable form */ + +static const char *mime_state_enc_name(int encoding) +{ + const MIME_ENCODING *cmp; + + for (cmp = mime_encoding_map; cmp->name != 0; cmp++) + if (encoding == cmp->encoding) + return (cmp->name); + return ("unknown"); +} + +/* mime_state_downgrade - convert 8-bit data to quoted-printable */ + +static void mime_state_downgrade(MIME_STATE *state, int rec_type, + const char *text, ssize_t len) +{ + static char hexchars[] = "0123456789ABCDEF"; + const unsigned char *cp; + int ch; + +#define QP_ENCODE(buffer, ch) { \ + VSTRING_ADDCH(buffer, '='); \ + VSTRING_ADDCH(buffer, hexchars[(ch >> 4) & 0xff]); \ + VSTRING_ADDCH(buffer, hexchars[ch & 0xf]); \ + } + + /* + * Insert a soft line break when the output reaches a critical length + * before we reach a hard line break. + */ + for (cp = CU_CHAR_PTR(text); cp < CU_CHAR_PTR(text + len); cp++) { + /* Critical length before hard line break. */ + if (LEN(state->output_buffer) > 72) { + VSTRING_ADDCH(state->output_buffer, '='); + VSTRING_TERMINATE(state->output_buffer); + BODY_OUT(state, REC_TYPE_NORM, + STR(state->output_buffer), + LEN(state->output_buffer)); + VSTRING_RESET(state->output_buffer); + } + /* Append the next character. */ + ch = *cp; + if ((ch < 32 && ch != '\t') || ch == '=' || ch > 126) { + QP_ENCODE(state->output_buffer, ch); + } else { + VSTRING_ADDCH(state->output_buffer, ch); + } + } + + /* + * Flush output after a hard line break (i.e. the end of a REC_TYPE_NORM + * record). Fix trailing whitespace as per the RFC: in the worst case, + * the output length will grow from 73 characters to 75 characters. + */ + if (rec_type == REC_TYPE_NORM) { + if (LEN(state->output_buffer) > 0 + && ((ch = END(state->output_buffer)[-1]) == ' ' || ch == '\t')) { + vstring_truncate(state->output_buffer, + LEN(state->output_buffer) - 1); + QP_ENCODE(state->output_buffer, ch); + } + VSTRING_TERMINATE(state->output_buffer); + BODY_OUT(state, REC_TYPE_NORM, + STR(state->output_buffer), + LEN(state->output_buffer)); + VSTRING_RESET(state->output_buffer); + } +} + +/* mime_state_update - update MIME state machine */ + +int mime_state_update(MIME_STATE *state, int rec_type, + const char *text, ssize_t len) +{ + int input_is_text = (rec_type == REC_TYPE_NORM + || rec_type == REC_TYPE_CONT); + MIME_STACK *sp; + const HEADER_OPTS *header_info; + const unsigned char *cp; + +#define SAVE_PREV_REC_TYPE_AND_RETURN_ERR_FLAGS(state, rec_type) do { \ + state->prev_rec_type = rec_type; \ + return (state->err_flags); \ + } while (0) + + /* + * Be sure to flush any partial output line that might still be buffered + * up before taking any other "end of input" actions. + */ + if (!input_is_text && state->prev_rec_type == REC_TYPE_CONT) + mime_state_update(state, REC_TYPE_NORM, "", 0); + + /* + * This message state machine is kept simple for the sake of robustness. + * Standards evolve over time, and we want to be able to correctly + * process messages that are not yet defined. This state machine knows + * about headers and bodies, understands that multipart/whatever has + * multiple body parts with a header and body, and that message/whatever + * has message headers at the start of a body part. + */ + switch (state->curr_state) { + + /* + * First, deal with header information that we have accumulated from + * previous input records. Discard text that does not fit in a header + * buffer. Our limit is quite generous; Sendmail will refuse mail + * with only 32kbyte in all the message headers combined. + */ + case MIME_STATE_PRIMARY: + case MIME_STATE_MULTIPART: + case MIME_STATE_NESTED: + if (LEN(state->output_buffer) > 0) { + if (input_is_text) { + if (state->prev_rec_type == REC_TYPE_CONT) { + if (LEN(state->output_buffer) < var_header_limit) { + vstring_strncat(state->output_buffer, text, len); + } else { + if (state->static_flags & MIME_OPT_REPORT_TRUNC_HEADER) + REPORT_ERROR_BUF(state, MIME_ERR_TRUNC_HEADER, + state->output_buffer); + } + SAVE_PREV_REC_TYPE_AND_RETURN_ERR_FLAGS(state, rec_type); + } + if (IS_SPACE_TAB(*text)) { + if (LEN(state->output_buffer) < var_header_limit) { + vstring_strcat(state->output_buffer, "\n"); + vstring_strncat(state->output_buffer, text, len); + } else { + if (state->static_flags & MIME_OPT_REPORT_TRUNC_HEADER) + REPORT_ERROR_BUF(state, MIME_ERR_TRUNC_HEADER, + state->output_buffer); + } + SAVE_PREV_REC_TYPE_AND_RETURN_ERR_FLAGS(state, rec_type); + } + } + + /* + * The input is (the beginning of) another message header, or is + * not a message header, or is not even a text record. With no + * more input to append to this saved header, do output + * processing and reset the saved header buffer. Hold on to the + * content transfer encoding header if we have to do a 8->7 + * transformation, because the proper information depends on the + * content type header: message and multipart require a domain, + * leaf entities have either a transformation or a domain. + */ + if (LEN(state->output_buffer) > 0) { + header_info = header_opts_find(STR(state->output_buffer)); + if (!(state->static_flags & MIME_OPT_DISABLE_MIME) + && header_info != 0) { + if (header_info->type == HDR_CONTENT_TYPE) + mime_state_content_type(state, header_info); + if (header_info->type == HDR_CONTENT_TRANSFER_ENCODING) + mime_state_content_encoding(state, header_info); + } + if ((state->static_flags & MIME_OPT_REPORT_8BIT_IN_HEADER) != 0 + && (state->err_flags & MIME_ERR_8BIT_IN_HEADER) == 0) { + for (cp = CU_CHAR_PTR(STR(state->output_buffer)); + cp < CU_CHAR_PTR(END(state->output_buffer)); cp++) + if (*cp & 0200) { + REPORT_ERROR_BUF(state, MIME_ERR_8BIT_IN_HEADER, + state->output_buffer); + break; + } + } + /* Output routine is explicitly allowed to change the data. */ + if (header_info == 0 + || header_info->type != HDR_CONTENT_TRANSFER_ENCODING + || (state->static_flags & MIME_OPT_DOWNGRADE) == 0 + || state->curr_domain == MIME_ENC_7BIT) + HEAD_OUT(state, header_info, len); + state->prev_rec_type = 0; + VSTRING_RESET(state->output_buffer); + } + } + + /* + * With past header information moved out of the way, proceed with a + * clean slate. + */ + if (input_is_text) { + ssize_t header_len; + + /* + * See if this input is (the beginning of) a message header. + * + * Normalize obsolete "name space colon" syntax to "name colon". + * Things would be too confusing otherwise. + * + * Don't assume that the input is null terminated. + */ + if ((header_len = is_header_buf(text, len)) > 0) { + vstring_strncpy(state->output_buffer, text, header_len); + for (text += header_len, len -= header_len; + len > 0 && IS_SPACE_TAB(*text); + text++, len--) + /* void */ ; + vstring_strncat(state->output_buffer, text, len); + SAVE_PREV_REC_TYPE_AND_RETURN_ERR_FLAGS(state, rec_type); + } + } + + /* + * This input terminates a block of message headers. When converting + * 8-bit to 7-bit mail, this is the right place to emit the correct + * content-transfer-encoding header. With message or multipart we + * specify 7bit, with leaf entities we specify quoted-printable. + * + * We're not going to convert non-text data into base 64. If they send + * arbitrary binary data as 8-bit text, then the data is already + * broken beyond recovery, because the Postfix SMTP server sanitizes + * record boundaries, treating broken record boundaries as CRLF. + * + * Clear the output buffer, we will need it for storage of the + * conversion result. + */ + if ((state->static_flags & MIME_OPT_DOWNGRADE) + && state->curr_domain != MIME_ENC_7BIT) { + if ((state->curr_ctype == MIME_CTYPE_MESSAGE + && state->curr_stype != MIME_STYPE_GLOBAL) + || state->curr_ctype == MIME_CTYPE_MULTIPART) + cp = CU_CHAR_PTR("7bit"); + else + cp = CU_CHAR_PTR("quoted-printable"); + vstring_sprintf(state->output_buffer, + "Content-Transfer-Encoding: %s", cp); + HEAD_OUT(state, (HEADER_OPTS *) 0, len); + VSTRING_RESET(state->output_buffer); + } + + /* + * This input terminates a block of message headers. Call the + * optional header end routine at the end of the first header block. + */ + if (state->curr_state == MIME_STATE_PRIMARY && state->head_end) + state->head_end(state->app_context); + + /* + * This is the right place to check if the sender specified an + * appropriate identity encoding (7bit, 8bit, binary) for multipart + * and for message. + */ + if (state->static_flags & MIME_OPT_REPORT_ENCODING_DOMAIN) { + if (state->curr_ctype == MIME_CTYPE_MESSAGE) { + if (state->curr_stype == MIME_STYPE_PARTIAL + || state->curr_stype == MIME_STYPE_EXTERN_BODY) { + if (state->curr_domain != MIME_ENC_7BIT) + REPORT_ERROR(state, MIME_ERR_ENCODING_DOMAIN, + mime_state_enc_name(state->curr_encoding)); + } + /* EAI: message/global allows non-identity encoding. */ + else if (state->curr_stype == MIME_STYPE_RFC822) { + if (state->curr_encoding != state->curr_domain) + REPORT_ERROR(state, MIME_ERR_ENCODING_DOMAIN, + mime_state_enc_name(state->curr_encoding)); + } + } else if (state->curr_ctype == MIME_CTYPE_MULTIPART) { + if (state->curr_encoding != state->curr_domain) + REPORT_ERROR(state, MIME_ERR_ENCODING_DOMAIN, + mime_state_enc_name(state->curr_encoding)); + } + } + + /* + * Find out if the next body starts with its own message headers. In + * aggressive mode, examine headers of partial and external-body + * messages. Otherwise, treat such headers as part of the "body". Set + * the proper encoding information for the multipart prolog. + * + * XXX We parse headers inside message/* content even when the encoding + * is invalid (encoding != domain). With base64 we won't recognize + * any headers, and with quoted-printable we won't recognize MIME + * boundary strings, but the MIME processor will still resynchronize + * when it runs into the higher-level boundary string at the end of + * the message/* content. Although we will treat some headers as body + * text, we will still do a better job than if we were treating the + * entire message/* content as body text. + * + * XXX This changes state to MIME_STATE_NESTED and then outputs a body + * line, so that the body offset is not properly reset. + * + * Don't assume that the input is null terminated. + */ + if (input_is_text) { + if (len == 0) { + state->body_offset = 0; /* XXX */ + if (state->curr_ctype == MIME_CTYPE_MESSAGE) { + if (state->curr_stype == MIME_STYPE_RFC822) + SET_MIME_STATE(state, MIME_STATE_NESTED, + MIME_CTYPE_TEXT, MIME_STYPE_PLAIN, + MIME_ENC_7BIT, MIME_ENC_7BIT); + else if (state->curr_stype == MIME_STYPE_GLOBAL + && ((state->static_flags & MIME_OPT_DOWNGRADE) == 0 + || state->curr_domain == MIME_ENC_7BIT)) + /* XXX EAI: inspect encoded message/global. */ + SET_MIME_STATE(state, MIME_STATE_NESTED, + MIME_CTYPE_TEXT, MIME_STYPE_PLAIN, + MIME_ENC_7BIT, MIME_ENC_7BIT); + else + SET_CURR_STATE(state, MIME_STATE_BODY); + } else if (state->curr_ctype == MIME_CTYPE_MULTIPART) { + SET_MIME_STATE(state, MIME_STATE_BODY, + MIME_CTYPE_OTHER, MIME_STYPE_OTHER, + MIME_ENC_7BIT, MIME_ENC_7BIT); + } else { + SET_CURR_STATE(state, MIME_STATE_BODY); + } + } + + /* + * Invalid input. Force output of one blank line and jump to the + * body state, leaving all other state alone. + * + * We don't break legitimate mail by inserting a blank line + * separator between primary headers and a non-empty body. Many + * MTA's don't even record the presence or absence of this + * separator, nor does the Milter protocol pass it on to Milter + * applications. + * + * XXX We don't insert a blank line separator into attachments, to + * avoid breaking digital signatures. Postfix shall not do a + * worse mail delivery job than MTAs that can't even parse MIME. + * We switch to body state anyway, to avoid treating body text as + * header text, and mis-interpreting or truncating it. The code + * below for initial From_ lines is for educational purposes. + * + * Sites concerned about MIME evasion can use a MIME normalizer. + * Postfix has a different mission. + */ + else { + if (msg_verbose) + msg_info("garbage in %s header", + state->curr_state == MIME_STATE_MULTIPART ? "multipart" : + state->curr_state == MIME_STATE_PRIMARY ? "primary" : + state->curr_state == MIME_STATE_NESTED ? "nested" : + "other"); + switch (state->curr_state) { + case MIME_STATE_PRIMARY: + BODY_OUT(state, REC_TYPE_NORM, "", 0); + SET_CURR_STATE(state, MIME_STATE_BODY); + break; +#if 0 + case MIME_STATE_NESTED: + if (state->body_offset <= 1 + && rec_type == REC_TYPE_NORM + && len > 7 + && (strncmp(text + (*text == '>'), "From ", 5) == 0 + || strncmp(text, "=46rom ", 7) == 0)) + break; + /* FALLTHROUGH */ +#endif + default: + SET_CURR_STATE(state, MIME_STATE_BODY); + break; + } + } + } + + /* + * This input is not text. Go to body state, unconditionally. + */ + else { + SET_CURR_STATE(state, MIME_STATE_BODY); + } + /* FALLTHROUGH */ + + /* + * Body text. Look for message boundaries, and recover from missing + * boundary strings. Missing boundaries can happen in aggressive mode + * with text/rfc822-headers or with message/partial. Ignore non-space + * cruft after --boundary or --boundary--, because some MUAs do, and + * because only perverse software would take advantage of this to + * escape detection. We have to ignore trailing cruft anyway, because + * our saved copy of the boundary string may have been truncated for + * safety reasons. + * + * Optionally look for 8-bit data in content that was announced as, or + * that defaults to, 7-bit. Unfortunately, we cannot turn this on by + * default. Majordomo sends requests for approval that do not + * propagate the MIME information from the enclosed message to the + * message headers of the approval request. + * + * Set the proper state information after processing a message boundary + * string. + * + * Don't look for boundary strings at the start of a continued record. + * + * Don't assume that the input is null terminated. + */ + case MIME_STATE_BODY: + if (input_is_text) { + if ((state->static_flags & MIME_OPT_REPORT_8BIT_IN_7BIT_BODY) != 0 + && state->curr_encoding == MIME_ENC_7BIT + && (state->err_flags & MIME_ERR_8BIT_IN_7BIT_BODY) == 0) { + for (cp = CU_CHAR_PTR(text); cp < CU_CHAR_PTR(text + len); cp++) + if (*cp & 0200) { + REPORT_ERROR_LEN(state, MIME_ERR_8BIT_IN_7BIT_BODY, + text, len); + break; + } + } + if (state->stack && state->prev_rec_type != REC_TYPE_CONT + && len > 2 && text[0] == '-' && text[1] == '-') { + for (sp = state->stack; sp != 0; sp = sp->next) { + if (len >= 2 + sp->bound_len && + strncmp(text + 2, sp->boundary, sp->bound_len) == 0) { + while (sp != state->stack) + mime_state_pop(state); + if (len >= 4 + sp->bound_len && + strncmp(text + 2 + sp->bound_len, "--", 2) == 0) { + mime_state_pop(state); + SET_MIME_STATE(state, MIME_STATE_BODY, + MIME_CTYPE_OTHER, MIME_STYPE_OTHER, + MIME_ENC_7BIT, MIME_ENC_7BIT); + } else { + SET_MIME_STATE(state, MIME_STATE_MULTIPART, + sp->def_ctype, sp->def_stype, + MIME_ENC_7BIT, MIME_ENC_7BIT); + } + break; + } + } + } + /* Put last for consistency with header output routine. */ + if ((state->static_flags & MIME_OPT_DOWNGRADE) + && state->curr_domain != MIME_ENC_7BIT) + mime_state_downgrade(state, rec_type, text, len); + else + BODY_OUT(state, rec_type, text, len); + } + + /* + * The input is not a text record. Inform the application that this + * is the last opportunity to send any pending output. + */ + else { + if (state->body_end) + state->body_end(state->app_context); + } + SAVE_PREV_REC_TYPE_AND_RETURN_ERR_FLAGS(state, rec_type); + + /* + * Oops. This can't happen. + */ + default: + msg_panic("mime_state_update: unknown state: %d", state->curr_state); + } +} + + /* + * Mime error to (DSN, text) mapping. Order matters; more serious errors + * must precede less serious errors, because the error-to-text conversion + * can report only one error. + */ +static const MIME_STATE_DETAIL mime_err_detail[] = { + MIME_ERR_NESTING, "5.6.0", "MIME nesting exceeds safety limit", + MIME_ERR_TRUNC_HEADER, "5.6.0", "message header length exceeds safety limit", + MIME_ERR_8BIT_IN_HEADER, "5.6.0", "improper use of 8-bit data in message header", + MIME_ERR_8BIT_IN_7BIT_BODY, "5.6.0", "improper use of 8-bit data in message body", + MIME_ERR_ENCODING_DOMAIN, "5.6.0", "invalid message/* or multipart/* encoding domain", + 0, +}; + +/* mime_state_error - error code to string */ + +const char *mime_state_error(int error_code) +{ + const MIME_STATE_DETAIL *mp; + + if (error_code == 0) + msg_panic("mime_state_error: there is no error"); + for (mp = mime_err_detail; mp->code; mp++) + if (mp->code & error_code) + return (mp->text); + msg_panic("mime_state_error: unknown error code %d", error_code); +} + +/* mime_state_detail - error code to table entry with assorted data */ + +const MIME_STATE_DETAIL *mime_state_detail(int error_code) +{ + const MIME_STATE_DETAIL *mp; + + if (error_code == 0) + msg_panic("mime_state_detail: there is no error"); + for (mp = mime_err_detail; mp->code; mp++) + if (mp->code & error_code) + return (mp); + msg_panic("mime_state_detail: unknown error code %d", error_code); +} + +#ifdef TEST + +#include <stdlib.h> +#include <stringops.h> +#include <vstream.h> +#include <msg_vstream.h> +#include <rec_streamlf.h> + + /* + * Stress test the REC_TYPE_CONT/NORM handling, but don't break header + * labels. + */ +/*#define REC_LEN 40*/ + +#define REC_LEN 1024 + +static void head_out(void *context, int class, const HEADER_OPTS *unused_info, + VSTRING *buf, off_t offset) +{ + VSTREAM *stream = (VSTREAM *) context; + + vstream_fprintf(stream, "%s %ld\t|%s\n", + class == MIME_HDR_PRIMARY ? "MAIN" : + class == MIME_HDR_MULTIPART ? "MULT" : + class == MIME_HDR_NESTED ? "NEST" : + "ERROR", (long) offset, STR(buf)); +} + +static void head_end(void *context) +{ + VSTREAM *stream = (VSTREAM *) context; + + vstream_fprintf(stream, "HEADER END\n"); +} + +static void body_out(void *context, int rec_type, const char *buf, ssize_t len, + off_t offset) +{ + VSTREAM *stream = (VSTREAM *) context; + + vstream_fprintf(stream, "BODY %c %ld\t|", rec_type, (long) offset); + vstream_fwrite(stream, buf, len); + if (rec_type == REC_TYPE_NORM) + VSTREAM_PUTC('\n', stream); +} + +static void body_end(void *context) +{ + VSTREAM *stream = (VSTREAM *) context; + + vstream_fprintf(stream, "BODY END\n"); +} + +static void err_print(void *unused_context, int err_flag, + const char *text, ssize_t len) +{ + msg_warn("%s: %.*s", mime_state_error(err_flag), + len < 100 ? (int) len : 100, text); +} + +int var_header_limit = 2000; +int var_mime_maxdepth = 20; +int var_mime_bound_len = 2000; +char *var_drop_hdrs = DEF_DROP_HDRS; + +int main(int unused_argc, char **argv) +{ + int rec_type; + int last = 0; + VSTRING *buf; + MIME_STATE *state; + int err; + + /* + * Initialize. + */ +#define MIME_OPTIONS \ + (MIME_OPT_REPORT_8BIT_IN_7BIT_BODY \ + | MIME_OPT_REPORT_8BIT_IN_HEADER \ + | MIME_OPT_REPORT_ENCODING_DOMAIN \ + | MIME_OPT_REPORT_TRUNC_HEADER \ + | MIME_OPT_REPORT_NESTING \ + | MIME_OPT_DOWNGRADE) + + msg_vstream_init(basename(argv[0]), VSTREAM_OUT); + msg_verbose = 1; + buf = vstring_alloc(10); + state = mime_state_alloc(MIME_OPTIONS, + head_out, head_end, + body_out, body_end, + err_print, + (void *) VSTREAM_OUT); + + /* + * Main loop. + */ + do { + rec_type = rec_streamlf_get(VSTREAM_IN, buf, REC_LEN); + VSTRING_TERMINATE(buf); + err = mime_state_update(state, last = rec_type, STR(buf), LEN(buf)); + vstream_fflush(VSTREAM_OUT); + } while (rec_type > 0); + + /* + * Error reporting. + */ + if (err & MIME_ERR_TRUNC_HEADER) + msg_warn("message header length exceeds safety limit"); + if (err & MIME_ERR_NESTING) + msg_warn("MIME nesting exceeds safety limit"); + if (err & MIME_ERR_8BIT_IN_HEADER) + msg_warn("improper use of 8-bit data in message header"); + if (err & MIME_ERR_8BIT_IN_7BIT_BODY) + msg_warn("improper use of 8-bit data in message body"); + if (err & MIME_ERR_ENCODING_DOMAIN) + msg_warn("improper message/* or multipart/* encoding domain"); + + /* + * Cleanup. + */ + mime_state_free(state); + vstring_free(buf); + exit(0); +} + +#endif |