src/src/pdkim/pdkim.h

   1 /*
   2  *  PDKIM - a RFC4871 (DKIM) implementation
   3  *
   4  *  Copyright (C) 2009 - 2012  Tom Kistner <tom@duncanthrax.net>
   5  *  Copyright (c) 2016 - 2018  Jeremy Harris
   6  *
   7  *  http://duncanthrax.net/pdkim/
   8  *
   9  *  This program is free software; you can redistribute it and/or modify
  10  *  it under the terms of the GNU General Public License as published by
  11  *  the Free Software Foundation; either version 2 of the License, or
  12  *  (at your option) any later version.
  13  *
  14  *  This program is distributed in the hope that it will be useful,
  15  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17  *  GNU General Public License for more details.
  18  *
  19  *  You should have received a copy of the GNU General Public License along
  20  *  with this program; if not, write to the Free Software Foundation, Inc.,
  21  *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  22  */
  23 #ifndef PDKIM_H
  24 #define PDKIM_H
  25
  26 #include "../blob.h"
  27 #include "../hash.h"
  28
  29 #define PDKIM_DEFAULT_SIGN_HEADERS "From:Sender:Reply-To:Subject:Date:"\
  30                              "Message-ID:To:Cc:MIME-Version:Content-Type:"\
  31                              "Content-Transfer-Encoding:Content-ID:"\
  32                              "Content-Description:Resent-Date:Resent-From:"\
  33                              "Resent-Sender:Resent-To:Resent-Cc:"\
  34                              "Resent-Message-ID:In-Reply-To:References:"\
  35                              "List-Id:List-Help:List-Unsubscribe:"\
  36                              "List-Subscribe:List-Post:List-Owner:List-Archive"
  37
  38 /* -------------------------------------------------------------------------- */
  39 /* Length of the preallocated buffer for the "answer" from the dns/txt
  40    callback function. This should match the maximum RDLENGTH from DNS. */
  41 #define PDKIM_DNS_TXT_MAX_RECLEN    (1 << 16)
  42
  43 /* -------------------------------------------------------------------------- */
  44 /* Function success / error codes */
  45 #define PDKIM_OK                      0
  46 #define PDKIM_FAIL                   -1
  47 #define PDKIM_ERR_RSA_PRIVKEY      -101
  48 #define PDKIM_ERR_RSA_SIGNING      -102
  49 #define PDKIM_ERR_LONG_LINE        -103
  50 #define PDKIM_ERR_BUFFER_TOO_SMALL -104
  51 #define PDKIM_ERR_EXCESS_SIGS      -105
  52 #define PDKIM_SIGN_PRIVKEY_WRAP    -106
  53 #define PDKIM_SIGN_PRIVKEY_B64D    -107
  54
  55 /* -------------------------------------------------------------------------- */
  56 /* Main/Extended verification status */
  57 #define PDKIM_VERIFY_NONE      0
  58 #define PDKIM_VERIFY_INVALID   1
  59 #define PDKIM_VERIFY_FAIL      2
  60 #define PDKIM_VERIFY_PASS      3
  61 #define PDKIM_VERIFY_POLICY    BIT(31)
  62
  63 #define PDKIM_VERIFY_FAIL_BODY                    1
  64 #define PDKIM_VERIFY_FAIL_MESSAGE                 2
  65 #define PDKIM_VERIFY_FAIL_SIG_ALGO_MISMATCH       3
  66 #define PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE   4
  67 #define PDKIM_VERIFY_INVALID_BUFFER_SIZE          5
  68 #define PDKIM_VERIFY_INVALID_PUBKEY_DNSRECORD     6
  69 #define PDKIM_VERIFY_INVALID_PUBKEY_IMPORT        7
  70 #define PDKIM_VERIFY_INVALID_SIGNATURE_ERROR      8
  71 #define PDKIM_VERIFY_INVALID_DKIM_VERSION         9
  72
  73 /* -------------------------------------------------------------------------- */
  74 /* Some parameter values */
  75 #define PDKIM_QUERYMETHOD_DNS_TXT 0
  76
  77 #define PDKIM_CANON_SIMPLE        0
  78 #define PDKIM_CANON_RELAXED       1
  79
  80 /* -------------------------------------------------------------------------- */
  81 /* Some required forward declarations, please ignore */
  82 typedef struct pdkim_stringlist pdkim_stringlist;
  83 typedef struct pdkim_str pdkim_str;
  84 typedef struct sha1_context sha1_context;
  85 typedef struct sha2_context sha2_context;
  86 #define HAVE_SHA1_CONTEXT
  87 #define HAVE_SHA2_CONTEXT
  88
  89 /* -------------------------------------------------------------------------- */
  90 /* Some concessions towards Redmond */
  91 #ifdef WINDOWS
  92 #define snprintf _snprintf
  93 #define strcasecmp _stricmp
  94 #define strncasecmp _strnicmp
  95 #define DLLEXPORT __declspec(dllexport)
  96 #else
  97 #define DLLEXPORT
  98 #endif
  99
 100
 101 /* -------------------------------------------------------------------------- */
 102 /* Public key as (usually) fetched from DNS */
 103 typedef struct pdkim_pubkey {
 104   const uschar * version;         /* v=  */
 105   const uschar *granularity;      /* g=  */
 106
 107   const uschar * hashes;          /* h=  */
 108   const uschar * keytype;         /* k=  */
 109   const uschar * srvtype;         /* s=  */
 110   uschar *notes;                  /* n=  */
 111
 112   blob  key;                      /* p=  */
 113   int   testing;                  /* t=y */
 114   int   no_subdomaining;          /* t=s */
 115 } pdkim_pubkey;
 116
 117 /* -------------------------------------------------------------------------- */
 118 /* Body-hash to be calculated */
 119 typedef struct pdkim_bodyhash {
 120   struct pdkim_bodyhash *       next;
 121   int                           hashtype;
 122   int                           canon_method;
 123   long                          bodylength;
 124
 125   hctx                          body_hash_ctx;
 126   unsigned long                 signed_body_bytes;      /* done so far */
 127   int                           num_buffered_blanklines;
 128
 129   blob                          bh;                     /* completed hash */
 130 } pdkim_bodyhash;
 131
 132 /* -------------------------------------------------------------------------- */
 133 /* Signature as it appears in a DKIM-Signature header */
 134 typedef struct pdkim_signature {
 135   struct pdkim_signature * next;
 136
 137   /* Bits stored in a DKIM signature header --------------------------- */
 138
 139   /* (v=) The version, as an integer. Currently, always "1" */
 140   int version;
 141
 142   /* (a=) The signature algorithm. */
 143   int keytype;  /* pdkim_keytypes index */
 144   int hashtype; /* pdkim_hashes index */
 145
 146   /* (c=x/) Header canonicalization method. Either PDKIM_CANON_SIMPLE
 147      or PDKIM_CANON_RELAXED */
 148   int canon_headers;
 149
 150   /* (c=/x) Body canonicalization method. Either PDKIM_CANON_SIMPLE
 151      or PDKIM_CANON_RELAXED */
 152   int canon_body;
 153
 154   /* (q=) Query Method. Currently, only PDKIM_QUERYMETHOD_DNS_TXT
 155      is specified */
 156   int querymethod;
 157
 158   /* (s=) The selector string as given in the signature */
 159   uschar *selector;
 160
 161   /* (d=) The domain as given in the signature */
 162   uschar *domain;
 163
 164   /* (i=) The identity as given in the signature */
 165   uschar *identity;
 166
 167   /* (t=) Timestamp of signature creation */
 168   unsigned long created;
 169
 170   /* (x=) Timestamp of expiry of signature */
 171   unsigned long expires;
 172
 173   /* (l=) Amount of hashed body bytes (after canonicalization). Default
 174      is -1. Note: a value of 0 means that the body is unsigned! */
 175   long bodylength;
 176
 177   /* (h=) Colon-separated list of header names that are included in the
 178      signature */
 179   uschar *headernames;
 180
 181   /* (z=) */
 182   uschar *copiedheaders;
 183
 184   /* (b=) Raw signature data, along with its length in bytes */
 185   blob sighash;
 186
 187   /* (bh=) Raw body hash data, along with its length in bytes */
 188   blob bodyhash;
 189
 190   /* Folded DKIM-Signature: header. Signing only, NULL for verifying.
 191      Ready for insertion into the message. Note: Folded using CRLFTB,
 192      but final line terminator is NOT included. Note2: This buffer is
 193      free()d when you call pdkim_free_ctx(). */
 194   uschar *signature_header;
 195
 196   /* The main verification status. Verification only. One of:
 197
 198      PDKIM_VERIFY_NONE      Verification was not attempted. This status
 199                             should not appear.
 200
 201      PDKIM_VERIFY_INVALID   There was an error while trying to verify
 202                             the signature. A more precise description
 203                             is available in verify_ext_status.
 204
 205      PDKIM_VERIFY_FAIL      Verification failed because either the body
 206                             hash did not match, or the signature verification
 207                             failed. This means the message was modified.
 208                             Check verify_ext_status for the exact reason.
 209
 210      PDKIM_VERIFY_PASS      Verification succeeded.
 211   */
 212   int verify_status;
 213
 214   /* Extended verification status. Verification only. Depending on the value
 215      of verify_status, it can contain:
 216
 217      For verify_status == PDKIM_VERIFY_INVALID:
 218
 219         PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE
 220           Unable to retrieve a public key container.
 221
 222         PDKIM_VERIFY_INVALID_BUFFER_SIZE
 223           Either the DNS name constructed to retrieve the public key record
 224           does not fit into PDKIM_DNS_TXT_MAX_NAMELEN bytes, or the retrieved
 225           record is longer than PDKIM_DNS_TXT_MAX_RECLEN bytes.
 226
 227         PDKIM_VERIFY_INVALID_PUBKEY_PARSING
 228           (Syntax) error while parsing the retrieved public key record.
 229
 230
 231      For verify_status == PDKIM_VERIFY_FAIL:
 232
 233         PDKIM_VERIFY_FAIL_BODY
 234           The calculated body hash does not match the advertised body hash
 235           from the bh= tag of the signature.
 236
 237         PDKIM_VERIFY_FAIL_MESSAGE
 238           RSA verification of the signature (b= tag) failed.
 239   */
 240   int verify_ext_status;
 241
 242   /* Pointer to a public key record that was used to verify the signature.
 243      See pdkim_pubkey declaration above for more information.
 244      Caution: is NULL if signing or if no record was retrieved. */
 245   pdkim_pubkey *pubkey;
 246
 247   /* Properties below this point are used internally only ------------- */
 248
 249   /* Per-signature helper variables ----------------------------------- */
 250   pdkim_bodyhash *calc_body_hash;       /* hash to be / being calculated */
 251
 252   pdkim_stringlist *headers;            /* Raw headers included in the sig */
 253
 254   /* Signing specific ------------------------------------------------- */
 255   uschar * privkey;          /* Private key                                 */
 256   uschar * sign_headers;    /* To-be-signed header names                   */
 257   uschar * rawsig_no_b_val; /* Original signature header w/o b= tag value. */
 258 } pdkim_signature;
 259
 260
 261 /* -------------------------------------------------------------------------- */
 262 /* Context to keep state between all operations. */
 263 typedef struct pdkim_ctx {
 264
 265 #define PDKIM_MODE_SIGN   BIT(0)        /* if unset, mode==verify */
 266 #define PDKIM_DOT_TERM    BIT(1)        /* dot termination and unstuffing */
 267 #define PDKIM_SEEN_CR     BIT(2)
 268 #define PDKIM_SEEN_LF     BIT(3)
 269 #define PDKIM_PAST_HDRS   BIT(4)
 270 #define PDKIM_SEEN_EOD    BIT(5)
 271   unsigned   flags;
 272
 273   /* One (signing) or several chained (verification) signatures */
 274   pdkim_signature *sig;
 275
 276   /* One (signing) or several chained (verification) bodyhashes */
 277   pdkim_bodyhash *bodyhash;
 278
 279   /* Callback for dns/txt query method (verification only) */
 280   uschar * (*dns_txt_callback)(const uschar *);
 281
 282   /* Coder's little helpers */
 283   gstring   *cur_header;
 284   uschar    *linebuf;
 285   int        linebuf_offset;
 286   int        num_headers;
 287   pdkim_stringlist *headers; /* Raw headers for verification         */
 288 } pdkim_ctx;
 289
 290
 291 /******************************************************************************/
 292
 293 typedef struct {
 294   const uschar * dkim_hashname;
 295   hashmethod     exim_hashmethod;
 296 } pdkim_hashtype;
 297 extern const pdkim_hashtype pdkim_hashes[];
 298
 299 /******************************************************************************/
 300
 301
 302 /* -------------------------------------------------------------------------- */
 303 /* API functions. Please see the sample code in sample/test_sign.c and
 304    sample/test_verify.c for documentation.
 305 */
 306
 307 #ifdef __cplusplus
 308 extern "C" {
 309 #endif
 310
 311 void       pdkim_init         (void);
 312
 313 void       pdkim_init_context (pdkim_ctx *, BOOL, uschar * (*)(const uschar *));
 314
 315 DLLEXPORT
 316 pdkim_signature *pdkim_init_sign    (pdkim_ctx *,
 317                                uschar *, uschar *, uschar *, uschar *,
 318                                const uschar **);
 319
 320 DLLEXPORT
 321 pdkim_ctx *pdkim_init_verify  (uschar * (*)(const uschar *), BOOL);
 322
 323 DLLEXPORT
 324 void       pdkim_set_optional (pdkim_signature *, char *, char *,int, int,
 325                                long,
 326                                unsigned long,
 327                                unsigned long);
 328
 329 int             pdkim_hashname_to_hashtype(const uschar *, unsigned);
 330 void            pdkim_cstring_to_canons(const uschar *, unsigned, int *, int *);
 331 pdkim_bodyhash *pdkim_set_bodyhash(pdkim_ctx *, int, int, long);
 332 pdkim_bodyhash *pdkim_set_sig_bodyhash(pdkim_ctx *, pdkim_signature *);
 333
 334 DLLEXPORT
 335 int        pdkim_feed         (pdkim_ctx *, uschar *, int);
 336 DLLEXPORT
 337 int        pdkim_feed_finish  (pdkim_ctx *, pdkim_signature **, const uschar **);
 338
 339 DLLEXPORT
 340 void       pdkim_free_ctx     (pdkim_ctx *);
 341
 342
 343 const uschar *  pdkim_errstr(int);
 344
 345 extern uschar *         pdkim_encode_base64(blob *);
 346 extern void             pdkim_decode_base64(const uschar *, blob *);
 347 extern void             pdkim_hexprint(const uschar *, int);
 348 extern void             pdkim_quoteprint(const uschar *, int);
 349 extern pdkim_pubkey *   pdkim_parse_pubkey_record(const uschar *);
 350 extern uschar *         pdkim_relax_header_n(const uschar *, int, BOOL);
 351 extern uschar *         pdkim_relax_header(const uschar *, BOOL);
 352 extern uschar *         dkim_sig_to_a_tag(const pdkim_signature *);
 353
 354 #ifdef __cplusplus
 355 }
 356 #endif
 357
 358 #endif