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 #define PDKIM_OVERSIGN_HEADERS "+From:+Sender:+Reply-To:+Subject:+Date:"\
  39                              "+Message-ID:+To:+Cc:+MIME-Version:+Content-Type:"\
  40                              "+Content-Transfer-Encoding:+Content-ID:"\
  41                              "+Content-Description:+Resent-Date:+Resent-From:"\
  42                              "+Resent-Sender:+Resent-To:+Resent-Cc:"\
  43                              "+Resent-Message-ID:+In-Reply-To:+References:"\
  44                              "+List-Id:+List-Help:+List-Unsubscribe:"\
  45                              "+List-Subscribe:+List-Post:+List-Owner:+List-Archive"
  46
  47 /* -------------------------------------------------------------------------- */
  48 /* Length of the preallocated buffer for the "answer" from the dns/txt
  49    callback function. This should match the maximum RDLENGTH from DNS. */
  50 #define PDKIM_DNS_TXT_MAX_RECLEN    (1 << 16)
  51
  52 /* -------------------------------------------------------------------------- */
  53 /* Function success / error codes */
  54 #define PDKIM_OK                      0
  55 #define PDKIM_FAIL                   -1
  56 #define PDKIM_ERR_RSA_PRIVKEY      -101
  57 #define PDKIM_ERR_RSA_SIGNING      -102
  58 #define PDKIM_ERR_LONG_LINE        -103
  59 #define PDKIM_ERR_BUFFER_TOO_SMALL -104
  60 #define PDKIM_ERR_EXCESS_SIGS      -105
  61 #define PDKIM_SIGN_PRIVKEY_WRAP    -106
  62 #define PDKIM_SIGN_PRIVKEY_B64D    -107
  63
  64 /* -------------------------------------------------------------------------- */
  65 /* Main/Extended verification status */
  66 #define PDKIM_VERIFY_NONE      0
  67 #define PDKIM_VERIFY_INVALID   1
  68 #define PDKIM_VERIFY_FAIL      2
  69 #define PDKIM_VERIFY_PASS      3
  70 #define PDKIM_VERIFY_POLICY    BIT(31)
  71
  72 #define PDKIM_VERIFY_FAIL_BODY                    1
  73 #define PDKIM_VERIFY_FAIL_MESSAGE                 2
  74 #define PDKIM_VERIFY_FAIL_SIG_ALGO_MISMATCH       3
  75 #define PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE   4
  76 #define PDKIM_VERIFY_INVALID_BUFFER_SIZE          5
  77 #define PDKIM_VERIFY_INVALID_PUBKEY_DNSRECORD     6
  78 #define PDKIM_VERIFY_INVALID_PUBKEY_IMPORT        7
  79 #define PDKIM_VERIFY_INVALID_SIGNATURE_ERROR      8
  80 #define PDKIM_VERIFY_INVALID_DKIM_VERSION         9
  81
  82 /* -------------------------------------------------------------------------- */
  83 /* Some parameter values */
  84 #define PDKIM_QUERYMETHOD_DNS_TXT 0
  85
  86 #define PDKIM_CANON_SIMPLE        0
  87 #define PDKIM_CANON_RELAXED       1
  88
  89 /* -------------------------------------------------------------------------- */
  90 /* Some required forward declarations, please ignore */
  91 typedef struct pdkim_stringlist pdkim_stringlist;
  92 typedef struct pdkim_str pdkim_str;
  93 typedef struct sha1_context sha1_context;
  94 typedef struct sha2_context sha2_context;
  95 #define HAVE_SHA1_CONTEXT
  96 #define HAVE_SHA2_CONTEXT
  97
  98 /* -------------------------------------------------------------------------- */
  99 /* Some concessions towards Redmond */
 100 #ifdef WINDOWS
 101 #define snprintf _snprintf
 102 #define strcasecmp _stricmp
 103 #define strncasecmp _strnicmp
 104 #define DLLEXPORT __declspec(dllexport)
 105 #else
 106 #define DLLEXPORT
 107 #endif
 108
 109
 110 /* -------------------------------------------------------------------------- */
 111 /* Public key as (usually) fetched from DNS */
 112 typedef struct pdkim_pubkey {
 113   const uschar * version;         /* v=  */
 114   const uschar *granularity;      /* g=  */
 115
 116   const uschar * hashes;          /* h=  */
 117   const uschar * keytype;         /* k=  */
 118   const uschar * srvtype;         /* s=  */
 119   uschar *notes;                  /* n=  */
 120
 121   blob  key;                      /* p=  */
 122   int   testing;                  /* t=y */
 123   int   no_subdomaining;          /* t=s */
 124 } pdkim_pubkey;
 125
 126 /* -------------------------------------------------------------------------- */
 127 /* Body-hash to be calculated */
 128 typedef struct pdkim_bodyhash {
 129   struct pdkim_bodyhash *       next;
 130   int                           hashtype;
 131   int                           canon_method;
 132   long                          bodylength;
 133
 134   hctx                          body_hash_ctx;
 135   unsigned long                 signed_body_bytes;      /* done so far */
 136   int                           num_buffered_blanklines;
 137
 138   blob                          bh;                     /* completed hash */
 139 } pdkim_bodyhash;
 140
 141 /* -------------------------------------------------------------------------- */
 142 /* Signature as it appears in a DKIM-Signature header */
 143 typedef struct pdkim_signature {
 144   struct pdkim_signature * next;
 145
 146   /* Bits stored in a DKIM signature header --------------------------- */
 147
 148   /* (v=) The version, as an integer. Currently, always "1" */
 149   int version;
 150
 151   /* (a=) The signature algorithm. */
 152   int           keytype;        /* pdkim_keytypes index */
 153   unsigned      keybits;        /* size of the key */
 154   int           hashtype;       /* pdkim_hashes index */
 155
 156   /* (c=x/) Header canonicalization method. Either PDKIM_CANON_SIMPLE
 157      or PDKIM_CANON_RELAXED */
 158   int canon_headers;
 159
 160   /* (c=/x) Body canonicalization method. Either PDKIM_CANON_SIMPLE
 161      or PDKIM_CANON_RELAXED */
 162   int canon_body;
 163
 164   /* (q=) Query Method. Currently, only PDKIM_QUERYMETHOD_DNS_TXT
 165      is specified */
 166   int querymethod;
 167
 168   /* (s=) The selector string as given in the signature */
 169   uschar *selector;
 170
 171   /* (d=) The domain as given in the signature */
 172   uschar *domain;
 173
 174   /* (i=) The identity as given in the signature */
 175   uschar *identity;
 176
 177   /* (t=) Timestamp of signature creation */
 178   unsigned long created;
 179
 180   /* (x=) Timestamp of expiry of signature */
 181   unsigned long expires;
 182
 183   /* (l=) Amount of hashed body bytes (after canonicalization). Default
 184      is -1. Note: a value of 0 means that the body is unsigned! */
 185   long bodylength;
 186
 187   /* (h=) Colon-separated list of header names that are included in the
 188      signature */
 189   uschar *headernames;
 190
 191   /* (z=) */
 192   uschar *copiedheaders;
 193
 194   /* (b=) Raw signature data, along with its length in bytes */
 195   blob sighash;
 196
 197   /* (bh=) Raw body hash data, along with its length in bytes */
 198   blob bodyhash;
 199
 200   /* Folded DKIM-Signature: header. Signing only, NULL for verifying.
 201      Ready for insertion into the message. Note: Folded using CRLFTB,
 202      but final line terminator is NOT included. Note2: This buffer is
 203      free()d when you call pdkim_free_ctx(). */
 204   uschar *signature_header;
 205
 206   /* The main verification status. Verification only. One of:
 207
 208      PDKIM_VERIFY_NONE      Verification was not attempted. This status
 209                             should not appear.
 210
 211      PDKIM_VERIFY_INVALID   There was an error while trying to verify
 212                             the signature. A more precise description
 213                             is available in verify_ext_status.
 214
 215      PDKIM_VERIFY_FAIL      Verification failed because either the body
 216                             hash did not match, or the signature verification
 217                             failed. This means the message was modified.
 218                             Check verify_ext_status for the exact reason.
 219
 220      PDKIM_VERIFY_PASS      Verification succeeded.
 221   */
 222   int verify_status;
 223
 224   /* Extended verification status. Verification only. Depending on the value
 225      of verify_status, it can contain:
 226
 227      For verify_status == PDKIM_VERIFY_INVALID:
 228
 229         PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE
 230           Unable to retrieve a public key container.
 231
 232         PDKIM_VERIFY_INVALID_BUFFER_SIZE
 233           Either the DNS name constructed to retrieve the public key record
 234           does not fit into PDKIM_DNS_TXT_MAX_NAMELEN bytes, or the retrieved
 235           record is longer than PDKIM_DNS_TXT_MAX_RECLEN bytes.
 236
 237         PDKIM_VERIFY_INVALID_PUBKEY_PARSING
 238           (Syntax) error while parsing the retrieved public key record.
 239
 240
 241      For verify_status == PDKIM_VERIFY_FAIL:
 242
 243         PDKIM_VERIFY_FAIL_BODY
 244           The calculated body hash does not match the advertised body hash
 245           from the bh= tag of the signature.
 246
 247         PDKIM_VERIFY_FAIL_MESSAGE
 248           RSA verification of the signature (b= tag) failed.
 249   */
 250   int verify_ext_status;
 251
 252   /* Pointer to a public key record that was used to verify the signature.
 253      See pdkim_pubkey declaration above for more information.
 254      Caution: is NULL if signing or if no record was retrieved. */
 255   pdkim_pubkey *pubkey;
 256
 257   /* Properties below this point are used internally only ------------- */
 258
 259   /* Per-signature helper variables ----------------------------------- */
 260   pdkim_bodyhash *calc_body_hash;       /* hash to be / being calculated */
 261
 262   pdkim_stringlist *headers;            /* Raw headers included in the sig */
 263
 264   /* Signing specific ------------------------------------------------- */
 265   uschar * privkey;          /* Private key                                 */
 266   uschar * sign_headers;    /* To-be-signed header names                   */
 267   uschar * rawsig_no_b_val; /* Original signature header w/o b= tag value. */
 268 } pdkim_signature;
 269
 270
 271 /* -------------------------------------------------------------------------- */
 272 /* Context to keep state between all operations. */
 273 typedef struct pdkim_ctx {
 274
 275 #define PDKIM_MODE_SIGN   BIT(0)        /* if unset, mode==verify */
 276 #define PDKIM_DOT_TERM    BIT(1)        /* dot termination and unstuffing */
 277 #define PDKIM_SEEN_CR     BIT(2)
 278 #define PDKIM_SEEN_LF     BIT(3)
 279 #define PDKIM_PAST_HDRS   BIT(4)
 280 #define PDKIM_SEEN_EOD    BIT(5)
 281   unsigned   flags;
 282
 283   /* One (signing) or several chained (verification) signatures */
 284   pdkim_signature *sig;
 285
 286   /* One (signing) or several chained (verification) bodyhashes */
 287   pdkim_bodyhash *bodyhash;
 288
 289   /* Callback for dns/txt query method (verification only) */
 290   uschar * (*dns_txt_callback)(const uschar *);
 291
 292   /* Coder's little helpers */
 293   gstring   *cur_header;
 294   uschar    *linebuf;
 295   int        linebuf_offset;
 296   int        num_headers;
 297   pdkim_stringlist *headers; /* Raw headers for verification         */
 298 } pdkim_ctx;
 299
 300
 301 /******************************************************************************/
 302
 303 typedef struct {
 304   const uschar * dkim_hashname;
 305   hashmethod     exim_hashmethod;
 306 } pdkim_hashtype;
 307 extern const pdkim_hashtype pdkim_hashes[];
 308
 309 /******************************************************************************/
 310
 311
 312 /* -------------------------------------------------------------------------- */
 313 /* API functions. Please see the sample code in sample/test_sign.c and
 314    sample/test_verify.c for documentation.
 315 */
 316
 317 #ifdef __cplusplus
 318 extern "C" {
 319 #endif
 320
 321 void       pdkim_init         (void);
 322
 323 void       pdkim_init_context (pdkim_ctx *, BOOL, uschar * (*)(const uschar *));
 324
 325 DLLEXPORT
 326 pdkim_signature *pdkim_init_sign    (pdkim_ctx *,
 327                                uschar *, uschar *, uschar *, uschar *,
 328                                const uschar **);
 329
 330 DLLEXPORT
 331 pdkim_ctx *pdkim_init_verify  (uschar * (*)(const uschar *), BOOL);
 332
 333 DLLEXPORT
 334 void       pdkim_set_optional (pdkim_signature *, char *, char *,int, int,
 335                                long,
 336                                unsigned long,
 337                                unsigned long);
 338
 339 int             pdkim_hashname_to_hashtype(const uschar *, unsigned);
 340 void            pdkim_cstring_to_canons(const uschar *, unsigned, int *, int *);
 341 pdkim_bodyhash *pdkim_set_bodyhash(pdkim_ctx *, int, int, long);
 342 pdkim_bodyhash *pdkim_set_sig_bodyhash(pdkim_ctx *, pdkim_signature *);
 343
 344 DLLEXPORT
 345 int        pdkim_feed         (pdkim_ctx *, uschar *, int);
 346 DLLEXPORT
 347 int        pdkim_feed_finish  (pdkim_ctx *, pdkim_signature **, const uschar **);
 348
 349 DLLEXPORT
 350 void       pdkim_free_ctx     (pdkim_ctx *);
 351
 352
 353 const uschar *  pdkim_errstr(int);
 354
 355 extern uschar *         pdkim_encode_base64(blob *);
 356 extern void             pdkim_decode_base64(const uschar *, blob *);
 357 extern void             pdkim_hexprint(const uschar *, int);
 358 extern void             pdkim_quoteprint(const uschar *, int);
 359 extern pdkim_pubkey *   pdkim_parse_pubkey_record(const uschar *);
 360 extern uschar *         pdkim_relax_header_n(const uschar *, int, BOOL);
 361 extern uschar *         pdkim_relax_header(const uschar *, BOOL);
 362 extern uschar *         dkim_sig_to_a_tag(const pdkim_signature *);
 363
 364 #ifdef __cplusplus
 365 }
 366 #endif
 367
 368 #endif