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   int hashtype; /* pdkim_hashes index */
 154
 155   /* (c=x/) Header canonicalization method. Either PDKIM_CANON_SIMPLE
 156      or PDKIM_CANON_RELAXED */
 157   int canon_headers;
 158
 159   /* (c=/x) Body canonicalization method. Either PDKIM_CANON_SIMPLE
 160      or PDKIM_CANON_RELAXED */
 161   int canon_body;
 162
 163   /* (q=) Query Method. Currently, only PDKIM_QUERYMETHOD_DNS_TXT
 164      is specified */
 165   int querymethod;
 166
 167   /* (s=) The selector string as given in the signature */
 168   uschar *selector;
 169
 170   /* (d=) The domain as given in the signature */
 171   uschar *domain;
 172
 173   /* (i=) The identity as given in the signature */
 174   uschar *identity;
 175
 176   /* (t=) Timestamp of signature creation */
 177   unsigned long created;
 178
 179   /* (x=) Timestamp of expiry of signature */
 180   unsigned long expires;
 181
 182   /* (l=) Amount of hashed body bytes (after canonicalization). Default
 183      is -1. Note: a value of 0 means that the body is unsigned! */
 184   long bodylength;
 185
 186   /* (h=) Colon-separated list of header names that are included in the
 187      signature */
 188   uschar *headernames;
 189
 190   /* (z=) */
 191   uschar *copiedheaders;
 192
 193   /* (b=) Raw signature data, along with its length in bytes */
 194   blob sighash;
 195
 196   /* (bh=) Raw body hash data, along with its length in bytes */
 197   blob bodyhash;
 198
 199   /* Folded DKIM-Signature: header. Signing only, NULL for verifying.
 200      Ready for insertion into the message. Note: Folded using CRLFTB,
 201      but final line terminator is NOT included. Note2: This buffer is
 202      free()d when you call pdkim_free_ctx(). */
 203   uschar *signature_header;
 204
 205   /* The main verification status. Verification only. One of:
 206
 207      PDKIM_VERIFY_NONE      Verification was not attempted. This status
 208                             should not appear.
 209
 210      PDKIM_VERIFY_INVALID   There was an error while trying to verify
 211                             the signature. A more precise description
 212                             is available in verify_ext_status.
 213
 214      PDKIM_VERIFY_FAIL      Verification failed because either the body
 215                             hash did not match, or the signature verification
 216                             failed. This means the message was modified.
 217                             Check verify_ext_status for the exact reason.
 218
 219      PDKIM_VERIFY_PASS      Verification succeeded.
 220   */
 221   int verify_status;
 222
 223   /* Extended verification status. Verification only. Depending on the value
 224      of verify_status, it can contain:
 225
 226      For verify_status == PDKIM_VERIFY_INVALID:
 227
 228         PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE
 229           Unable to retrieve a public key container.
 230
 231         PDKIM_VERIFY_INVALID_BUFFER_SIZE
 232           Either the DNS name constructed to retrieve the public key record
 233           does not fit into PDKIM_DNS_TXT_MAX_NAMELEN bytes, or the retrieved
 234           record is longer than PDKIM_DNS_TXT_MAX_RECLEN bytes.
 235
 236         PDKIM_VERIFY_INVALID_PUBKEY_PARSING
 237           (Syntax) error while parsing the retrieved public key record.
 238
 239
 240      For verify_status == PDKIM_VERIFY_FAIL:
 241
 242         PDKIM_VERIFY_FAIL_BODY
 243           The calculated body hash does not match the advertised body hash
 244           from the bh= tag of the signature.
 245
 246         PDKIM_VERIFY_FAIL_MESSAGE
 247           RSA verification of the signature (b= tag) failed.
 248   */
 249   int verify_ext_status;
 250
 251   /* Pointer to a public key record that was used to verify the signature.
 252      See pdkim_pubkey declaration above for more information.
 253      Caution: is NULL if signing or if no record was retrieved. */
 254   pdkim_pubkey *pubkey;
 255
 256   /* Properties below this point are used internally only ------------- */
 257
 258   /* Per-signature helper variables ----------------------------------- */
 259   pdkim_bodyhash *calc_body_hash;       /* hash to be / being calculated */
 260
 261   pdkim_stringlist *headers;            /* Raw headers included in the sig */
 262
 263   /* Signing specific ------------------------------------------------- */
 264   uschar * privkey;          /* Private key                                 */
 265   uschar * sign_headers;    /* To-be-signed header names                   */
 266   uschar * rawsig_no_b_val; /* Original signature header w/o b= tag value. */
 267 } pdkim_signature;
 268
 269
 270 /* -------------------------------------------------------------------------- */
 271 /* Context to keep state between all operations. */
 272 typedef struct pdkim_ctx {
 273
 274 #define PDKIM_MODE_SIGN   BIT(0)        /* if unset, mode==verify */
 275 #define PDKIM_DOT_TERM    BIT(1)        /* dot termination and unstuffing */
 276 #define PDKIM_SEEN_CR     BIT(2)
 277 #define PDKIM_SEEN_LF     BIT(3)
 278 #define PDKIM_PAST_HDRS   BIT(4)
 279 #define PDKIM_SEEN_EOD    BIT(5)
 280   unsigned   flags;
 281
 282   /* One (signing) or several chained (verification) signatures */
 283   pdkim_signature *sig;
 284
 285   /* One (signing) or several chained (verification) bodyhashes */
 286   pdkim_bodyhash *bodyhash;
 287
 288   /* Callback for dns/txt query method (verification only) */
 289   uschar * (*dns_txt_callback)(const uschar *);
 290
 291   /* Coder's little helpers */
 292   gstring   *cur_header;
 293   uschar    *linebuf;
 294   int        linebuf_offset;
 295   int        num_headers;
 296   pdkim_stringlist *headers; /* Raw headers for verification         */
 297 } pdkim_ctx;
 298
 299
 300 /******************************************************************************/
 301
 302 typedef struct {
 303   const uschar * dkim_hashname;
 304   hashmethod     exim_hashmethod;
 305 } pdkim_hashtype;
 306 extern const pdkim_hashtype pdkim_hashes[];
 307
 308 /******************************************************************************/
 309
 310
 311 /* -------------------------------------------------------------------------- */
 312 /* API functions. Please see the sample code in sample/test_sign.c and
 313    sample/test_verify.c for documentation.
 314 */
 315
 316 #ifdef __cplusplus
 317 extern "C" {
 318 #endif
 319
 320 void       pdkim_init         (void);
 321
 322 void       pdkim_init_context (pdkim_ctx *, BOOL, uschar * (*)(const uschar *));
 323
 324 DLLEXPORT
 325 pdkim_signature *pdkim_init_sign    (pdkim_ctx *,
 326                                uschar *, uschar *, uschar *, uschar *,
 327                                const uschar **);
 328
 329 DLLEXPORT
 330 pdkim_ctx *pdkim_init_verify  (uschar * (*)(const uschar *), BOOL);
 331
 332 DLLEXPORT
 333 void       pdkim_set_optional (pdkim_signature *, char *, char *,int, int,
 334                                long,
 335                                unsigned long,
 336                                unsigned long);
 337
 338 int             pdkim_hashname_to_hashtype(const uschar *, unsigned);
 339 void            pdkim_cstring_to_canons(const uschar *, unsigned, int *, int *);
 340 pdkim_bodyhash *pdkim_set_bodyhash(pdkim_ctx *, int, int, long);
 341 pdkim_bodyhash *pdkim_set_sig_bodyhash(pdkim_ctx *, pdkim_signature *);
 342
 343 DLLEXPORT
 344 int        pdkim_feed         (pdkim_ctx *, uschar *, int);
 345 DLLEXPORT
 346 int        pdkim_feed_finish  (pdkim_ctx *, pdkim_signature **, const uschar **);
 347
 348 DLLEXPORT
 349 void       pdkim_free_ctx     (pdkim_ctx *);
 350
 351
 352 const uschar *  pdkim_errstr(int);
 353
 354 extern uschar *         pdkim_encode_base64(blob *);
 355 extern void             pdkim_decode_base64(const uschar *, blob *);
 356 extern void             pdkim_hexprint(const uschar *, int);
 357 extern void             pdkim_quoteprint(const uschar *, int);
 358 extern pdkim_pubkey *   pdkim_parse_pubkey_record(const uschar *);
 359 extern uschar *         pdkim_relax_header_n(const uschar *, int, BOOL);
 360 extern uschar *         pdkim_relax_header(const uschar *, BOOL);
 361 extern uschar *         dkim_sig_to_a_tag(const pdkim_signature *);
 362
 363 #ifdef __cplusplus
 364 }
 365 #endif
 366
 367 #endif