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 - 2020  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_PUBKEY_KEYSIZE       8
  80 #define PDKIM_VERIFY_INVALID_SIGNATURE_ERROR      9
  81 #define PDKIM_VERIFY_INVALID_DKIM_VERSION         10
  82
  83 /* -------------------------------------------------------------------------- */
  84 /* Some parameter values */
  85 #define PDKIM_QUERYMETHOD_DNS_TXT 0
  86
  87 #define PDKIM_CANON_SIMPLE        0
  88 #define PDKIM_CANON_RELAXED       1
  89
  90 /* -------------------------------------------------------------------------- */
  91 /* Some required forward declarations, please ignore */
  92 typedef struct pdkim_stringlist pdkim_stringlist;
  93 typedef struct pdkim_str pdkim_str;
  94 typedef struct sha1_context sha1_context;
  95 typedef struct sha2_context sha2_context;
  96 #define HAVE_SHA1_CONTEXT
  97 #define HAVE_SHA2_CONTEXT
  98
  99 /* -------------------------------------------------------------------------- */
 100 /* Some concessions towards Redmond */
 101 #ifdef WINDOWS
 102 #define snprintf _snprintf
 103 #define strcasecmp _stricmp
 104 #define strncasecmp _strnicmp
 105 #define DLLEXPORT __declspec(dllexport)
 106 #else
 107 #define DLLEXPORT
 108 #endif
 109
 110
 111 /* -------------------------------------------------------------------------- */
 112 /* Public key as (usually) fetched from DNS */
 113 typedef struct pdkim_pubkey {
 114   const uschar * version;         /* v=  */
 115   const uschar *granularity;      /* g=  */
 116
 117   const uschar * hashes;          /* h=  */
 118   const uschar * keytype;         /* k=  */
 119   const uschar * srvtype;         /* s=  */
 120   uschar *notes;                  /* n=  */
 121
 122   blob  key;                      /* p=  */
 123   int   testing;                  /* t=y */
 124   int   no_subdomaining;          /* t=s */
 125 } pdkim_pubkey;
 126
 127 /* -------------------------------------------------------------------------- */
 128 /* Body-hash to be calculated */
 129 typedef struct pdkim_bodyhash {
 130   struct pdkim_bodyhash *       next;
 131   int                           hashtype;
 132   int                           canon_method;
 133   long                          bodylength;
 134
 135   hctx                          body_hash_ctx;
 136   unsigned long                 signed_body_bytes;      /* done so far */
 137   int                           num_buffered_blanklines;
 138
 139   blob                          bh;                     /* completed hash */
 140 } pdkim_bodyhash;
 141
 142 /* -------------------------------------------------------------------------- */
 143 /* Signature as it appears in a DKIM-Signature header */
 144 typedef struct pdkim_signature {
 145   struct pdkim_signature * next;
 146
 147   /* Bits stored in a DKIM signature header --------------------------- */
 148
 149   /* (v=) The version, as an integer. Currently, always "1" */
 150   int version;
 151
 152   /* (a=) The signature algorithm. */
 153   int           keytype;        /* pdkim_keytypes index */
 154   unsigned      keybits;        /* size of the key */
 155   int           hashtype;       /* pdkim_hashes index */
 156
 157   /* (c=x/) Header canonicalization method. Either PDKIM_CANON_SIMPLE
 158      or PDKIM_CANON_RELAXED */
 159   int canon_headers;
 160
 161   /* (c=/x) Body canonicalization method. Either PDKIM_CANON_SIMPLE
 162      or PDKIM_CANON_RELAXED */
 163   int canon_body;
 164
 165   /* (q=) Query Method. Currently, only PDKIM_QUERYMETHOD_DNS_TXT
 166      is specified */
 167   int querymethod;
 168
 169   /* (s=) The selector string as given in the signature */
 170   uschar *selector;
 171
 172   /* (d=) The domain as given in the signature */
 173   uschar *domain;
 174
 175   /* (i=) The identity as given in the signature */
 176   uschar *identity;
 177
 178   /* (t=) Timestamp of signature creation */
 179   unsigned long created;
 180
 181   /* (x=) Timestamp of expiry of signature */
 182   unsigned long expires;
 183
 184   /* (l=) Amount of hashed body bytes (after canonicalization). Default
 185      is -1. Note: a value of 0 means that the body is unsigned! */
 186   long bodylength;
 187
 188   /* (h=) Colon-separated list of header names that are included in the
 189      signature */
 190   uschar *headernames;
 191
 192   /* (z=) */
 193   uschar *copiedheaders;
 194
 195   /* (b=) Raw signature data, along with its length in bytes */
 196   blob sighash;
 197
 198   /* (bh=) Raw body hash data, along with its length in bytes */
 199   blob bodyhash;
 200
 201   /* Folded DKIM-Signature: header. Signing only, NULL for verifying.
 202      Ready for insertion into the message. Note: Folded using CRLFTB,
 203      but final line terminator is NOT included. Note2: This buffer is
 204      free()d when you call pdkim_free_ctx(). */
 205   uschar *signature_header;
 206
 207   /* The main verification status. Verification only. One of:
 208
 209      PDKIM_VERIFY_NONE      Verification was not attempted. This status
 210                             should not appear.
 211
 212      PDKIM_VERIFY_INVALID   There was an error while trying to verify
 213                             the signature. A more precise description
 214                             is available in verify_ext_status.
 215
 216      PDKIM_VERIFY_FAIL      Verification failed because either the body
 217                             hash did not match, or the signature verification
 218                             failed. This means the message was modified.
 219                             Check verify_ext_status for the exact reason.
 220
 221      PDKIM_VERIFY_PASS      Verification succeeded.
 222   */
 223   int verify_status;
 224
 225   /* Extended verification status. Verification only. Depending on the value
 226      of verify_status, it can contain:
 227
 228      For verify_status == PDKIM_VERIFY_INVALID:
 229
 230         PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE
 231           Unable to retrieve a public key container.
 232
 233         PDKIM_VERIFY_INVALID_BUFFER_SIZE
 234           Either the DNS name constructed to retrieve the public key record
 235           does not fit into PDKIM_DNS_TXT_MAX_NAMELEN bytes, or the retrieved
 236           record is longer than PDKIM_DNS_TXT_MAX_RECLEN bytes.
 237
 238         PDKIM_VERIFY_INVALID_PUBKEY_PARSING
 239           (Syntax) error while parsing the retrieved public key record.
 240
 241
 242      For verify_status == PDKIM_VERIFY_FAIL:
 243
 244         PDKIM_VERIFY_FAIL_BODY
 245           The calculated body hash does not match the advertised body hash
 246           from the bh= tag of the signature.
 247
 248         PDKIM_VERIFY_FAIL_MESSAGE
 249           RSA verification of the signature (b= tag) failed.
 250   */
 251   int verify_ext_status;
 252
 253   /* Pointer to a public key record that was used to verify the signature.
 254      See pdkim_pubkey declaration above for more information.
 255      Caution: is NULL if signing or if no record was retrieved. */
 256   pdkim_pubkey *pubkey;
 257
 258   /* Properties below this point are used internally only ------------- */
 259
 260   /* Per-signature helper variables ----------------------------------- */
 261   pdkim_bodyhash *calc_body_hash;       /* hash to be / being calculated */
 262
 263   pdkim_stringlist *headers;            /* Raw headers included in the sig */
 264
 265   /* Signing specific ------------------------------------------------- */
 266   uschar * privkey;          /* Private key                                 */
 267   uschar * sign_headers;    /* To-be-signed header names                   */
 268   uschar * rawsig_no_b_val; /* Original signature header w/o b= tag value. */
 269 } pdkim_signature;
 270
 271
 272 /* -------------------------------------------------------------------------- */
 273 /* Context to keep state between all operations. */
 274 typedef struct pdkim_ctx {
 275
 276 #define PDKIM_MODE_SIGN   BIT(0)        /* if unset, mode==verify */
 277 #define PDKIM_DOT_TERM    BIT(1)        /* dot termination and unstuffing */
 278 #define PDKIM_SEEN_CR     BIT(2)
 279 #define PDKIM_SEEN_LF     BIT(3)
 280 #define PDKIM_PAST_HDRS   BIT(4)
 281 #define PDKIM_SEEN_EOD    BIT(5)
 282   unsigned   flags;
 283
 284   /* One (signing) or several chained (verification) signatures */
 285   pdkim_signature *sig;
 286
 287   /* One (signing) or several chained (verification) bodyhashes */
 288   pdkim_bodyhash *bodyhash;
 289
 290   /* Callback for dns/txt query method (verification only) */
 291   uschar * (*dns_txt_callback)(const uschar *);
 292
 293   /* Coder's little helpers */
 294   gstring   *cur_header;
 295   uschar    *linebuf;
 296   int        linebuf_offset;
 297   int        num_headers;
 298   pdkim_stringlist *headers; /* Raw headers for verification         */
 299 } pdkim_ctx;
 300
 301
 302 /******************************************************************************/
 303
 304 typedef struct {
 305   const uschar * dkim_hashname;
 306   hashmethod     exim_hashmethod;
 307 } pdkim_hashtype;
 308 extern const pdkim_hashtype pdkim_hashes[];
 309
 310 /******************************************************************************/
 311
 312
 313 /* -------------------------------------------------------------------------- */
 314 /* API functions. Please see the sample code in sample/test_sign.c and
 315    sample/test_verify.c for documentation.
 316 */
 317
 318 #ifdef __cplusplus
 319 extern "C" {
 320 #endif
 321
 322 void       pdkim_init         (void);
 323
 324 void       pdkim_init_context (pdkim_ctx *, BOOL, uschar * (*)(const uschar *));
 325
 326 DLLEXPORT
 327 pdkim_signature *pdkim_init_sign    (pdkim_ctx *,
 328                                uschar *, uschar *, uschar *, uschar *,
 329                                const uschar **);
 330
 331 DLLEXPORT
 332 pdkim_ctx *pdkim_init_verify  (uschar * (*)(const uschar *), BOOL);
 333
 334 DLLEXPORT
 335 void       pdkim_set_optional (pdkim_signature *, char *, char *,int, int,
 336                                long,
 337                                unsigned long,
 338                                unsigned long);
 339
 340 int             pdkim_hashname_to_hashtype(const uschar *, unsigned);
 341 void            pdkim_cstring_to_canons(const uschar *, unsigned, int *, int *);
 342 pdkim_bodyhash *pdkim_set_bodyhash(pdkim_ctx *, int, int, long);
 343 pdkim_bodyhash *pdkim_set_sig_bodyhash(pdkim_ctx *, pdkim_signature *);
 344
 345 DLLEXPORT
 346 int        pdkim_feed         (pdkim_ctx *, uschar *, int);
 347 DLLEXPORT
 348 int        pdkim_feed_finish  (pdkim_ctx *, pdkim_signature **, const uschar **);
 349
 350 DLLEXPORT
 351 void       pdkim_free_ctx     (pdkim_ctx *);
 352
 353
 354 const uschar *  pdkim_errstr(int);
 355
 356 extern uschar *         pdkim_encode_base64(blob *);
 357 extern void             pdkim_decode_base64(const uschar *, blob *);
 358 extern void             pdkim_hexprint(const uschar *, int);
 359 extern void             pdkim_quoteprint(const uschar *, int);
 360 extern pdkim_pubkey *   pdkim_parse_pubkey_record(const uschar *);
 361 extern uschar *         pdkim_relax_header_n(const uschar *, int, BOOL);
 362 extern uschar *         pdkim_relax_header(const uschar *, BOOL);
 363 extern uschar *         dkim_sig_to_a_tag(const pdkim_signature *);
 364
 365 #ifdef __cplusplus
 366 }
 367 #endif
 368
 369 #endif