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_ALGO_RSA_SHA256     0 */
  78 /*#define PDKIM_ALGO_RSA_SHA1       1 */
  79
  80 #define PDKIM_CANON_SIMPLE        0
  81 #define PDKIM_CANON_RELAXED       1
  82
  83 /* -------------------------------------------------------------------------- */
  84 /* Some required forward declarations, please ignore */
  85 typedef struct pdkim_stringlist pdkim_stringlist;
  86 typedef struct pdkim_str pdkim_str;
  87 typedef struct sha1_context sha1_context;
  88 typedef struct sha2_context sha2_context;
  89 #define HAVE_SHA1_CONTEXT
  90 #define HAVE_SHA2_CONTEXT
  91
  92 /* -------------------------------------------------------------------------- */
  93 /* Some concessions towards Redmond */
  94 #ifdef WINDOWS
  95 #define snprintf _snprintf
  96 #define strcasecmp _stricmp
  97 #define strncasecmp _strnicmp
  98 #define DLLEXPORT __declspec(dllexport)
  99 #else
 100 #define DLLEXPORT
 101 #endif
 102
 103
 104 /* -------------------------------------------------------------------------- */
 105 /* Public key as (usually) fetched from DNS */
 106 typedef struct pdkim_pubkey {
 107   const uschar * version;         /* v=  */
 108   const uschar *granularity;      /* g=  */
 109
 110   const uschar * hashes;          /* h=  */
 111   const uschar * keytype;         /* k=  */
 112   const uschar * srvtype;         /* s=  */
 113   uschar *notes;                  /* n=  */
 114
 115   blob  key;                      /* p=  */
 116   int   testing;                  /* t=y */
 117   int   no_subdomaining;          /* t=s */
 118 } pdkim_pubkey;
 119
 120 /* -------------------------------------------------------------------------- */
 121 /* Body-hash to be calculated */
 122 typedef struct pdkim_bodyhash {
 123   struct pdkim_bodyhash *       next;
 124   int                           hashtype;
 125   int                           canon_method;
 126   long                          bodylength;
 127
 128   hctx                          body_hash_ctx;
 129   unsigned long                 signed_body_bytes;      /* done so far */
 130   int                           num_buffered_blanklines;
 131
 132   blob                          bh;                     /* completed hash */
 133 } pdkim_bodyhash;
 134
 135 /* -------------------------------------------------------------------------- */
 136 /* Signature as it appears in a DKIM-Signature header */
 137 typedef struct pdkim_signature {
 138   struct pdkim_signature * next;
 139
 140   /* Bits stored in a DKIM signature header --------------------------- */
 141
 142   /* (v=) The version, as an integer. Currently, always "1" */
 143   int version;
 144
 145   /* (a=) The signature algorithm. Either PDKIM_ALGO_RSA_SHA256 */
 146   int keytype;  /* pdkim_keytypes index */
 147   int hashtype; /* pdkim_hashes index */
 148
 149   /* (c=x/) Header canonicalization method. Either PDKIM_CANON_SIMPLE
 150      or PDKIM_CANON_RELAXED */
 151   int canon_headers;
 152
 153   /* (c=/x) Body canonicalization method. Either PDKIM_CANON_SIMPLE
 154      or PDKIM_CANON_RELAXED */
 155   int canon_body;
 156
 157   /* (q=) Query Method. Currently, only PDKIM_QUERYMETHOD_DNS_TXT
 158      is specified */
 159   int querymethod;
 160
 161   /* (s=) The selector string as given in the signature */
 162   uschar *selector;
 163
 164   /* (d=) The domain as given in the signature */
 165   uschar *domain;
 166
 167   /* (i=) The identity as given in the signature */
 168   uschar *identity;
 169
 170   /* (t=) Timestamp of signature creation */
 171   unsigned long created;
 172
 173   /* (x=) Timestamp of expiry of signature */
 174   unsigned long expires;
 175
 176   /* (l=) Amount of hashed body bytes (after canonicalization). Default
 177      is -1. Note: a value of 0 means that the body is unsigned! */
 178   long bodylength;
 179
 180   /* (h=) Colon-separated list of header names that are included in the
 181      signature */
 182   uschar *headernames;
 183
 184   /* (z=) */
 185   uschar *copiedheaders;
 186
 187   /* (b=) Raw signature data, along with its length in bytes */
 188   blob sighash;
 189
 190   /* (bh=) Raw body hash data, along with its length in bytes */
 191   blob bodyhash;
 192
 193   /* Folded DKIM-Signature: header. Signing only, NULL for verifying.
 194      Ready for insertion into the message. Note: Folded using CRLFTB,
 195      but final line terminator is NOT included. Note2: This buffer is
 196      free()d when you call pdkim_free_ctx(). */
 197   uschar *signature_header;
 198
 199   /* The main verification status. Verification only. One of:
 200
 201      PDKIM_VERIFY_NONE      Verification was not attempted. This status
 202                             should not appear.
 203
 204      PDKIM_VERIFY_INVALID   There was an error while trying to verify
 205                             the signature. A more precise description
 206                             is available in verify_ext_status.
 207
 208      PDKIM_VERIFY_FAIL      Verification failed because either the body
 209                             hash did not match, or the signature verification
 210                             failed. This means the message was modified.
 211                             Check verify_ext_status for the exact reason.
 212
 213      PDKIM_VERIFY_PASS      Verification succeeded.
 214   */
 215   int verify_status;
 216
 217   /* Extended verification status. Verification only. Depending on the value
 218      of verify_status, it can contain:
 219
 220      For verify_status == PDKIM_VERIFY_INVALID:
 221
 222         PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE
 223           Unable to retrieve a public key container.
 224
 225         PDKIM_VERIFY_INVALID_BUFFER_SIZE
 226           Either the DNS name constructed to retrieve the public key record
 227           does not fit into PDKIM_DNS_TXT_MAX_NAMELEN bytes, or the retrieved
 228           record is longer than PDKIM_DNS_TXT_MAX_RECLEN bytes.
 229
 230         PDKIM_VERIFY_INVALID_PUBKEY_PARSING
 231           (Syntax) error while parsing the retrieved public key record.
 232
 233
 234      For verify_status == PDKIM_VERIFY_FAIL:
 235
 236         PDKIM_VERIFY_FAIL_BODY
 237           The calculated body hash does not match the advertised body hash
 238           from the bh= tag of the signature.
 239
 240         PDKIM_VERIFY_FAIL_MESSAGE
 241           RSA verification of the signature (b= tag) failed.
 242   */
 243   int verify_ext_status;
 244
 245   /* Pointer to a public key record that was used to verify the signature.
 246      See pdkim_pubkey declaration above for more information.
 247      Caution: is NULL if signing or if no record was retrieved. */
 248   pdkim_pubkey *pubkey;
 249
 250   /* Properties below this point are used internally only ------------- */
 251
 252   /* Per-signature helper variables ----------------------------------- */
 253   pdkim_bodyhash *calc_body_hash;       /* hash to be / being calculated */
 254
 255   pdkim_stringlist *headers;            /* Raw headers included in the sig */
 256
 257   /* Signing specific ------------------------------------------------- */
 258   uschar * privkey;          /* Private key                                 */
 259   uschar * sign_headers;    /* To-be-signed header names                   */
 260   uschar * rawsig_no_b_val; /* Original signature header w/o b= tag value. */
 261 } pdkim_signature;
 262
 263
 264 /* -------------------------------------------------------------------------- */
 265 /* Context to keep state between all operations. */
 266 typedef struct pdkim_ctx {
 267
 268 #define PDKIM_MODE_SIGN   BIT(0)        /* if unset, mode==verify */
 269 #define PDKIM_DOT_TERM    BIT(1)        /* dot termination and unstuffing */
 270 #define PDKIM_SEEN_CR     BIT(2)
 271 #define PDKIM_SEEN_LF     BIT(3)
 272 #define PDKIM_PAST_HDRS   BIT(4)
 273 #define PDKIM_SEEN_EOD    BIT(5)
 274   unsigned   flags;
 275
 276   /* One (signing) or several chained (verification) signatures */
 277   pdkim_signature *sig;
 278
 279   /* One (signing) or several chained (verification) bodyhashes */
 280   pdkim_bodyhash *bodyhash;
 281
 282   /* Callback for dns/txt query method (verification only) */
 283   uschar * (*dns_txt_callback)(uschar *);
 284
 285   /* Coder's little helpers */
 286   gstring   *cur_header;
 287   uschar    *linebuf;
 288   int        linebuf_offset;
 289   int        num_headers;
 290   pdkim_stringlist *headers; /* Raw headers for verification         */
 291 } pdkim_ctx;
 292
 293
 294 /******************************************************************************/
 295
 296 typedef struct {
 297   const uschar * dkim_hashname;
 298   hashmethod     exim_hashmethod;
 299 } pdkim_hashtype;
 300 extern const pdkim_hashtype pdkim_hashes[];
 301
 302 /******************************************************************************/
 303
 304
 305 /* -------------------------------------------------------------------------- */
 306 /* API functions. Please see the sample code in sample/test_sign.c and
 307    sample/test_verify.c for documentation.
 308 */
 309
 310 #ifdef __cplusplus
 311 extern "C" {
 312 #endif
 313
 314 void       pdkim_init         (void);
 315
 316 void       pdkim_init_context (pdkim_ctx *, BOOL, uschar * (*)(uschar *));
 317
 318 DLLEXPORT
 319 pdkim_signature *pdkim_init_sign    (pdkim_ctx *,
 320                                uschar *, uschar *, uschar *, uschar *,
 321                                const uschar **);
 322
 323 DLLEXPORT
 324 pdkim_ctx *pdkim_init_verify  (uschar * (*)(uschar *), BOOL);
 325
 326 DLLEXPORT
 327 void       pdkim_set_optional (pdkim_signature *, char *, char *,int, int,
 328                                long,
 329                                unsigned long,
 330                                unsigned long);
 331
 332 int             pdkim_hashname_to_hashtype(const uschar *, unsigned);
 333 void            pdkim_cstring_to_canons(const uschar *, unsigned, int *, int *);
 334 pdkim_bodyhash *pdkim_set_bodyhash(pdkim_ctx *, int, int, long);
 335 pdkim_bodyhash *pdkim_set_sig_bodyhash(pdkim_ctx *, pdkim_signature *);
 336
 337 DLLEXPORT
 338 int        pdkim_feed         (pdkim_ctx *, uschar *, int);
 339 DLLEXPORT
 340 int        pdkim_feed_finish  (pdkim_ctx *, pdkim_signature **, const uschar **);
 341
 342 DLLEXPORT
 343 void       pdkim_free_ctx     (pdkim_ctx *);
 344
 345
 346 const uschar *  pdkim_errstr(int);
 347
 348 extern uschar *         pdkim_encode_base64(blob *);
 349 extern void             pdkim_decode_base64(const uschar *, blob *);
 350 extern void             pdkim_hexprint(const uschar *, int);
 351 extern void             pdkim_quoteprint(const uschar *, int);
 352 extern pdkim_pubkey *   pdkim_parse_pubkey_record(const uschar *);
 353 extern uschar *         pdkim_relax_header_n(const uschar *, int, BOOL);
 354 extern uschar *         pdkim_relax_header(const uschar *, BOOL);
 355 extern uschar *         dkim_sig_to_a_tag(const pdkim_signature *);
 356
 357 #ifdef __cplusplus
 358 }
 359 #endif
 360
 361 #endif