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_SIGN_PRIVKEY_WRAP    -105
  52 #define PDKIM_SIGN_PRIVKEY_B64D    -106
  53
  54 /* -------------------------------------------------------------------------- */
  55 /* Main/Extended verification status */
  56 #define PDKIM_VERIFY_NONE      0
  57 #define PDKIM_VERIFY_INVALID   1
  58 #define PDKIM_VERIFY_FAIL      2
  59 #define PDKIM_VERIFY_PASS      3
  60 #define PDKIM_VERIFY_POLICY    BIT(31)
  61
  62 #define PDKIM_VERIFY_FAIL_BODY                    1
  63 #define PDKIM_VERIFY_FAIL_MESSAGE                 2
  64 #define PDKIM_VERIFY_FAIL_SIG_ALGO_MISMATCH       3
  65 #define PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE   4
  66 #define PDKIM_VERIFY_INVALID_BUFFER_SIZE          5
  67 #define PDKIM_VERIFY_INVALID_PUBKEY_DNSRECORD     6
  68 #define PDKIM_VERIFY_INVALID_PUBKEY_IMPORT        7
  69 #define PDKIM_VERIFY_INVALID_SIGNATURE_ERROR      8
  70 #define PDKIM_VERIFY_INVALID_DKIM_VERSION         9
  71
  72 /* -------------------------------------------------------------------------- */
  73 /* Some parameter values */
  74 #define PDKIM_QUERYMETHOD_DNS_TXT 0
  75
  76 /*#define PDKIM_ALGO_RSA_SHA256     0 */
  77 /*#define PDKIM_ALGO_RSA_SHA1       1 */
  78
  79 #define PDKIM_CANON_SIMPLE        0
  80 #define PDKIM_CANON_RELAXED       1
  81
  82 /* -------------------------------------------------------------------------- */
  83 /* Some required forward declarations, please ignore */
  84 typedef struct pdkim_stringlist pdkim_stringlist;
  85 typedef struct pdkim_str pdkim_str;
  86 typedef struct sha1_context sha1_context;
  87 typedef struct sha2_context sha2_context;
  88 #define HAVE_SHA1_CONTEXT
  89 #define HAVE_SHA2_CONTEXT
  90
  91 /* -------------------------------------------------------------------------- */
  92 /* Some concessions towards Redmond */
  93 #ifdef WINDOWS
  94 #define snprintf _snprintf
  95 #define strcasecmp _stricmp
  96 #define strncasecmp _strnicmp
  97 #define DLLEXPORT __declspec(dllexport)
  98 #else
  99 #define DLLEXPORT
 100 #endif
 101
 102
 103 /* -------------------------------------------------------------------------- */
 104 /* Public key as (usually) fetched from DNS */
 105 typedef struct pdkim_pubkey {
 106   const uschar * version;         /* v=  */
 107   const uschar *granularity;      /* g=  */
 108
 109   const uschar * hashes;          /* h=  */
 110   const uschar * keytype;         /* k=  */
 111   const uschar * srvtype;         /* s=  */
 112   uschar *notes;                  /* n=  */
 113
 114   blob  key;                      /* p=  */
 115   int   testing;                  /* t=y */
 116   int   no_subdomaining;          /* t=s */
 117 } pdkim_pubkey;
 118
 119 /* -------------------------------------------------------------------------- */
 120 /* Body-hash to be calculated */
 121 typedef struct pdkim_bodyhash {
 122   struct pdkim_bodyhash *       next;
 123   int                           hashtype;
 124   int                           canon_method;
 125   long                          bodylength;
 126
 127   hctx                          body_hash_ctx;
 128   unsigned long                 signed_body_bytes;      /* done so far */
 129   int                           num_buffered_blanklines;
 130
 131   blob                          bh;                     /* completed hash */
 132 } pdkim_bodyhash;
 133
 134 /* -------------------------------------------------------------------------- */
 135 /* Signature as it appears in a DKIM-Signature header */
 136 typedef struct pdkim_signature {
 137   struct pdkim_signature * next;
 138
 139   /* Bits stored in a DKIM signature header --------------------------- */
 140
 141   /* (v=) The version, as an integer. Currently, always "1" */
 142   int version;
 143
 144   /* (a=) The signature algorithm. Either PDKIM_ALGO_RSA_SHA256 */
 145   int keytype;  /* pdkim_keytypes index */
 146   int hashtype; /* pdkim_hashes index */
 147
 148   /* (c=x/) Header canonicalization method. Either PDKIM_CANON_SIMPLE
 149      or PDKIM_CANON_RELAXED */
 150   int canon_headers;
 151
 152   /* (c=/x) Body canonicalization method. Either PDKIM_CANON_SIMPLE
 153      or PDKIM_CANON_RELAXED */
 154   int canon_body;
 155
 156   /* (q=) Query Method. Currently, only PDKIM_QUERYMETHOD_DNS_TXT
 157      is specified */
 158   int querymethod;
 159
 160   /* (s=) The selector string as given in the signature */
 161   uschar *selector;
 162
 163   /* (d=) The domain as given in the signature */
 164   uschar *domain;
 165
 166   /* (i=) The identity as given in the signature */
 167   uschar *identity;
 168
 169   /* (t=) Timestamp of signature creation */
 170   unsigned long created;
 171
 172   /* (x=) Timestamp of expiry of signature */
 173   unsigned long expires;
 174
 175   /* (l=) Amount of hashed body bytes (after canonicalization). Default
 176      is -1. Note: a value of 0 means that the body is unsigned! */
 177   long bodylength;
 178
 179   /* (h=) Colon-separated list of header names that are included in the
 180      signature */
 181   uschar *headernames;
 182
 183   /* (z=) */
 184   uschar *copiedheaders;
 185
 186   /* (b=) Raw signature data, along with its length in bytes */
 187   blob sighash;
 188
 189   /* (bh=) Raw body hash data, along with its length in bytes */
 190   blob bodyhash;
 191
 192   /* Folded DKIM-Signature: header. Signing only, NULL for verifying.
 193      Ready for insertion into the message. Note: Folded using CRLFTB,
 194      but final line terminator is NOT included. Note2: This buffer is
 195      free()d when you call pdkim_free_ctx(). */
 196   uschar *signature_header;
 197
 198   /* The main verification status. Verification only. One of:
 199
 200      PDKIM_VERIFY_NONE      Verification was not attempted. This status
 201                             should not appear.
 202
 203      PDKIM_VERIFY_INVALID   There was an error while trying to verify
 204                             the signature. A more precise description
 205                             is available in verify_ext_status.
 206
 207      PDKIM_VERIFY_FAIL      Verification failed because either the body
 208                             hash did not match, or the signature verification
 209                             failed. This means the message was modified.
 210                             Check verify_ext_status for the exact reason.
 211
 212      PDKIM_VERIFY_PASS      Verification succeeded.
 213   */
 214   int verify_status;
 215
 216   /* Extended verification status. Verification only. Depending on the value
 217      of verify_status, it can contain:
 218
 219      For verify_status == PDKIM_VERIFY_INVALID:
 220
 221         PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE
 222           Unable to retrieve a public key container.
 223
 224         PDKIM_VERIFY_INVALID_BUFFER_SIZE
 225           Either the DNS name constructed to retrieve the public key record
 226           does not fit into PDKIM_DNS_TXT_MAX_NAMELEN bytes, or the retrieved
 227           record is longer than PDKIM_DNS_TXT_MAX_RECLEN bytes.
 228
 229         PDKIM_VERIFY_INVALID_PUBKEY_PARSING
 230           (Syntax) error while parsing the retrieved public key record.
 231
 232
 233      For verify_status == PDKIM_VERIFY_FAIL:
 234
 235         PDKIM_VERIFY_FAIL_BODY
 236           The calculated body hash does not match the advertised body hash
 237           from the bh= tag of the signature.
 238
 239         PDKIM_VERIFY_FAIL_MESSAGE
 240           RSA verification of the signature (b= tag) failed.
 241   */
 242   int verify_ext_status;
 243
 244   /* Pointer to a public key record that was used to verify the signature.
 245      See pdkim_pubkey declaration above for more information.
 246      Caution: is NULL if signing or if no record was retrieved. */
 247   pdkim_pubkey *pubkey;
 248
 249   /* Properties below this point are used internally only ------------- */
 250
 251   /* Per-signature helper variables ----------------------------------- */
 252   pdkim_bodyhash *calc_body_hash;       /* hash to be / being calculated */
 253
 254   pdkim_stringlist *headers;            /* Raw headers included in the sig */
 255
 256   /* Signing specific ------------------------------------------------- */
 257   uschar * privkey;          /* Private key                                 */
 258   uschar * sign_headers;    /* To-be-signed header names                   */
 259   uschar * rawsig_no_b_val; /* Original signature header w/o b= tag value. */
 260 } pdkim_signature;
 261
 262
 263 /* -------------------------------------------------------------------------- */
 264 /* Context to keep state between all operations. */
 265 typedef struct pdkim_ctx {
 266
 267 #define PDKIM_MODE_SIGN   BIT(0)        /* if unset, mode==verify */
 268 #define PDKIM_DOT_TERM    BIT(1)        /* dot termination and unstuffing */
 269 #define PDKIM_SEEN_CR     BIT(2)
 270 #define PDKIM_SEEN_LF     BIT(3)
 271 #define PDKIM_PAST_HDRS   BIT(4)
 272 #define PDKIM_SEEN_EOD    BIT(5)
 273   unsigned   flags;
 274
 275   /* One (signing) or several chained (verification) signatures */
 276   pdkim_signature *sig;
 277
 278   /* One (signing) or several chained (verification) bodyhashes */
 279   pdkim_bodyhash *bodyhash;
 280
 281   /* Callback for dns/txt query method (verification only) */
 282   uschar * (*dns_txt_callback)(char *);
 283
 284   /* Coder's little helpers */
 285   gstring   *cur_header;
 286   uschar    *linebuf;
 287   int        linebuf_offset;
 288   int        num_headers;
 289   pdkim_stringlist *headers; /* Raw headers for verification         */
 290 } pdkim_ctx;
 291
 292
 293 /* -------------------------------------------------------------------------- */
 294 /* API functions. Please see the sample code in sample/test_sign.c and
 295    sample/test_verify.c for documentation.
 296 */
 297
 298 #ifdef __cplusplus
 299 extern "C" {
 300 #endif
 301
 302 void       pdkim_init         (void);
 303
 304 void       pdkim_init_context (pdkim_ctx *, BOOL, uschar * (*)(char *));
 305
 306 DLLEXPORT
 307 pdkim_signature *pdkim_init_sign    (pdkim_ctx *,
 308                                uschar *, uschar *, uschar *, uschar *,
 309                                const uschar **);
 310
 311 DLLEXPORT
 312 pdkim_ctx *pdkim_init_verify  (uschar * (*)(char *), BOOL);
 313
 314 DLLEXPORT
 315 void       pdkim_set_optional (pdkim_signature *, char *, char *,int, int,
 316                                long,
 317                                unsigned long,
 318                                unsigned long);
 319
 320 pdkim_bodyhash *pdkim_set_bodyhash(pdkim_ctx *, pdkim_signature *);
 321
 322 DLLEXPORT
 323 int        pdkim_feed         (pdkim_ctx *, uschar *, int);
 324 DLLEXPORT
 325 int        pdkim_feed_finish  (pdkim_ctx *, pdkim_signature **, const uschar **);
 326
 327 DLLEXPORT
 328 void       pdkim_free_ctx     (pdkim_ctx *);
 329
 330
 331 const uschar *  pdkim_errstr(int);
 332
 333 uschar *        dkim_sig_to_a_tag(const pdkim_signature * sig);
 334
 335 #ifdef __cplusplus
 336 }
 337 #endif
 338
 339 #endif