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 - 2017  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 /* -------------------------------------------------------------------------- */
  30 /* Length of the preallocated buffer for the "answer" from the dns/txt
  31    callback function. This should match the maximum RDLENGTH from DNS. */
  32 #define PDKIM_DNS_TXT_MAX_RECLEN    (1 << 16)
  33
  34 /* -------------------------------------------------------------------------- */
  35 /* Function success / error codes */
  36 #define PDKIM_OK                      0
  37 #define PDKIM_FAIL                   -1
  38 #define PDKIM_ERR_RSA_PRIVKEY      -101
  39 #define PDKIM_ERR_RSA_SIGNING      -102
  40 #define PDKIM_ERR_LONG_LINE        -103
  41 #define PDKIM_ERR_BUFFER_TOO_SMALL -104
  42 #define PDKIM_SIGN_PRIVKEY_WRAP    -105
  43 #define PDKIM_SIGN_PRIVKEY_B64D    -106
  44
  45 /* -------------------------------------------------------------------------- */
  46 /* Main/Extended verification status */
  47 #define PDKIM_VERIFY_NONE      0
  48 #define PDKIM_VERIFY_INVALID   1
  49 #define PDKIM_VERIFY_FAIL      2
  50 #define PDKIM_VERIFY_PASS      3
  51
  52 #define PDKIM_VERIFY_FAIL_BODY                    1
  53 #define PDKIM_VERIFY_FAIL_MESSAGE                 2
  54 #define PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE   3
  55 #define PDKIM_VERIFY_INVALID_BUFFER_SIZE          4
  56 #define PDKIM_VERIFY_INVALID_PUBKEY_DNSRECORD     5
  57 #define PDKIM_VERIFY_INVALID_PUBKEY_IMPORT        6
  58 #define PDKIM_VERIFY_INVALID_SIGNATURE_ERROR      7
  59 #define PDKIM_VERIFY_INVALID_DKIM_VERSION         8
  60
  61 /* -------------------------------------------------------------------------- */
  62 /* Some parameter values */
  63 #define PDKIM_QUERYMETHOD_DNS_TXT 0
  64
  65 #define PDKIM_ALGO_RSA_SHA256     0
  66 #define PDKIM_ALGO_RSA_SHA1       1
  67
  68 #define PDKIM_CANON_SIMPLE        0
  69 #define PDKIM_CANON_RELAXED       1
  70
  71 #define PDKIM_HASH_SHA256         0
  72 #define PDKIM_HASH_SHA1           1
  73
  74 #define PDKIM_KEYTYPE_RSA         0
  75
  76 /* -------------------------------------------------------------------------- */
  77 /* Some required forward declarations, please ignore */
  78 typedef struct pdkim_stringlist pdkim_stringlist;
  79 typedef struct pdkim_str pdkim_str;
  80 typedef struct sha1_context sha1_context;
  81 typedef struct sha2_context sha2_context;
  82 #define HAVE_SHA1_CONTEXT
  83 #define HAVE_SHA2_CONTEXT
  84
  85 /* -------------------------------------------------------------------------- */
  86 /* Some concessions towards Redmond */
  87 #ifdef WINDOWS
  88 #define snprintf _snprintf
  89 #define strcasecmp _stricmp
  90 #define strncasecmp _strnicmp
  91 #define DLLEXPORT __declspec(dllexport)
  92 #else
  93 #define DLLEXPORT
  94 #endif
  95
  96
  97 /* -------------------------------------------------------------------------- */
  98 /* Public key as (usually) fetched from DNS */
  99 typedef struct pdkim_pubkey {
 100   uschar *version;                /* v=  */
 101   uschar *granularity;            /* g=  */
 102
 103 #ifdef notdef
 104   uschar *hashes;                 /* h=  */
 105   uschar *keytype;                /* k=  */
 106 #endif
 107   uschar *srvtype;                /* s=  */
 108   uschar *notes;                  /* n=  */
 109
 110   blob  key;                      /* p=  */
 111   int   testing;                  /* t=y */
 112   int   no_subdomaining;          /* t=s */
 113 } pdkim_pubkey;
 114
 115 /* -------------------------------------------------------------------------- */
 116 /* Signature as it appears in a DKIM-Signature header */
 117 typedef struct pdkim_signature {
 118
 119   /* Bits stored in a DKIM signature header --------------------------- */
 120
 121   /* (v=) The version, as an integer. Currently, always "1" */
 122   int version;
 123
 124   /* (a=) The signature algorithm. Either PDKIM_ALGO_RSA_SHA256
 125      or PDKIM_ALGO_RSA_SHA1 */
 126   int algo;
 127
 128   /* (c=x/) Header canonicalization method. Either PDKIM_CANON_SIMPLE
 129      or PDKIM_CANON_RELAXED */
 130   int canon_headers;
 131
 132   /* (c=/x) Body canonicalization method. Either PDKIM_CANON_SIMPLE
 133      or PDKIM_CANON_RELAXED */
 134   int canon_body;
 135
 136   /* (q=) Query Method. Currently, only PDKIM_QUERYMETHOD_DNS_TXT
 137      is specified */
 138   int querymethod;
 139
 140   /* (s=) The selector string as given in the signature */
 141   uschar *selector;
 142
 143   /* (d=) The domain as given in the signature */
 144   uschar *domain;
 145
 146   /* (i=) The identity as given in the signature */
 147   uschar *identity;
 148
 149   /* (t=) Timestamp of signature creation */
 150   unsigned long created;
 151
 152   /* (x=) Timestamp of expiry of signature */
 153   unsigned long expires;
 154
 155   /* (l=) Amount of hashed body bytes (after canonicalization). Default
 156      is -1. Note: a value of 0 means that the body is unsigned! */
 157   long bodylength;
 158
 159   /* (h=) Colon-separated list of header names that are included in the
 160      signature */
 161   uschar *headernames;
 162
 163   /* (z=) */
 164   uschar *copiedheaders;
 165
 166   /* (b=) Raw signature data, along with its length in bytes */
 167   blob sighash;
 168
 169   /* (bh=) Raw body hash data, along with its length in bytes */
 170   blob bodyhash;
 171
 172   /* Folded DKIM-Signature: header. Singing only, NULL for verifying.
 173      Ready for insertion into the message. Note: Folded using CRLFTB,
 174      but final line terminator is NOT included. Note2: This buffer is
 175      free()d when you call pdkim_free_ctx(). */
 176   uschar *signature_header;
 177
 178   /* The main verification status. Verification only. One of:
 179
 180      PDKIM_VERIFY_NONE      Verification was not attempted. This status
 181                             should not appear.
 182
 183      PDKIM_VERIFY_INVALID   There was an error while trying to verify
 184                             the signature. A more precise description
 185                             is available in verify_ext_status.
 186
 187      PDKIM_VERIFY_FAIL      Verification failed because either the body
 188                             hash did not match, or the signature verification
 189                             failed. This means the message was modified.
 190                             Check verify_ext_status for the exact reason.
 191
 192      PDKIM_VERIFY_PASS      Verification succeeded.
 193   */
 194   int verify_status;
 195
 196   /* Extended verification status. Verification only. Depending on the value
 197      of verify_status, it can contain:
 198
 199      For verify_status == PDKIM_VERIFY_INVALID:
 200
 201         PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE
 202           Unable to retrieve a public key container.
 203
 204         PDKIM_VERIFY_INVALID_BUFFER_SIZE
 205           Either the DNS name constructed to retrieve the public key record
 206           does not fit into PDKIM_DNS_TXT_MAX_NAMELEN bytes, or the retrieved
 207           record is longer than PDKIM_DNS_TXT_MAX_RECLEN bytes.
 208
 209         PDKIM_VERIFY_INVALID_PUBKEY_PARSING
 210           (Syntax) error while parsing the retrieved public key record.
 211
 212
 213      For verify_status == PDKIM_VERIFY_FAIL:
 214
 215         PDKIM_VERIFY_FAIL_BODY
 216           The calculated body hash does not match the advertised body hash
 217           from the bh= tag of the signature.
 218
 219         PDKIM_VERIFY_FAIL_MESSAGE
 220           RSA verification of the signature (b= tag) failed.
 221   */
 222   int verify_ext_status;
 223
 224   /* Pointer to a public key record that was used to verify the signature.
 225      See pdkim_pubkey declaration above for more information.
 226      Caution: is NULL if signing or if no record was retrieved. */
 227   pdkim_pubkey *pubkey;
 228
 229   /* Pointer to the next pdkim_signature signature. NULL if signing or if
 230      this is the last signature. */
 231   void *next;
 232
 233   /* Properties below this point are used internally only ------------- */
 234
 235   /* Per-signature helper variables ----------------------------------- */
 236   hctx         body_hash_ctx;
 237
 238   unsigned long signed_body_bytes; /* How many body bytes we hashed     */
 239   pdkim_stringlist *headers; /* Raw headers included in the sig         */
 240   /* Signing specific ------------------------------------------------- */
 241   uschar * rsa_privkey;     /* Private RSA key                             */
 242   uschar * sign_headers;    /* To-be-signed header names                   */
 243   uschar * rawsig_no_b_val; /* Original signature header w/o b= tag value. */
 244 } pdkim_signature;
 245
 246
 247 /* -------------------------------------------------------------------------- */
 248 /* Context to keep state between all operations. */
 249 typedef struct pdkim_ctx {
 250
 251 #define PDKIM_MODE_SIGN   BIT(0)        /* if unset, mode==verify */
 252 #define PDKIM_DOT_TERM    BIT(1)        /* dot termination and unstuffing */
 253 #define PDKIM_SEEN_CR     BIT(2)
 254 #define PDKIM_SEEN_LF     BIT(3)
 255 #define PDKIM_PAST_HDRS   BIT(4)
 256 #define PDKIM_SEEN_EOD    BIT(5)
 257   unsigned   flags;
 258
 259   /* One (signing) or several chained (verification) signatures */
 260   pdkim_signature *sig;
 261
 262   /* Callback for dns/txt query method (verification only) */
 263   int(*dns_txt_callback)(char *, char *);
 264
 265   /* Coder's little helpers */
 266   uschar    *cur_header;
 267   int        cur_header_size;
 268   int        cur_header_len;
 269   char      *linebuf;
 270   int        linebuf_offset;
 271   int        num_buffered_crlf;
 272   int        num_headers;
 273   pdkim_stringlist *headers; /* Raw headers for verification         */
 274 } pdkim_ctx;
 275
 276
 277 /* -------------------------------------------------------------------------- */
 278 /* API functions. Please see the sample code in sample/test_sign.c and
 279    sample/test_verify.c for documentation.
 280 */
 281
 282 #ifdef __cplusplus
 283 extern "C" {
 284 #endif
 285
 286 void       pdkim_init         (void);
 287
 288 DLLEXPORT
 289 pdkim_ctx *pdkim_init_sign    (char *, char *, char *, int,
 290                               BOOL, int(*)(char *, char *));
 291
 292 DLLEXPORT
 293 pdkim_ctx *pdkim_init_verify  (int(*)(char *, char *), BOOL);
 294
 295 DLLEXPORT
 296 int        pdkim_set_optional (pdkim_ctx *, char *, char *,int, int,
 297                                long,
 298                                unsigned long,
 299                                unsigned long);
 300
 301 DLLEXPORT
 302 int        pdkim_feed         (pdkim_ctx *, char *, int);
 303 DLLEXPORT
 304 int        pdkim_feed_finish  (pdkim_ctx *, pdkim_signature **);
 305
 306 DLLEXPORT
 307 void       pdkim_free_ctx     (pdkim_ctx *);
 308
 309
 310 const char *    pdkim_errstr(int);
 311
 312 #ifdef __cplusplus
 313 }
 314 #endif
 315
 316 #endif