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 370