doc/man1/openssl-smime.pod.in

   1 =pod
   2 {- OpenSSL::safe::output_do_not_edit_headers(); -}
   3
   4 =head1 NAME
   5
   6 openssl-smime - S/MIME utility
   7
   8 =head1 SYNOPSIS
   9
  10 B<openssl> B<smime>
  11 [B<-help>]
  12 [B<-encrypt>]
  13 [B<-decrypt>]
  14 [B<-sign>]
  15 [B<-resign>]
  16 [B<-verify>]
  17 [B<-pk7out>]
  18 [B<-binary>]
  19 [B<-crlfeol>]
  20 [B<-I<cipher>>]
  21 [B<-in> I<file>]
  22 [B<-certfile> I<file>]
  23 [B<-signer> I<file>]
  24 [B<-recip> I< file>]
  25 [B<-inform> B<DER>|B<PEM>|B<SMIME>]
  26 [B<-outform> B<DER>|B<PEM>|B<SMIME>]
  27 [B<-keyform> B<DER>|B<PEM>|B<ENGINE>]
  28 [B<-passin> I<arg>]
  29 [B<-inkey> I<file_or_id>]
  30 [B<-out> I<file>]
  31 [B<-content> I<file>]
  32 [B<-to> I<addr>]
  33 [B<-from> I<ad>]
  34 [B<-subject> I<s>]
  35 [B<-text>]
  36 [B<-indef>]
  37 [B<-noindef>]
  38 [B<-stream>]
  39 [B<-md> I<digest>]
  40 {- $OpenSSL::safe::opt_trust_synopsis -}
  41 {- $OpenSSL::safe::opt_r_synopsis -}
  42 {- $OpenSSL::safe::opt_v_synopsis -}
  43 I<cert.pem> ...
  44
  45 =for openssl ifdef engine
  46
  47 =head1 DESCRIPTION
  48
  49 This command handles S/MIME mail. It can encrypt, decrypt, sign
  50 and verify S/MIME messages.
  51
  52 =head1 OPTIONS
  53
  54 There are six operation options that set the type of operation to be performed.
  55 The meaning of the other options varies according to the operation type.
  56
  57 =over 4
  58
  59 =item B<-help>
  60
  61 Print out a usage message.
  62
  63 =item B<-encrypt>
  64
  65 Encrypt mail for the given recipient certificates. Input file is the message
  66 to be encrypted. The output file is the encrypted mail in MIME format.
  67
  68 Note that no revocation check is done for the recipient cert, so if that
  69 key has been compromised, others may be able to decrypt the text.
  70
  71 =item B<-decrypt>
  72
  73 Decrypt mail using the supplied certificate and private key. Expects an
  74 encrypted mail message in MIME format for the input file. The decrypted mail
  75 is written to the output file.
  76
  77 =item B<-sign>
  78
  79 Sign mail using the supplied certificate and private key. Input file is
  80 the message to be signed. The signed message in MIME format is written
  81 to the output file.
  82
  83 =item B<-verify>
  84
  85 Verify signed mail. Expects a signed mail message on input and outputs
  86 the signed data. Both clear text and opaque signing is supported.
  87
  88 =item B<-pk7out>
  89
  90 Takes an input message and writes out a PEM encoded PKCS#7 structure.
  91
  92 =item B<-resign>
  93
  94 Resign a message: take an existing message and one or more new signers.
  95
  96 =item B<-in> I<filename>
  97
  98 The input message to be encrypted or signed or the MIME message to
  99 be decrypted or verified.
 100
 101 =item B<-out> I<filename>
 102
 103 The message text that has been decrypted or verified or the output MIME
 104 format message that has been signed or verified.
 105
 106 =item B<-inform> B<DER>|B<PEM>|B<SMIME>
 107
 108 The input format of the PKCS#7 (S/MIME) structure (if one is being read);
 109 the default is B<SMIME>.
 110 See L<openssl(1)/Format Options> for details.
 111
 112 =item B<-outform> B<DER>|B<PEM>|B<SMIME>
 113
 114 The output format of the PKCS#7 (S/MIME) structure (if one is being written);
 115 the default is B<SMIME>.
 116 See L<openssl(1)/Format Options> for details.
 117
 118 =item B<-keyform> B<DER>|B<PEM>
 119
 120 The key format; the default is B<PEM>.
 121 See L<openssl(1)/Format Options> for details.
 122
 123 =item B<-stream>, B<-indef>, B<-noindef>
 124
 125 The B<-stream> and B<-indef> options are equivalent and enable streaming I/O
 126 for encoding operations. This permits single pass processing of data without
 127 the need to hold the entire contents in memory, potentially supporting very
 128 large files. Streaming is automatically set for S/MIME signing with detached
 129 data if the output format is B<SMIME> it is currently off by default for all
 130 other operations.
 131
 132 =item B<-noindef>
 133
 134 Disable streaming I/O where it would produce and indefinite length constructed
 135 encoding. This option currently has no effect. In future streaming will be
 136 enabled by default on all relevant operations and this option will disable it.
 137
 138 =item B<-content> I<filename>
 139
 140 This specifies a file containing the detached content, this is only
 141 useful with the B<-verify> command. This is only usable if the PKCS#7
 142 structure is using the detached signature form where the content is
 143 not included. This option will override any content if the input format
 144 is S/MIME and it uses the multipart/signed MIME content type.
 145
 146 =item B<-text>
 147
 148 This option adds plain text (text/plain) MIME headers to the supplied
 149 message if encrypting or signing. If decrypting or verifying it strips
 150 off text headers: if the decrypted or verified message is not of MIME
 151 type text/plain then an error occurs.
 152
 153 =item B<-md> I<digest>
 154
 155 Digest algorithm to use when signing or resigning. If not present then the
 156 default digest algorithm for the signing key will be used (usually SHA1).
 157
 158 =item B<-I<cipher>>
 159
 160 The encryption algorithm to use. For example DES  (56 bits) - B<-des>,
 161 triple DES (168 bits) - B<-des3>,
 162 EVP_get_cipherbyname() function) can also be used preceded by a dash, for
 163 example B<-aes-128-cbc>. See L<openssl-enc(1)> for list of ciphers
 164 supported by your version of OpenSSL.
 165
 166 If not specified triple DES is used. Only used with B<-encrypt>.
 167
 168 =item B<-nointern>
 169
 170 When verifying a message normally certificates (if any) included in
 171 the message are searched for the signing certificate. With this option
 172 only the certificates specified in the B<-certfile> option are used.
 173 The supplied certificates can still be used as untrusted CAs however.
 174
 175 =item B<-noverify>
 176
 177 Do not verify the signers certificate of a signed message.
 178
 179 =item B<-nochain>
 180
 181 Do not do chain verification of signers certificates: that is don't
 182 use the certificates in the signed message as untrusted CAs.
 183
 184 =item B<-nosigs>
 185
 186 Don't try to verify the signatures on the message.
 187
 188 =item B<-nocerts>
 189
 190 When signing a message the signer's certificate is normally included
 191 with this option it is excluded. This will reduce the size of the
 192 signed message but the verifier must have a copy of the signers certificate
 193 available locally (passed using the B<-certfile> option for example).
 194
 195 =item B<-noattr>
 196
 197 Normally when a message is signed a set of attributes are included which
 198 include the signing time and supported symmetric algorithms. With this
 199 option they are not included.
 200
 201 =item B<-binary>
 202
 203 Normally the input message is converted to "canonical" format which is
 204 effectively using CR and LF as end of line: as required by the S/MIME
 205 specification. When this option is present no translation occurs. This
 206 is useful when handling binary data which may not be in MIME format.
 207
 208 =item B<-crlfeol>
 209
 210 Normally the output file uses a single B<LF> as end of line. When this
 211 option is present B<CRLF> is used instead.
 212
 213 =item B<-nodetach>
 214
 215 When signing a message use opaque signing: this form is more resistant
 216 to translation by mail relays but it cannot be read by mail agents that
 217 do not support S/MIME.  Without this option cleartext signing with
 218 the MIME type multipart/signed is used.
 219
 220 =item B<-certfile> I<file>
 221
 222 Allows additional certificates to be specified. When signing these will
 223 be included with the message. When verifying these will be searched for
 224 the signers certificates. The certificates should be in PEM format.
 225
 226 =item B<-signer> I<file>
 227
 228 A signing certificate when signing or resigning a message, this option can be
 229 used multiple times if more than one signer is required. If a message is being
 230 verified then the signers certificates will be written to this file if the
 231 verification was successful.
 232
 233 =item B<-recip> I<file>
 234
 235 The recipients certificate when decrypting a message. This certificate
 236 must match one of the recipients of the message or an error occurs.
 237
 238 =item B<-inkey> I<file_or_id>
 239
 240 The private key to use when signing or decrypting. This must match the
 241 corresponding certificate. If this option is not specified then the
 242 private key must be included in the certificate file specified with
 243 the B<-recip> or B<-signer> file. When signing this option can be used
 244 multiple times to specify successive keys.
 245 If no engine is used, the argument is taken as a file; if an engine is
 246 specified, the argument is given to the engine as a key identifier.
 247
 248 =item B<-passin> I<arg>
 249
 250 The private key password source. For more information about the format of I<arg>
 251 see L<openssl(1)/Pass Phrase Options>.
 252
 253 =item B<-to>, B<-from>, B<-subject>
 254
 255 The relevant mail headers. These are included outside the signed
 256 portion of a message so they may be included manually. If signing
 257 then many S/MIME mail clients check the signers certificate's email
 258 address matches that specified in the From: address.
 259
 260 {- $OpenSSL::safe::opt_v_item -}
 261
 262 Any verification errors cause the command to exit.
 263
 264 {- $OpenSSL::safe::opt_trust_item -}
 265
 266 {- $OpenSSL::safe::opt_r_item -}
 267
 268 =item I<cert.pem> ...
 269
 270 One or more certificates of message recipients, used when encrypting
 271 a message.
 272
 273 =back
 274
 275 =head1 NOTES
 276
 277 The MIME message must be sent without any blank lines between the
 278 headers and the output. Some mail programs will automatically add
 279 a blank line. Piping the mail directly to sendmail is one way to
 280 achieve the correct format.
 281
 282 The supplied message to be signed or encrypted must include the
 283 necessary MIME headers or many S/MIME clients won't display it
 284 properly (if at all). You can use the B<-text> option to automatically
 285 add plain text headers.
 286
 287 A "signed and encrypted" message is one where a signed message is
 288 then encrypted. This can be produced by encrypting an already signed
 289 message: see the examples section.
 290
 291 This version of the program only allows one signer per message but it
 292 will verify multiple signers on received messages. Some S/MIME clients
 293 choke if a message contains multiple signers. It is possible to sign
 294 messages "in parallel" by signing an already signed message.
 295
 296 The options B<-encrypt> and B<-decrypt> reflect common usage in S/MIME
 297 clients. Strictly speaking these process PKCS#7 enveloped data: PKCS#7
 298 encrypted data is used for other purposes.
 299
 300 The B<-resign> option uses an existing message digest when adding a new
 301 signer. This means that attributes must be present in at least one existing
 302 signer using the same message digest or this operation will fail.
 303
 304 The B<-stream> and B<-indef> options enable streaming I/O support.
 305 As a result the encoding is BER using indefinite length constructed encoding
 306 and no longer DER. Streaming is supported for the B<-encrypt> operation and the
 307 B<-sign> operation if the content is not detached.
 308
 309 Streaming is always used for the B<-sign> operation with detached data but
 310 since the content is no longer part of the PKCS#7 structure the encoding
 311 remains DER.
 312
 313 =head1 EXIT CODES
 314
 315 =over 4
 316
 317 =item Z<>0
 318
 319 The operation was completely successfully.
 320
 321 =item Z<>1
 322
 323 An error occurred parsing the command options.
 324
 325 =item Z<>2
 326
 327 One of the input files could not be read.
 328
 329 =item Z<>3
 330
 331 An error occurred creating the PKCS#7 file or when reading the MIME
 332 message.
 333
 334 =item Z<>4
 335
 336 An error occurred decrypting or verifying the message.
 337
 338 =item Z<>5
 339
 340 The message was verified correctly but an error occurred writing out
 341 the signers certificates.
 342
 343 =back
 344
 345 =head1 EXAMPLES
 346
 347 Create a cleartext signed message:
 348
 349  openssl smime -sign -in message.txt -text -out mail.msg \
 350         -signer mycert.pem
 351
 352 Create an opaque signed message:
 353
 354  openssl smime -sign -in message.txt -text -out mail.msg -nodetach \
 355         -signer mycert.pem
 356
 357 Create a signed message, include some additional certificates and
 358 read the private key from another file:
 359
 360  openssl smime -sign -in in.txt -text -out mail.msg \
 361         -signer mycert.pem -inkey mykey.pem -certfile mycerts.pem
 362
 363 Create a signed message with two signers:
 364
 365  openssl smime -sign -in message.txt -text -out mail.msg \
 366         -signer mycert.pem -signer othercert.pem
 367
 368 Send a signed message under Unix directly to sendmail, including headers:
 369
 370  openssl smime -sign -in in.txt -text -signer mycert.pem \
 371         -from steve@openssl.org -to someone@somewhere \
 372         -subject "Signed message" | sendmail someone@somewhere
 373
 374 Verify a message and extract the signer's certificate if successful:
 375
 376  openssl smime -verify -in mail.msg -signer user.pem -out signedtext.txt
 377
 378 Send encrypted mail using triple DES:
 379
 380  openssl smime -encrypt -in in.txt -from steve@openssl.org \
 381         -to someone@somewhere -subject "Encrypted message" \
 382         -des3 user.pem -out mail.msg
 383
 384 Sign and encrypt mail:
 385
 386  openssl smime -sign -in ml.txt -signer my.pem -text \
 387         | openssl smime -encrypt -out mail.msg \
 388         -from steve@openssl.org -to someone@somewhere \
 389         -subject "Signed and Encrypted message" -des3 user.pem
 390
 391 Note: the encryption command does not include the B<-text> option because the
 392 message being encrypted already has MIME headers.
 393
 394 Decrypt mail:
 395
 396  openssl smime -decrypt -in mail.msg -recip mycert.pem -inkey key.pem
 397
 398 The output from Netscape form signing is a PKCS#7 structure with the
 399 detached signature format. You can use this program to verify the
 400 signature by line wrapping the base64 encoded structure and surrounding
 401 it with:
 402
 403  -----BEGIN PKCS7-----
 404  -----END PKCS7-----
 405
 406 and using the command:
 407
 408  openssl smime -verify -inform PEM -in signature.pem -content content.txt
 409
 410 Alternatively you can base64 decode the signature and use:
 411
 412  openssl smime -verify -inform DER -in signature.der -content content.txt
 413
 414 Create an encrypted message using 128 bit Camellia:
 415
 416  openssl smime -encrypt -in plain.txt -camellia128 -out mail.msg cert.pem
 417
 418 Add a signer to an existing message:
 419
 420  openssl smime -resign -in mail.msg -signer newsign.pem -out mail2.msg
 421
 422 =head1 BUGS
 423
 424 The MIME parser isn't very clever: it seems to handle most messages that I've
 425 thrown at it but it may choke on others.
 426
 427 The code currently will only write out the signer's certificate to a file: if
 428 the signer has a separate encryption certificate this must be manually
 429 extracted. There should be some heuristic that determines the correct
 430 encryption certificate.
 431
 432 Ideally a database should be maintained of a certificates for each email
 433 address.
 434
 435 The code doesn't currently take note of the permitted symmetric encryption
 436 algorithms as supplied in the SMIMECapabilities signed attribute. This means the
 437 user has to manually include the correct encryption algorithm. It should store
 438 the list of permitted ciphers in a database and only use those.
 439
 440 No revocation checking is done on the signer's certificate.
 441
 442 The current code can only handle S/MIME v2 messages, the more complex S/MIME v3
 443 structures may cause parsing errors.
 444
 445 =head1 SEE ALSO
 446
 447 L<ossl_store-file(7)>
 448
 449 =head1 HISTORY
 450
 451 The use of multiple B<-signer> options and the B<-resign> command were first
 452 added in OpenSSL 1.0.0
 453
 454 The -no_alt_chains option was added in OpenSSL 1.1.0.
 455
 456 =head1 COPYRIGHT
 457
 458 Copyright 2000-2019 The OpenSSL Project Authors. All Rights Reserved.
 459
 460 Licensed under the Apache License 2.0 (the "License").  You may not use
 461 this file except in compliance with the License.  You can obtain a copy
 462 in the file LICENSE in the source distribution or at
 463 L<https://www.openssl.org/source/license.html>.
 464
 465 =cut