1=pod 2{- OpenSSL::safe::output_do_not_edit_headers(); -} 3 4=head1 NAME 5 6openssl-smime - S/MIME command 7 8=head1 SYNOPSIS 9 10B<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<-nointern>] 25[B<-noverify>] 26[B<-nochain>] 27[B<-nosigs>] 28[B<-nocerts>] 29[B<-noattr>] 30[B<-nodetach>] 31[B<-nosmimecap>] 32[B<-recip> I< file>] 33[B<-inform> B<DER>|B<PEM>|B<SMIME>] 34[B<-outform> B<DER>|B<PEM>|B<SMIME>] 35[B<-keyform> B<DER>|B<PEM>|B<P12>|B<ENGINE>] 36[B<-passin> I<arg>] 37[B<-inkey> I<filename>|I<uri>] 38[B<-out> I<file>] 39[B<-content> I<file>] 40[B<-to> I<addr>] 41[B<-from> I<ad>] 42[B<-subject> I<s>] 43[B<-text>] 44[B<-indef>] 45[B<-noindef>] 46[B<-stream>] 47[B<-md> I<digest>] 48{- $OpenSSL::safe::opt_trust_synopsis -} 49{- $OpenSSL::safe::opt_engine_synopsis -}{- $OpenSSL::safe::opt_r_synopsis -} 50{- $OpenSSL::safe::opt_v_synopsis -} 51{- $OpenSSL::safe::opt_provider_synopsis -} 52{- $OpenSSL::safe::opt_config_synopsis -} 53I<recipcert> ... 54 55=head1 DESCRIPTION 56 57This command handles S/MIME mail. It can encrypt, decrypt, sign 58and verify S/MIME messages. 59 60=head1 OPTIONS 61 62There are six operation options that set the type of operation to be performed: 63B<-encrypt>, B<-decrypt>, B<-sign>, B<-resign>, B<-verify>, and B<-pk7out>. 64These are mutually exclusive. 65The meaning of the other options varies according to the operation type. 66 67=over 4 68 69=item B<-help> 70 71Print out a usage message. 72 73=item B<-encrypt> 74 75Encrypt mail for the given recipient certificates. Input file is the message 76to be encrypted. The output file is the encrypted mail in MIME format. 77 78Note that no revocation check is done for the recipient cert, so if that 79key has been compromised, others may be able to decrypt the text. 80 81=item B<-decrypt> 82 83Decrypt mail using the supplied certificate and private key. Expects an 84encrypted mail message in MIME format for the input file. The decrypted mail 85is written to the output file. 86 87=item B<-sign> 88 89Sign mail using the supplied certificate and private key. Input file is 90the message to be signed. The signed message in MIME format is written 91to the output file. 92 93=item B<-resign> 94 95Resign a message: take an existing message and one or more new signers. 96 97=item B<-verify> 98 99Verify signed mail. Expects a signed mail message on input and outputs 100the signed data. Both clear text and opaque signing is supported. 101 102=item B<-pk7out> 103 104Takes an input message and writes out a PEM encoded PKCS#7 structure. 105 106=item B<-in> I<filename> 107 108The input message to be encrypted or signed or the MIME message to 109be decrypted or verified. 110 111=item B<-out> I<filename> 112 113The message text that has been decrypted or verified or the output MIME 114format message that has been signed or verified. 115 116=item B<-inform> B<DER>|B<PEM>|B<SMIME> 117 118The input format of the PKCS#7 (S/MIME) structure (if one is being read); 119the default is B<SMIME>. 120See L<openssl-format-options(1)> for details. 121 122=item B<-outform> B<DER>|B<PEM>|B<SMIME> 123 124The output format of the PKCS#7 (S/MIME) structure (if one is being written); 125the default is B<SMIME>. 126See L<openssl-format-options(1)> for details. 127 128=item B<-keyform> B<DER>|B<PEM>|B<P12>|B<ENGINE> 129 130The key format; unspecified by default. 131See L<openssl-format-options(1)> for details. 132 133=item B<-stream>, B<-indef>, B<-noindef> 134 135The B<-stream> and B<-indef> options are equivalent and enable streaming I/O 136for encoding operations. This permits single pass processing of data without 137the need to hold the entire contents in memory, potentially supporting very 138large files. Streaming is automatically set for S/MIME signing with detached 139data if the output format is B<SMIME> it is currently off by default for all 140other operations. 141 142=item B<-noindef> 143 144Disable streaming I/O where it would produce and indefinite length constructed 145encoding. This option currently has no effect. In future streaming will be 146enabled by default on all relevant operations and this option will disable it. 147 148=item B<-content> I<filename> 149 150This specifies a file containing the detached content, this is only 151useful with the B<-verify> command. This is only usable if the PKCS#7 152structure is using the detached signature form where the content is 153not included. This option will override any content if the input format 154is S/MIME and it uses the multipart/signed MIME content type. 155 156=item B<-text> 157 158This option adds plain text (text/plain) MIME headers to the supplied 159message if encrypting or signing. If decrypting or verifying it strips 160off text headers: if the decrypted or verified message is not of MIME 161type text/plain then an error occurs. 162 163=item B<-md> I<digest> 164 165Digest algorithm to use when signing or resigning. If not present then the 166default digest algorithm for the signing key will be used (usually SHA1). 167 168=item B<-I<cipher>> 169 170The encryption algorithm to use. For example DES (56 bits) - B<-des>, 171triple DES (168 bits) - B<-des3>, 172EVP_get_cipherbyname() function) can also be used preceded by a dash, for 173example B<-aes-128-cbc>. See L<openssl-enc(1)> for list of ciphers 174supported by your version of OpenSSL. 175 176If not specified triple DES is used. Only used with B<-encrypt>. 177 178=item B<-nointern> 179 180When verifying a message normally certificates (if any) included in 181the message are searched for the signing certificate. With this option 182only the certificates specified in the B<-certfile> option are used. 183The supplied certificates can still be used as untrusted CAs however. 184 185=item B<-noverify> 186 187Do not verify the signers certificate of a signed message. 188 189=item B<-nochain> 190 191Do not do chain verification of signers certificates; that is, do not 192use the certificates in the signed message as untrusted CAs. 193 194=item B<-nosigs> 195 196Don't try to verify the signatures on the message. 197 198=item B<-nocerts> 199 200When signing a message, the signer's certificate is normally included. 201With this option it is excluded. This will reduce the size of the 202signed message, but the verifier must have a copy of the signers certificate 203available locally (passed using the B<-certfile> option for example). 204 205=item B<-noattr> 206 207Normally, when a message is signed, a set of attributes are included which 208include the signing time and supported symmetric algorithms. With this 209option they are not included. 210 211=item B<-nodetach> 212 213When signing a message use opaque signing. This form is more resistant 214to translation by mail relays but it cannot be read by mail agents that 215do not support S/MIME. Without this option cleartext signing with 216the MIME type multipart/signed is used. 217 218=item B<-nosmimecap> 219 220When signing a message, do not include the B<SMIMECapabilities> attribute. 221 222=item B<-binary> 223 224Normally the input message is converted to "canonical" format which is 225effectively using CR and LF as end of line: as required by the S/MIME 226specification. When this option is present no translation occurs. This 227is useful when handling binary data which may not be in MIME format. 228 229=item B<-crlfeol> 230 231Normally the output file uses a single B<LF> as end of line. When this 232option is present B<CRLF> is used instead. 233 234=item B<-certfile> I<file> 235 236Allows additional certificates to be specified. When signing these will 237be included with the message. When verifying these will be searched for 238the signers certificates. 239The input can be in PEM, DER, or PKCS#12 format. 240 241=item B<-signer> I<file> 242 243A signing certificate when signing or resigning a message, this option can be 244used multiple times if more than one signer is required. If a message is being 245verified then the signers certificates will be written to this file if the 246verification was successful. 247 248=item B<-recip> I<file> 249 250The recipients certificate when decrypting a message. This certificate 251must match one of the recipients of the message or an error occurs. 252 253=item B<-inkey> I<filename>|I<uri> 254 255The private key to use when signing or decrypting. This must match the 256corresponding certificate. If this option is not specified then the 257private key must be included in the certificate file specified with 258the B<-recip> or B<-signer> file. When signing this option can be used 259multiple times to specify successive keys. 260 261=item B<-passin> I<arg> 262 263The private key password source. For more information about the format of I<arg> 264see L<openssl-passphrase-options(1)>. 265 266=item B<-to>, B<-from>, B<-subject> 267 268The relevant mail headers. These are included outside the signed 269portion of a message so they may be included manually. If signing 270then many S/MIME mail clients check the signers certificate's email 271address matches that specified in the From: address. 272 273{- $OpenSSL::safe::opt_v_item -} 274 275Any verification errors cause the command to exit. 276 277{- $OpenSSL::safe::opt_trust_item -} 278 279{- $OpenSSL::safe::opt_engine_item -} 280 281{- $OpenSSL::safe::opt_r_item -} 282 283{- $OpenSSL::safe::opt_provider_item -} 284 285{- $OpenSSL::safe::opt_config_item -} 286 287=item I<recipcert> ... 288 289One or more certificates of message recipients, used when encrypting 290a message. 291 292=back 293 294=head1 NOTES 295 296The MIME message must be sent without any blank lines between the 297headers and the output. Some mail programs will automatically add 298a blank line. Piping the mail directly to sendmail is one way to 299achieve the correct format. 300 301The supplied message to be signed or encrypted must include the 302necessary MIME headers or many S/MIME clients won't display it 303properly (if at all). You can use the B<-text> option to automatically 304add plain text headers. 305 306A "signed and encrypted" message is one where a signed message is 307then encrypted. This can be produced by encrypting an already signed 308message: see the examples section. 309 310This version of the program only allows one signer per message but it 311will verify multiple signers on received messages. Some S/MIME clients 312choke if a message contains multiple signers. It is possible to sign 313messages "in parallel" by signing an already signed message. 314 315The options B<-encrypt> and B<-decrypt> reflect common usage in S/MIME 316clients. Strictly speaking these process PKCS#7 enveloped data: PKCS#7 317encrypted data is used for other purposes. 318 319The B<-resign> option uses an existing message digest when adding a new 320signer. This means that attributes must be present in at least one existing 321signer using the same message digest or this operation will fail. 322 323The B<-stream> and B<-indef> options enable streaming I/O support. 324As a result the encoding is BER using indefinite length constructed encoding 325and no longer DER. Streaming is supported for the B<-encrypt> operation and the 326B<-sign> operation if the content is not detached. 327 328Streaming is always used for the B<-sign> operation with detached data but 329since the content is no longer part of the PKCS#7 structure the encoding 330remains DER. 331 332=head1 EXIT CODES 333 334=over 4 335 336=item Z<>0 337 338The operation was completely successfully. 339 340=item Z<>1 341 342An error occurred parsing the command options. 343 344=item Z<>2 345 346One of the input files could not be read. 347 348=item Z<>3 349 350An error occurred creating the PKCS#7 file or when reading the MIME 351message. 352 353=item Z<>4 354 355An error occurred decrypting or verifying the message. 356 357=item Z<>5 358 359The message was verified correctly but an error occurred writing out 360the signers certificates. 361 362=back 363 364=head1 EXAMPLES 365 366Create a cleartext signed message: 367 368 openssl smime -sign -in message.txt -text -out mail.msg \ 369 -signer mycert.pem 370 371Create an opaque signed message: 372 373 openssl smime -sign -in message.txt -text -out mail.msg -nodetach \ 374 -signer mycert.pem 375 376Create a signed message, include some additional certificates and 377read the private key from another file: 378 379 openssl smime -sign -in in.txt -text -out mail.msg \ 380 -signer mycert.pem -inkey mykey.pem -certfile mycerts.pem 381 382Create a signed message with two signers: 383 384 openssl smime -sign -in message.txt -text -out mail.msg \ 385 -signer mycert.pem -signer othercert.pem 386 387Send a signed message under Unix directly to sendmail, including headers: 388 389 openssl smime -sign -in in.txt -text -signer mycert.pem \ 390 -from steve@openssl.org -to someone@somewhere \ 391 -subject "Signed message" | sendmail someone@somewhere 392 393Verify a message and extract the signer's certificate if successful: 394 395 openssl smime -verify -in mail.msg -signer user.pem -out signedtext.txt 396 397Send encrypted mail using triple DES: 398 399 openssl smime -encrypt -in in.txt -from steve@openssl.org \ 400 -to someone@somewhere -subject "Encrypted message" \ 401 -des3 user.pem -out mail.msg 402 403Sign and encrypt mail: 404 405 openssl smime -sign -in ml.txt -signer my.pem -text \ 406 | openssl smime -encrypt -out mail.msg \ 407 -from steve@openssl.org -to someone@somewhere \ 408 -subject "Signed and Encrypted message" -des3 user.pem 409 410Note: the encryption command does not include the B<-text> option because the 411message being encrypted already has MIME headers. 412 413Decrypt mail: 414 415 openssl smime -decrypt -in mail.msg -recip mycert.pem -inkey key.pem 416 417The output from Netscape form signing is a PKCS#7 structure with the 418detached signature format. You can use this program to verify the 419signature by line wrapping the base64 encoded structure and surrounding 420it with: 421 422 -----BEGIN PKCS7----- 423 -----END PKCS7----- 424 425and using the command: 426 427 openssl smime -verify -inform PEM -in signature.pem -content content.txt 428 429Alternatively you can base64 decode the signature and use: 430 431 openssl smime -verify -inform DER -in signature.der -content content.txt 432 433Create an encrypted message using 128 bit Camellia: 434 435 openssl smime -encrypt -in plain.txt -camellia128 -out mail.msg cert.pem 436 437Add a signer to an existing message: 438 439 openssl smime -resign -in mail.msg -signer newsign.pem -out mail2.msg 440 441=head1 BUGS 442 443The MIME parser isn't very clever: it seems to handle most messages that I've 444thrown at it but it may choke on others. 445 446The code currently will only write out the signer's certificate to a file: if 447the signer has a separate encryption certificate this must be manually 448extracted. There should be some heuristic that determines the correct 449encryption certificate. 450 451Ideally a database should be maintained of a certificates for each email 452address. 453 454The code doesn't currently take note of the permitted symmetric encryption 455algorithms as supplied in the SMIMECapabilities signed attribute. This means the 456user has to manually include the correct encryption algorithm. It should store 457the list of permitted ciphers in a database and only use those. 458 459No revocation checking is done on the signer's certificate. 460 461The current code can only handle S/MIME v2 messages, the more complex S/MIME v3 462structures may cause parsing errors. 463 464=head1 SEE ALSO 465 466L<ossl_store-file(7)> 467 468=head1 HISTORY 469 470The use of multiple B<-signer> options and the B<-resign> command were first 471added in OpenSSL 1.0.0 472 473The -no_alt_chains option was added in OpenSSL 1.1.0. 474 475The B<-engine> option was deprecated in OpenSSL 3.0. 476 477=head1 COPYRIGHT 478 479Copyright 2000-2023 The OpenSSL Project Authors. All Rights Reserved. 480 481Licensed under the Apache License 2.0 (the "License"). You may not use 482this file except in compliance with the License. You can obtain a copy 483in the file LICENSE in the source distribution or at 484L<https://www.openssl.org/source/license.html>. 485 486=cut 487