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>, or AES (256 bits) - B<-aes256>. 172Any standard algorithm name (as used by the EVP_get_cipherbyname() function) 173can also be used, preceded by a dash, for example B<-aes-128-cbc>. 174See L<openssl-enc(1)> for a list of ciphers supported by your version of OpenSSL. 175 176If not specified, AES-256-CBC is used as the default. 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 238signer certificates and will be used for chain building. 239 240The input can be in PEM, DER, or PKCS#12 format. 241 242=item B<-signer> I<file> 243 244A signing certificate when signing or resigning a message, this option can be 245used multiple times if more than one signer is required. If a message is being 246verified then the signers certificates will be written to this file if the 247verification was successful. 248 249=item B<-recip> I<file> 250 251The recipients certificate when decrypting a message. This certificate 252must match one of the recipients of the message or an error occurs. 253 254=item B<-inkey> I<filename>|I<uri> 255 256The private key to use when signing or decrypting. This must match the 257corresponding certificate. If this option is not specified then the 258private key must be included in the certificate file specified with 259the B<-recip> or B<-signer> file. When signing this option can be used 260multiple times to specify successive keys. 261 262=item B<-passin> I<arg> 263 264The private key password source. For more information about the format of I<arg> 265see L<openssl-passphrase-options(1)>. 266 267=item B<-to>, B<-from>, B<-subject> 268 269The relevant mail headers. These are included outside the signed 270portion of a message so they may be included manually. If signing 271then many S/MIME mail clients check the signers certificate's email 272address matches that specified in the From: address. 273 274{- $OpenSSL::safe::opt_v_item -} 275 276Any verification errors cause the command to exit. 277 278{- $OpenSSL::safe::opt_trust_item -} 279 280{- $OpenSSL::safe::opt_engine_item -} 281 282{- $OpenSSL::safe::opt_r_item -} 283 284{- $OpenSSL::safe::opt_provider_item -} 285 286{- $OpenSSL::safe::opt_config_item -} 287 288=item I<recipcert> ... 289 290One or more certificates of message recipients, used when encrypting 291a message. 292 293=back 294 295=head1 NOTES 296 297The MIME message must be sent without any blank lines between the 298headers and the output. Some mail programs will automatically add 299a blank line. Piping the mail directly to sendmail is one way to 300achieve the correct format. 301 302The supplied message to be signed or encrypted must include the 303necessary MIME headers or many S/MIME clients won't display it 304properly (if at all). You can use the B<-text> option to automatically 305add plain text headers. 306 307A "signed and encrypted" message is one where a signed message is 308then encrypted. This can be produced by encrypting an already signed 309message: see the examples section. 310 311This version of the program only allows one signer per message but it 312will verify multiple signers on received messages. Some S/MIME clients 313choke if a message contains multiple signers. It is possible to sign 314messages "in parallel" by signing an already signed message. 315 316The options B<-encrypt> and B<-decrypt> reflect common usage in S/MIME 317clients. Strictly speaking these process PKCS#7 enveloped data: PKCS#7 318encrypted data is used for other purposes. 319 320The B<-resign> option uses an existing message digest when adding a new 321signer. This means that attributes must be present in at least one existing 322signer using the same message digest or this operation will fail. 323 324The B<-stream> and B<-indef> options enable streaming I/O support. 325As a result the encoding is BER using indefinite length constructed encoding 326and no longer DER. Streaming is supported for the B<-encrypt> operation and the 327B<-sign> operation if the content is not detached. 328 329Streaming is always used for the B<-sign> operation with detached data but 330since the content is no longer part of the PKCS#7 structure the encoding 331remains DER. 332 333=head1 EXIT CODES 334 335=over 4 336 337=item Z<>0 338 339The operation was completely successfully. 340 341=item Z<>1 342 343An error occurred parsing the command options. 344 345=item Z<>2 346 347One of the input files could not be read. 348 349=item Z<>3 350 351An error occurred creating the PKCS#7 file or when reading the MIME 352message. 353 354=item Z<>4 355 356An error occurred decrypting or verifying the message. 357 358=item Z<>5 359 360The message was verified correctly but an error occurred writing out 361the signers certificates. 362 363=back 364 365=head1 EXAMPLES 366 367Create a cleartext signed message: 368 369 openssl smime -sign -in message.txt -text -out mail.msg \ 370 -signer mycert.pem 371 372Create an opaque signed message: 373 374 openssl smime -sign -in message.txt -text -out mail.msg -nodetach \ 375 -signer mycert.pem 376 377Create a signed message, include some additional certificates and 378read the private key from another file: 379 380 openssl smime -sign -in in.txt -text -out mail.msg \ 381 -signer mycert.pem -inkey mykey.pem -certfile mycerts.pem 382 383Create a signed message with two signers: 384 385 openssl smime -sign -in message.txt -text -out mail.msg \ 386 -signer mycert.pem -signer othercert.pem 387 388Send a signed message under Unix directly to sendmail, including headers: 389 390 openssl smime -sign -in in.txt -text -signer mycert.pem \ 391 -from steve@openssl.org -to someone@somewhere \ 392 -subject "Signed message" | sendmail someone@somewhere 393 394Verify a message and extract the signer's certificate if successful: 395 396 openssl smime -verify -in mail.msg -signer user.pem -out signedtext.txt 397 398Send encrypted mail using triple DES: 399 400 openssl smime -encrypt -in in.txt -out mail.msg -from steve@openssl.org \ 401 -to someone@somewhere -subject "Encrypted message" \ 402 -des3 user.pem 403 404Sign and encrypt mail: 405 406 openssl smime -sign -in ml.txt -signer my.pem -text \ 407 | openssl smime -encrypt -out mail.msg \ 408 -from steve@openssl.org -to someone@somewhere \ 409 -subject "Signed and Encrypted message" -des3 user.pem 410 411Note: the encryption command does not include the B<-text> option because the 412message being encrypted already has MIME headers. 413 414Decrypt mail: 415 416 openssl smime -decrypt -in mail.msg -recip mycert.pem -inkey key.pem 417 418The output from Netscape form signing is a PKCS#7 structure with the 419detached signature format. You can use this program to verify the 420signature by line wrapping the base64 encoded structure and surrounding 421it with: 422 423 -----BEGIN PKCS7----- 424 -----END PKCS7----- 425 426and using the command: 427 428 openssl smime -verify -inform PEM -in signature.pem -content content.txt 429 430Alternatively you can base64 decode the signature and use: 431 432 openssl smime -verify -inform DER -in signature.der -content content.txt 433 434Create an encrypted message using 128 bit Camellia: 435 436 openssl smime -encrypt -in plain.txt -camellia128 -out mail.msg cert.pem 437 438Add a signer to an existing message: 439 440 openssl smime -resign -in mail.msg -signer newsign.pem -out mail2.msg 441 442=head1 BUGS 443 444The MIME parser isn't very clever: it seems to handle most messages that I've 445thrown at it but it may choke on others. 446 447The code currently will only write out the signer's certificate to a file: if 448the signer has a separate encryption certificate this must be manually 449extracted. There should be some heuristic that determines the correct 450encryption certificate. 451 452Ideally a database should be maintained of a certificates for each email 453address. 454 455The code doesn't currently take note of the permitted symmetric encryption 456algorithms as supplied in the SMIMECapabilities signed attribute. This means the 457user has to manually include the correct encryption algorithm. It should store 458the list of permitted ciphers in a database and only use those. 459 460No revocation checking is done on the signer's certificate. 461 462The current code can only handle S/MIME v2 messages, the more complex S/MIME v3 463structures may cause parsing errors. 464 465=head1 SEE ALSO 466 467L<ossl_store-file(7)> 468 469=head1 HISTORY 470 471The default encryption cipher was changed from 3DES to AES-256 in OpenSSL 3.5. 472 473The use of multiple B<-signer> options and the B<-resign> command were first 474added in OpenSSL 1.0.0 475 476The -no_alt_chains option was added in OpenSSL 1.1.0. 477 478The B<-engine> option was deprecated in OpenSSL 3.0. 479 480=head1 COPYRIGHT 481 482Copyright 2000-2024 The OpenSSL Project Authors. All Rights Reserved. 483 484Licensed under the Apache License 2.0 (the "License"). You may not use 485this file except in compliance with the License. You can obtain a copy 486in the file LICENSE in the source distribution or at 487L<https://www.openssl.org/source/license.html>. 488 489=cut 490
