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. 63The meaning of the other options varies according to the operation type. 64 65=over 4 66 67=item B<-help> 68 69Print out a usage message. 70 71=item B<-encrypt> 72 73Encrypt mail for the given recipient certificates. Input file is the message 74to be encrypted. The output file is the encrypted mail in MIME format. 75 76Note that no revocation check is done for the recipient cert, so if that 77key has been compromised, others may be able to decrypt the text. 78 79=item B<-decrypt> 80 81Decrypt mail using the supplied certificate and private key. Expects an 82encrypted mail message in MIME format for the input file. The decrypted mail 83is written to the output file. 84 85=item B<-sign> 86 87Sign mail using the supplied certificate and private key. Input file is 88the message to be signed. The signed message in MIME format is written 89to the output file. 90 91=item B<-verify> 92 93Verify signed mail. Expects a signed mail message on input and outputs 94the signed data. Both clear text and opaque signing is supported. 95 96=item B<-pk7out> 97 98Takes an input message and writes out a PEM encoded PKCS#7 structure. 99 100=item B<-resign> 101 102Resign a message: take an existing message and one or more new signers. 103 104=item B<-in> I<filename> 105 106The input message to be encrypted or signed or the MIME message to 107be decrypted or verified. 108 109=item B<-out> I<filename> 110 111The message text that has been decrypted or verified or the output MIME 112format message that has been signed or verified. 113 114=item B<-inform> B<DER>|B<PEM>|B<SMIME> 115 116The input format of the PKCS#7 (S/MIME) structure (if one is being read); 117the default is B<SMIME>. 118See L<openssl-format-options(1)> for details. 119 120=item B<-outform> B<DER>|B<PEM>|B<SMIME> 121 122The output format of the PKCS#7 (S/MIME) structure (if one is being written); 123the default is B<SMIME>. 124See L<openssl-format-options(1)> for details. 125 126=item B<-keyform> B<DER>|B<PEM>|B<P12>|B<ENGINE> 127 128The key format; unspecified by default. 129See L<openssl-format-options(1)> for details. 130 131=item B<-stream>, B<-indef>, B<-noindef> 132 133The B<-stream> and B<-indef> options are equivalent and enable streaming I/O 134for encoding operations. This permits single pass processing of data without 135the need to hold the entire contents in memory, potentially supporting very 136large files. Streaming is automatically set for S/MIME signing with detached 137data if the output format is B<SMIME> it is currently off by default for all 138other operations. 139 140=item B<-noindef> 141 142Disable streaming I/O where it would produce and indefinite length constructed 143encoding. This option currently has no effect. In future streaming will be 144enabled by default on all relevant operations and this option will disable it. 145 146=item B<-content> I<filename> 147 148This specifies a file containing the detached content, this is only 149useful with the B<-verify> command. This is only usable if the PKCS#7 150structure is using the detached signature form where the content is 151not included. This option will override any content if the input format 152is S/MIME and it uses the multipart/signed MIME content type. 153 154=item B<-text> 155 156This option adds plain text (text/plain) MIME headers to the supplied 157message if encrypting or signing. If decrypting or verifying it strips 158off text headers: if the decrypted or verified message is not of MIME 159type text/plain then an error occurs. 160 161=item B<-md> I<digest> 162 163Digest algorithm to use when signing or resigning. If not present then the 164default digest algorithm for the signing key will be used (usually SHA1). 165 166=item B<-I<cipher>> 167 168The encryption algorithm to use. For example DES (56 bits) - B<-des>, 169triple DES (168 bits) - B<-des3>, 170EVP_get_cipherbyname() function) can also be used preceded by a dash, for 171example B<-aes-128-cbc>. See L<openssl-enc(1)> for list of ciphers 172supported by your version of OpenSSL. 173 174If not specified triple DES is used. Only used with B<-encrypt>. 175 176=item B<-nointern> 177 178When verifying a message normally certificates (if any) included in 179the message are searched for the signing certificate. With this option 180only the certificates specified in the B<-certfile> option are used. 181The supplied certificates can still be used as untrusted CAs however. 182 183=item B<-noverify> 184 185Do not verify the signers certificate of a signed message. 186 187=item B<-nochain> 188 189Do not do chain verification of signers certificates; that is, do not 190use the certificates in the signed message as untrusted CAs. 191 192=item B<-nosigs> 193 194Don't try to verify the signatures on the message. 195 196=item B<-nocerts> 197 198When signing a message, the signer's certificate is normally included. 199With this option it is excluded. This will reduce the size of the 200signed message, but the verifier must have a copy of the signers certificate 201available locally (passed using the B<-certfile> option for example). 202 203=item B<-noattr> 204 205Normally, when a message is signed, a set of attributes are included which 206include the signing time and supported symmetric algorithms. With this 207option they are not included. 208 209=item B<-nodetach> 210 211When signing a message use opaque signing. This form is more resistant 212to translation by mail relays but it cannot be read by mail agents that 213do not support S/MIME. Without this option cleartext signing with 214the MIME type multipart/signed is used. 215 216=item B<-nosmimecap> 217 218When signing a message, do not include the B<SMIMECapabilities> attribute. 219 220=item B<-binary> 221 222Normally the input message is converted to "canonical" format which is 223effectively using CR and LF as end of line: as required by the S/MIME 224specification. When this option is present no translation occurs. This 225is useful when handling binary data which may not be in MIME format. 226 227=item B<-crlfeol> 228 229Normally the output file uses a single B<LF> as end of line. When this 230option is present B<CRLF> is used instead. 231 232=item B<-certfile> I<file> 233 234Allows additional certificates to be specified. When signing these will 235be included with the message. When verifying these will be searched for 236the signers certificates. 237The input can be in PEM, DER, or PKCS#12 format. 238 239=item B<-signer> I<file> 240 241A signing certificate when signing or resigning a message, this option can be 242used multiple times if more than one signer is required. If a message is being 243verified then the signers certificates will be written to this file if the 244verification was successful. 245 246=item B<-recip> I<file> 247 248The recipients certificate when decrypting a message. This certificate 249must match one of the recipients of the message or an error occurs. 250 251=item B<-inkey> I<filename>|I<uri> 252 253The private key to use when signing or decrypting. This must match the 254corresponding certificate. If this option is not specified then the 255private key must be included in the certificate file specified with 256the B<-recip> or B<-signer> file. When signing this option can be used 257multiple times to specify successive keys. 258 259=item B<-passin> I<arg> 260 261The private key password source. For more information about the format of I<arg> 262see L<openssl-passphrase-options(1)>. 263 264=item B<-to>, B<-from>, B<-subject> 265 266The relevant mail headers. These are included outside the signed 267portion of a message so they may be included manually. If signing 268then many S/MIME mail clients check the signers certificate's email 269address matches that specified in the From: address. 270 271{- $OpenSSL::safe::opt_v_item -} 272 273Any verification errors cause the command to exit. 274 275{- $OpenSSL::safe::opt_trust_item -} 276 277{- $OpenSSL::safe::opt_engine_item -} 278 279{- $OpenSSL::safe::opt_r_item -} 280 281{- $OpenSSL::safe::opt_provider_item -} 282 283{- $OpenSSL::safe::opt_config_item -} 284 285=item I<recipcert> ... 286 287One or more certificates of message recipients, used when encrypting 288a message. 289 290=back 291 292=head1 NOTES 293 294The MIME message must be sent without any blank lines between the 295headers and the output. Some mail programs will automatically add 296a blank line. Piping the mail directly to sendmail is one way to 297achieve the correct format. 298 299The supplied message to be signed or encrypted must include the 300necessary MIME headers or many S/MIME clients won't display it 301properly (if at all). You can use the B<-text> option to automatically 302add plain text headers. 303 304A "signed and encrypted" message is one where a signed message is 305then encrypted. This can be produced by encrypting an already signed 306message: see the examples section. 307 308This version of the program only allows one signer per message but it 309will verify multiple signers on received messages. Some S/MIME clients 310choke if a message contains multiple signers. It is possible to sign 311messages "in parallel" by signing an already signed message. 312 313The options B<-encrypt> and B<-decrypt> reflect common usage in S/MIME 314clients. Strictly speaking these process PKCS#7 enveloped data: PKCS#7 315encrypted data is used for other purposes. 316 317The B<-resign> option uses an existing message digest when adding a new 318signer. This means that attributes must be present in at least one existing 319signer using the same message digest or this operation will fail. 320 321The B<-stream> and B<-indef> options enable streaming I/O support. 322As a result the encoding is BER using indefinite length constructed encoding 323and no longer DER. Streaming is supported for the B<-encrypt> operation and the 324B<-sign> operation if the content is not detached. 325 326Streaming is always used for the B<-sign> operation with detached data but 327since the content is no longer part of the PKCS#7 structure the encoding 328remains DER. 329 330=head1 EXIT CODES 331 332=over 4 333 334=item Z<>0 335 336The operation was completely successfully. 337 338=item Z<>1 339 340An error occurred parsing the command options. 341 342=item Z<>2 343 344One of the input files could not be read. 345 346=item Z<>3 347 348An error occurred creating the PKCS#7 file or when reading the MIME 349message. 350 351=item Z<>4 352 353An error occurred decrypting or verifying the message. 354 355=item Z<>5 356 357The message was verified correctly but an error occurred writing out 358the signers certificates. 359 360=back 361 362=head1 EXAMPLES 363 364Create a cleartext signed message: 365 366 openssl smime -sign -in message.txt -text -out mail.msg \ 367 -signer mycert.pem 368 369Create an opaque signed message: 370 371 openssl smime -sign -in message.txt -text -out mail.msg -nodetach \ 372 -signer mycert.pem 373 374Create a signed message, include some additional certificates and 375read the private key from another file: 376 377 openssl smime -sign -in in.txt -text -out mail.msg \ 378 -signer mycert.pem -inkey mykey.pem -certfile mycerts.pem 379 380Create a signed message with two signers: 381 382 openssl smime -sign -in message.txt -text -out mail.msg \ 383 -signer mycert.pem -signer othercert.pem 384 385Send a signed message under Unix directly to sendmail, including headers: 386 387 openssl smime -sign -in in.txt -text -signer mycert.pem \ 388 -from steve@openssl.org -to someone@somewhere \ 389 -subject "Signed message" | sendmail someone@somewhere 390 391Verify a message and extract the signer's certificate if successful: 392 393 openssl smime -verify -in mail.msg -signer user.pem -out signedtext.txt 394 395Send encrypted mail using triple DES: 396 397 openssl smime -encrypt -in in.txt -from steve@openssl.org \ 398 -to someone@somewhere -subject "Encrypted message" \ 399 -des3 user.pem -out mail.msg 400 401Sign and encrypt mail: 402 403 openssl smime -sign -in ml.txt -signer my.pem -text \ 404 | openssl smime -encrypt -out mail.msg \ 405 -from steve@openssl.org -to someone@somewhere \ 406 -subject "Signed and Encrypted message" -des3 user.pem 407 408Note: the encryption command does not include the B<-text> option because the 409message being encrypted already has MIME headers. 410 411Decrypt mail: 412 413 openssl smime -decrypt -in mail.msg -recip mycert.pem -inkey key.pem 414 415The output from Netscape form signing is a PKCS#7 structure with the 416detached signature format. You can use this program to verify the 417signature by line wrapping the base64 encoded structure and surrounding 418it with: 419 420 -----BEGIN PKCS7----- 421 -----END PKCS7----- 422 423and using the command: 424 425 openssl smime -verify -inform PEM -in signature.pem -content content.txt 426 427Alternatively you can base64 decode the signature and use: 428 429 openssl smime -verify -inform DER -in signature.der -content content.txt 430 431Create an encrypted message using 128 bit Camellia: 432 433 openssl smime -encrypt -in plain.txt -camellia128 -out mail.msg cert.pem 434 435Add a signer to an existing message: 436 437 openssl smime -resign -in mail.msg -signer newsign.pem -out mail2.msg 438 439=head1 BUGS 440 441The MIME parser isn't very clever: it seems to handle most messages that I've 442thrown at it but it may choke on others. 443 444The code currently will only write out the signer's certificate to a file: if 445the signer has a separate encryption certificate this must be manually 446extracted. There should be some heuristic that determines the correct 447encryption certificate. 448 449Ideally a database should be maintained of a certificates for each email 450address. 451 452The code doesn't currently take note of the permitted symmetric encryption 453algorithms as supplied in the SMIMECapabilities signed attribute. This means the 454user has to manually include the correct encryption algorithm. It should store 455the list of permitted ciphers in a database and only use those. 456 457No revocation checking is done on the signer's certificate. 458 459The current code can only handle S/MIME v2 messages, the more complex S/MIME v3 460structures may cause parsing errors. 461 462=head1 SEE ALSO 463 464L<ossl_store-file(7)> 465 466=head1 HISTORY 467 468The use of multiple B<-signer> options and the B<-resign> command were first 469added in OpenSSL 1.0.0 470 471The -no_alt_chains option was added in OpenSSL 1.1.0. 472 473The B<-engine> option was deprecated in OpenSSL 3.0. 474 475=head1 COPYRIGHT 476 477Copyright 2000-2024 The OpenSSL Project Authors. All Rights Reserved. 478 479Licensed under the Apache License 2.0 (the "License"). You may not use 480this file except in compliance with the License. You can obtain a copy 481in the file LICENSE in the source distribution or at 482L<https://www.openssl.org/source/license.html>. 483 484=cut 485