1=pod 2 3=head1 NAME 4 5smime - S/MIME utility 6 7=head1 SYNOPSIS 8 9B<openssl> B<smime> 10[B<-encrypt>] 11[B<-decrypt>] 12[B<-sign>] 13[B<-resign>] 14[B<-verify>] 15[B<-pk7out>] 16[B<-[cipher]>] 17[B<-in file>] 18[B<-no_alt_chains>] 19[B<-certfile file>] 20[B<-signer file>] 21[B<-recip file>] 22[B<-inform SMIME|PEM|DER>] 23[B<-passin arg>] 24[B<-inkey file>] 25[B<-out file>] 26[B<-outform SMIME|PEM|DER>] 27[B<-content file>] 28[B<-to addr>] 29[B<-from ad>] 30[B<-subject s>] 31[B<-text>] 32[B<-indef>] 33[B<-noindef>] 34[B<-stream>] 35[B<-rand file(s)>] 36[B<-md digest>] 37[cert.pem]... 38 39=head1 DESCRIPTION 40 41The B<smime> command handles S/MIME mail. It can encrypt, decrypt, sign and 42verify S/MIME messages. 43 44=head1 COMMAND OPTIONS 45 46There are six operation options that set the type of operation to be performed. 47The meaning of the other options varies according to the operation type. 48 49=over 4 50 51=item B<-encrypt> 52 53encrypt mail for the given recipient certificates. Input file is the message 54to be encrypted. The output file is the encrypted mail in MIME format. 55 56Note that no revocation check is done for the recipient cert, so if that 57key has been compromised, others may be able to decrypt the text. 58 59=item B<-decrypt> 60 61decrypt mail using the supplied certificate and private key. Expects an 62encrypted mail message in MIME format for the input file. The decrypted mail 63is written to the output file. 64 65=item B<-sign> 66 67sign mail using the supplied certificate and private key. Input file is 68the message to be signed. The signed message in MIME format is written 69to the output file. 70 71=item B<-verify> 72 73verify signed mail. Expects a signed mail message on input and outputs 74the signed data. Both clear text and opaque signing is supported. 75 76=item B<-pk7out> 77 78takes an input message and writes out a PEM encoded PKCS#7 structure. 79 80=item B<-resign> 81 82resign a message: take an existing message and one or more new signers. 83 84=item B<-in filename> 85 86the input message to be encrypted or signed or the MIME message to 87be decrypted or verified. 88 89=item B<-inform SMIME|PEM|DER> 90 91this specifies the input format for the PKCS#7 structure. The default 92is B<SMIME> which reads an S/MIME format message. B<PEM> and B<DER> 93format change this to expect PEM and DER format PKCS#7 structures 94instead. This currently only affects the input format of the PKCS#7 95structure, if no PKCS#7 structure is being input (for example with 96B<-encrypt> or B<-sign>) this option has no effect. 97 98=item B<-out filename> 99 100the message text that has been decrypted or verified or the output MIME 101format message that has been signed or verified. 102 103=item B<-outform SMIME|PEM|DER> 104 105this specifies the output format for the PKCS#7 structure. The default 106is B<SMIME> which write an S/MIME format message. B<PEM> and B<DER> 107format change this to write PEM and DER format PKCS#7 structures 108instead. This currently only affects the output format of the PKCS#7 109structure, if no PKCS#7 structure is being output (for example with 110B<-verify> or B<-decrypt>) this option has no effect. 111 112=item B<-stream -indef -noindef> 113 114the B<-stream> and B<-indef> options are equivalent and enable streaming I/O 115for encoding operations. This permits single pass processing of data without 116the need to hold the entire contents in memory, potentially supporting very 117large files. Streaming is automatically set for S/MIME signing with detached 118data if the output format is B<SMIME> it is currently off by default for all 119other operations. 120 121=item B<-noindef> 122 123disable streaming I/O where it would produce and indefinite length constructed 124encoding. This option currently has no effect. In future streaming will be 125enabled by default on all relevant operations and this option will disable it. 126 127=item B<-content filename> 128 129This specifies a file containing the detached content, this is only 130useful with the B<-verify> command. This is only usable if the PKCS#7 131structure is using the detached signature form where the content is 132not included. This option will override any content if the input format 133is S/MIME and it uses the multipart/signed MIME content type. 134 135=item B<-text> 136 137this option adds plain text (text/plain) MIME headers to the supplied 138message if encrypting or signing. If decrypting or verifying it strips 139off text headers: if the decrypted or verified message is not of MIME 140type text/plain then an error occurs. 141 142=item B<-CAfile file> 143 144a file containing trusted CA certificates, only used with B<-verify>. 145 146=item B<-CApath dir> 147 148a directory containing trusted CA certificates, only used with 149B<-verify>. This directory must be a standard certificate directory: that 150is a hash of each subject name (using B<x509 -hash>) should be linked 151to each certificate. 152 153=item B<-md digest> 154 155digest algorithm to use when signing or resigning. If not present then the 156default digest algorithm for the signing key will be used (usually SHA1). 157 158=item B<-[cipher]> 159 160the encryption algorithm to use. For example DES (56 bits) - B<-des>, 161triple DES (168 bits) - B<-des3>, 162EVP_get_cipherbyname() function) can also be used preceded by a dash, for 163example B<-aes_128_cbc>. See L<B<enc>|enc(1)> for list of ciphers 164supported by your version of OpenSSL. 165 166If not specified triple DES is used. Only used with B<-encrypt>. 167 168=item B<-nointern> 169 170when verifying a message normally certificates (if any) included in 171the message are searched for the signing certificate. With this option 172only the certificates specified in the B<-certfile> option are used. 173The supplied certificates can still be used as untrusted CAs however. 174 175=item B<-noverify> 176 177do not verify the signers certificate of a signed message. 178 179=item B<-nochain> 180 181do not do chain verification of signers certificates: that is don't 182use the certificates in the signed message as untrusted CAs. 183 184=item B<-nosigs> 185 186don't try to verify the signatures on the message. 187 188=item B<-nocerts> 189 190when signing a message the signer's certificate is normally included 191with this option it is excluded. This will reduce the size of the 192signed message but the verifier must have a copy of the signers certificate 193available locally (passed using the B<-certfile> option for example). 194 195=item B<-noattr> 196 197normally when a message is signed a set of attributes are included which 198include the signing time and supported symmetric algorithms. With this 199option they are not included. 200 201=item B<-binary> 202 203normally the input message is converted to "canonical" format which is 204effectively using CR and LF as end of line: as required by the S/MIME 205specification. When this option is present no translation occurs. This 206is useful when handling binary data which may not be in MIME format. 207 208=item B<-nodetach> 209 210when signing a message use opaque signing: this form is more resistant 211to translation by mail relays but it cannot be read by mail agents that 212do not support S/MIME. Without this option cleartext signing with 213the MIME type multipart/signed is used. 214 215=item B<-certfile file> 216 217allows additional certificates to be specified. When signing these will 218be included with the message. When verifying these will be searched for 219the signers certificates. The certificates should be in PEM format. 220 221=item B<-signer file> 222 223a signing certificate when signing or resigning a message, this option can be 224used multiple times if more than one signer is required. If a message is being 225verified then the signers certificates will be written to this file if the 226verification was successful. 227 228=item B<-recip file> 229 230the recipients certificate when decrypting a message. This certificate 231must match one of the recipients of the message or an error occurs. 232 233=item B<-inkey file> 234 235the private key to use when signing or decrypting. This must match the 236corresponding certificate. If this option is not specified then the 237private key must be included in the certificate file specified with 238the B<-recip> or B<-signer> file. When signing this option can be used 239multiple times to specify successive keys. 240 241=item B<-passin arg> 242 243the private key password source. For more information about the format of B<arg> 244see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)|openssl(1)>. 245 246=item B<-rand file(s)> 247 248a file or files containing random data used to seed the random number 249generator, or an EGD socket (see L<RAND_egd(3)|RAND_egd(3)>). 250Multiple files can be specified separated by a OS-dependent character. 251The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for 252all others. 253 254=item B<cert.pem...> 255 256one or more certificates of message recipients: used when encrypting 257a message. 258 259=item B<-to, -from, -subject> 260 261the relevant mail headers. These are included outside the signed 262portion of a message so they may be included manually. If signing 263then many S/MIME mail clients check the signers certificate's email 264address matches that specified in the From: address. 265 266=item B<-purpose, -ignore_critical, -issuer_checks, -crl_check, -crl_check_all, -policy_check, -extended_crl, -x509_strict, -policy -check_ss_sig -no_alt_chains> 267 268Set various options of certificate chain verification. See 269L<B<verify>|verify(1)> manual page for details. 270 271=back 272 273=head1 NOTES 274 275The MIME message must be sent without any blank lines between the 276headers and the output. Some mail programs will automatically add 277a blank line. Piping the mail directly to sendmail is one way to 278achieve the correct format. 279 280The supplied message to be signed or encrypted must include the 281necessary MIME headers or many S/MIME clients wont display it 282properly (if at all). You can use the B<-text> option to automatically 283add plain text headers. 284 285A "signed and encrypted" message is one where a signed message is 286then encrypted. This can be produced by encrypting an already signed 287message: see the examples section. 288 289This version of the program only allows one signer per message but it 290will verify multiple signers on received messages. Some S/MIME clients 291choke if a message contains multiple signers. It is possible to sign 292messages "in parallel" by signing an already signed message. 293 294The options B<-encrypt> and B<-decrypt> reflect common usage in S/MIME 295clients. Strictly speaking these process PKCS#7 enveloped data: PKCS#7 296encrypted data is used for other purposes. 297 298The B<-resign> option uses an existing message digest when adding a new 299signer. This means that attributes must be present in at least one existing 300signer using the same message digest or this operation will fail. 301 302The B<-stream> and B<-indef> options enable experimental streaming I/O support. 303As a result the encoding is BER using indefinite length constructed encoding 304and no longer DER. Streaming is supported for the B<-encrypt> operation and the 305B<-sign> operation if the content is not detached. 306 307Streaming is always used for the B<-sign> operation with detached data but 308since the content is no longer part of the PKCS#7 structure the encoding 309remains DER. 310 311=head1 EXIT CODES 312 313=over 4 314 315=item Z<>0 316 317the operation was completely successfully. 318 319=item Z<>1 320 321an error occurred parsing the command options. 322 323=item Z<>2 324 325one of the input files could not be read. 326 327=item Z<>3 328 329an error occurred creating the PKCS#7 file or when reading the MIME 330message. 331 332=item Z<>4 333 334an error occurred decrypting or verifying the message. 335 336=item Z<>5 337 338the message was verified correctly but an error occurred writing out 339the signers certificates. 340 341=back 342 343=head1 EXAMPLES 344 345Create a cleartext signed message: 346 347 openssl smime -sign -in message.txt -text -out mail.msg \ 348 -signer mycert.pem 349 350Create an opaque signed message: 351 352 openssl smime -sign -in message.txt -text -out mail.msg -nodetach \ 353 -signer mycert.pem 354 355Create a signed message, include some additional certificates and 356read the private key from another file: 357 358 openssl smime -sign -in in.txt -text -out mail.msg \ 359 -signer mycert.pem -inkey mykey.pem -certfile mycerts.pem 360 361Create a signed message with two signers: 362 363 openssl smime -sign -in message.txt -text -out mail.msg \ 364 -signer mycert.pem -signer othercert.pem 365 366Send a signed message under Unix directly to sendmail, including headers: 367 368 openssl smime -sign -in in.txt -text -signer mycert.pem \ 369 -from steve@openssl.org -to someone@somewhere \ 370 -subject "Signed message" | sendmail someone@somewhere 371 372Verify a message and extract the signer's certificate if successful: 373 374 openssl smime -verify -in mail.msg -signer user.pem -out signedtext.txt 375 376Send encrypted mail using triple DES: 377 378 openssl smime -encrypt -in in.txt -from steve@openssl.org \ 379 -to someone@somewhere -subject "Encrypted message" \ 380 -des3 user.pem -out mail.msg 381 382Sign and encrypt mail: 383 384 openssl smime -sign -in ml.txt -signer my.pem -text \ 385 | openssl smime -encrypt -out mail.msg \ 386 -from steve@openssl.org -to someone@somewhere \ 387 -subject "Signed and Encrypted message" -des3 user.pem 388 389Note: the encryption command does not include the B<-text> option because the 390message being encrypted already has MIME headers. 391 392Decrypt mail: 393 394 openssl smime -decrypt -in mail.msg -recip mycert.pem -inkey key.pem 395 396The output from Netscape form signing is a PKCS#7 structure with the 397detached signature format. You can use this program to verify the 398signature by line wrapping the base64 encoded structure and surrounding 399it with: 400 401 -----BEGIN PKCS7----- 402 -----END PKCS7----- 403 404and using the command: 405 406 openssl smime -verify -inform PEM -in signature.pem -content content.txt 407 408Alternatively you can base64 decode the signature and use: 409 410 openssl smime -verify -inform DER -in signature.der -content content.txt 411 412Create an encrypted message using 128 bit Camellia: 413 414 openssl smime -encrypt -in plain.txt -camellia128 -out mail.msg cert.pem 415 416Add a signer to an existing message: 417 418 openssl smime -resign -in mail.msg -signer newsign.pem -out mail2.msg 419 420=head1 BUGS 421 422The MIME parser isn't very clever: it seems to handle most messages that I've 423thrown at it but it may choke on others. 424 425The code currently will only write out the signer's certificate to a file: if 426the signer has a separate encryption certificate this must be manually 427extracted. There should be some heuristic that determines the correct 428encryption certificate. 429 430Ideally a database should be maintained of a certificates for each email 431address. 432 433The code doesn't currently take note of the permitted symmetric encryption 434algorithms as supplied in the SMIMECapabilities signed attribute. This means the 435user has to manually include the correct encryption algorithm. It should store 436the list of permitted ciphers in a database and only use those. 437 438No revocation checking is done on the signer's certificate. 439 440The current code can only handle S/MIME v2 messages, the more complex S/MIME v3 441structures may cause parsing errors. 442 443=head1 HISTORY 444 445The use of multiple B<-signer> options and the B<-resign> command were first 446added in OpenSSL 1.0.0 447 448The -no_alt_chains options was first added to OpenSSL 1.0.2b. 449 450=cut 451