smime.pod revision 267256
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<-certfile file>] 19[B<-signer file>] 20[B<-recip file>] 21[B<-inform SMIME|PEM|DER>] 22[B<-passin arg>] 23[B<-inkey file>] 24[B<-out file>] 25[B<-outform SMIME|PEM|DER>] 26[B<-content file>] 27[B<-to addr>] 28[B<-from ad>] 29[B<-subject s>] 30[B<-text>] 31[B<-indef>] 32[B<-noindef>] 33[B<-stream>] 34[B<-rand file(s)>] 35[B<-md digest>] 36[cert.pem]... 37 38=head1 DESCRIPTION 39 40The B<smime> command handles S/MIME mail. It can encrypt, decrypt, sign and 41verify S/MIME messages. 42 43=head1 COMMAND OPTIONS 44 45There are six operation options that set the type of operation to be performed. 46The meaning of the other options varies according to the operation type. 47 48=over 4 49 50=item B<-encrypt> 51 52encrypt mail for the given recipient certificates. Input file is the message 53to be encrypted. The output file is the encrypted mail in MIME format. 54 55=item B<-decrypt> 56 57decrypt mail using the supplied certificate and private key. Expects an 58encrypted mail message in MIME format for the input file. The decrypted mail 59is written to the output file. 60 61=item B<-sign> 62 63sign mail using the supplied certificate and private key. Input file is 64the message to be signed. The signed message in MIME format is written 65to the output file. 66 67=item B<-verify> 68 69verify signed mail. Expects a signed mail message on input and outputs 70the signed data. Both clear text and opaque signing is supported. 71 72=item B<-pk7out> 73 74takes an input message and writes out a PEM encoded PKCS#7 structure. 75 76=item B<-resign> 77 78resign a message: take an existing message and one or more new signers. 79 80=item B<-in filename> 81 82the input message to be encrypted or signed or the MIME message to 83be decrypted or verified. 84 85=item B<-inform SMIME|PEM|DER> 86 87this specifies the input format for the PKCS#7 structure. The default 88is B<SMIME> which reads an S/MIME format message. B<PEM> and B<DER> 89format change this to expect PEM and DER format PKCS#7 structures 90instead. This currently only affects the input format of the PKCS#7 91structure, if no PKCS#7 structure is being input (for example with 92B<-encrypt> or B<-sign>) this option has no effect. 93 94=item B<-out filename> 95 96the message text that has been decrypted or verified or the output MIME 97format message that has been signed or verified. 98 99=item B<-outform SMIME|PEM|DER> 100 101this specifies the output format for the PKCS#7 structure. The default 102is B<SMIME> which write an S/MIME format message. B<PEM> and B<DER> 103format change this to write PEM and DER format PKCS#7 structures 104instead. This currently only affects the output format of the PKCS#7 105structure, if no PKCS#7 structure is being output (for example with 106B<-verify> or B<-decrypt>) this option has no effect. 107 108=item B<-stream -indef -noindef> 109 110the B<-stream> and B<-indef> options are equivalent and enable streaming I/O 111for encoding operations. This permits single pass processing of data without 112the need to hold the entire contents in memory, potentially supporting very 113large files. Streaming is automatically set for S/MIME signing with detached 114data if the output format is B<SMIME> it is currently off by default for all 115other operations. 116 117=item B<-noindef> 118 119disable streaming I/O where it would produce and indefinite length constructed 120encoding. This option currently has no effect. In future streaming will be 121enabled by default on all relevant operations and this option will disable it. 122 123=item B<-content filename> 124 125This specifies a file containing the detached content, this is only 126useful with the B<-verify> command. This is only usable if the PKCS#7 127structure is using the detached signature form where the content is 128not included. This option will override any content if the input format 129is S/MIME and it uses the multipart/signed MIME content type. 130 131=item B<-text> 132 133this option adds plain text (text/plain) MIME headers to the supplied 134message if encrypting or signing. If decrypting or verifying it strips 135off text headers: if the decrypted or verified message is not of MIME 136type text/plain then an error occurs. 137 138=item B<-CAfile file> 139 140a file containing trusted CA certificates, only used with B<-verify>. 141 142=item B<-CApath dir> 143 144a directory containing trusted CA certificates, only used with 145B<-verify>. This directory must be a standard certificate directory: that 146is a hash of each subject name (using B<x509 -hash>) should be linked 147to each certificate. 148 149=item B<-md digest> 150 151digest algorithm to use when signing or resigning. If not present then the 152default digest algorithm for the signing key will be used (usually SHA1). 153 154=item B<-[cipher]> 155 156the encryption algorithm to use. For example DES (56 bits) - B<-des>, 157triple DES (168 bits) - B<-des3>, 158EVP_get_cipherbyname() function) can also be used preceded by a dash, for 159example B<-aes_128_cbc>. See L<B<enc>|enc(1)> for list of ciphers 160supported by your version of OpenSSL. 161 162If not specified triple DES is used. Only used with B<-encrypt>. 163 164=item B<-nointern> 165 166when verifying a message normally certificates (if any) included in 167the message are searched for the signing certificate. With this option 168only the certificates specified in the B<-certfile> option are used. 169The supplied certificates can still be used as untrusted CAs however. 170 171=item B<-noverify> 172 173do not verify the signers certificate of a signed message. 174 175=item B<-nochain> 176 177do not do chain verification of signers certificates: that is don't 178use the certificates in the signed message as untrusted CAs. 179 180=item B<-nosigs> 181 182don't try to verify the signatures on the message. 183 184=item B<-nocerts> 185 186when signing a message the signer's certificate is normally included 187with this option it is excluded. This will reduce the size of the 188signed message but the verifier must have a copy of the signers certificate 189available locally (passed using the B<-certfile> option for example). 190 191=item B<-noattr> 192 193normally when a message is signed a set of attributes are included which 194include the signing time and supported symmetric algorithms. With this 195option they are not included. 196 197=item B<-binary> 198 199normally the input message is converted to "canonical" format which is 200effectively using CR and LF as end of line: as required by the S/MIME 201specification. When this option is present no translation occurs. This 202is useful when handling binary data which may not be in MIME format. 203 204=item B<-nodetach> 205 206when signing a message use opaque signing: this form is more resistant 207to translation by mail relays but it cannot be read by mail agents that 208do not support S/MIME. Without this option cleartext signing with 209the MIME type multipart/signed is used. 210 211=item B<-certfile file> 212 213allows additional certificates to be specified. When signing these will 214be included with the message. When verifying these will be searched for 215the signers certificates. The certificates should be in PEM format. 216 217=item B<-signer file> 218 219a signing certificate when signing or resigning a message, this option can be 220used multiple times if more than one signer is required. If a message is being 221verified then the signers certificates will be written to this file if the 222verification was successful. 223 224=item B<-recip file> 225 226the recipients certificate when decrypting a message. This certificate 227must match one of the recipients of the message or an error occurs. 228 229=item B<-inkey file> 230 231the private key to use when signing or decrypting. This must match the 232corresponding certificate. If this option is not specified then the 233private key must be included in the certificate file specified with 234the B<-recip> or B<-signer> file. When signing this option can be used 235multiple times to specify successive keys. 236 237=item B<-passin arg> 238 239the private key password source. For more information about the format of B<arg> 240see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)|openssl(1)>. 241 242=item B<-rand file(s)> 243 244a file or files containing random data used to seed the random number 245generator, or an EGD socket (see L<RAND_egd(3)|RAND_egd(3)>). 246Multiple files can be specified separated by a OS-dependent character. 247The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for 248all others. 249 250=item B<cert.pem...> 251 252one or more certificates of message recipients: used when encrypting 253a message. 254 255=item B<-to, -from, -subject> 256 257the relevant mail headers. These are included outside the signed 258portion of a message so they may be included manually. If signing 259then many S/MIME mail clients check the signers certificate's email 260address matches that specified in the From: address. 261 262=item B<-purpose, -ignore_critical, -issuer_checks, -crl_check, -crl_check_all, -policy_check, -extended_crl, -x509_strict, -policy -check_ss_sig> 263 264Set various options of certificate chain verification. See 265L<B<verify>|verify(1)> manual page for details. 266 267=back 268 269=head1 NOTES 270 271The MIME message must be sent without any blank lines between the 272headers and the output. Some mail programs will automatically add 273a blank line. Piping the mail directly to sendmail is one way to 274achieve the correct format. 275 276The supplied message to be signed or encrypted must include the 277necessary MIME headers or many S/MIME clients wont display it 278properly (if at all). You can use the B<-text> option to automatically 279add plain text headers. 280 281A "signed and encrypted" message is one where a signed message is 282then encrypted. This can be produced by encrypting an already signed 283message: see the examples section. 284 285This version of the program only allows one signer per message but it 286will verify multiple signers on received messages. Some S/MIME clients 287choke if a message contains multiple signers. It is possible to sign 288messages "in parallel" by signing an already signed message. 289 290The options B<-encrypt> and B<-decrypt> reflect common usage in S/MIME 291clients. Strictly speaking these process PKCS#7 enveloped data: PKCS#7 292encrypted data is used for other purposes. 293 294The B<-resign> option uses an existing message digest when adding a new 295signer. This means that attributes must be present in at least one existing 296signer using the same message digest or this operation will fail. 297 298The B<-stream> and B<-indef> options enable experimental streaming I/O support. 299As a result the encoding is BER using indefinite length constructed encoding 300and no longer DER. Streaming is supported for the B<-encrypt> operation and the 301B<-sign> operation if the content is not detached. 302 303Streaming is always used for the B<-sign> operation with detached data but 304since the content is no longer part of the PKCS#7 structure the encoding 305remains DER. 306 307=head1 EXIT CODES 308 309=over 4 310 311=item Z<>0 312 313the operation was completely successfully. 314 315=item Z<>1 316 317an error occurred parsing the command options. 318 319=item Z<>2 320 321one of the input files could not be read. 322 323=item Z<>3 324 325an error occurred creating the PKCS#7 file or when reading the MIME 326message. 327 328=item Z<>4 329 330an error occurred decrypting or verifying the message. 331 332=item Z<>5 333 334the message was verified correctly but an error occurred writing out 335the signers certificates. 336 337=back 338 339=head1 EXAMPLES 340 341Create a cleartext signed message: 342 343 openssl smime -sign -in message.txt -text -out mail.msg \ 344 -signer mycert.pem 345 346Create an opaque signed message: 347 348 openssl smime -sign -in message.txt -text -out mail.msg -nodetach \ 349 -signer mycert.pem 350 351Create a signed message, include some additional certificates and 352read the private key from another file: 353 354 openssl smime -sign -in in.txt -text -out mail.msg \ 355 -signer mycert.pem -inkey mykey.pem -certfile mycerts.pem 356 357Create a signed message with two signers: 358 359 openssl smime -sign -in message.txt -text -out mail.msg \ 360 -signer mycert.pem -signer othercert.pem 361 362Send a signed message under Unix directly to sendmail, including headers: 363 364 openssl smime -sign -in in.txt -text -signer mycert.pem \ 365 -from steve@openssl.org -to someone@somewhere \ 366 -subject "Signed message" | sendmail someone@somewhere 367 368Verify a message and extract the signer's certificate if successful: 369 370 openssl smime -verify -in mail.msg -signer user.pem -out signedtext.txt 371 372Send encrypted mail using triple DES: 373 374 openssl smime -encrypt -in in.txt -from steve@openssl.org \ 375 -to someone@somewhere -subject "Encrypted message" \ 376 -des3 user.pem -out mail.msg 377 378Sign and encrypt mail: 379 380 openssl smime -sign -in ml.txt -signer my.pem -text \ 381 | openssl smime -encrypt -out mail.msg \ 382 -from steve@openssl.org -to someone@somewhere \ 383 -subject "Signed and Encrypted message" -des3 user.pem 384 385Note: the encryption command does not include the B<-text> option because the 386message being encrypted already has MIME headers. 387 388Decrypt mail: 389 390 openssl smime -decrypt -in mail.msg -recip mycert.pem -inkey key.pem 391 392The output from Netscape form signing is a PKCS#7 structure with the 393detached signature format. You can use this program to verify the 394signature by line wrapping the base64 encoded structure and surrounding 395it with: 396 397 -----BEGIN PKCS7----- 398 -----END PKCS7----- 399 400and using the command: 401 402 openssl smime -verify -inform PEM -in signature.pem -content content.txt 403 404Alternatively you can base64 decode the signature and use: 405 406 openssl smime -verify -inform DER -in signature.der -content content.txt 407 408Create an encrypted message using 128 bit Camellia: 409 410 openssl smime -encrypt -in plain.txt -camellia128 -out mail.msg cert.pem 411 412Add a signer to an existing message: 413 414 openssl smime -resign -in mail.msg -signer newsign.pem -out mail2.msg 415 416=head1 BUGS 417 418The MIME parser isn't very clever: it seems to handle most messages that I've 419thrown at it but it may choke on others. 420 421The code currently will only write out the signer's certificate to a file: if 422the signer has a separate encryption certificate this must be manually 423extracted. There should be some heuristic that determines the correct 424encryption certificate. 425 426Ideally a database should be maintained of a certificates for each email 427address. 428 429The code doesn't currently take note of the permitted symmetric encryption 430algorithms as supplied in the SMIMECapabilities signed attribute. This means the 431user has to manually include the correct encryption algorithm. It should store 432the list of permitted ciphers in a database and only use those. 433 434No revocation checking is done on the signer's certificate. 435 436The current code can only handle S/MIME v2 messages, the more complex S/MIME v3 437structures may cause parsing errors. 438 439=head1 HISTORY 440 441The use of multiple B<-signer> options and the B<-resign> command were first 442added in OpenSSL 1.0.0 443 444 445=cut 446