smime.pod revision 325337
1=pod 2 3=head1 NAME 4 5openssl-smime, 6smime - S/MIME utility 7 8=head1 SYNOPSIS 9 10B<openssl> B<smime> 11[B<-encrypt>] 12[B<-decrypt>] 13[B<-sign>] 14[B<-resign>] 15[B<-verify>] 16[B<-pk7out>] 17[B<-[cipher]>] 18[B<-in file>] 19[B<-no_alt_chains>] 20[B<-certfile file>] 21[B<-signer file>] 22[B<-recip file>] 23[B<-inform SMIME|PEM|DER>] 24[B<-passin arg>] 25[B<-inkey file>] 26[B<-out file>] 27[B<-outform SMIME|PEM|DER>] 28[B<-content file>] 29[B<-to addr>] 30[B<-from ad>] 31[B<-subject s>] 32[B<-text>] 33[B<-indef>] 34[B<-noindef>] 35[B<-stream>] 36[B<-rand file(s)>] 37[B<-md digest>] 38[cert.pem]... 39 40=head1 DESCRIPTION 41 42The B<smime> command handles S/MIME mail. It can encrypt, decrypt, sign and 43verify S/MIME messages. 44 45=head1 COMMAND OPTIONS 46 47There are six operation options that set the type of operation to be performed. 48The meaning of the other options varies according to the operation type. 49 50=over 4 51 52=item B<-encrypt> 53 54encrypt mail for the given recipient certificates. Input file is the message 55to be encrypted. The output file is the encrypted mail in MIME format. 56 57Note that no revocation check is done for the recipient cert, so if that 58key has been compromised, others may be able to decrypt the text. 59 60=item B<-decrypt> 61 62decrypt mail using the supplied certificate and private key. Expects an 63encrypted mail message in MIME format for the input file. The decrypted mail 64is written to the output file. 65 66=item B<-sign> 67 68sign mail using the supplied certificate and private key. Input file is 69the message to be signed. The signed message in MIME format is written 70to the output file. 71 72=item B<-verify> 73 74verify signed mail. Expects a signed mail message on input and outputs 75the signed data. Both clear text and opaque signing is supported. 76 77=item B<-pk7out> 78 79takes an input message and writes out a PEM encoded PKCS#7 structure. 80 81=item B<-resign> 82 83resign a message: take an existing message and one or more new signers. 84 85=item B<-in filename> 86 87the input message to be encrypted or signed or the MIME message to 88be decrypted or verified. 89 90=item B<-inform SMIME|PEM|DER> 91 92this specifies the input format for the PKCS#7 structure. The default 93is B<SMIME> which reads an S/MIME format message. B<PEM> and B<DER> 94format change this to expect PEM and DER format PKCS#7 structures 95instead. This currently only affects the input format of the PKCS#7 96structure, if no PKCS#7 structure is being input (for example with 97B<-encrypt> or B<-sign>) this option has no effect. 98 99=item B<-out filename> 100 101the message text that has been decrypted or verified or the output MIME 102format message that has been signed or verified. 103 104=item B<-outform SMIME|PEM|DER> 105 106this specifies the output format for the PKCS#7 structure. The default 107is B<SMIME> which write an S/MIME format message. B<PEM> and B<DER> 108format change this to write PEM and DER format PKCS#7 structures 109instead. This currently only affects the output format of the PKCS#7 110structure, if no PKCS#7 structure is being output (for example with 111B<-verify> or B<-decrypt>) this option has no effect. 112 113=item B<-stream -indef -noindef> 114 115the B<-stream> and B<-indef> options are equivalent and enable streaming I/O 116for encoding operations. This permits single pass processing of data without 117the need to hold the entire contents in memory, potentially supporting very 118large files. Streaming is automatically set for S/MIME signing with detached 119data if the output format is B<SMIME> it is currently off by default for all 120other operations. 121 122=item B<-noindef> 123 124disable streaming I/O where it would produce and indefinite length constructed 125encoding. This option currently has no effect. In future streaming will be 126enabled by default on all relevant operations and this option will disable it. 127 128=item B<-content filename> 129 130This specifies a file containing the detached content, this is only 131useful with the B<-verify> command. This is only usable if the PKCS#7 132structure is using the detached signature form where the content is 133not included. This option will override any content if the input format 134is S/MIME and it uses the multipart/signed MIME content type. 135 136=item B<-text> 137 138this option adds plain text (text/plain) MIME headers to the supplied 139message if encrypting or signing. If decrypting or verifying it strips 140off text headers: if the decrypted or verified message is not of MIME 141type text/plain then an error occurs. 142 143=item B<-CAfile file> 144 145a file containing trusted CA certificates, only used with B<-verify>. 146 147=item B<-CApath dir> 148 149a directory containing trusted CA certificates, only used with 150B<-verify>. This directory must be a standard certificate directory: that 151is a hash of each subject name (using B<x509 -hash>) should be linked 152to each certificate. 153 154=item B<-md digest> 155 156digest algorithm to use when signing or resigning. If not present then the 157default digest algorithm for the signing key will be used (usually SHA1). 158 159=item B<-[cipher]> 160 161the encryption algorithm to use. For example DES (56 bits) - B<-des>, 162triple DES (168 bits) - B<-des3>, 163EVP_get_cipherbyname() function) can also be used preceded by a dash, for 164example B<-aes_128_cbc>. See L<B<enc>|enc(1)> for list of ciphers 165supported by your version of OpenSSL. 166 167If not specified triple DES is used. Only used with B<-encrypt>. 168 169=item B<-nointern> 170 171when verifying a message normally certificates (if any) included in 172the message are searched for the signing certificate. With this option 173only the certificates specified in the B<-certfile> option are used. 174The supplied certificates can still be used as untrusted CAs however. 175 176=item B<-noverify> 177 178do not verify the signers certificate of a signed message. 179 180=item B<-nochain> 181 182do not do chain verification of signers certificates: that is don't 183use the certificates in the signed message as untrusted CAs. 184 185=item B<-nosigs> 186 187don't try to verify the signatures on the message. 188 189=item B<-nocerts> 190 191when signing a message the signer's certificate is normally included 192with this option it is excluded. This will reduce the size of the 193signed message but the verifier must have a copy of the signers certificate 194available locally (passed using the B<-certfile> option for example). 195 196=item B<-noattr> 197 198normally when a message is signed a set of attributes are included which 199include the signing time and supported symmetric algorithms. With this 200option they are not included. 201 202=item B<-binary> 203 204normally the input message is converted to "canonical" format which is 205effectively using CR and LF as end of line: as required by the S/MIME 206specification. When this option is present no translation occurs. This 207is useful when handling binary data which may not be in MIME format. 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<-certfile file> 217 218allows additional certificates to be specified. When signing these will 219be included with the message. When verifying these will be searched for 220the signers certificates. The certificates should be in PEM format. 221 222=item B<-signer file> 223 224a signing certificate when signing or resigning a message, this option can be 225used multiple times if more than one signer is required. If a message is being 226verified then the signers certificates will be written to this file if the 227verification was successful. 228 229=item B<-recip file> 230 231the recipients certificate when decrypting a message. This certificate 232must match one of the recipients of the message or an error occurs. 233 234=item B<-inkey file> 235 236the private key to use when signing or decrypting. This must match the 237corresponding certificate. If this option is not specified then the 238private key must be included in the certificate file specified with 239the B<-recip> or B<-signer> file. When signing this option can be used 240multiple times to specify successive keys. 241 242=item B<-passin arg> 243 244the private key password source. For more information about the format of B<arg> 245see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)|openssl(1)>. 246 247=item B<-rand file(s)> 248 249a file or files containing random data used to seed the random number 250generator, or an EGD socket (see L<RAND_egd(3)|RAND_egd(3)>). 251Multiple files can be specified separated by a OS-dependent character. 252The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for 253all others. 254 255=item B<cert.pem...> 256 257one or more certificates of message recipients: used when encrypting 258a message. 259 260=item B<-to, -from, -subject> 261 262the relevant mail headers. These are included outside the signed 263portion of a message so they may be included manually. If signing 264then many S/MIME mail clients check the signers certificate's email 265address matches that specified in the From: address. 266 267=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> 268 269Set various options of certificate chain verification. See 270L<B<verify>|verify(1)> manual page for details. 271 272=back 273 274=head1 NOTES 275 276The MIME message must be sent without any blank lines between the 277headers and the output. Some mail programs will automatically add 278a blank line. Piping the mail directly to sendmail is one way to 279achieve the correct format. 280 281The supplied message to be signed or encrypted must include the 282necessary MIME headers or many S/MIME clients wont display it 283properly (if at all). You can use the B<-text> option to automatically 284add plain text headers. 285 286A "signed and encrypted" message is one where a signed message is 287then encrypted. This can be produced by encrypting an already signed 288message: see the examples section. 289 290This version of the program only allows one signer per message but it 291will verify multiple signers on received messages. Some S/MIME clients 292choke if a message contains multiple signers. It is possible to sign 293messages "in parallel" by signing an already signed message. 294 295The options B<-encrypt> and B<-decrypt> reflect common usage in S/MIME 296clients. Strictly speaking these process PKCS#7 enveloped data: PKCS#7 297encrypted data is used for other purposes. 298 299The B<-resign> option uses an existing message digest when adding a new 300signer. This means that attributes must be present in at least one existing 301signer using the same message digest or this operation will fail. 302 303The B<-stream> and B<-indef> options enable experimental streaming I/O support. 304As a result the encoding is BER using indefinite length constructed encoding 305and no longer DER. Streaming is supported for the B<-encrypt> operation and the 306B<-sign> operation if the content is not detached. 307 308Streaming is always used for the B<-sign> operation with detached data but 309since the content is no longer part of the PKCS#7 structure the encoding 310remains DER. 311 312=head1 EXIT CODES 313 314=over 4 315 316=item Z<>0 317 318the operation was completely successfully. 319 320=item Z<>1 321 322an error occurred parsing the command options. 323 324=item Z<>2 325 326one of the input files could not be read. 327 328=item Z<>3 329 330an error occurred creating the PKCS#7 file or when reading the MIME 331message. 332 333=item Z<>4 334 335an error occurred decrypting or verifying the message. 336 337=item Z<>5 338 339the message was verified correctly but an error occurred writing out 340the signers certificates. 341 342=back 343 344=head1 EXAMPLES 345 346Create a cleartext signed message: 347 348 openssl smime -sign -in message.txt -text -out mail.msg \ 349 -signer mycert.pem 350 351Create an opaque signed message: 352 353 openssl smime -sign -in message.txt -text -out mail.msg -nodetach \ 354 -signer mycert.pem 355 356Create a signed message, include some additional certificates and 357read the private key from another file: 358 359 openssl smime -sign -in in.txt -text -out mail.msg \ 360 -signer mycert.pem -inkey mykey.pem -certfile mycerts.pem 361 362Create a signed message with two signers: 363 364 openssl smime -sign -in message.txt -text -out mail.msg \ 365 -signer mycert.pem -signer othercert.pem 366 367Send a signed message under Unix directly to sendmail, including headers: 368 369 openssl smime -sign -in in.txt -text -signer mycert.pem \ 370 -from steve@openssl.org -to someone@somewhere \ 371 -subject "Signed message" | sendmail someone@somewhere 372 373Verify a message and extract the signer's certificate if successful: 374 375 openssl smime -verify -in mail.msg -signer user.pem -out signedtext.txt 376 377Send encrypted mail using triple DES: 378 379 openssl smime -encrypt -in in.txt -from steve@openssl.org \ 380 -to someone@somewhere -subject "Encrypted message" \ 381 -des3 user.pem -out mail.msg 382 383Sign and encrypt mail: 384 385 openssl smime -sign -in ml.txt -signer my.pem -text \ 386 | openssl smime -encrypt -out mail.msg \ 387 -from steve@openssl.org -to someone@somewhere \ 388 -subject "Signed and Encrypted message" -des3 user.pem 389 390Note: the encryption command does not include the B<-text> option because the 391message being encrypted already has MIME headers. 392 393Decrypt mail: 394 395 openssl smime -decrypt -in mail.msg -recip mycert.pem -inkey key.pem 396 397The output from Netscape form signing is a PKCS#7 structure with the 398detached signature format. You can use this program to verify the 399signature by line wrapping the base64 encoded structure and surrounding 400it with: 401 402 -----BEGIN PKCS7----- 403 -----END PKCS7----- 404 405and using the command: 406 407 openssl smime -verify -inform PEM -in signature.pem -content content.txt 408 409Alternatively you can base64 decode the signature and use: 410 411 openssl smime -verify -inform DER -in signature.der -content content.txt 412 413Create an encrypted message using 128 bit Camellia: 414 415 openssl smime -encrypt -in plain.txt -camellia128 -out mail.msg cert.pem 416 417Add a signer to an existing message: 418 419 openssl smime -resign -in mail.msg -signer newsign.pem -out mail2.msg 420 421=head1 BUGS 422 423The MIME parser isn't very clever: it seems to handle most messages that I've 424thrown at it but it may choke on others. 425 426The code currently will only write out the signer's certificate to a file: if 427the signer has a separate encryption certificate this must be manually 428extracted. There should be some heuristic that determines the correct 429encryption certificate. 430 431Ideally a database should be maintained of a certificates for each email 432address. 433 434The code doesn't currently take note of the permitted symmetric encryption 435algorithms as supplied in the SMIMECapabilities signed attribute. This means the 436user has to manually include the correct encryption algorithm. It should store 437the list of permitted ciphers in a database and only use those. 438 439No revocation checking is done on the signer's certificate. 440 441The current code can only handle S/MIME v2 messages, the more complex S/MIME v3 442structures may cause parsing errors. 443 444=head1 HISTORY 445 446The use of multiple B<-signer> options and the B<-resign> command were first 447added in OpenSSL 1.0.0 448 449The -no_alt_chains options was first added to OpenSSL 1.0.2b. 450 451=cut 452