smime.pod revision 127128
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<-verify>] 14[B<-pk7out>] 15[B<-des>] 16[B<-des3>] 17[B<-rc2-40>] 18[B<-rc2-64>] 19[B<-rc2-128>] 20[B<-aes128>] 21[B<-aes192>] 22[B<-aes256>] 23[B<-in file>] 24[B<-certfile file>] 25[B<-signer file>] 26[B<-recip file>] 27[B<-inform SMIME|PEM|DER>] 28[B<-passin arg>] 29[B<-inkey file>] 30[B<-out file>] 31[B<-outform SMIME|PEM|DER>] 32[B<-content file>] 33[B<-to addr>] 34[B<-from ad>] 35[B<-subject s>] 36[B<-text>] 37[B<-rand file(s)>] 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 five 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 57=item B<-decrypt> 58 59decrypt mail using the supplied certificate and private key. Expects an 60encrypted mail message in MIME format for the input file. The decrypted mail 61is written to the output file. 62 63=item B<-sign> 64 65sign mail using the supplied certificate and private key. Input file is 66the message to be signed. The signed message in MIME format is written 67to the output file. 68 69=item B<-verify> 70 71verify signed mail. Expects a signed mail message on input and outputs 72the signed data. Both clear text and opaque signing is supported. 73 74=item B<-pk7out> 75 76takes an input message and writes out a PEM encoded PKCS#7 structure. 77 78=item B<-in filename> 79 80the input message to be encrypted or signed or the MIME message to 81be decrypted or verified. 82 83=item B<-inform SMIME|PEM|DER> 84 85this specifies the input format for the PKCS#7 structure. The default 86is B<SMIME> which reads an S/MIME format message. B<PEM> and B<DER> 87format change this to expect PEM and DER format PKCS#7 structures 88instead. This currently only affects the input format of the PKCS#7 89structure, if no PKCS#7 structure is being input (for example with 90B<-encrypt> or B<-sign>) this option has no effect. 91 92=item B<-out filename> 93 94the message text that has been decrypted or verified or the output MIME 95format message that has been signed or verified. 96 97=item B<-outform SMIME|PEM|DER> 98 99this specifies the output format for the PKCS#7 structure. The default 100is B<SMIME> which write an S/MIME format message. B<PEM> and B<DER> 101format change this to write PEM and DER format PKCS#7 structures 102instead. This currently only affects the output format of the PKCS#7 103structure, if no PKCS#7 structure is being output (for example with 104B<-verify> or B<-decrypt>) this option has no effect. 105 106=item B<-content filename> 107 108This specifies a file containing the detached content, this is only 109useful with the B<-verify> command. This is only usable if the PKCS#7 110structure is using the detached signature form where the content is 111not included. This option will override any content if the input format 112is S/MIME and it uses the multipart/signed MIME content type. 113 114=item B<-text> 115 116this option adds plain text (text/plain) MIME headers to the supplied 117message if encrypting or signing. If decrypting or verifying it strips 118off text headers: if the decrypted or verified message is not of MIME 119type text/plain then an error occurs. 120 121=item B<-CAfile file> 122 123a file containing trusted CA certificates, only used with B<-verify>. 124 125=item B<-CApath dir> 126 127a directory containing trusted CA certificates, only used with 128B<-verify>. This directory must be a standard certificate directory: that 129is a hash of each subject name (using B<x509 -hash>) should be linked 130to each certificate. 131 132=item B<-des -des3 -rc2-40 -rc2-64 -rc2-128 -aes128 -aes192 -aes256> 133 134the encryption algorithm to use. DES (56 bits), triple DES (168 bits), 13540, 64 or 128 bit RC2 or 128, 192 or 256 bit AES respectively. If not 136specified 40 bit RC2 is used. Only used with B<-encrypt>. 137 138=item B<-nointern> 139 140when verifying a message normally certificates (if any) included in 141the message are searched for the signing certificate. With this option 142only the certificates specified in the B<-certfile> option are used. 143The supplied certificates can still be used as untrusted CAs however. 144 145=item B<-noverify> 146 147do not verify the signers certificate of a signed message. 148 149=item B<-nochain> 150 151do not do chain verification of signers certificates: that is don't 152use the certificates in the signed message as untrusted CAs. 153 154=item B<-nosigs> 155 156don't try to verify the signatures on the message. 157 158=item B<-nocerts> 159 160when signing a message the signer's certificate is normally included 161with this option it is excluded. This will reduce the size of the 162signed message but the verifier must have a copy of the signers certificate 163available locally (passed using the B<-certfile> option for example). 164 165=item B<-noattr> 166 167normally when a message is signed a set of attributes are included which 168include the signing time and supported symmetric algorithms. With this 169option they are not included. 170 171=item B<-binary> 172 173normally the input message is converted to "canonical" format which is 174effectively using CR and LF as end of line: as required by the S/MIME 175specification. When this option is present no translation occurs. This 176is useful when handling binary data which may not be in MIME format. 177 178=item B<-nodetach> 179 180when signing a message use opaque signing: this form is more resistant 181to translation by mail relays but it cannot be read by mail agents that 182do not support S/MIME. Without this option cleartext signing with 183the MIME type multipart/signed is used. 184 185=item B<-certfile file> 186 187allows additional certificates to be specified. When signing these will 188be included with the message. When verifying these will be searched for 189the signers certificates. The certificates should be in PEM format. 190 191=item B<-signer file> 192 193the signers certificate when signing a message. If a message is 194being verified then the signers certificates will be written to this 195file if the verification was successful. 196 197=item B<-recip file> 198 199the recipients certificate when decrypting a message. This certificate 200must match one of the recipients of the message or an error occurs. 201 202=item B<-inkey file> 203 204the private key to use when signing or decrypting. This must match the 205corresponding certificate. If this option is not specified then the 206private key must be included in the certificate file specified with 207the B<-recip> or B<-signer> file. 208 209=item B<-passin arg> 210 211the private key password source. For more information about the format of B<arg> 212see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)|openssl(1)>. 213 214=item B<-rand file(s)> 215 216a file or files containing random data used to seed the random number 217generator, or an EGD socket (see L<RAND_egd(3)|RAND_egd(3)>). 218Multiple files can be specified separated by a OS-dependent character. 219The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for 220all others. 221 222=item B<cert.pem...> 223 224one or more certificates of message recipients: used when encrypting 225a message. 226 227=item B<-to, -from, -subject> 228 229the relevant mail headers. These are included outside the signed 230portion of a message so they may be included manually. If signing 231then many S/MIME mail clients check the signers certificate's email 232address matches that specified in the From: address. 233 234=back 235 236=head1 NOTES 237 238The MIME message must be sent without any blank lines between the 239headers and the output. Some mail programs will automatically add 240a blank line. Piping the mail directly to sendmail is one way to 241achieve the correct format. 242 243The supplied message to be signed or encrypted must include the 244necessary MIME headers or many S/MIME clients wont display it 245properly (if at all). You can use the B<-text> option to automatically 246add plain text headers. 247 248A "signed and encrypted" message is one where a signed message is 249then encrypted. This can be produced by encrypting an already signed 250message: see the examples section. 251 252This version of the program only allows one signer per message but it 253will verify multiple signers on received messages. Some S/MIME clients 254choke if a message contains multiple signers. It is possible to sign 255messages "in parallel" by signing an already signed message. 256 257The options B<-encrypt> and B<-decrypt> reflect common usage in S/MIME 258clients. Strictly speaking these process PKCS#7 enveloped data: PKCS#7 259encrypted data is used for other purposes. 260 261=head1 EXIT CODES 262 263=over 4 264 265=item 0 266 267the operation was completely successfully. 268 269=item 1 270 271an error occurred parsing the command options. 272 273=item 2 274 275one of the input files could not be read. 276 277=item 3 278 279an error occurred creating the PKCS#7 file or when reading the MIME 280message. 281 282=item 4 283 284an error occurred decrypting or verifying the message. 285 286=item 5 287 288the message was verified correctly but an error occurred writing out 289the signers certificates. 290 291=back 292 293=head1 EXAMPLES 294 295Create a cleartext signed message: 296 297 openssl smime -sign -in message.txt -text -out mail.msg \ 298 -signer mycert.pem 299 300Create and opaque signed message 301 302 openssl smime -sign -in message.txt -text -out mail.msg -nodetach \ 303 -signer mycert.pem 304 305Create a signed message, include some additional certificates and 306read the private key from another file: 307 308 openssl smime -sign -in in.txt -text -out mail.msg \ 309 -signer mycert.pem -inkey mykey.pem -certfile mycerts.pem 310 311Send a signed message under Unix directly to sendmail, including headers: 312 313 openssl smime -sign -in in.txt -text -signer mycert.pem \ 314 -from steve@openssl.org -to someone@somewhere \ 315 -subject "Signed message" | sendmail someone@somewhere 316 317Verify a message and extract the signer's certificate if successful: 318 319 openssl smime -verify -in mail.msg -signer user.pem -out signedtext.txt 320 321Send encrypted mail using triple DES: 322 323 openssl smime -encrypt -in in.txt -from steve@openssl.org \ 324 -to someone@somewhere -subject "Encrypted message" \ 325 -des3 user.pem -out mail.msg 326 327Sign and encrypt mail: 328 329 openssl smime -sign -in ml.txt -signer my.pem -text \ 330 | openssl smime -encrypt -out mail.msg \ 331 -from steve@openssl.org -to someone@somewhere \ 332 -subject "Signed and Encrypted message" -des3 user.pem 333 334Note: the encryption command does not include the B<-text> option because the message 335being encrypted already has MIME headers. 336 337Decrypt mail: 338 339 openssl smime -decrypt -in mail.msg -recip mycert.pem -inkey key.pem 340 341The output from Netscape form signing is a PKCS#7 structure with the 342detached signature format. You can use this program to verify the 343signature by line wrapping the base64 encoded structure and surrounding 344it with: 345 346 -----BEGIN PKCS7----- 347 -----END PKCS7----- 348 349and using the command, 350 351 openssl smime -verify -inform PEM -in signature.pem -content content.txt 352 353alternatively you can base64 decode the signature and use 354 355 openssl smime -verify -inform DER -in signature.der -content content.txt 356 357=head1 BUGS 358 359The MIME parser isn't very clever: it seems to handle most messages that I've thrown 360at it but it may choke on others. 361 362The code currently will only write out the signer's certificate to a file: if the 363signer has a separate encryption certificate this must be manually extracted. There 364should be some heuristic that determines the correct encryption certificate. 365 366Ideally a database should be maintained of a certificates for each email address. 367 368The code doesn't currently take note of the permitted symmetric encryption 369algorithms as supplied in the SMIMECapabilities signed attribute. this means the 370user has to manually include the correct encryption algorithm. It should store 371the list of permitted ciphers in a database and only use those. 372 373No revocation checking is done on the signer's certificate. 374 375The current code can only handle S/MIME v2 messages, the more complex S/MIME v3 376structures may cause parsing errors. 377 378=cut 379