smime.pod revision 100936
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<-in file>] 21[B<-certfile file>] 22[B<-signer file>] 23[B<-recip file>] 24[B<-inform SMIME|PEM|DER>] 25[B<-passin arg>] 26[B<-inkey file>] 27[B<-out file>] 28[B<-outform SMIME|PEM|DER>] 29[B<-content file>] 30[B<-to addr>] 31[B<-from ad>] 32[B<-subject s>] 33[B<-text>] 34[B<-rand file(s)>] 35[cert.pem]... 36 37=head1 DESCRIPTION 38 39The B<smime> command handles S/MIME mail. It can encrypt, decrypt, sign and 40verify S/MIME messages. 41 42=head1 COMMAND OPTIONS 43 44There are five operation options that set the type of operation to be performed. 45The meaning of the other options varies according to the operation type. 46 47=over 4 48 49=item B<-encrypt> 50 51encrypt mail for the given recipient certificates. Input file is the message 52to be encrypted. The output file is the encrypted mail in MIME format. 53 54=item B<-decrypt> 55 56decrypt mail using the supplied certificate and private key. Expects an 57encrypted mail message in MIME format for the input file. The decrypted mail 58is written to the output file. 59 60=item B<-sign> 61 62sign mail using the supplied certificate and private key. Input file is 63the message to be signed. The signed message in MIME format is written 64to the output file. 65 66=item B<-verify> 67 68verify signed mail. Expects a signed mail message on input and outputs 69the signed data. Both clear text and opaque signing is supported. 70 71=item B<-pk7out> 72 73takes an input message and writes out a PEM encoded PKCS#7 structure. 74 75=item B<-in filename> 76 77the input message to be encrypted or signed or the MIME message to 78be decrypted or verified. 79 80=item B<-inform SMIME|PEM|DER> 81 82this specifies the input format for the PKCS#7 structure. The default 83is B<SMIME> which reads an S/MIME format message. B<PEM> and B<DER> 84format change this to expect PEM and DER format PKCS#7 structures 85instead. This currently only affects the input format of the PKCS#7 86structure, if no PKCS#7 structure is being input (for example with 87B<-encrypt> or B<-sign>) this option has no effect. 88 89=item B<-out filename> 90 91the message text that has been decrypted or verified or the output MIME 92format message that has been signed or verified. 93 94=item B<-outform SMIME|PEM|DER> 95 96this specifies the output format for the PKCS#7 structure. The default 97is B<SMIME> which write an S/MIME format message. B<PEM> and B<DER> 98format change this to write PEM and DER format PKCS#7 structures 99instead. This currently only affects the output format of the PKCS#7 100structure, if no PKCS#7 structure is being output (for example with 101B<-verify> or B<-decrypt>) this option has no effect. 102 103=item B<-content filename> 104 105This specifies a file containing the detached content, this is only 106useful with the B<-verify> command. This is only usable if the PKCS#7 107structure is using the detached signature form where the content is 108not included. This option will override any content if the input format 109is S/MIME and it uses the multipart/signed MIME content type. 110 111=item B<-text> 112 113this option adds plain text (text/plain) MIME headers to the supplied 114message if encrypting or signing. If decrypting or verifying it strips 115off text headers: if the decrypted or verified message is not of MIME 116type text/plain then an error occurs. 117 118=item B<-CAfile file> 119 120a file containing trusted CA certificates, only used with B<-verify>. 121 122=item B<-CApath dir> 123 124a directory containing trusted CA certificates, only used with 125B<-verify>. This directory must be a standard certificate directory: that 126is a hash of each subject name (using B<x509 -hash>) should be linked 127to each certificate. 128 129=item B<-des -des3 -rc2-40 -rc2-64 -rc2-128> 130 131the encryption algorithm to use. DES (56 bits), triple DES (168 bits) 132or 40, 64 or 128 bit RC2 respectively if not specified 40 bit RC2 is 133used. Only used with B<-encrypt>. 134 135=item B<-nointern> 136 137when verifying a message normally certificates (if any) included in 138the message are searched for the signing certificate. With this option 139only the certificates specified in the B<-certfile> option are used. 140The supplied certificates can still be used as untrusted CAs however. 141 142=item B<-noverify> 143 144do not verify the signers certificate of a signed message. 145 146=item B<-nochain> 147 148do not do chain verification of signers certificates: that is don't 149use the certificates in the signed message as untrusted CAs. 150 151=item B<-nosigs> 152 153don't try to verify the signatures on the message. 154 155=item B<-nocerts> 156 157when signing a message the signer's certificate is normally included 158with this option it is excluded. This will reduce the size of the 159signed message but the verifier must have a copy of the signers certificate 160available locally (passed using the B<-certfile> option for example). 161 162=item B<-noattr> 163 164normally when a message is signed a set of attributes are included which 165include the signing time and supported symmetric algorithms. With this 166option they are not included. 167 168=item B<-binary> 169 170normally the input message is converted to "canonical" format which is 171effectively using CR and LF as end of line: as required by the S/MIME 172specification. When this option is present no translation occurs. This 173is useful when handling binary data which may not be in MIME format. 174 175=item B<-nodetach> 176 177when signing a message use opaque signing: this form is more resistant 178to translation by mail relays but it cannot be read by mail agents that 179do not support S/MIME. Without this option cleartext signing with 180the MIME type multipart/signed is used. 181 182=item B<-certfile file> 183 184allows additional certificates to be specified. When signing these will 185be included with the message. When verifying these will be searched for 186the signers certificates. The certificates should be in PEM format. 187 188=item B<-signer file> 189 190the signers certificate when signing a message. If a message is 191being verified then the signers certificates will be written to this 192file if the verification was successful. 193 194=item B<-recip file> 195 196the recipients certificate when decrypting a message. This certificate 197must match one of the recipients of the message or an error occurs. 198 199=item B<-inkey file> 200 201the private key to use when signing or decrypting. This must match the 202corresponding certificate. If this option is not specified then the 203private key must be included in the certificate file specified with 204the B<-recip> or B<-signer> file. 205 206=item B<-passin arg> 207 208the private key password source. For more information about the format of B<arg> 209see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)|openssl(1)>. 210 211=item B<-rand file(s)> 212 213a file or files containing random data used to seed the random number 214generator, or an EGD socket (see L<RAND_egd(3)|RAND_egd(3)>). 215Multiple files can be specified separated by a OS-dependent character. 216The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for 217all others. 218 219=item B<cert.pem...> 220 221one or more certificates of message recipients: used when encrypting 222a message. 223 224=item B<-to, -from, -subject> 225 226the relevant mail headers. These are included outside the signed 227portion of a message so they may be included manually. If signing 228then many S/MIME mail clients check the signers certificate's email 229address matches that specified in the From: address. 230 231=back 232 233=head1 NOTES 234 235The MIME message must be sent without any blank lines between the 236headers and the output. Some mail programs will automatically add 237a blank line. Piping the mail directly to sendmail is one way to 238achieve the correct format. 239 240The supplied message to be signed or encrypted must include the 241necessary MIME headers or many S/MIME clients wont display it 242properly (if at all). You can use the B<-text> option to automatically 243add plain text headers. 244 245A "signed and encrypted" message is one where a signed message is 246then encrypted. This can be produced by encrypting an already signed 247message: see the examples section. 248 249This version of the program only allows one signer per message but it 250will verify multiple signers on received messages. Some S/MIME clients 251choke if a message contains multiple signers. It is possible to sign 252messages "in parallel" by signing an already signed message. 253 254The options B<-encrypt> and B<-decrypt> reflect common usage in S/MIME 255clients. Strictly speaking these process PKCS#7 enveloped data: PKCS#7 256encrypted data is used for other purposes. 257 258=head1 EXIT CODES 259 260=over 4 261 262=item 0 263 264the operation was completely successfully. 265 266=item 1 267 268an error occurred parsing the command options. 269 270=item 2 271 272one of the input files could not be read. 273 274=item 3 275 276an error occurred creating the PKCS#7 file or when reading the MIME 277message. 278 279=item 4 280 281an error occurred decrypting or verifying the message. 282 283=item 5 284 285the message was verified correctly but an error occurred writing out 286the signers certificates. 287 288=back 289 290=head1 EXAMPLES 291 292Create a cleartext signed message: 293 294 openssl smime -sign -in message.txt -text -out mail.msg \ 295 -signer mycert.pem 296 297Create and opaque signed message 298 299 openssl smime -sign -in message.txt -text -out mail.msg -nodetach \ 300 -signer mycert.pem 301 302Create a signed message, include some additional certificates and 303read the private key from another file: 304 305 openssl smime -sign -in in.txt -text -out mail.msg \ 306 -signer mycert.pem -inkey mykey.pem -certfile mycerts.pem 307 308Send a signed message under Unix directly to sendmail, including headers: 309 310 openssl smime -sign -in in.txt -text -signer mycert.pem \ 311 -from steve@openssl.org -to someone@somewhere \ 312 -subject "Signed message" | sendmail someone@somewhere 313 314Verify a message and extract the signer's certificate if successful: 315 316 openssl smime -verify -in mail.msg -signer user.pem -out signedtext.txt 317 318Send encrypted mail using triple DES: 319 320 openssl smime -encrypt -in in.txt -from steve@openssl.org \ 321 -to someone@somewhere -subject "Encrypted message" \ 322 -des3 user.pem -out mail.msg 323 324Sign and encrypt mail: 325 326 openssl smime -sign -in ml.txt -signer my.pem -text \ 327 | openssl smime -encrypt -out mail.msg \ 328 -from steve@openssl.org -to someone@somewhere \ 329 -subject "Signed and Encrypted message" -des3 user.pem 330 331Note: the encryption command does not include the B<-text> option because the message 332being encrypted already has MIME headers. 333 334Decrypt mail: 335 336 openssl smime -decrypt -in mail.msg -recip mycert.pem -inkey key.pem 337 338The output from Netscape form signing is a PKCS#7 structure with the 339detached signature format. You can use this program to verify the 340signature by line wrapping the base64 encoded structure and surrounding 341it with: 342 343 -----BEGIN PKCS7---- 344 -----END PKCS7---- 345 346and using the command, 347 348 openssl smime -verify -inform PEM -in signature.pem -content content.txt 349 350alternatively you can base64 decode the signature and use 351 352 openssl smime -verify -inform DER -in signature.der -content content.txt 353 354=head1 BUGS 355 356The MIME parser isn't very clever: it seems to handle most messages that I've thrown 357at it but it may choke on others. 358 359The code currently will only write out the signer's certificate to a file: if the 360signer has a separate encryption certificate this must be manually extracted. There 361should be some heuristic that determines the correct encryption certificate. 362 363Ideally a database should be maintained of a certificates for each email address. 364 365The code doesn't currently take note of the permitted symmetric encryption 366algorithms as supplied in the SMIMECapabilities signed attribute. this means the 367user has to manually include the correct encryption algorithm. It should store 368the list of permitted ciphers in a database and only use those. 369 370No revocation checking is done on the signer's certificate. 371 372The current code can only handle S/MIME v2 messages, the more complex S/MIME v3 373structures may cause parsing errors. 374 375=cut 376