smime.pod 14 KB

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