> On Dec 15, 2015, at 12:03 PM, Stephen Smalley <sds@xxxxxxxxxxxxx> wrote: > > On 12/15/2015 12:19 PM, Joe Nall wrote: >> >>> On Dec 15, 2015, at 10:06 AM, Casey Schaufler <casey@xxxxxxxxxxxxxxxx> wrote: >>> >>> ... >>> I have long wondered why SELinux generates the context string >>> of the secid more than once. Audit performance alone would >>> justify keeping it around. The variable length issue isn't >>> so difficult as you make it out. As William pointed out earlier, >>> most SELinux contexts are short. Two protocols, one with a >>> fixed length of 16 chars (typical is 7) and one with a fixed >>> length of 256 (for abnormal contexts) solve the problem without >>> complicating the code hardly at all. >> >> We have 'abnormal' contexts over 1024 bytes in production MLS systems. It is possible, though unlikely, to see raw contexts over 5k bytes with 1024 category bits. Thinking like this broke the original RHEL 5 racoon and more recently RHEL 6 openswan for us. >> >> joe >> >> system_u:system_r:silly_test_t:s2:c0,c2,c4,c6,c8,c10,c12,c14,c16,c18,c20,c22,c24,c26,c28,c30,c32,c34,c36,c38,c40,c42,c44,c46,c48,c50,c52,c54,c56,c58,c60,c62,c64,c66,c68,c70,c72,c74,c76,c78,c80,c82,c84,c86,c88,c90,c92,c94,c96,c98,c100,c102,c104,c106,c108,c110,c112,c114,c116,c118,c120,c122,c124,c126,c128,c130,c132,c134,c136,c138,c140,c142,c144,c146,c148,c150,c152,c154,c156,c158,c160,c162,c164,c166,c168,c170,c172,c174,c176,c178,c180,c182,c184,c186,c188,c190,c192,c194,c196,c198,c200,c202,c204,c206,c208,c210,c212,c214,c216,c218,c220,c222,c224,c226,c228,c230,c232,c234,c236,c238,c240,c242,c244,c246,c248,c250,c252,c254,c256,c258,c260,c262,c264,c266,c268,c270,c272,c274,c276,c278,c280,c282,c284,c286,c288,c290,c292,c294,c296,c298,c300,c302,c304,c306,c308,c310,c312,c314,c316,c318,c320,c322,c324,c326,c328,c330,c332,c334,c336,c338,c340,c342,c344,c346,c348,c350,c352,c354,c356,c358,c360,c362,c364,c366,c368,c370,c372,c374,c376,c378,c380,c382,c384,c386,c388,c390,c392,c394,c396,c398,c400,c402,c404,c40 > 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> 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> 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> ,c998,c1000,c1002,c1004,c1006,c1008,c1010,c1012,c1014,c1016,c1018,c1020.c1022 > > Are you patching the kernel to support > 4K contexts? > Otherwise, I'd expect you run up against the proc and selinuxfs API limitations (page size) and/or the filesystem xattr storage limitations (block size). No. The example was a contrived example of what is possible within the format. We use a couple of 2500 byte labels in formal test these days to make sure that we don't have an OS regression. I just get tired of code like this in openswan: #ifdef HAVE_LABELED_IPSEC /* security label length should not exceed 256 in most cases, * (discussed with kernel and selinux people). */ #define MAX_SECCTX_LEN 257 /* including '\0'*/ joe _______________________________________________ Selinux mailing list Selinux@xxxxxxxxxxxxx To unsubscribe, send email to Selinux-leave@xxxxxxxxxxxxx. To get help, send an email containing "help" to Selinux-request@xxxxxxxxxxxxx.
