From 67787844f11fd7614bb26452fda1a1de3ed005ef Mon Sep 17 00:00:00 2001 From: Viktor Dukhovni Date: Sun, 24 Apr 2016 19:48:50 -0400 Subject: Improve and document low-level PEM read routines PEM_read(), PEM_read_bio(), PEM_get_EVP_CIPHER_INFO() and PEM_do_header(). Reviewed-by: Dr. Stephen Henson --- crypto/pem/pem_lib.c | 157 ++++++++++++++++++++++++++++++++------------------- 1 file changed, 98 insertions(+), 59 deletions(-) (limited to 'crypto/pem') diff --git a/crypto/pem/pem_lib.c b/crypto/pem/pem_lib.c index 56865541aa..42b46dc4d5 100644 --- a/crypto/pem/pem_lib.c +++ b/crypto/pem/pem_lib.c @@ -9,6 +9,7 @@ #include #include +#include #include "internal/cryptlib.h" #include #include @@ -389,115 +390,153 @@ int PEM_ASN1_write_bio(i2d_of_void *i2d, const char *name, BIO *bp, int PEM_do_header(EVP_CIPHER_INFO *cipher, unsigned char *data, long *plen, pem_password_cb *callback, void *u) { - int i = 0, j, o, klen; - long len; + int ok; + int keylen; + long len = *plen; + int ilen = (int) len; /* EVP_DecryptUpdate etc. take int lengths */ EVP_CIPHER_CTX *ctx; unsigned char key[EVP_MAX_KEY_LENGTH]; char buf[PEM_BUFSIZE]; - len = *plen; +#if LONG_MAX > INT_MAX + /* Check that we did not truncate the length */ + if (len > INT_MAX) { + PEMerr(PEM_F_PEM_DO_HEADER, PEM_R_HEADER_TOO_LONG); + return 0; + } +#endif if (cipher->cipher == NULL) - return (1); + return 1; if (callback == NULL) - klen = PEM_def_callback(buf, PEM_BUFSIZE, 0, u); + keylen = PEM_def_callback(buf, PEM_BUFSIZE, 0, u); else - klen = callback(buf, PEM_BUFSIZE, 0, u); - if (klen <= 0) { + keylen = callback(buf, PEM_BUFSIZE, 0, u); + if (keylen <= 0) { PEMerr(PEM_F_PEM_DO_HEADER, PEM_R_BAD_PASSWORD_READ); - return (0); + return 0; } #ifdef CHARSET_EBCDIC /* Convert the pass phrase from EBCDIC */ - ebcdic2ascii(buf, buf, klen); + ebcdic2ascii(buf, buf, keylen); #endif if (!EVP_BytesToKey(cipher->cipher, EVP_md5(), &(cipher->iv[0]), - (unsigned char *)buf, klen, 1, key, NULL)) + (unsigned char *)buf, keylen, 1, key, NULL)) return 0; - j = (int)len; ctx = EVP_CIPHER_CTX_new(); if (ctx == NULL) return 0; - o = EVP_DecryptInit_ex(ctx, cipher->cipher, NULL, key, &(cipher->iv[0])); - if (o) - o = EVP_DecryptUpdate(ctx, data, &i, data, j); - if (o) - o = EVP_DecryptFinal_ex(ctx, &(data[i]), &j); + + ok = EVP_DecryptInit_ex(ctx, cipher->cipher, NULL, key, &(cipher->iv[0])); + if (ok) + ok = EVP_DecryptUpdate(ctx, data, &ilen, data, ilen); + if (ok) { + /* Squirrel away the length of data decrypted so far. */ + *plen = ilen; + ok = EVP_DecryptFinal_ex(ctx, &(data[ilen]), &ilen); + } + if (ok) + *plen += ilen; + else + PEMerr(PEM_F_PEM_DO_HEADER, PEM_R_BAD_DECRYPT); + EVP_CIPHER_CTX_free(ctx); OPENSSL_cleanse((char *)buf, sizeof(buf)); OPENSSL_cleanse((char *)key, sizeof(key)); - if (o) - j += i; - else { - PEMerr(PEM_F_PEM_DO_HEADER, PEM_R_BAD_DECRYPT); - return (0); - } - *plen = j; - return (1); + return ok; } +/* + * This implements a very limited PEM header parser that does not support the + * full grammar of rfc1421. In particular, folded headers are not supported, + * nor is additional whitespace. + * + * A robust implementation would make use of a library that turns the headers + * into a BIO from which one folded line is read at a time, and is then split + * into a header label and content. We would then parse the content of the + * headers we care about. This is overkill for just this limited use-case, but + * presumably we also parse rfc822-style headers for S/MIME, so a common + * abstraction might well be more generally useful. + */ int PEM_get_EVP_CIPHER_INFO(char *header, EVP_CIPHER_INFO *cipher) { + static const char ProcType[] = "Proc-Type:"; + static const char ENCRYPTED[] = "ENCRYPTED"; + static const char DEKInfo[] = "DEK-Info:"; const EVP_CIPHER *enc = NULL; + int ivlen; char *dekinfostart, c; cipher->cipher = NULL; if ((header == NULL) || (*header == '\0') || (*header == '\n')) - return (1); - if (strncmp(header, "Proc-Type: ", 11) != 0) { + return 1; + + if (strncmp(header, ProcType, sizeof(ProcType)-1) != 0) { PEMerr(PEM_F_PEM_GET_EVP_CIPHER_INFO, PEM_R_NOT_PROC_TYPE); - return (0); + return 0; } - header += 11; - if (*header != '4') - return (0); - header++; - if (*header != ',') - return (0); - header++; - if (strncmp(header, "ENCRYPTED", 9) != 0) { + header += sizeof(ProcType)-1; + header += strspn(header, " \t"); + + if (*header++ != '4' || *header++ != ',') + return 0; + header += strspn(header, " \t"); + + /* We expect "ENCRYPTED" followed by optional white-space + line break */ + if (strncmp(header, ENCRYPTED, sizeof(ENCRYPTED)-1) != 0 || + strspn(header+sizeof(ENCRYPTED)-1, " \t\r\n") == 0) { PEMerr(PEM_F_PEM_GET_EVP_CIPHER_INFO, PEM_R_NOT_ENCRYPTED); - return (0); + return 0; } - for (; (*header != '\n') && (*header != '\0'); header++) ; - if (*header == '\0') { + header += sizeof(ENCRYPTED)-1; + header += strspn(header, " \t\r"); + if (*header++ != '\n') { PEMerr(PEM_F_PEM_GET_EVP_CIPHER_INFO, PEM_R_SHORT_HEADER); - return (0); + return 0; } - header++; - if (strncmp(header, "DEK-Info: ", 10) != 0) { + + /*- + * https://tools.ietf.org/html/rfc1421#section-4.6.1.3 + * We expect "DEK-Info: algo[,hex-parameters]" + */ + if (strncmp(header, DEKInfo, sizeof(DEKInfo)-1) != 0) { PEMerr(PEM_F_PEM_GET_EVP_CIPHER_INFO, PEM_R_NOT_DEK_INFO); - return (0); + return 0; } - header += 10; + header += sizeof(DEKInfo)-1; + header += strspn(header, " \t"); + /* + * DEK-INFO is a comma-separated combination of algorithm name and optional + * parameters. + */ dekinfostart = header; - for (;;) { - c = *header; -#ifndef CHARSET_EBCDIC - if (!(((c >= 'A') && (c <= 'Z')) || (c == '-') || - ((c >= '0') && (c <= '9')))) - break; -#else - if (!(isupper(c) || (c == '-') || isdigit(c))) - break; -#endif - header++; - } + header += strcspn(header, " \t,"); + c = *header; *header = '\0'; cipher->cipher = enc = EVP_get_cipherbyname(dekinfostart); - *header++ = c; + *header = c; + header += strspn(header, " \t"); if (enc == NULL) { PEMerr(PEM_F_PEM_GET_EVP_CIPHER_INFO, PEM_R_UNSUPPORTED_ENCRYPTION); - return (0); + return 0; } + ivlen = EVP_CIPHER_iv_length(enc); + if (ivlen > 0 && *header++ != ',') { + PEMerr(PEM_F_PEM_GET_EVP_CIPHER_INFO, PEM_R_MISSING_DEK_IV); + return 0; + } else if (ivlen == 0 && *header == ',') { + PEMerr(PEM_F_PEM_GET_EVP_CIPHER_INFO, PEM_R_UNEXPECTED_DEK_IV); + return 0; + } + if (!load_iv(&header, cipher->iv, EVP_CIPHER_iv_length(enc))) - return (0); + return 0; - return (1); + return 1; } static int load_iv(char **fromp, unsigned char *to, int num) -- cgit v1.2.3